0 Sawatzky, C. L. Wurtsbaugh, W. A. Luecke, C. 2006 JOURNAL OF PLANKTON RESEARCH OXFORD OXFORD UNIV PRESS 28 1 65-86 JAN 0142-7873 TOTAL NITROGEN PHYTOPLANKTON GROWTH PRIMARY PRODUCTIVITY COMMUNITY STRUCTURE VERTICAL PROFILES TOTAL PHOSPHORUS SOCKEYE-SALMON NATURAL-WATERS TROPHIC STATUS CASTLE LAKE Deep chlorophyll layers (DCL) are a common feature of oligotrophic lakes, yet the mechanisms that form and maintain them are not understood fully. These phytoplankton populations occur in the metalimnia of lakes where light levels are moderate to low, and where nutrient levels and zooplankton grazing pressure are different than in the epilimnion. To test the importance of nutrients and grazing pressure for algal growth in different lake strata, microcosm experiments and monitoring were conducted in two oligotrophic lakes in the Rocky Mountains of North America that contain DCL. In situ microcosm experiments with natural phytoplankton communities from three depth strata were conducted with macronutrient additions and with and without the natural zooplankton grazing communities. Alkaline phosphatase assays and the in situ microcosm experiments indicated less nutrient limitation in the metalimnia than in the epilimnia of both lakes. Zooplankton grazing in the experiments decreased algal population growth rates by as much as 6% day(-1), with impacts shifting to progressively deeper strata over the summer. Zooplankton grazing losses, however, were partially offset by nutrient recycling that increased algal growth rates. Depth-differential nutrient deficiency and zooplankton grazing and recycling interacted to maintain the DCL in these lakes. 0 Vander Zanden, M. J. Chandra, S. Park, S. K. Vadeboncoeur, Y. Goldman, C. R. 2006 CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES 63 12 2608-2620 DEC 0706-652X STABLE-ISOTOPE ANALYSIS FRESH-WATER ECOSYSTEMS FOOD-WEB STRUCTURE OLIGOTROPHIC LAKE BIOGENIC METHANE SUBALPINE LAKE CARBON FLOW CASTLE-LAKE DELTA-N-15 DELTA-C-13 Although the study of lakes has traditionally focused on pelagic production pathways, recent stable isotope and diet evidence indicates that benthic algal production is an important contributor to fish production. This has led to the suggestion that energy may be more efficiently passed along benthic food chains relative to their pelagic counterparts. To test this idea, we combined stable isotope based assessments of energy flow pathways with estimates of pelagic and benthic-based primary and secondary production in Castle Lake, California. Approximately 50% of whole-lake primary production and 30% of whole-lake secondary production occurred in benthic habitats. Stable carbon isotopes and dietary data indicated that fish were predominantly supported by benthic (63%) and terrestrial (24%) secondary production. Ecological efficiencies (algal production/invertebrate production) were low in Castle Lake (< 3%), though zoobenthic production was more efficiently passed to fish than was zooplankton production. The larger size of benthic prey relative to pelagic prey may affect fish prey selection and foraging efficiency, resulting in differences in ecological efficiency between pelagic and benthic trophic pathways. Download [.pdf] http://pubs.nrc-cnrc.gc.ca/cgi-bin/rp/rp2_tocs_e?cjfas_cjfas12-06_63 0 Park, S. Brett, M. T. Muller-Solger, A. Goldman, C. R. 2004 LIMNOLOGY AND OCEANOGRAPHY WACO AMER SOC LIMNOLOGY OCEANOGRAPHY 49 2 614-619 MAR 0024-3590 NORTH-ATLANTIC OSCILLATION PLANKTON DYNAMICS EUROPEAN LAKES CASTLE LAKE FLUCTUATIONS PROJECTIONS CALIFORNIA GROWTH We analyzed a 42-yr record of primary productivity in small, subalpine Castle Lake to determine how climatic variability might influence lake primary productivity. A Pacific Decadal Oscillation (PDO) polarity reversal in 1977 significantly affected winter air and summer water temperatures in Castle Lake. The timing of lake ice-out was explained by spring air temperature and winter total precipitation (r(2) = 0.72) and significantly affected water temperature (r(2) = 0.74). Primary productivity was negatively correlated with ice-out date and positively correlated with primary productivity during the previous year (r(2) = 0.47). Alternatively, primary productivity was positively correlated with water temperature and primary productivity during the previous year (r(2) = 0.49). Ammonium availability immediately after ice-out was significantly related to primary productivity from the previous and the current year, suggesting that nutrient availability is an important mechanism for the serial correlation. Daphnia and cyanobacteria biomass also increased during warmer years. Our results suggest that variability in air temperature and precipitation from global warming, PDO, and the El Nino Southern Oscillation (ENSO) influence primary productivity and plankton communities in North American dimictic lakes. 0 Park, S. Chandra, S. Muller-Navarra, D. C. Goldman, C. R. 2004 JOURNAL OF PLANKTON RESEARCH OXFORD OXFORD UNIV PRESS 26 12 1489-1498 DEC 0142-7873 SEASONAL-CHANGES CASTLE LAKE DAPHNIA ZOOPLANKTON MIGRATION WATER TEMPERATURE PHOSPHORUS LIMITATION GROWTH Vertical profiles of seston food qualify and quantity) were measured in subalpine Castle Lake for particulate carbon, chlorophyll a fatty acids and phosphorus in addition to abiotic parameters including water temperature and dissolved oxygen levels. Field and laboratory incubation experiments were employed to manipulate Daphnia rosea growth environments. Sestonic eicosapentaenoic acid (EPA) content was much lower, whereas carbon to phosphorus (C.-P) ratios were much higher in the epilimnion compared to the deep-water chlorophyll maximum (16 20 in). In a temperature-controlled incubation, Daphnia grew faster when fed seston from the deep-water chlorophyll maximum. In in situ cage incubations, D. rosea grew fastest in the epilimmon. Daphnia rosea in a migrating treatment exhibited intermediate growth rates between the ones for epilimnion and hypolimnion. A projection of D. rosea growth rates by growth models without regard to water temperature showed much higher growth potentials in the hypolimmon. However, with inclusion of water temperature, epilimnetic water always gave higher potential growth rates. In this lake, warmer temperatures of epilimnetic water override the higher food qualify and quantity provided by the deep-water chlorophyll maximum. 0 Vander Zanden, M. J. Chandra, Sudeep Vadeboncoeur, Yvonne 2004 Ecological Society of America Annual Meeting Abstracts 89 2004 0 Park, S. Brett, M. T. Oshel, E. T. Goldman, C. R. 2003 AQUATIC ECOLOGY DORDRECHT KLUWER ACADEMIC PUBL 37 2 123-136 APR 1386-2588 C : P ratio energy transfer efficiency highly unsaturated fatty acids phytoplankton composition UNSATURATED FATTY-ACIDS NUTRIENT ELEMENT LIMITATION ZOOPLANKTON PRODUCTION EGG-PRODUCTION PLANKTONIC CLADOCERANS PHOSPHORUS LIMITATION MINERAL LIMITA Because of major biochemical imbalances between plants and animals, ecological efficiency at this interface may have a major impact on overall energy flow in ecosystems. In order to study relationships between seston food quality and energy transfer between primary producers and herbivores, we conducted five microcosm experiments in Castle Lake, California, USA during the summer of 1996. We simultaneously performed life table experiments to determine the effects of highly unsaturated fatty acids (HUFA) on Daphnia rosea growth, reproduction and survival. The results of these experiments suggest strong energy limitation of D. rosea growth in Castle lake during the study. D. rosea production was coupled with primary production in Castle Lake and in the microcosm experiments. D. rosea production efficiencies, i.e., the ratios of D. rosea productivity to primary productivity, decreased towards the end of the summer. A food quality index based on phytoplankton species composition and seston carbon to phosphorus ( C: P) ratio were good predictors of D. rosea production efficiencies. The predicted D. rosea production pattern based on phytoplankton composition and primary productivity matched the zooplankton biomass dynamics in Castle Lake during 1991. Life table experiments showed HUFA effects on D. rosea population growth rates, reproduction and survival in support of the HUFA limitation hypothesis. 0 Wurtsbaugh, W. A. Gross, H. P. Budy, P. Luecke, C. 2001 CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES OTTAWA NATL RESEARCH COUNCIL CANADA 58 11 2156-2166 NOV 0706-652X OLIGOTROPHIC LAKE SOCKEYE-SALMON CASTLE-LAKE PRIMARY PRODUCTIVITY NUTRIENT LIMITATION VERTICAL MIGRATION CALIFORNIA GROWTH DYNAMICS ALGAE Nutrients can load directly to either the epilimnion or metalimnion of lakes via either differential inflow depths of tributaries or intentional fertilization of discrete strata. We evaluated the differential effects of epilimnetic versus metalimnetic nutrient loading using 17-m-deep mesocosms that extended into the deep chlorophyll layer of oligotrophic Pettit Lake in the Sawtooth Mountains of Idaho. Addition of nitrogen plus phosphorus stimulated primary production nearly identically (2.4- to 4-fold on different dates) in both treatments, with the production peaks occurring in the strata where nutrients were added. The metalimnetic fertilization, however, resulted in equal or greater stimulation of chlorophyll a and phytoplankton biovolume than when nutrients were added directly to the epilimnion. Periphyton growth was stimulated 10-100 times more by epilimnetic fertilization than by metalimnetic fertilization and diverted nutrients from the planktonic autotrophs. These results suggest that the development of deep chlorophyll layers may be influenced by plunging river inflows that carry nutrients to the metalimnion and that metalimnetic lake fertilization may be useful as a tool for increasing lake productivity while reducing the impact on water quality. 