%0 Magazine Article %D 2006 %T Back from the "Dead": Changes in Brooktrout Lake Suggest Ecosystem Recovery after Acidification %A C. A. Siegfried %K biology %B Legacy: The Magazine of the New York State Museum %V 2 %P 6-7 %G eng %0 Book Section %B The Encyclopedia of New York State %D 2005 %T Zebra Mussels %A C. A. Siegfried %A D. P. Molloy %E Eisenstadt, P. %E L. E-. Moss %K biology %B The Encyclopedia of New York State %I Syracuse University Press %C Syracuse, NY %P 1744 %G eng %0 Magazine Article %D 2004 %T Tales from the Field %A C. A. Siegfried %K biology %B Members Update %V 14 %P 6-7 %G eng %0 Journal Article %J Lake and Reservoir Management %D 1996 %T Changes in the Zooplankton of Onondaga Lake: Causes and Implications %A C. A. Siegfried %A Auer, N. A. %A Effler, S. W. %K clarity %K cyanobacteria %K daphnid %K diversity %K grazing %K ionic waste %K Secchi disc %K Species richness %K zooplankton %X

The zooplankton assemblage of ionically polluted, culturally eutrophic Onondaga Lake was monitored over the 1979–1989 interval, and compared to surveys conducted in 1968 and 1978. A major shift in the assemblage was apparent by 1987, soon after the closure (1986) of an industrial discharger of ionic (Cl; Na+ and Ca2+) waste. Species richness increased from 8 to 18 common species, and more efficient grazers, large-bodied cladocera and the calanoid copepod Diaptomus sitihides, became dominants. Until 1987, a single cyclopoid copepod, Cyclops vernalis, was the dominant component of zooplankton biomass. The most likely cause for the shift in the zooplankton assemblage of the lake is the reduction in salinity, and attendant precipitation of calcium carbonate, associated with the closure of the industry. Improved clarity in the lake, manifested largely as intervals of dramatic increases described as ‘clearing events’, observed annually since 1987, has been attributed to die shift to more efficient grazers. The increased grazing pressure, particularly from large daphnids, may also be responsible for the return of late summer nuisance blooms of filamentous cyanobacteria, not observed in the lake since the early 1970s.

%B Lake and Reservoir Management %V 12 %P 59-71 %G eng %U http://www.tandfonline.com/doi/abs/10.1080/07438149609353997 %R 10.1080/07438149609353997 %0 Book Section %B Limnological and Engineering Analysis of a Polluted Urban Lake. Engineering Analysis %D 1996 %T Zooplankton Biology %A C. A. Siegfried %A Auer, N. A. %A Effler, S. W. %E Effler, S. W. %K biology %B Limnological and Engineering Analysis of a Polluted Urban Lake. Engineering Analysis %I Springler-Verlag %C New York, New York %P 421-436 %G eng %0 Journal Article %J Journal of Freshwater Ecology %D 1992 %T Zooplankton Communities of Adirondack Lakes: Changes in Community Structure Associated with Acidification %A C. A. Siegfried %A Sutherland, J.W. %K biology %X

The structure of the zooplankton (rotifers + crustaceans) community of Adirondack lakes was evaluated relative to generalizations derived from the literature on the impacts of acidification. The generalization that the number of zooplankton species is reduced in acid lakes was strongly supported by the results of Adirondack studies. Acidity status appeared to be the most important factor determining zooplankton species richness in Adirondack lakes. Generalizations regarding community composition were not strongly supported. Although the relative biomass of daphnids and cyclopoid copepods tended to be reduced in acidic lakes they were also frequent dominants of the communities of acidic lakes. Only two of the “generalist” species of the Adirondack region, Diaptomus minutus and Keratella taurocephala, increased in relative importance in acidic lakes. Acidification had a significant effect on zooplankton biomass.