0 Park, Sangkyu Chandra, Sudeep Goldman, Charles R. 2001 Ecological Society of America Annual Meeting Abstracts 86 2001 0 Higley, B. Carrick, H. J. Brett, M. T. Luecke, C. Goldman, C. R. 2001 INTERNATIONAL REVIEW OF HYDROBIOLOGY BERLIN WILEY-V C H VERLAG GMBH 86 2 147-163 1434-2944 periphyton nutrients UV radiation lakes INORGANIC NITROGEN UPTAKE FRESH-WATER ECOSYSTEMS SOLAR UV-RADIATION B RADIATION OZONE DEPLETION COMMUNITY STRUCTURE SUBALPINE LAKE NITRATE UPTAKE CARBON UPTAKE ARCTIC LAKE Rising levels of ultraviolet radiation (UVR) striking the Earth's surface have led to numerous studies assessing its inhibitory effects on phytoplankton and periphyton in aquatic systems. Mineral nutrients such as nitrogen (Nj and phosphorus (P) have been shown to increase aspects of algal metabolism and compensate fur UVR inhibition. An in situ substratum enrichment technique and UV shielding was used to assess the effects of nutrient additions on pcriphyton exposed to different levels of UVR in Castle Lake. California during July-August, 1997. UV shielding had no effect on total periphyton biomass, but caused shifts in species composition. The dominant periphyton species, Anabaena circinalis R-AB., demonstrated sensitivity to ambient levels of UV radiation possibly due to UV inhibition of N-2-fixation. Total diatom biovolume decreased when shielded from UVR. Phosphorus additions continually elicited an increase in periphyton biovolume at all levels of analysis. These results suggest an interaction between nutrient status/availability and UV sensitivity. 0 Cyr, H. Curtis, J. M. 1999 OECOLOGIA NEW YORK SPRINGER VERLAG 118 3 306-315 MAR 0029-8549 zooplankton Daphnia grazing feeding selectivity community size structure FRESH-WATER ZOOPLANKTON CRUSTACEAN ZOOPLANKTON RESOURCE UTILIZATION PLANKTON COMMUNITY PELAGIC ECOSYSTEMS CALANOID COPEPODS FILTERING RATES ALGAL PARTICLES FOOD SELECTIO The body size of an individual zooplankton is well related to its grazing rate and to the range of particle sizes it can ingest? and since cladocerans and copepods feed differently, they follow different relationships. Based on these general patterns in individual organisms. we tested whether the size structure and taxonomic composition of more complex natural zooplankton communities are related to their in situ grazing rate and to the range of algal sizes they graze. We compared community grazing rates on individual algal taxa in two communities dominated by small cladocerans, three communities dominated by large cladocerans and three copepod-dominated communities. Small algae were usually grazed most intensively, but grazing rates were poorly related to algal size alone. The range in size of grazed algae increased with increasing mean zooplankton body size, but differed systematically with their taxonomic composition. Communities dominated by Ceriodaphnia or Holopedium grazed a narrower size range of algae [maximum greatest axial length dimension (GALD)=16-36 mu m] than communities with large biomasses of Bosmina or Daphnia (maximum GALD=28-78 mu m). Copepod-dominated communities followed the same general relationship as cladocerans, Daphnia-dominated communities grazed the broadest range of algal sizes, and their total grazing rates were up to 2.4 times their grazing rates on small (<35 mu m) "highly edible" algae, a difference of similar magnitude to those found in successful trophic cascade biomanipulations. 0 Huovinen, P. S. Brett, M. T. Goldman, C. R. 1999 JOURNAL OF PLANKTON RESEARCH OXFORD OXFORD UNIV PRESS 21 2 373-385 FEB 0142-7873 SUBALPINE LAKE INTERANNUAL FLUCTUATIONS ZOOPLANKTON PRODUCTIVITY ENRICHMENTS POPULATIONS LIMITATION NITROGEN The impact of nutrient additions, zooplankton grazing and light intensity on phytoplankton net growth with depth and season was studied with five microcosm experiments in meso-oligotrophic, subalpine Castle Lake, California, during the period of summer stratification in June-September 1994. The incubations (4 day) were performed at 5 m intervals from the surface to the bottom using natural phytoplankton and zooplankton assemblages, with enrichments of phosphorus and nitrogen. The phytoplankton community was only limited by nutrients in the upper 5 m (epilimnion), as indicated by change in chlorophyll concentration. Nutrient enrichments had the greatest effect on the phytoplankton net growth in June and July. High light inhibited the phytoplankton net growth at the surface. Low light intensities limited phytoplankton at 20 m and below, and at the end of the growing season already around 10-15 m. A deep chlorophyll maximum in the hypolimnion in June-August was not limited by either light or nutrients. The results showed variation in grazers' impact on phytoplankton. These results suggest the importance of nutrient limitation only in the epilimnion with light inhibition at the surface, light limitation in the hypolimnion, and varying impact of zooplankton grazing in influencing the development of the phytoplankton in Castle Lake. 0 Brett, Michael T. Lubnow, Fred S. Villar-Argaiz, Manuel Muller-Solger, Anke Goldman, Charles R. 1999 Aquatic Ecology 33 2 135-145 1999 1386-2588 To determine whether positive correlations between phytoplankton and bacterioplankton growth in nutrient addition experiments are due to growth coupling or growth stimulation by the same nutrients, we examined phyto- and bacterioplankton growth in a series of eleven nutrient addition (N X P) and light/dark experiments. In mesotrophic Castle Lake, the phyto- and bacterioplankton growth responses to phosphorus (P) addition were strongly correlated (r2 = 0.59), while only a weak correlation (r2 = 0.10) was observed for the nitrogen addition treatments. After normalizing the N + P treatments for the growth stimulation observed in the respective P treatments, we found a substantial stimulation of the phytoplankton (e.g., costimulation by N + P) and no stimulation of the bacterioplankton. Bacteria growth rates were similar in both light and dark incubated P treatments. In the experiments, we found clear evidence suggesting the dynamics of bacteria and phytoplankton were correlated because they are often limited by the same resource (mainly inorganic phosphorus). We found only limited evidence that bacterioplankton growth coupling to algal dynamics was occurring in these experiments. However, we did not consider several factors such as dissolved organic nutrient availability, bacterivory, availability of physical substrates, and temperature which are also thought to influence the nature of bacteria/phytoplankton interactions. Based on the results of our experiments, we conclude the biomas of the bacterio- and phytoplankton covaried because they were stimulated by the same nutrients. 0 Jassby, A. D. 1998 ECOLOGICAL APPLICATIONS WASHINGTON ECOLOGICAL SOC AMER 8 2 277-287 MAY 1051-0761 Castle Lake chlorophyll estuaries interannual variability Lake Tahoe lakes phytoplankton primary productivity San Francisco Bay Delta sentinel sites spatial structure SAN-FRANCISCO BAY TAHOE CALIFORNIA NEVADA LAKE-TAHOE ATMOSPHERIC DEPOSITIO In the sentinel-site approach to monitoring ecological resources, relatively small numbers of locations are chosen for intensive study, each location being selected to represent a certain, preferably large, class of ecosystems. This paper examines long-term studies at three inland aquatic ecosystems in California that, although never intended as sentinel sites, nevertheless illustrate the challenges posed by sentinel-site networks. The main mechanisms of interannual variability in primary productivity or producers are described for Castle Lake, Lake Tahoe, and northern San Francisco Bay. The external forces behind the variability include climate (in the form of both snowfall and total precipitation), fishing intensity, anthropogenic nitrogen emissions, spring weather systems, intrinsic population cycles, forest fires, water diversions, and invasions of exotics. Each mechanism is associated with certain critical ecosystem features (such as hydraulic residence time) that condition a responsiveness to one or a combination of these external forces (such as precipitation); these critical features are identified for each mechanism. Three demanding conditions must be fulfilled in order for a sentinel site to function with regard to a given stressor: (1) some subset of the network must encounter the stressor; (2) at least some sites in the subset must have the critical features that cause responsiveness to that stressor; and (3) the background variability at those sites must not disguise the response to the stressor of interest. In practice, reliable extrapolation from sentinel-site networks to regional trends appears to be beyond our ecological understanding at the present time. 0 MacKay, N. A. Elser, J. J. 1998 LIMNOLOGY AND OCEANOGRAPHY WACO AMER SOC LIMNOLOGY OCEANOGRAPHY 43 2 339-347 MAR 0024-3590 FRESH-WATER ECOSYSTEMS NUTRIENT LIMITATION ZOOPLANKTON COMMUNITIES PHYTOPLANKTON GROWTH VARYING QUALITY DAPHNIA GROWTH GREEN-ALGAE CASTLE LAKE BIOMANIPULATION PHOSPHORUS Recent laboratory work on food quality constraints on zooplankton growth and reproduction, as well as several examples of weak effects of food-web manipulations on lower trophic levels in lakes with phosphorus-deficient phytoplankton, suggests that food quality effects may have currently unappreciated effects on zooplankton success and food-web interactions under field conditions. We experimentally manipulated two factors that we anticipated might play a role in suppressing Daphnia in P-limited lakes-the quality of phytoplankton food and the presence of the invertebrate predator Chaoborus punctipennis. We used a two-factor design, manipulating food source and presence of Chaoborus, and measured growth rate, survivorship, and fecundity of Daphnia rosea neonates incubated at fixed food levels in flow-through growth chambers. D. rosea grew significantly faster and was significantly mon fecund when fed seston from a high-food quality lake (Lake 979) relative to a treatment fed seston from a low-food quality lake (Lake 110). Chaoborus reduced survivorship of D. rosea but the food source-predator interaction term was not significant, indicating that invertebrate predation and phytoplankton food quality did not influence Daphnia populations synergistically in this experiment. A second experiment was conducted to determine if variation in Daphnia growth rate and fecundity when fed food of varying quality was caused by a change in feeding rate. Daphnia feeding rate increased with improved food quality, suggesting that Daphnia responds to increases in food quality, at least in part, by increasing feeding rate. We conclude that food quality can strongly affect Daphnia feeding, growth, and reproduction, thereby constraining food-web dynamics in nutrient-deficient lakes. 0 Cyr, H. 1998 CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES OTTAWA NATL RESEARCH COUNCIL CANADA 55 2 414-422 FEB 0706-652X FRESH-WATER ZOOPLANKTON EUDIAPTOMUS-GRACILIS HOLOPEDIUM-GIBBERUM NITROGEN-EXCRETION FILTERING RATES EUTROPHIC LAKE CASTLE LAKE ALGAL SIZE FOOD SIZE PHYTOPLANKTON Many studies suggest that the taxonomic composition of a zooplankton community should determine its grazing rate and selectivity for different types of particles. It is generally believed that copepod-dominated communities should (i) have lower grazing rates and (ii) consume larger particles than communities dominated by large cladocerans. I tested these hypotheses in situ by comparing zooplankton grazing in 19 communities from low-productivity lakes where the zooplankton ranged from >99% copepod biomass to >90% large cladoceran biomass (Holopedium gibberum, Daphnia spp.). The zooplankton grazed 1-14% of total chlorophyll per day and 0-17% of the chlorophyll in algae <35 mu m per day. Grazing rates increased with increasing zooplankton biomass (r(2) = 0.34, P < 0.01), but once the effect of zooplankton biomass was accounted for, similar grazing rates were found in copepod-and in cladoceran-dominated communities. The difference in grazing rates on small algae and on the whole phytoplankton assemblage, on the other hand, varied systematically with zooplankton taxonomic composition. Holopedium-dominate communities were most efficient at grazing algae <35 mu m, Bosmina-dominated communities had similar grazing rates on algae <35 mu m and on the whole phytoplankton assemblage, and copepod-dominated communities had similar or slightly higher grazing rates on the whole phytoplankton assemblage. Qualitative differences in grazing selectivity of different zooplankton taxa are observed in complex natural communities. 0 Dobberfuhl, D. R. Miller, R. Elser, J. J. 1997 AQUATIC MICROBIAL ECOLOGY OLDENDORF LUHE INTER-RESEARCH 12 1 29-37 JAN 30 0948-3055 Diacyclops thomasi cyclopoid microconsumer grazing phytoplankton bacteria CILIATED PROTOZOA GRAZING IMPACT CASTLE LAKE ZOOPLANKTON FRESH PREDATION CALIFORNIA ROTIFERS ASSEMBLAGES ECOSYSTEM A plankton community unconditioned by Diacyclops thomasi predation was incubated with and without D, thomasi for 10 d to test the hypothesis that a recent manipulation of the food web of Castle Lake, CA: USA, altered phytoplankton biomass and productivity via effects of cyclopoid predation on microconsumers. Microconsumer grazing rates on bacteria and phytoplankton, ciliate abundance, chlorophyll, phytoplankton biovolume, and bacterial abundance were quantified before and after incubation. D, thomasi significantly reduced ciliate abundances relative to controls lacking D. thomasi. D, thomasi treatments also had higher chlorophyll concentration, bacterial abundance and maximum growth capacity of phytoplankton relative to controls. These results are consistent with the hypothesis that increases in D. thomasi in Castle Lake following food web manipulation affected limnological processes by affecting microconsumer abundances with subsequent effects on algae and bacteria. 0 Muller-Solger, A. Brett, M. T. Luecke, C. Elser, J. J. Goldman, C. R. 1997 JOURNAL OF PLANKTON RESEARCH OXFORD OXFORD UNIV PRESS 19 12 1815-1828 DEC 0142-7873 MICROBIAL FOOD-WEB NOTEMIGONUS-CRYSOLEUCAS PLANKTONIC PROTOZOA TROPHIC CASCADE CASTLE LAKE MICHIGAN ZOOPLANKTON ABUNDANCE PREDATORS ROTIFERS A whole-lake food web manipulation suggested that planktivorous fish can play an important role in regulating the pelagic food web structure of mesotrophic lakes. In this study, we examined the impact of golden shiners (Notemigonus crysoleucas) on zooplankton, ciliates, phytoplankton and nutrients. We conducted a mesocosm experiment using treatments with and without golden shiners with three replicates per treatment in summer. We monitored plankton and nutrient dynamics in these mesocosms for 6 weeks. Total macrozooplankton biomass acid the proportion of large crustaceans decreased dramatically in the golden shiner treatment, while rotifer biomass decreased only in the second half of the experiment. In the mesocosms with golden shiners, total ciliate biovolume increased. However, the impact of golden shiners on ciliates was species specific. Chlorophyll a concentrations increased and dissolved nutrients (inorganic nitrogen and phosphorus) were statistically unaffected in the golden shiner treatment. This experiment showed that golden shiners had a strong negative impact on macrozooplankton, a variable impact on rotifers, weak positive impacts on ciliates and phytoplankton, and no discernible impact on dissolved inorganic nutrient concentrations. The results of this study help integrate aspects of previous research in mesotrophic lakes and provide evidence for cascading trophic interactions from fish to protozoans in a mesotrophic lake. 0 Sarnelle, O. 1997 ECOLOGY WASHINGTON ECOLOGICAL SOC AMER 78 3 913-928 APR 0012-9658 ciliates competition Daphnia enclosure size experimental duration lakes microcosms microzooplankton phytoplankton predation rotifers spatial scale COMMUNITY STRUCTURE FIELD EXPERIMENTS EUTROPHIC LAKE CASTLE LAKE ZOOPLANKTON POPULATION SU The effects of the herbivorous zooplankter, Daphnia, on a natural community of microzooplankton (rotifers, ciliates, and nanoflagellates) were compared in enclosures of two sizes (15 and 10 000 L) and in a eutrophic lake before and after a fish kill. The magnitude of Daphnia's effect on microzooplankton taxa varied quantitatively and qualitatively between experiments. The rotifer Synchaeta pectinata and the ciliate, Didinium sp., showed extreme differences between experiments, exhibiting opposite responses in small vs. large enclosures. The relative rankings of responses for two rotifers (Polyarthra dolichoptera and Synchaeta pectinata) and two ciliates (Coleps sp. and Didinium sp.) were reversed in small vs. large enclosures. Polyarthra was depressed by Daphnia more than Synchaeta in small enclosures, while Synchaeta was depressed more than Polyarthra in the large enclosures. Didinium was depressed more than Coleps in the small enclosures, while the reverse occurred in large enclosures. Microzooplankton responses also changed over time in the large-enclosure experiment. Daphnia significantly suppressed total ciliate dry biomass, but not total rotifer biomass after 6 d, but suppressed dry biomass of both groups by the end of the 23-d experiment. This result may reflect changes in the relative importance of Daphnia's predatory and competitive effects over time. Daphnia's effects on the rotifers, Polyarthra and Hexarthra mira, took 3 wk to be expressed but were very strong by the end of the large-enclosure experiment, suggesting that short-term experiments may underestimate competitive effects. Polyarthra's delayed response was associated with a delayed response of cryptophytes to the Daphnia manipulation. Comparisons of enclosure results with temporal correlations in lake data and with microzooplankton abundances before and after a fish kill indicated better congruence between lake data and the large-enclosure results. More importantly, large-enclosure results agreed more closely with whole-lake dynamics than with small-enclosure results. Consequently, large-scale enclosure experiments may provide reliable predictions of whole-lake phenomena, but small-scale (microcosm) experiments may not. 0 Carrillo, P. Reche, I. CruzPizarro, L. 1996 FRESHWATER BIOLOGY OXFORD BLACKWELL SCIENCE LTD 36 2 363-374 OCT 0046-5070 FRESH-WATER ZOOPLANKTON EXCRETION RATES NUTRIENT LIMITATION OLIGOTROPHIC LAKE CASTLE LAKE DAPHNIA HERBIVORES RELEASE GROWTH CALIFORNIA 1. An in situ experiment was carried out in a high-mountain oligotrophic lake (La Caldera) to quantify the specific release rates of ammonium and phosphorus in different phases of the seasonal succession of plankton. The zooplankton community was dominated by the calanoid copepod Mixodiaptomus laciniatus. 