%B Journal of Freshwater Ecology %V 7 %P 97-112 %G eng %U http://www.tandfonline.com/doi/abs/10.1080/02705060.1992.9664676 %R 10.1080/02705060.1992.9664676 %0 Journal Article %J Archiv fur Hydrobiologie %D 1991 %T The Pelagic Rotifer Community of an Acidic Clearwater Lake in the Adirondack Mountains of New York State %A C. A. Siegfried %K biology %B Archiv fur Hydrobiologie %V 122 %P 441-462 %G eng %0 Journal Article %J Hydrobiologia %D 1989 %T Acidity Status and Phytoplankton Species Richness, Standing Crop, and Community Composition in Adirondack, New York, U.S.A. Lakes %A C. A. Siegfried %A Bloomfield, J. A. %A Sutherland, J. W. %K biology %X

The mid-summer phytoplankton communities of more than 100 Adirondack lakes ranging in pH from 4.0 to 7.2 were characterized in relation to 25 physical-chemical parameters. Phytoplankton species richness declined significantly with increasing acidity. Acidic lakes (pH < 5.0) averaged fewer than 20 species while more circumneutral waters (pH > 6.5) averaged more than 33 species. Phytoplankton abundance was not significantly correlated with any of the measured physical-chemical parameters, but standing crop parameters, i.e., chlorophyll a and phytoplankton biovolume, did correlate significantly with several parameters. Midsummer standing crop correlated best with total phosphorus concentration but acidity status affected the standing crop-phosphorus relationship. Circumneutral waters of low phosphorus content, i.e. < 10 µg·1−1 TP, averaged 3.62 µg·1−1 chlorophyll a whereas acidic lakes of the same phosphorus content averaged only 1.96 µg·1−1 chlorophyll a. The midsummer chlorophyll content of lakes of high phosphorus content, i.e. > 10 µg·1−1 TP, was not significantly affected by acidity status.

Adirondack phytoplankton community composition changes with increasing acidity. The numbers of species in midsummer collections within all major taxonomic groups of algae are reduced with increasing acidity. The midsummer phytoplankton communities of acidic Adirondack lakes can generally be characterized into four broad types; 1) the depauperate clear water acid lake assemblage dominated by dinoflagellates, 2) the more diverse oligotrophic acid lake community dominated by cryptomonads, green algae, and chrysophytes, 3) the productive acid lake assemblage dominated by green algae, and 4) the chrysophyte dominated community. The major phytoplankton community types of acid lakes are associated with different levels of nutrients, aluminum concentrations, and humic influences.

%B Hydrobiologia %V 175 %P 13-32 %G eng %U http://link.springer.com/article/10.1007/BF00008472 %R 10.1007/BF00008472 %0 Journal Article %J Lake and Reservoir Management %D 1989 %T Empirical Prediction of Zooplankton Biomass in Adirondack Lake %A C. A. Siegfried %A Sutherland, J. W. %K biology %X

Empirical models of zooplankton biomass (rotifer, crustacean, and rotifer + crustacean biomass) in relation to selected morphometric (depth, surface area, flushing rate, and watershed area) and chemical variables were developed for 20 Adirondack lakes. The chemical variables were selected to characterize acidity status (pH, acid neutralizing capacity, and aluminum concentrations), trophic status (total phosphorus, chlorophyll a, phytoplankton biovolume, and Secchi depth), and humic influences (with dissolved organic carbon and color serving as surrogates of humic materials). Additional independent variables included major cations and anions (Ca++, Mg++, Na+, K+, Cl−, and SO4 −), specific conductance, dissolved oxygen, and temperature. Zooplankton biomass averaged 85.2 mg/m3 in the study lakes. Crustacean biomass accounted for an average of 65.9 mg/m3 and rotifer biomass for 19.4 mg/m3. Rotifer biomass was a significant component of zooplankton biomass in many circumneutral as well as acidic Adirondack lakes. The relative importance of rotifer biomass–as a percentage of total zooplankton biomass–could be predicted from an empirical relationship including the log of chlorophyll a, the log of monomeric aluminum, and true color as independent variables (R2 = .70). Rotifer biomass was particularly important in acidic lakes largely as a result of crustacean zooplankton loss rather than enhanced rotifer biomass. The best fit rotifer biomass empirical model included the log of total phosphorus and maximum depth as predictor variables (R2 = .69). Crustacean biomass was best described by a relationship that included the log of monomeric aluminum, the log of chlorophyll a, and the log of dissolved organic carbon (R2 = .70). The best fit empirical model for total zooplankton biomass was a combination of the above models including all the above independent variables except total phosphorus. This model, reflecting the interactions of acidity and productivity status and humic influences, accounted for 74 percent of the lake to lake variability in mean zooplankton biomass.