2. The rates of release of N and P (from non-detectable to 3.58 mu gN mg(-1) DW h(-1) and from 0.26 to 2.29 mu g P mg(-1) DW h(-1), respectively) and the N : P released ratio (not detectable to 4.77) fell within the range typical of oligotrophic lakes dominated by copepodite assemblages. 3. The values of the zooplankton N : P ratio (5 : 1 to 10 : 1 by weight) were lower than those established for other species of calanoids, and followed a well-established pattern of seasonal variation from year to year with higher values after ice thaw and lower values as individual size increased (ontogenetic development). 4. The elemental composition of the zooplankton depended on individual size, while the released N : P ratio was inversely related to the N : P ratio of the food. This pattern conforms to the predictions of the homeostasis theory of Sterner (1990). 5. A feedback regulation was established between the stoichiometric composition of the zooplankton, their food and the released N : P ratio that can help explain changes in pelagic community structure during the ice-free period. 0 Axler, R. P. Reuter, J. E. 1996 LIMNOLOGY AND OCEANOGRAPHY LAWRENCE AMER SOC LIMNOLOGY OCEANOGRAPH 41 4 659-671 JUN 0024-3590 INORGANIC NITROGEN UPTAKE DISSOLVED ORGANIC NITROGEN CASTLE-LAKE INTERANNUAL FLUCTUATIONS EPILITHIC PERIPHYTON SUBALPINE LAKE DEFICIENT LAKE FRESH-WATERS LIMITATION NUTRIENT Periphyton nitrate uptake and denitrification, not phytoplankton assimilation, accounted for similar to 90% and 73% of the depletion of similar to 35 mu g NO3-N liter(-1) added as whole-epilimnion enrichments of ammonium nitrate to Castle Lake, California, in midsummer 1980 and 1981. The importance of benthic processes is suggested by similar rates of depletion for nitrate and ammonium in the whole-lake experiments; these rates are inconsistent with previous microcosm studies of phytoplankton that showed strong preferential uptake of ammonium and low uptake rates of nitrate. The importance of the benthic pathways was confirmed by an (NH4SNO3)-S-15 mesocosm experiment, which simulated the whole-epilimnion experiments. Less than 9% of the N-15 transformed was associated with water-column pools; the remainder was incorporated into epipelic periphyton and sediments (56%) or attributed to N-15(2)-(N2O)-N-15 loss via denitrification. Historical analysis of nitrate depletion in the epilimnion during spring suggests that periphyton may outcompete phytoplankton for water-column nutrients. 0 Luecke, Chris 1996 Bulletin of the Ecological Society of America 77 3 SUPPL. P 1996 0012-9623 0 Axler, R.P. Reuter, J.E. 1996 Limnology and Oceanography 41 659-671 0 ELSER, JJ LUECKE, C. BRETT, MT GOLDMAN, CR 1995 ECOLOGY TEMPE ECOLOGICAL SOC AMER 76 1 52-69 JAN 0012-9658 CASCADING TROPHIC INTERACTIONS ECOSYSTEM VARIABILITY FOOD WEB COMPENSATION LAKE FOOD WEBS PRIMARY PRODUCTIVITY COMPLEX TROPHIC INTERACTIONS CASTLE LAKE PHYTOPLANKTON PRODUCTIVITY INTERANNUAL FLUCTUATIONS RECRUITMENT MECHANISMS INTRAGUILD PREDATI Stocking of the dominant planktivore of Castle Lake (rainbow trout) was discontinued to examine the impact of food web interactions on zooplankton communities and inter- and intra-annual dynamics of ecosystem properties (light penetration, primary productivity). Dynamics of zooplankton and ecosystem processes were examined for 3 yr following the manipulation and compared to 2-3 yr of premanipulation data. Sampling of vertebrate and invertebrate planktivores documented shifts in other members of the zooplanktivore guild as rainbow trout declined. Reduction of rainbow trout densities led to compensatory responses in other components of the Castle Lake fish assemblage as brook trout and golden shiners increased in abundance. This compensation resulted in increased rates of vertebrate planktivory on daphnids within 2 yr after trout stocking was discontinued. Zooplankton shifts in response to discontinuance of trout stocking were more rapid, particularly an immediate increase in a previously rare invertebrate predator (Diacyclops thomasi). Other limnological parameters also responded rapidly following the manipulation: water transparency declined and primary productivity (PPr) increased. In addition, intra-annual patterns (i.e., seasonal development) and the vertical distribution (shallow vs. deep) of PPr appeared to be affected by the food web manipulation. Our results indicate that complexities of real food webs complicate the prediction of the outcome of food web perturbations. Reduction of the previously dominant planktivore (rainbow trout) led to increases in other zooplanktivores (Diacyclops, golden shiners, brook trout) that resulted in enhanced predation pressure on zooplankton herbivores. Our results also indicate that alterations in water quality parameters (transparency, PPr) in response to food web alterations need not necessarily be mediated through changes in the abundance of Daphnia, as strong limnological responses preceded reductions in Daphnia by a year. We hypothesize an alternative mechanism for food-web-induced changes in lake ecosystem dynamics: changes in water clarity and productivity can result when cyclopoid predation strongly affects micrograzers. 0 ELSER, JJ LUBNOW, FS MARZOLF, ER BRETT, MT DION, G. GOLDMAN, CR 1995 CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES OTTAWA NATL RESEARCH COUNCIL CANADA 52 1 93-104 JAN 0706-652X PHOSPHORUS ZOOPLANKTON NITROGEN PRODUCTIVITY ENRICHMENT GRAZERS In a 3-year study of Castle Lake, California, potential nutrient (N,P) limitation of phytoplankton growth occurred rapidly (within 1-4 d of ice-out). Both N and P acted as potential limiting factors to phytoplankton growth in short-term (4-5 d) bioassays. Phytoplankton responded strongly to single additions of N or P in 1990 and 1992 but weakly so in 1991. This difference was associated with low inorganic N concentrations during spring 1991. In 1990 and 1991, variation of the primary limiting element correlated with the N:P ratio df the zooplankton community; phytoplankton tended to be N limited when the zooplankton was dominated by species with high N:P ratios (Diaptomus novamexicanus and Diacyclops thomasi: N:P ratios, by mass = 10.6-12.5) but limited by P when low N:P taxa (Daphnia rosea, N:P = 4.7) dominated. However, N vs. P limitation and zooplankton elemental data for 1992 did not fit the 1990-1991 pattern and there was no correlation for the 3-year data set. A field experiment demonstrated that the inorganic N:P ratio (NH4/SRP) increased dramatically with elevated Daphnia grazing but declined significantly with increased Diaptomus; this supported the 1990-1991 -correlation between phytoplankton N/P limitation status and zooplankton community elemental ratio. 0 ELSER, JJ FREES, DL 1995 LIMNOLOGY AND OCEANOGRAPHY LAWRENCE AMER SOC LIMNOLOGY OCEANOGRAPH 40 1 1-16 JAN 0024-3590 PHOSPHORUS MICROZOOPLANKTON NITROGEN LAKE ENRICHMENT LIMITATION HERBIVORES DYNAMICS GRAZERS CARBON A series of eight nutrient-deletion/dilution-gradient experiments was performed in Castle Lake during summer 1993 to quantify and characterize microconsumer grazing and contributions of nutrient supply sources (external, cell quota, recycling) supporting phytoplankton production. Responses of net chlorophyll production rate to dilution under nutrient-saturated conditions were frequently nonlinear, indicating saturation of micrograzer feeding at low biomass levels within the dilution gradient (dilutions of < 10-30% whole lake water). Despite feeding saturation, micrograzers exerted substantial grazing pressure on phytoplankton: microconsumer grazing coefficients (0.05-0.22 d(-1), mean:0.14 d(-1)) exceeded previous measures of crustacean grazing in this system. Nonlinear feeding kinetics required that piecewise multiple regression be used to estimate contributions of external, cell quota, and recycling to N and P supply. In deep-water layers, phytoplankton were growing at nutrient-saturated rates, indicating that phytoplankton growth was more likely light limited. In the epilimnion, recycled and internal sources were important for both N and P in different experiments, but the importance of various supply sources did not systematically differ for N and P. Tn epilimnetic experiments, there was strong experiment-to-experiment variation in contributions of recycling sources of N and P, suggesting that resupply of N and P via grazers was decoupled. Comparison of phytoplankton responses to nutrient deletion in undiluted vs. highly diluted treatments indicated that inferences regarding frequency and magnitude of nutrient limitation, as well as identity of the primary limiting nutrient, depended on dilution. 0 WIACKOWSKI, K. BRETT, MT GOLDMAN, CR 1994 LIMNOLOGY AND OCEANOGRAPHY LAWRENCE AMER SOC LIMNOLOGY OCEANOGRAPH 39 3 486-492 MAY 0024-3590 NATURAL ROTIFER DAPHNIA PROTOZOANS PREDATION LAKE An in situ bioassay experiment using Diacyclops bicuspidatus thomasi, Daphnia rosea, Diaptomus novamexicanus, and Holopedium gibberum single-species treatments was conducted to assess the influence of these zooplankters on the ciliate community structure of Castle Lake, California. At peak ambient abundances for adult individuals, these zooplankters all strongly depressed ciliate population growth rates. The ranking of the zooplankton-imposed ciliate death rates, from least to most severe, was Holopedium << Daphnia = Diaptomus <<< Diacyclops. The ranking of ciliate-taxa-response death rates to the zooplankton treatments was Halteria = Mesodinium < Askenasia = Urotricha = (Askenasia <) Strobilidium << Strombidium. As total ciliate abundance was depressed by the zooplankton treatments, the relative frequency of the small ciliates (approximately 5,000 mum3) increased, and the relative frequency of the larger ciliates (approximately 20,000 mum3) decreased. These results suggest that both seasonal and long-term shifts in zooplankton community structure have the potential to dramatically alter the dynamics and structure of ciliate communities. 0 BRETT, MT WIACKOWSKI, K. LUBNOW, FS MUELLERSOLGER, A. ELSER, JJ GOLDMAN, CR 1994 ECOLOGY WASHINGTON ECOLOGICAL SOC AMER 75 8 2243-2254 DEC 0012-9658 CASTLE LAKE DAPHNIA DIACYCLOPS DIAPTOMUS GRAZING IMPACTS HOLOPEDIUM PLANKTONIC ECOSYSTEM ZOOPLANKTON FRESH-WATER ZOOPLANKTON PHYTOPLANKTON COMMUNITY NATURAL ROTIFER GROWTH CLADOCERANS CHLOROPHYLL HERBIVORES SELECTION NUTRIENTS Freshwater zooplankton communities typically undergo pronounced seasonal succession and often show dramatic responses to external factors such as changes in zooplanktivore abundance. For this reason it is important to assess how common zooplankton species differ in their grazing impacts on planktonic ecosystems. To accomplish this we used single-species treatments with Diacyclops bicuspidatus thomasi, Daphnia rosea, Diaptomus novamexicanus, and Holopedium gibberum in situ in Castle Lake, California. These taxonomically diverse zooplankters differ markedly in feeding modes and typical seasonal population dynamics. We measured the response of nutrient concentrations, bacterioplankton abundance, phytoplankton species composition and biomass, primary production, a grazing index (phaeophytin/chlorophyll a), and microzooplankton to our single-species treatments. The filter-feeding cladocerans Daphnia and Holopedium and the raptorial filter-feeding calanoid copepod Diaptomus showed several effects typical of herbivorous zooplankton. These included increasing dissolved nutrient concentrations, decreasing algal biomass and the abundance of several common algae, increasing a grazing index, increasing the ratio of bacterial to algal biomass, as well as depressing ciliate microzooplankton abundance. The raptorial cyclopoid copepod Diacyclops was apparently exclusively predaceous as it decimated the ciliate and rotifer microzooplankton, but had no notable effect on the other measured parameters relative to zooplankton-free controls. Diacyclops had the greatest effect on the microzooplankton and Daphnia and Diaptomus had the greatest effect on inorganic nutrients and characteristics of the phytoplankton, Holopedium had qualitatively similar but weaker impacts compared to Daphnia and Diaptomus. None of the zooplankton treatments had an effect on bacterioplankton abundance, nor did grazing by any of these zooplankters increase total algal primary production. Our results suggest differences in the grazing effects of common freshwater zooplankton can be pronounced and indicate that both seasonal succession and long-term shifts in the zooplankton community structure should have marked effects on microzooplankton competitors and prey, the phytoplankton, and nutrient cycling. 0 ELSER, JJ JUNGE, C. GOLDMAN, CR 1994 GREAT BASIN NATURALIST PROVO BRIGHAM YOUNG UNIV 54 2 162-169 APR 0017-3614 CRAYFISH HERBIVORY MACROPHYTES PACIFASTACUS-LENIUSCULUS The recent appearance of the ''California crayfish,'' Pacifastacus leniusculus, in Castle Lake, California, and interest in its potential impacts on the lake ecosystem provided motivation for a study of the population structure and habitat use of this species and its effects on aquatic macrophytes. Mark-recapture studies indicated that the total number of adult (3+ yr or older) crayfish in the lake was ca 10,100 individuals, yielding an estimate of lakewide crayfish density in preferred crayfish habitats of 0. 13 adults m-2. Using mean body mass of individuals, we estimated that ambient biomass density was 5.9 g M-2. Length-weight relationships determined for captured individuals were sex dependent, with males having greater body mass for a given carapace length. Length-frequency and weight-frequency diagrams indicated that P. leniusculus reaches larger sizes in Castle Lake than do populations of P. leniusculus in ultraoligotrophic Lake Tahoe. Population-wide, males were significantly larger in both carapace length and body mass than females. We also examined sex dependence of interhabitat differences in crayfish body size by comparing animals trapped in rocky areas with those from areas with macrophytes and soft sediments. No significant differences in overall body size were found between habitats, but a significant habitat-sex interaction term occurred because the sex-dependent size differences were more pronounced in sediment than in rocky areas. Exclosure and enclosure experiments indicated that crayfish had large but differential impacts on Castle Lake macrophyte species, as the abundance of two of the dominant species (Chara sp., Potamogeton richardsonii) declined in the presence of crayfish and, in one case, increased in exclosures. These effects occurred via both consumptive and nonconsumptive mechanisms. These studies indicate that an expanding population of P. leniusculus in Castle Lake may be producing sizable impacts on the littoral zone habitat. 0 ELSER, JJ GEORGE, NB 1993 JOURNAL OF PLANKTON RESEARCH OXFORD OXFORD UNIV PRESS UNITED KINGDOM 15 8 977-992 AUG 0142-7873 FRESH-WATER ZOOPLANKTON BLUE-GREEN-ALGAE ORGANIC PHOSPHORUS NITROGEN PHYTOPLANKTON LIMITATION PRODUCTIVITY ECOSYSTEMS DYNAMICS RATIO We measured the concentrations, as well as lake-wide amounts, of nitrogen (N) and phosphorus (P) in dissolved, seston and zooplankton pools throughout the water column of Castle Lake, California, during summer, 1991. This allowed us to determine the stoichiometric ratios of important elements in each pool (C:N, C:P, N:P) as well as for the entire lake. Dissolved and seston pools were the predominant storage compartments for both N and P; zooplankton never contained >5% of N or 10% of P lake wide. However, by late summer, the concentrations of P in seston and in zooplankton were similar in the upper portions of the water column, suggesting that changes in food web structure that alter zooplankton biomass and community composition (and hence elemental storage in the zooplankton) may produce significant shifts in nutrient storage among pelagic pools. Lake-wide levels of dissolved N were largely constant over the study period; however, lake-wide dissolved P increased. These dynamics suggested that the Majority of nutrients stored in dissolved pools were unavailable for phytoplankton growth. N:P and C:P ratios indicated that Castle Lake phytoplankton became severely deficient in P during the course of our observations. These ratios also greatly exceeded recently reported threshold values for elemental constraints on growth and reproduction for several species of zooplankton. The ratio of N to P in the zooplankton pool was relatively constant and consistently lower than that in the sestion. As a result, the predicted N:P ratio of zooplankton-regenerated nutrients exceeded the N:P ratio of the seston, implying that zooplankton nutrient regeneration further skewed N and P supply ratios, and potentially enhanced P limitation of phytoplankton in Castle Lake. 0 Elser, J. J. Brett, M. T. Luecke, C. Goldman, C. R. 1993 Bulletin of the Ecological Society of America 74 2 SUPPL. 226-227 0012-9623 0 GOLDMAN, CR LUBNOW, FS 1992 RESOURCES CONSERVATION AND RECYCLING AMSTERDAM ELSEVIER SCIENCE BV 7 1-3 51-67 OCT 0921-3449 Conventional road salt has long been responsible for corrosive effects on cars and highway structures, as well as some undesirable impacts on terrestrial and aquatic ecosystems. This has resulted in investigations of a variety of alternative deicing compounds. Early studies in northern California demonstrated the formation of a salt-stabilized chemocline in Putt's Lake along Interstate 80 in the Sierra Nevada. Current studies on natural populations of algae and bacteria indicate that calcium magnesium acetate (CMA) appears to be a good alternative to sodium chloride. Bioassays of 10 northern Californian lakes were conducted in situ with various concentrations of CMA. During the summer, eight out of the 10 lakes showed no significant response in algal biomass with the CMA concentrations. Bioassays done during the late spring and early winter showed only slight deviations from these results. Temperature, prevailing weather conditions, and standing stock of microbial populations appear to be the dominant factors in determining whether or not an algal response was evident in these seasonal CMA bioassays. In a series of laboratory bioassays with natural microbial communities from Castle Lake, CMA had no significant effects on primary production or the uptake of acetate by bacteria. A significant increase in phosphorus uptake by the "algal" fraction ( > 3 mum) in lakewater occurred at CMA concentrations of 10 ppm. This increase in P-uptake was attributed to bacteria that were associated with detrital particles in the water. At the same time we observed a significant decrease in algal biomass. Within the scope of this investigation, CMA appeared to have minimal effects on phytoplankton biomass other than the observed stimulation of P-uptake which may be due to competition between the natural bacterial and algal populations. 