%B Lake and Reservoir Management %V 51 %P 91-97 %G eng %U http://www.tandfonline.com/doi/abs/10.1080/07438148909354403 %R 10.1080/07438148909354403 %0 Journal Article %J Hydrobiologia %D 1989 %T Planktonic Rotifer Community Structure in Adirondack, New York, U.S.A. Lakes in Relation to Acidity, Trophic Status and Related Water Quality Characteristics %A C. A. Siegfried %A Bloomfield, J. A. %A Sutherland, J. W. %K biology %X

The structure of the mid-summer planktonic rotifer communities of 101 Adirondack lakes ranging in pH from 4.0 to 7.3 were characterized in relation to acidity and selected water quality parameters. More than 70 rotifer species were identified from collections in 1982 and 1984. None of the species collected could be considered acidobiontic or alkalibiontic.

Keratella taurocephala was the most commonly collected rotifer, occurring in 94 of the study lakes. It was abundant throughout the range of pH investigated but was particularly dominant in acidic waters, averaging > 85 % of the rotifers collected from waters of pH < 5.0.

Rotifer community structure can be related to three groups of water quality parameters. Community parameters (richness and diversity) are most highly correlated with parameters indicative of acidity status. Rotifer abundance correlates with trophic state indicators, i.e. chlorophyll a and total phosphorus, over the full range of pH investigated. However, in acidic lakes, rotifer abundance is related to true color and DOC, indicators of humic influences.

The rotifer communities of the Adirondacks can be classified into four broad types: 1) A diverse, productive community of the more alkaline lakes, generally with ∼ 13 species, and dominated by Conochilus unicornis, Kellicottia bostoniensis, Kellicottia longispina, and Polyarthra major; 2) Relatively diverse communities of productive, highly colored acid lakes, with ∼ 8 species, and often with very large populations (> 200 · 1−1) dominated by K. bostoniensis and K. taurocephala; 3) Depauperate (< 4 species) communities of clear water acid lakes with generally low density populations dominated by K. taurocephala (> 90 % of rotifers in each sample); and 4) Extremely depauperate (2–3 species) acid lake communities associated with small lakes with high flushing rates dominated by C. unicornis.

%B Hydrobiologia %V 175 %P 33-48 %G eng %U http://link.springer.com/article/10.1007/BF00008473 %R 10.1007/BF00008473 %0 Report %D 1989 %T Species Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (Pacific Southwest) -Crangonid Shrimp %A C. A. Siegfried %K biology %C Albany, New York %G eng %0 Journal Article %J Lake and Reservoir Management %D 1988 %T Planktonic indicators of lake acidification in the Adirondack region of New York State %A C. A. Siegfried %K biology %X

Recent studies of plankton community structure in Adirondack lakes are summarized in relation to lake acidity status. Species richness of phytoplankton, planktonic rotifers, and crustacean zooplankton declines with decreasing pH. Highly acidic waters (pH < 5.0) average fewer than 20 phytoplankton and fewer than 12 zooplankton species in midsummer collections. More circumneutral lakes (pH > 6.0) average more than 33 phytoplankton and 20 zooplankton species. This decline in species number represents a simplification of plankton community structure rather than the invasion of new species. Very few Adirondack plankton species can be considered alkalibiontic or acidobiontic. The dominant species of acidic lakes are also generally important in non-acidic lakes of the region. Thus, presence or absence is generally not a very good indicator of lake acidity. However, shifts in the relative abundance/biomass of some species or species groups appear to be consistent with changes in pH. The relative biomass of acidobiontic diatoms and mallomonads is reported to provide a good index of acidity status. The relative biomass of the rotifer, Keratella taurocephala provides a consistent indicator of acidity. Among the crustacean zooplankton it appears that the combined relative biomass of Diaptomus minutus and Bosmina longirostris may be a useful indicator of water quality changes associated with acidification.