0 ELSER, JJ 1992 ECOLOGY WASHINGTON ECOLOGICAL SOC AMER 73 3 887-902 JUN 0012-9658 HERBIVORY INDIRECT EFFECTS MESOCOSMS NUTRIENTS PHYTOPLANKTON ZOOPLANKTON SEASONAL SUCCESSION FEEDING-BEHAVIOR EUTROPHIC LAKE POPULATIONS COMMUNITIES HERBIVORES PATTERNS DAPHNIA FOOD During summer 1987, a series of experiments was performed in conjunction with monitoring of in situ plankton dynamics in nutrient-deficient Castle Lake, California. These factorial manipulations of nutrients and zooplankton were designed to separate the direct (grazing mortality) and indirect (stimulation of algal growth by nutrient recycling) effects of grazers on both species-specific phytoplankton dynamics, as well as aggregate properties such as total biomass, productivity, and biomass turnover. Grazing loss rates differed significantly among algal species with the mean grazing loss rate suffered by an algal species a negative function of cell or colony size. Stimulation of division rates in the presence of zooplankton (compared to an unenriched treatment lacking zooplankton) was commonly observed. Nutrient and grazer treatments also had significant impacts on algal biomass (indicated by chlorophyll concentration), productivity (PPR), and PPR/chlorophyll, and significant nutrient-grazer interactions were frequently observed. Species-specific algal responses to grazers were aggregated across the phytoplankton by weighting species-specific parameters by the contribution of each species to total community biomass in order to provide community-wide estimates of the importance of direct and indirect effects on algal dynamics. Finally, linkages between population-level responses and aggregate properties were demonstrated by examining relationships between total phytoplankton biovolume concentration and chlorophyll concentration in various treatments, by comparing community-wide grazing rates estimated from aggregated species-specific grazing rates and from changes in chlorophyll growth rates, and by relating the aggregated degree of species-specific growth stimulation to stimulation of biomass turnover. These results indicate that phytoplankton responses to grazers in Castle Lake reflect a mix of direct and indirect effects that varies considerably both between species and through time during the stratified season. 0 REUTER, JE AXLER, RP 1992 FRESHWATER BIOLOGY OXFORD BLACKWELL SCIENCE LTD 27 2 227-236 APR 0046-5070 HALF-SATURATION CONSTANTS NUTRIENT AVAILABILITY MARINE PHYTOPLANKTON EPILITHIC PERIPHYTON SUBALPINE LAKE NITRATE UPTAKE GREAT-LAKES CASTLE-LAKE WATER TRANSPORT 1. The physiological characteristics of nitrogen uptake by sublittoral and eulittoral (splash zone) epilithic periphyton as well as epipelic periphyton in N-deficient Castle Lake, California were determined by evaluating the half-saturation constants (K(t)) and initial slopes (V(max)/K(t)) of uptake kinetics curves. These results were compared to similar studies of phytoplankton nitrogen uptake in this lake. 2. The strategies of nitrogen uptake differed among the various communities and were largely determined by the proximity of each to pools of available dissolved inorganic N (DIN). 3. The sublittoral algae did not have a high biological affinity for either NH4 or NO3 and depended on nitrogen fixation for their N supply. The eulittoral community showed an increased capacity for DIN uptake at low substrate concentration, but not as high as measured for the phytoplankton community. Epipelic algae live immediately adjacent to a large pool of interstitial sediment NH4 and showed no physiological adaptations for surviving in a N-deficient environment. 4. K(t) values for all benthic communities were approximately two orders of magnitude greater than ambient substrate levels. In contrast, the half-saturation constants for NH4 + NO3 uptake by phytoplankton were very similar to in situ levels of these nutrients. 0 Reuter, J.E. Axler, R.P. 1992 Freshwater Biology 27 227-236 0 Wiackowski, K. Brett, M. T. Lubnow, F. Mueller-Solger, A. Goldman, C. R. 1992 European Journal of Protistology 28 3 0932-4739 0 ELSER, JJ GOLDMAN, CR 1991 LIMNOLOGY AND OCEANOGRAPHY LAWRENCE AMER SOC LIMNOLOGY OCEANOGRAPH 36 1 64-90 JAN 0024-3590 NUTRIENT-LIMITED LAKES PRODUCTIVITY ECOSYSTEMS ALGAE POPULATIONS HERBIVORES RESPONSES PATTERNS FIXATION DAPHNIA Studies were carried out in three lakes of strongly contrasting trophic state to evaluate how the effects of zooplankton on phytoplankton vary as a function of lake productivity. Chlorophyll and total P concentrations differed by 2-3 orders of magnitude among ultra-oligotrophic Lake Tahoe, meso-oligotrophic Castle Lake, and strongly eutrophic Clear Lake. Three experimental designs involving short-term (4 d) manipulations of nutrients, ambient zooplankton, and the common crustacean grazer Daphnia were performed in each lake. Algal responses were assessed at both the "aggregate," community (Chl, primary productivity, nutrient status) and species levels. Experiments in Lake Tahoe revealed a high degree of nutrient sensitivity but negligible grazing impacts by the very low densities of ambient zooplankton. Daphnia grazing had substantial impacts on Tahoe phytoplankton, however, indicating high susceptibility to grazing in this assemblage of relatively small-sized algal species. Castle Lake experiments revealed strong direct and indirect impacts of both ambient zooplankton and Daphnia on the nutrient-limited algal assemblage. The cyanobacteria-dominated algal community of Clear Lake was resistant to grazing impacts, responding relatively weakly only to the highest densities of Daphnia. Good correspondence between estimates of algal biomass made from chlorophyll measurements and microscopic examination were obtained, and, in Castle Lake, concordance between estimated community productivity turnover times made from species-specific growth determinations and community productivity measurements was observed. The contrasting responses to experimental zooplankton manipulations in the three lakes provide support for the view that the coupling between zooplankton and phytoplankton is strongest in lakes of intermediate productivity and imply that food-web alterations at the top of the food web are most likely to propagate to the level of the phytoplankton (and therefore lake water quality) in lakes of moderate trophic status. 0 J.J. ELSER 1991 Bulletin of the Ecological Society of America 72 2 SUPPL 0012-9623 0 C. LUECKE 1991 Bulletin of the Ecological Society of America 72 2 SUPPL 179-180 0012-9623 0 JASSBY, AD POWELL, TM GOLDMAN, CR 1990 LIMNOLOGY AND OCEANOGRAPHY LAWRENCE AMER SOC LIMNOLOGY OCEANOGRAPH 35 5 1021-1038 JUL 0024-3590 0 JASSBY, AD POWELL, TM 1990 ECOLOGY 71 6 2044-2052 DEC 0012-9658 0 BYRON, ER GOLDMAN, CR 1990 WATER RESOURCES BULLETIN HERNDON AMER WATER RESOURCES ASSOC 26 6 983-989 DEC 0043-1370 CLIMATE CHANGE GLOBAL WARMING PRIMARY PRODUCTIVITY WATER QUALITY MOUNTAIN LAKES CO2-INDUCED CLIMATIC-CHANGE GREAT-LAKES NITROGEN STREAM CARBON CANADA BASIN Atmospheric scientists have predicted that large-scale climatic changes will result from increasing levels of tropospheric CO2. We have investigated the potential effects of climate change on the primary productivity of Castle Lake, a mountain lake in Northern California. Annual algal productivity was modeled empirically using 25 years of limnological data in order to establish predictive relationships between productivity and the climatic variables of accumulated snow depth and precipitation. The outputs of monthly temperature and precipitation from three general circulation models (GCMs) of doubled atmospheric CO2 were then used in the regression model to predict annual algal productivity. In all cases, the GCM senarios predicted increased algal productivity for Castle Lake under conditions of doubled atmospheric CO2. The primary cause of enhanced productivity was the increased length of the growing season resulting from earlier spring ice-out. http://www.awra.org/jawra/papers/J89093.html 0 GOLDMAN, CR JASSBY, A. POWELL, T. 1989 LIMNOLOGY AND OCEANOGRAPHY LAWRENCE AMER SOC LIMNOLOGY OCEANOGRAPH 34 2 310-323 MAR 0024-3590 0 ZEHR, JP PAULSEN, SG AXLER, RP GOLDMAN, CR 1988 HYDROBIOLOGIA DORDRECHT KLUWER ACADEMIC PUBL 157 1 33-45 JAN 8 0018-8158 0 Reuter, J.E. Axler, R.P. 1988 Verh. Internat. Verein. Limnol. 23 915-918 0 Hagley, C.A. 1988 Verh. Internat. Verein. Limnol. 