%B Lake and Reservoir Management %V 4 %P 115-121 %G eng %U http://www.tandfonline.com/doi/abs/10.1080/07438148809354386 %R 10.1080/07438148809354386 %0 Journal Article %J Lake and Reservoir Management %D 1987 %T Acidification, Vertebrate, and Invertebrate Predators and the Structure of Zooplankton Communities in Adirondack Lakes %A C. A. Siegfried %A Bloomfield, J.A. %A Sutherland, J.W. %K biology %X

Midsummer zooplankton community structures of 50 Adirondack lakes were evaluated in relation to dominant vertebrate and invertebrate predators and selected limnological parameters. The most important factors structuring zooplankton grazer communities were extracted in a principal components analysis. The interaction of acidity status and vertebrate planktivore abundance explains the variation in lake scores for the first principal component. The second principal component was related to predation, while the third was related to lake trophic status and humic influence. The interaction of water quality and predator abundance structures grazer communities of Adirondack lakes.

%B Lake and Reservoir Management %V 3 %P 385-393 %G eng %U http://www.tandfonline.com/doi/abs/10.1080/07438148709354794 %R 10.1080/07438148709354794 %0 Book Section %B Acid Rain: Scientific and Technical Advances %D 1987 %T Analysis of Plankton Community Structure in Adirondack Lakes in Relation to Acidification %A C. A. Siegfried %A Sutherland, J.W. %A Bloomfield, J.A. %E Perry, R. %E Harrison, R.M. %E Bell, J.N.B. %E Lester, J.N. %K biology %B Acid Rain: Scientific and Technical Advances %I Selper Ltd. %C London, England %P 445-450 %G eng %0 Journal Article %J Journal of Plankton Research %D 1987 %T Large-bodied Crustacea and Rainbow Smelt in Lake George, New York: Trophic Interactions and Phytoplankton Community Composition %A C. A. Siegfried %K biology %X

The phytoplankton community of south Lake George, New York, has recently undergone a dramatic shift in composition; from a community dominated by Chrysophytes, Cryptomonads, and Chlorophyta (1975–1976) to one currently dominated by blue-green algae, i.e.Anacystis incerta and Aphanothece nidulans. No increases in nutrient concentrations or inputs have been documented before or during this period. This shift in dominance can be related to changes in higher trophic levels, i.e. grazers and planktivores. Standing crop and abundance of the small-bodied filter feeders, Bosmina longirostris, Daphnia galeata, D. dubia, Holopedium gibberum, Diaptomus minutus and D. sicilis are significantly greater in the south basin. Standing crop and abundance of the large-bodied Crustacea, Daphnia pulicaria, Epishura lacustris and Mysis relicta, are significantly greater in the north basin. The clutch sizes of all herbivorous species except D. minutus were significantly greater in the south basin populations. These differences are consistent with greater productivity and size slective planktivory in the south basin. Stomach analysis of the recently introduced rainbow smelt, Osmerus mordax indicates a marked selection for the large-bodied Crustacea. The establishment of large populations of rainbow smelt in the south basin of Lake George is responsible for significant basin differences in the abundance of large-bodied Crustacea and appears to have contributed to the changes in phytoplankton community composition. The shift to small-bodied Crustacea in the south basin has resulted in significantly lower grazing rates but generally higher P release rates in the south basin. These factors contribute to greater springtime phytoplankton production and silica depletion in the south basin. Coccoid blue-green algae are able to dominate waters with low phosphorus and silica concentrations, i.e. Lake George. Thus, the establishment of rainbow smelt in Lake George coincides with, and appears to be responsible for, changes in phytoplankton community composition.

%B Journal of Plankton Research %V 9 %P 27-39 %G eng %U http://plankt.oxfordjournals.org/content/9/1/27.abstract %R 10.1093/plankt/9.1.27 %0 Journal Article %J Lake and Reservoir Management %D 1987 %T Plankton Community Response to the Chemical Neutralization of Three Acidified Waters in the Adirondack Mountain Region of New York State %A C. A. Siegfried %A Sutherland, J.W. %A S. O. Quinn %K biology %X

The response of the phytoplankton and zooplankton communities of three acidic Adirondack lakes to chemical neutralization is reported. The addition of base to the three lakes effectively neutralized acid conditions, raising pH from ~4.50 to 6.02 to 7.3. Concentrations of major ions were generally unaffected by neutralization treatment but aluminum concentrations were reduced. The phytoplankton and planktonic rotifer communities were initially decimated by the water column treatments but recovered within the first growing season following treatment. Species richness and standing crops of phytoplankton and rotifers approached or exceeded pre-treatment values within a year of neutralization. The crustacean community was generally slower to respond to base additions. Phytoplankton, rotifer, and crustacean community composition was changed in all lakes following treatment.

%B Lake and Reservoir Management %V 3 %P 444-451 %G eng %U http://www.tandfonline.com/doi/abs/10.1080/07438148709354802 %R 10.1080/07438148709354802 %0 Journal Article %J Ecology %D 1987 %T Review of "Phytoplankton Ecology: Structure, Function and Fluctuation by Graham P. Harris" %A C. A. Siegfried %K biology %B Ecology %V 68 %P 460 %G eng %0 Book %B New York State Museum Educational Leaflet %D 1986 %T Understanding New York Lakes %A C. A. Siegfried %K biology %B New York State Museum Educational Leaflet %I The University of the State of New York %C Albany, New York %G eng %0 Journal Article %J Lake and Reservoir Management %D 1985 %T Dominance by Blue-green Algae in an Oligotrophic Lake: Interaction of Nutrient Availability and Trophic Relations in Structuring a Phytoplankton Community %A C. A. Siegfried %K biology %B Lake and Reservoir Management %V 1 %P 108-112 %G eng %0 Journal Article %J Hydrobiologia %D 1985 %T Life History, Population Dynamics and Production of Pontoporeia hoyi (Crustacea, Amphipoda) in Relation to the Trophic Gradient of Lake George, New York %A C. A. Siegfried %K Amphipoda %K benthos %K life history %K Pontoporeia hoyi %K production %X

The life history characteristics, population dynamics and production of Pontoporeia hoyi in Lake George, New York, were studied from May 1981 through October 1982. P. hoyi, in terms of both density and standing crop, is the most prevalent member of the deep water macrobenthos of Lake George. It reproduces in the winter, with young being released in the late winter-early spring. At the southernmost study site, young released in the spring grew to 6–7 mm in length and bred during their first winter. At the remaining sites, P. hoyi required two years to complete its life cycle. This difference in life history characteristics can be related to food availability and temperature differences. The open waters of the south end of Lake George are not only more productive but are also more closely associated with the littoral zone, providing a wealth of bacteria-rich detritus for benthic deposit feeders. The greater food availability in the south basin of Lake George is reflected in significantly larger brood sizes and smaller size at maturity for P. hoyi populations from the south end of the lake.

The southernmost study site has significantly greater P. hoyi density and standing crop than all other sites. The cohort of the year dominated density and standing crop at the southern site while the cohort of the previous year dominated standing crop at the other sites. Peak abundance ranged from 600 · m−2 at the north site to 2 900 · m−2 at the south site. Cohort production ranged from ∼2g · m–2 at the north site to ∼15g · m−2 at the south site.