23 1920-1926 0 AXLER, RP REUTER, JE 1987 CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES OTTAWA NATL RESEARCH COUNCIL CANADA 44 1 130-133 JAN 0706-652X 0 Hoenicke, R. Goldman, C.R. 1987 Plankton Res 9 3 397-417 0 Priscu, J.C. 1987 Freshwater Biology 17 331-339 0 Strub, P.T. Powell, T. Goldman, C.R. 1985 Science 227 55-57 0 Lane, J.L. Goldman, C.R. 1985 Hydrobiologia 118 219-223 0 ZEHR, JP AXLER, RP GOLDMAN, CR 1985 MARINE CHEMISTRY AMSTERDAM ELSEVIER SCIENCE BV 16 4 343-350 0304-4203 0 PRISCU, JC AXLER, RP GOLDMAN, CR 1985 OIKOS COPENHAGEN MUNKSGAARD INT PUBL LTD 45 1 137-147 0030-1299 0 REUTER, JE LOEB, SL AXLER, RP CARLTON, RG GOLDMAN, CR 1985 ARCHIV FUR HYDROBIOLOGIE STUTTGART E SCHWEIZERBART'SCHE VERLAGS 102 4 425-433 0003-9136 0 CARLTON, RG GOLDMAN, CR 1984 HYDROBIOLOGIA DORDRECHT KLUWER ACADEMIC PUBL 111 2 113-117 0018-8158 0 PRISCU, JC 1984 JOURNAL OF PLANKTON RESEARCH OXFORD OXFORD UNIV PRESS 6 4 531-542 0142-7873 0 G.W. Redfield 1984 Internationale Vereinigung fuer Theoretische und Angewandte Limnologie Verhandlungen 22 1417-1424 0 Goldman, C.R. de Amezaga, E. 1984 Verh. Internat. Verein. Limnol. 22 591-599 0 Hoenicke, R. 1984 Verh. Internat. Verein. Limnol. 22 573-577 0 Axler, R.P. Reuter, J.E. Priscu, J.C. Loeb, S. Carlton, R. Zehr, J.P., Goldman, C.R. 1984 Verh. Internat. Verein. Limnol. 22 583 0 PRISCU, JC 1984 JOURNAL OF PLANKTON RESEARCH OXFORD OXFORD UNIV PRESS 6 5 733-749 0142-7873 0 PRISCU, JC GOLDMAN, CR 1984 FRESHWATER BIOLOGY OXFORD BLACKWELL SCIENCE LTD 14 2 143-155 0046-5070 3 Axler, R.P. Goldman, C.R. Reuter, J.E. Loeb, S.L. Priscu, J.C. Carlton, R.G. 1983 FAO/IAEA Internat. Symp. Rome, Italy Fate of Agrochemical Residues in Food and the Environment 0 J.C. PRISCU C.R. GOLDMAN 1983 Pacific Science Congress Proceedings 15 1-2 0 PRISCU, JC GOLDMAN, CR 1983 LIMNOLOGY AND OCEANOGRAPHY LAWRENCE AMER SOC LIMNOLOGY OCEANOGRAPH 28 6 1168-1181 0024-3590 0 PRISCU, JC GOLDMAN, CR 1983 CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES OTTAWA NATL RESEARCH COUNCIL CANADA 40 2 208-214 0706-652X 0 PRISCU, JC 1983 ARCHIV FUR HYDROBIOLOGIE STUTTGART E SCHWEIZERBART'SCHE VERLAGS 97 4 425-433 0003-9136 0 PRISCU, JC GOLDMAN, CR 1983 ARCHIV FUR HYDROBIOLOGIE STUTTGART E SCHWEIZERBART'SCHE VERLAGS 97 3 373-388 0003-9136 0 Axler, R.P. Goldman, C.R. Reuter, J.E. Loeb, S.L. Priscu, J.C. Carlton, R.G. 1982 In Agrochemicals: Fate in food and the Environment, Proc. Symp. Internat. Atomic Energy Agency-Food and Agricultural Organization 315-318 0 AXLER, RP GERSBERG, RM GOLDMAN, CR 1982 LIMNOLOGY AND OCEANOGRAPHY WACO AMER SOC LIMNOLOGY OCEANOGRAPHY 27 1 53-65 0024-3590 2 Priscu, J.C 1982 Ecology Davis University of California 259 0 Dogge, D. 1982 neritic waters EOS63: 951 0 R.P. AXLER C.R. GOLDMAN 1981 Water Research 15 5 627-632 0043-1354 Previous studies conducted at Castle Lake suggested that phytoplankton growth could be limited by low levels of dissolved inorganic N during the summer growing season. The isotopes H14CO3-, 15NH4+, 15NO3+ and 13NO3- were used as tracers to determine the rates of inorganic C and N uptake by the natural phytoplankton community and their response to N enrichment. Experimental designs followed the procedures of several bioassay techniques which were developed to investigate algal nutrient deficiency. Apparently, the phytoplankton were N deficient throughout the growing season. Ammonium uptake was rate-limited by the external concentration of ammonium. Nitrate uptake was regulated by the availability of nitrate and Mo, and potentially by the assimilation of ammonium. Although N-enrichment enhanced photosynthesis in short-term experiments during the early portion of the growing season, the photosynthetic response was initially negative during midseason, and a positive response did not occur until 2-3 days had elapsed. This suggests that a lack of stimulation, or even inhibition, of inorganic C uptake upon N enrichment does not necessarily preclude N-deficiency. 0 G.W. Redfield 1981 Internationale Vereinigung fuer Theoretische und Angewandte Limnologie Verhandlungen 21 3 1550-1554 0 S. LOEB J. REUTER 1981 Internationale Vereinigung fuer Theoretische und Angewandte Limnologie Verhandlungen 21 1 346-352 0368-0770 0 AXLER, RP REDFIELD, GW GOLDMAN, CR 1981 ECOLOGY WASHINGTON ECOLOGICAL SOC AMER 62 2 345-354 0012-9658 0 Axler, R.P. Gersberg, R.M. 1981 Verh. Internat. Verein. Limnol. 21 294-300 3 Gersberg, R.M. Axler, R.P. Goldman, C.R. 1980 Agrochemical Residue Vienna, Austria 75-85 Biota Interactions in Soil and Aquatic Ecosystems 15/08/1978 0 Neame, P.A. Goldman, C.R. 1980 Microcosms in Ecological Research 267-278 0 REDFIELD, GW GOLDMAN, CR 1980 HYDROBIOLOGIA DORDRECHT KLUWER ACADEMIC PUBL 74 3 241-248 0018-8158 0 PAULSON, LJ 1980 CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES OTTAWA NATL RESEARCH COUNCIL CANADA 37 9 1421-1425 0706-652X 0 AXLER, RP GERSBERG, RM GOLDMAN, CR 1980 CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES OTTAWA NATL RESEARCH COUNCIL CANADA 37 4 707-712 0706-652X 0 REDFIELD, GW 1980 HYDROBIOLOGIA DORDRECHT KLUWER ACADEMIC PUBL 70 3 217-224 0018-8158 0 REDFIELD, GW VINCENT, WF 1979 FRESHWATER BIOLOGY OXFORD BLACKWELL SCIENCE LTD 9 6 503-& 0046-5070 3 Paulson, L.J. Goldman, C.R. 1978 Catchable Trout Symposium Eugene, OR 19-31 Wild Trout J.R. Moring 0 B.L. KIMMEL 1978 SLADECEK, V. (ED.). INTERNATIONALE VEREINIGUNG FUER THEORETISCHE UND ANGEWANDTE LIMNOLOGIE VERHANDLUNGEN. INTERNATIONAL ASSOCIATION OF THEORETICAL AND APPLIED LIMNOLOGY, PROCEEDINGS, VOL. 20. PART 1 AND 2. COPENHAGEN, DENMARK, AUG. 8, 1977. IV+748P.; VIII 393-400 3 Goldman, C.R. Kimmel, B.L. 1978 J. Cairns, Jr., E.F. Benefield and J.R. Webste North Amer. Benthol. Soc. 19-44 Current Perspectives on River-Reservoir Ecosystems 0 G.W. REDFIELD C.R. GOLDMAN 1978 SLADECEK, V. (ED.). INTERNATIONALE VEREINIGUNG FUER THEORETISCHE UND ANGEWANDTE LIMNOLOGIE VERHANDLUNGEN. INTERNATIONAL ASSOCIATION OF THEORETICAL AND APPLIED LIMNOLOGY, PROCEEDINGS, VOL. 20. PART 1 AND 2. COPENHAGEN, DENMARK, AUG. 8, 1977. IV+748P.; VIII 381-387 0 Gersberg, R. Axler, R.P. Krohn, K. Peek, N. Goldman, C.R. 1978 Verh. Internat. Verein. Limnol. 20 388-392 0 Goldman, C.R. 1978 Mitt. Internat. Verein. Limnol. 21 364-377 0 Kimmel, B.L. Axler, R.P. Goldman, C.R. 1977 Limnology and Oceanography 22 789-793 3 Richards, R.C. Goldman, C.R. 1977 California Trout 1-8 Management of High Mountain Lakes in California's National Parks 3 Kimmel, B.L. Goldman, C.R. 1977 SIL 148-155 Interactions between Sediments and Freshwater 0 Gersberg, R. Krohn, K. Peek, N. Axler, R. Goldman, C. 1976 Science 192 1229-1231 0 JASSBY, AD PLATT, T. 1976 LIMNOLOGY AND OCEANOGRAPHY 21 4 540-547 0024-3590 0 P.A. NEAME 1975 SLADECEK, V. (ED.). INTERNATIONALE VEREINIGUNG FUER THEORETISCHE UND ANGEWANDTE LIMNOLOGIE, VERHANDLUNGEN. INTERNATIONAL ASSOCIATION OF THEORETICAL AND APPLIED LIMNOLOGY, PROCEEDINGS, VOL. 19, PARTS 1-4. WINNIPEG, MANITOBA, CANADA, 1974. III+748P. (PT. 1. 792-799 0 JASSBY, AD 1975 ECOLOGY 56 3 627-636 0012-9658 0 JASSBY, AD 1975 CANADIAN JOURNAL OF MICROBIOLOGY OTTAWA NATL RESEARCH COUNCIL CANADA 21 3 270-274 0008-4166 0 JASSBY, AD 1975 LIMNOLOGY AND OCEANOGRAPHY 20 4 646-648 0024-3590 0 WURTSBAUGH, WA BROCKSEN, RW GOLDMAN, CR 1975 TRANSACTIONS OF THE AMERICAN FISHERIES SOCIETY BETHESDA AMER FISHERIES SOC 104 1 88-95 0002-8487 0 JASSBY, A. POWELL, T. 1975 LIMNOLOGY AND OCEANOGRAPHY WACO AMER SOC LIMNOLOGY OCEANOGRAPHY 20 4 530-543 0024-3590 0 P.A. NEAME 1974 MARSHALL, K. E. XIX CONGRESS INTERNATIONAL ASSOCIATION OF LIMNOLOGY, WINNIPEG, CANADA, AUG. 22-29, 1974. 238P. FRESHWATER INSTITUTE, DEPARTMENT OF ENVIRONMENT: WINNIPEG, MANITOBE, CANADA 0 POWELL, T. JASSBY, A. 1974 WATER RESOURCES RESEARCH 10 2 191-198 0043-1397 0 JASSBY, AD GOLDMAN, CR 1974 LIMNOLOGY AND OCEANOGRAPHY 19 4 618-627 0024-3590 0 JASSBY, AD GOLDMAN, CR 1974 AMERICAN NATURALIST 108 963 688-693 0003-0147 0 E DEAMEZAGA CR GOLDMAN EA STULL 1973 SLADECEK, V. (ED.). INTERNATIONALE VEREINIGUNG FUER THEORETISCHE UND ANGEWANDTE LIMNOLOGIE VERHANDLUNGEN. PROCEEDINGS OF THE INTERNATIONAL ASSOCIATION OF THEORETICAL AND APPLIED LIMNOLOGY, VOL. 18. PART 3. CONGRESS IN USSR 1971. 1889P. ILLUS. MAPS. PUBLIS 1768-1775 0 E.A. STULL E. DEAMEZAGA C.R. GOLDMAN 1973 SLADECEK, V. (ED.). INTERNATIONALE VEREINIGUNG FUER THEORETISCHE UND ANGEWANDTE LIMNOLOGIE VERHANDLUNGEN. PROCEEDINGS OF THE INTERNATIONAL ASSOCIATION OF THEORETICAL AND APPLIED LIMNOLOGY, VOL. 18. PART 3. CONGRESS IN USSR 1971. 1889P. ILLUS. MAPS. PUBLIS 1776-1783 0 C.R. GOLDMAN E.A. STULL E. DEAMEZAGA 1973 SLADECEK, V. (ED.). INTERNATIONALE VEREINIGUNG FUER THEORETISCHE UND ANGEWANDTE LIMNOLOGIE VERHANDLUNGEN. PROCEEDINGS OF THE INTERNATIONAL ASSOCIATION OF THEORETICAL AND APPLIED LIMNOLOGY, VOL. 18. PART 3. CONGRESS IN USSR 1971. 1889P. ILLUS. MAPS. PUBLIS 1760-1767 0 M.C. SWIFT 1970 California Fish and Game 56 2 77-140 0008-1078 0 CORDONE, A.J. NICOLA, S.J. 1970 California Fish and Game 56 2 77-140 0008-1078 0 CR GOLDMAN 1970 MALEK, IVAN (CHAIRMAN). PREDICTION AND MEASUREMENT OF PHOTOSYNTHETIC PRODUCTIVITY. SYMPOSIUM. 632P. ILLUS. CENTRE FOR AGRICULTURAL PUBLISHING AND DOCUMENTATION: WAGENINGEN, NETHERLANDS 507-517 0 GOLDMAN, CHARLES R. 1967 Chemical environment in the aquatic habitat. Proceedings of an International Biological Programme Symposium. 