%B Hydrobiologia %V 122 %P 175-180 %G eng %U http://link.springer.com/article/10.1007/BF00032105 %R 10.1007/BF00032105 %0 Report %D 1985 %T Post-neutralization Plankton Communities of Bone Pond, Franklin County, New York %A C. A. Siegfried %K biology %C Albany, New York %G eng %0 Journal Article %J California Fish and Game %D 1984 %T The Benthos of a Eutrophic Reservoir: Influence of Reservoir Level on Community Composition, Abundance, and Production %A C. A. Siegfried %K biology %B California Fish and Game %V 70 %P 28-37 %G eng %0 Journal Article %J Verhangen International Verein Limnology %D 1984 %T Lake Acidification and the Biology of Adirondack Lakes I. Rotifer Communities %A C. A. Siegfried %A Sutherland, J.W. %A S. O. Quinn %A Bloomfield, J.A. %K biology %B Verhangen International Verein Limnology %V 22 %P 549-558 %G eng %0 Magazine Article %D 1984 %T Why is Lake Myosotis so Green? %A C. A. Siegfried %K biology %B Edmund Niles Huyck Preserve Newsletter %V Fall Iss %P 1-3 %G eng %0 Journal Article %J California Fish and Game %D 1984 %T Zooplankton Dynamics in a High Mountain Reservoir of Southern California %A C. A. Siegfried %A Kopache, M.E. %K biology %B California Fish and Game %V 70 %P 16-27 %G eng %0 Book Section %B The Lake George Ecosystem 3 %D 1983 %T Dynamics of the Crustacean Zooplankton of Lake George; Or, There's a Rainbow over Lake George but Where's the Pot of Gold? %A C. A. Siegfried %E Collins, C.D. %K biology %B The Lake George Ecosystem 3 %I Lake George Association %C Lake George, New York %P 13-23 %G eng %0 Book Section %B The Lake George Ecosystem 2 %D 1982 %T Lake George Benthos Community Dynamics: Life History and Production of Pontoporeia hoyi %A C. A. Siegfried %E Schadler, M. %K biology %B The Lake George Ecosystem 2 %I Lake George Association %C Lake George, New York %P 27-39 %G eng %0 Journal Article %J California Fish and Game %D 1982 %T Limnology of a Eutrophic Reservoir; Big Bear Lake, California %A C. A. Siegfried %A Herrgesell, P.L. %A Kopache, M.E. %K biology %X

The limnology of Big Bear Lake, San Bernardino County, a high mountain reservoir in the San Bernardino Mountains of southern California was studied from Nov. 1976 through Nov. 1978. Although the 1st yr of study covered a period of severe drought involving the lowest water levels in 10 yr and the lake was at or near capacity during the 2nd yr, the general limnology was similar each year. The lake typically stratifies in early spring and surface temperatures reach about 22.degree. C by mid-summer. Complete mixing occurs by Sept. Anoxia develops in the hypolimnion during stratification, increasing internal nutrient loading from sediments. The annual phytoplankton cycle peaks in the spring and late summer. Diatoms dominate in early spring, green algae briefly dominates in early summer and blue-green algae dominates from mid-summer to fall. In 1977, Anabaena and Chroococcus were the most abundant algal genera. In 1978, Anabaena dominated the early summer community, but Aphanizomenon flos-aquae dominated from late summer to fall. Algal growth appears to be limited by P from winter to spring, while N is limiting in the fall. P and N loads from tributaries draining the urbanized southeast portion of the drainage are disproportionately high. Nutrient loading rates are excessive, and well into the eutrophic range. Trophic status was similar in both years. Big Bear Lake will likely remain eutrophic because of its shallow morphology, high nutrient content and basin orientation and development.

%B California Fish and Game %V 68 %P 90-108 %G eng %0 Journal Article %J Water Resources Bulletin %D 1982 %T Phosphorus Loading to a Mountain Reservoir in Southern California %A C. A. Siegfried %K eutrophication %K nitrogen %K nutrient loading %K phosphorus %K reservoir %X

Phosphorus loading from precipitation and more than a dozen tributaries of Big Beat Lake, Woman, was determined for the period from January to December 1978. Direct precipitation contributed 1120 kg·P·yr-1 (0.096 g P·m-2·yr-1) while tributary runoff contributed 21,560 kg for a total P loading of 1.84 g P·m-2 Rathbone creek, although accounting for only 4 percent of the hydro-logic input to Big Bear Lake, contributed >27 percent of the annual phosphorus load. Phosphorus loading increased with increased impervious geology and increased development. Nitrogen loading exhibited similar loading patterns. Big Beat Lake is currently eutrophic and is likely to remain eutrophic. Calculations based on Vollenweider's critical phosphorus loading concept indicated that tributary P-loading would have to be reduced by >95 percent to achieve mesotrophic conditions. The completion of Big Bear Dam created a “naturally” eutrophic re mix which dl require proper management to enhance its resource potential.

%B Water Resources Bulletin %V 18 %P 613-620 %G eng %U http://onlinelibrary.wiley.com/doi/10.1111/j.1752-1688.1982.tb00043.x/abstract %R 10.1111/j.1752-1688.1982.tb00043.x %0 Journal Article %J Hydrobiologia %D 1982 %T Trophic Relations of Crangon franciscorum Stimpson and Palaemon macrodactylus Rathbum: Predation on the Opossum Shrimp, Neomysis mercedis Holmes %A C. A. Siegfried %K biology %B Hydrobiologia %V 89 %P 129-139 %G eng %0 Report %D 1982 %T Water Quality and Phytoplankton of Lake George, New York: Urban Storm Runoff and Water Quality Gradients %A C. A. Siegfried %K biology %C Albany, New York %G eng %0 Book Section %B The Lake George Ecosystem %D 1981 %T Phytoplankton of Lake George: Seasonal and Geographic Patterns %A C. A. Siegfried %E C. W. Boylen %K biology %B The Lake George Ecosystem %I Lake George Association %C Lake George, New York %P 223-236 %G eng %0 Journal Article %J Biological Bulletin %D 1980 %T Feeding of Neomysis mercedis (Holmes) %A C. A. Siegfried %A Kopache, M.E. %K biology %X

The diet of the opossum shrimp, Neomysis mercedis, in the Sacramento River Estuary was studied in relation to food availability, i.e., plankton, from January through November, 1976. The composition of the diet of N. mercedis varied in relation to mysid size and prey availability. Mysids exhibited strong positive selection for the large diatom prey species while "avoiding" small diatom prey. Although diatoms were the most abundant prey identified from the guts of specimens of N. mercedis it was determined that predation on rotifers and copepods accounted for > 80% of the energy consumed by other-than-juvenile mysids (≥7 mm in length). Juvenile mysids (≤ 3 mm in length) ingested rotifers when rotifers were abundant but were not found to consume copepods. Laboratory feeding experiments indicate a density-dependent feeding by N. mercedis on copepods, i.e., as copepod density increases mysid predation on copepods also increases. Feeding observations indicate that N. mercedis is not a particularly active predator, capturing prey drawn into its feeding current but not actively pursuing prey. N. mercedis appears to feed continuously, with a peak in activity for mature mysids during darkness, a pattern not apparent in immature mysids. Consumption of the detritus was not considered significant. Although herbivory may be of direct importance during the spring diatom increase, carnivory was the major source of energy for N. mercedis in the Sacramento River during 1976.

%B Biological Bulletin %V 159 %P 193-205 %G eng %U http://www.biolbull.org/content/159/1/193.short %0 Journal Article %J Biological Bulletin %D 1980 %T Seasonal Abundance and Distribution of Crangon franciscorum and Palaemon macrodactylus (Decapoda, Caridae) in the San Francisco Bay Delta %A C. A. Siegfried %K biology %X

The seasonal abundance and distribution of the native caridean shrimp, Crangon franciscorum, and the introduced shrimp, Palaemon macrodactylus, in the channel areas of the San Francisco Bay Delta were studied from April, 1977, through October, 1978. C. franciscorum reproduces earlier in the year and grows to a larger size than P. macrodactylus. C. franciscorum reproduction occurs from December to June in the high salinity waters of San Francisco Bay and the Pacific Ocean. P. macrodactylus reproduction occurs from May to September in the delta as well as in higher salinity habitats. Length-weight and length-fecundity relationships differ significantly between the two shrimp. Both shrimp are limited upstream by low salinities, few shrimp occurring at salinities < 1‰. The downstream distribution of these shrimp is related to prey availability, i.e., Neomysis mercedis abundance.

Indices of spatial overlap, or interspecies patchiness, indicate a high degree of overlap which varied seasonally and exhibited markedly different patterns in 1977 and 1978. Directional crowding (intraspecific patchiness) also differed between 1977 and 1978. P. macrodactylus appears more tolerant of varied environmental conditions than C. franciscorum, occurring in the same habitats and also in additional ones not utilized by C. franciscorum. This may give P. macrodactylus a competitive advantage when trophic resources become limiting.

%B Biological Bulletin %V 159 %P 177-192 %G eng %U http://www.biolbull.org/content/159/1/177.short