10-16 October, 1966. Amsterdam and Nieuwersluis, Neth. Amsterdam, Neth. North Holland Publishing Company 229-238 Mo is an essential element for both N fixation and the formation of the plant enzyme nitrate reductase. After the discovery that Mo was a limiting factor for the growth of algae in Castle Lake, California, an experimental addition of 15.8 kg of sodium molybdate (Na2Mo4-2H2O) containing 6.27 kg Mo was made to the epi-limnion of the lake on 23 July 1963. Extensive sampling indicated that the epilimnion of the lake contained 7.7 [plus or minus] 1.2 mg of Mo/1. On a calculated basis the lake then contained 6.38 kg Mo which, considering errors of measurement, is in good agreement with the 6.27 kg added. Following a day of inhibition the primary productivity in the epilimnion for the rest of the season exceeded the previous year by about 40% and was accompanied by a 10 fold increase in cladocerans. This increase continued with both copepods and cladocerans during 1964. Fish yield at 14.9 lbs/acre was higher in 1964 than at any time in the preceding 26 years. The average of the preceding 7 years was 13.0 lbs/acre. Mo behaved very conservatively in this lake, remaining in the epilimnion until the fall overturn. Its gradual loss from the lake could be accounted for almost entirely through outflow until it reached about 1 part in 109. At this point the lake appears to be deriving Mo from the sediment, as the water remained at about 3 times the pre-fertilization level through 1965. || ABSTRACT AUTHORS: Author 0 BACHMANN, ROGER W. GOLDMAN, CHARLES R. 1965 LIMNOL OCEANOGR 10 (2) 233-239 1965 A 5-year series of summer temperature profiles was used to calculate the coefficient of eddy conductivity in a small (20.1 ha) mountain lake. The relatively high value obtained (6.22 x 10-2 g cm-1 sec-1) prompted us to evaluate the role of direct solar heating in the hypolimnion using data on total daily solar radiation, the spectral curve of sunlight, and the light transmission properties of the lake water. It was found that an estimated 65-85% of the heating in the upper hypolimnion could be accounted for by direct solar heating. It is postulated that in Castle Lake direct solar heating rather than turbulent mixing is responsible for the shape of the hypolimnetic thermal profile. || ABSTRACT AUTHORS: Authors 0 GOLDMAN, CHARLES R. 1965 MEM IST ITAL IDROBIOL DOTT MARCO DE MARCHI PALLANZA ITALY 18 (Suppl. 2) 121-135 1965 The requirements of natural phytoplankton populations for Mo, Cu, V, Co, Mn, Zn, Bo, Fe, Na, and Ca are reviewed. Although emphasis is placed on positive response to micronutrient additions, the importance of inhibitory effects is also considered. Data is presented from cultures of Castle Lake water where significant photosynthetic stimulation, as measured by C14 assimilation, was observed with Mo addition. Co, which is already at a high level in this lake, was found to be inhibiting. The sedimentary record of Mo, V, Co, and Mn concentration is examined in relation to present conditions in the lake. The use of response surfaces is suggested as a useful in situ experimental approach for solving problems of interaction of various macro- and micronutrient factors in natural phytoplankton populations. || ABSTRACT AUTHORS: M. Gerletti 0 GOLDMAN, CHARLES R. 1965 MEMORIE EST ITAL IDROBIOL DOTT MARCO MARCHI PALLANZA ITALY 18 (Suppl.) 121-138 1965 The requirements of natural phytoplankton populations for molybdenum, copper, vanadium, cobalt, manganese, zinc, boron, iron, sodium, and calcium are reviewed. Although emphasis is placed on positive response to micronutrient additions, the importance of inhibitory effects is also considered. Data is presented from cultures of Castle Lake water where significant photosynthetic stimulation, as measured by C14 assimulation, was observed with Mo addition. Co, which is already at a high level in this lake, was found to be inhibiting. The sedimentary record of Mo, Va, Co, and Mn concentration is examined in relation to present conditions in the lake. The use of response surfaces is suggested as a useful in situ experimental approach for solving problems of interaction of various macro- and micronutrient factors in natural phytoplankton populations. || ABSTRACT AUTHORS: Author 0 WALES, J. H. BORGESON, D. P. 1961 CALIFORNIA FISH AND GAME 47 (4) 399-414 1961 Castle Lake contains both rainbow and brook trout. Under heavy stocking with rainbows the natural production of brook trout declined due to competition. Various strains of rainbows were used in stocking studies. No conclusion was reached as to the best strain to use, although a single planting of the Kamloops rainbows showed considerable promise. The proper stocking rate for this lake was found to be 210 fingerlings per surface acre per year. || ABSTRACT AUTHORS: C. Ferrel 0 GOLDMAN, CR 1961 ECOLOGY WASHINGTON ECOLOGICAL SOC AMER 42 2 282- 0012-9658 0 GOLDMAN, CR 1960 SCIENCE WASHINGTON AMER ASSOC ADVANCEMENT SCIENCE 132 3433 1016-1017 0036-8075 0 BEST, E. A. BOLES, H. D. 1956 CALIFORNIA FISH AND GAME 42 (2) 109-115 1956 Four partial creel census methods are evaluated by applying each in a hypothetical census using actual data from complete censuses at Rush Creek and Castle Lake, California. Unstratified sampling chosen at random provides compatible estimates of angling effort only. Stratification by calendar months gives the best over-all coverage if the census must be limited to approximately 40 days per season. Least compatible estimates are obtained by stratifying weekends and weekdays. A 5-day week actual census supplemented by 2 theoretical days will substitute for a complete census with deviations of 12% or less from known data. || ABSTRACT AUTHORS: H. D. Boles 0 WALES, J. H. GERMAN, E. R. 1956 CALIFORNIA FISH AND GAME 42 (2) 93-108 1956 Survival to the angler of planted eastern brook trout fingerlings (Salvelinus fontinalis) was increased from 1.9 to 35% by the removal of predatory brown trout (Salmo trutta) and lake trout (Salvelinus namaycush) in 1946. Survival of planted yearling brook trout was increased from 40.0% to 43.8%. Eastern brook planted at 13/lb. in 1947 gave a total return to the angler of 48.3% over a 4-year period; when planted as fingerlings in 1947 and 1948 a return to the angler of 34.6% and 36.4%, respectively, was obtained over a 7-yr. period. Brook trout planting ceased in 1948. In 1952 rainbow trout (Salmo gairdneri) were planted and the catch consisted of both species beginning with 1952. In 1954, 84% of the catch was composed of brook trout, nearly all of which were naturally spawned. A yield of 978 lbs. was obtained from 1503 lbs. of yearling eastern brook planted in 1947, contrasted with a yield of 923 lb. from 100 lb. of fingerling brook trout planted in 1948. Upon removal of the brown and lake trout, the cost of brook trout in the creel decreased from $0.525 to $0.03 each for fish planted as fingerlings and from $0.375 to $0.35 each for fish planted as yearlings. The average annual yield of brook trout/acre was 10.3 lb. || ABSTRACT AUTHORS: J. B. Kimsey 0 WALES, J. H. 1947 CALIFORNIA FISH AND GAME 33 (4) 267-286 1947 In 1946, 667 anglers expended 2,674 hrs. at Castle lake, and caught 1,275 trout. The avg. catch per hour (0.48) and per angler-day (1.9 trout) indicates poor fishing. The number of zero catches (57% of all angler-days) was higher in 1946 than heretofore. As in previous yrs. the brown trout constituted over half the catch, less than 1/4 of the catch were rainbow trout, and a still smaller fraction were brook trout. This situation existed despite nearly equal plants of the 3 spp. Castle lake was poisoned on 10/9/46 to remove all fish and make possible the 2d phase of the investigation in which brook trout alone will be planted. The following fish were recovered after poisoning: 2,027 brown trout (Salmo trutta), 414 brook trout (S. fontinalis). 44 rainbow trout (S. gairdnerii stonei), 81 mackinaw trout (C. n. namaycush), several thousand black dace (Rhinichthys osculus) and several hundred golden shiners (Notemigonus crysoleucus auratus). These figures probably do not represent the true proportions of the spp. present, and not over half the actual number of all fish. || ABSTRACT AUTHORS: J. H. Wales 0 Wales, J. H. 1946 CALIFORNIA FISH AND GAME 32 (3) 109-143 1946 Starting in 1938, all rainbow trout (Salmo gairdnerii shasta), brown trout (S. trutta), and brook trout {Salvelinus fontinalis) planted in the lake have been marked. A small, self-propagating population of mackinaw trout (Cristivomer namaycush) also occurs in the lake. Since 1941, all trout taken from the lake by angling or otherwise have been recorded. Because there is almost no natural propagation except in the mackinaw, survival figures could be detd. Average survival to the angler of fingerlings was: rainbow, 3.5%; brown, 5.5%; brook, 1.9%. Of yearlings, average survival was: rainbow, 39%; brown, 35%; brook, 40%. From standpoint of growth, fingerlings can be planted early while still small. From standpoint of survival the size of fingerling rainbow and brown makes little difference, but brook fingerlings should be as large as possible. Food preferences varied considerably with species and age. From fingerling plants, each fish caught had cost the State: rainbow, $0.30; brown, 0.19; brook, 0.69. From yearling plants, each fish caught had cost: rainbow, 0.13; brown, 0.15; brook, 0.13. A population of several spp. is probably not as effective as one species alone. || ABSTRACT AUTHORS: J. H. Wales