Browsing by Subject "zooplankton"

Now showing 1 - 6 of 6
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    Data and R code for a zooplankton ethanol storage correction factor.
    (2023-04-05) Blechinger, Tristan; Link, Denver; Nelson, Jenna KR; Hansen, Gretchen JA; blech024@umn.edu; Blechinger, Tristan; University of Minnesota Department of Fisheries, Wildlife, and Conservation Biology
    This data set contains fresh and ethanol fixed zooplankton samples collected from five Minnesota lakes during June 2022. The data were collected with five paired sites at each lake. The samples were filtered to remove detritus, phytoplankton, and predatory invertebrates. After filtering, each sample was split between fresh processing and ethanol storage. Ethanol storage samples remained in storage for approximately one month. Samples were sent to the UC-Davis Stable Isotope Facility for analysis. Stable isotope values in addition to lake name, DOW, and site of collection are included in the data file. Bayesian Hierarchical models were used to establish correction factors for ethanol storage. Statistical analysis was performed using the R package brms and model output can be found in respective .rds files. Details for each file can be found in the readme file.
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    Distribution, Composition and Biomass of the Crustacean Zooplankton Population in Western Lake Superior
    (Water Resources Research Center, University of Minnesota, 1973-08) Conway, J.B.; Odlaug, T.O.; Olson, T.A.; Ruschmeyer, O.R.
    Although data were collected for two years, 1970 and 1971, the major portion of this research was carried out the second year. This research took place in western Lake Superior and most of the data were collected at two stations, Larsmont and Stony Point, which were twenty miles northeast of Duluth. Each of these stations included two sites, one a half mile and the second two miles from shore. The other area where samples were collected was at the Little Marais and Sugar Loaf Cove stations, some 70 miles north of Duluth. The major purposes of this research were to study the productivity and the vertical, seasonal and horizontal distribution of the crustacean zooplankton population in western Lake Superior. A limited study of the biology of the copepod, Limnocalanus macrurus, was also conducted. Productivity at the Larsmont and Stonv Point area averaged 323 crustaceans per 100 liters of water, and 60 grams per square meter (based on a fifty meter water column). Productivity at the Little Marais and Sugar Loaf Cove area averaged 95 crustaceans per 100 liters and 37 grams per square meter. In general, productivity decreased as the depth increased from zero to 50 meters. If a thermocline was present, then both the toted number of crustaceans and the biomass became relatively scarce below twenty meters. Cladocerans were most frequent1y found in the upper ten meters of the water column whereas copepods were present at every level. Adult copepods were usually heavier than adult cladocerans and it was not unusual to find the mean weight of an organism at 50 meters ten or more times that of one at five meters. Productivity at the Larsmont and Stony Point area was bimodal during the sampling season; the first peak occurred in July and contained primarily copepods and the second, which was the seasonal maximum, occurred in September and contained both copepocls and cladocerans. Surface water temperatures were also bimodal during the sampling season; the peak recorded in July was thirteen degrces centigrade and sixteen degrees was reached in September. The cladoceran, Bosmina, became abundant after the water temperature reached five degrees in July, Another cladoceran, Dapnia, Replaced Bosmina in September when the water temperature was about eleven degrees. Ephippia, the overwintering stage of Daphnia first appeared in late August. Three copepods, Diaptomus, Limnocalanus, and Cyclops were present during most of the sampling season. Limnocalanus was present at all depths from June to early August, but was most numerous at ten meters. When the water temperature warmed above twelve degrees, the population shifted downward and was usually below the thermocline during the davlight hours. At this time, they were most abundant at 40 meters, The copepod, Epischura, was numerous in the upper lavers after the water warmed above eleven degrees. Productivity differences were found between the various sites and stations. These differences point to the lack of homogeneity in the horizontal distribution of the crustacean zooplankton population and support the phenomenon of “zooplankton patchiness". Productivity levels at the Little Marais and Sugar Loaf Cove area were from one-third to two- thirds of those at Larsmont and Stony Point. The Larsmont station was slightly more productive than Stony Point. The Stony Point inshore site was slightly more productive than the offshore site. The period of maximum productivity occurred at the Larsmont inshore site amd at both Stony Point sites in September. Maximum productivity was recorded at the Larsmont offshore site in July. A phytoplankton bloom was observed at the Stony Point station on July 20, 1971, but was not seen on the same day at the Larsmont station. Limnocalanus macrurus contrihuted to the greatest percentage of the crustacean biomass (often more than 90 percent) at depths 30, 40 and 50 meters in western Lake Superior. The male to female ratio established was 1:2. The mean lengths of mature males and females were, 2.09 and 2.16 millimeters, respectively. The length-weight correlation was: Dry weight (mg/100) = 3.31 length (mm) - 2.95. Two cladocerans, new to Lake Superior, were identified. They were: Alona guttata Sars and Holopedium gibberum Zaddach.
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    A Flourometric Technique for Sampling in Large-River Ecosystems
    (Water Resources Research Center, University of Minnesota, 1971-06) Johann, D.R.; McNabb, C.D.; Miller, E.F.
    Boat-mounted equipment for detecting the movement of rhodamine WT was used in Pool 6 of the upper Mississippi Rover, between navigation dams at Trempealeau, Wisconsin and Winona, Minnesota, to develop a procedure for sampling on paths of turbulent flow in large-river ecosystems. A means of relating sampling points in space and time is described. The expression Cm = (c2 . n) -c1/n-1 where c1 and c2 are concentrations of suspended or dissolved materials on upstream and downstream transects and n is a measure of dilution, can be used to obtain the mean concentration of material in suspension or solution in the water between points that are separated by at least as much as 2400 meters. This procedure in combination with conventional sampling programs in quiet backwaters may allow for more rigorous analysis of large-river ecosystems than has been achieved.
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    Full-year data on crustacean zooplankton and environmental parameters of Lake Superior nearshore regions
    (2023-02-08) Shchapov, Kirill; Ozersky, Ted; shcha001@d.umn.edu; Shchapov, Kirill
    This data set contains the results of a whole-year study of crustacean zooplankton communities and environmental parameters in the Lake Superior nearshore region. Five stations ('Sites.csv') were sampled throughout the year, emphasizing the winter period for zooplankton abundance, taxonomic community composition, and environmental parameters. Zooplankton abundance and taxonomic identification were made for all stations ('Zooplankton.csv'); environmental conditions are presented in file' YSI_data.xlsx.'
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    Materials to re-create results of Austin et al Zooplankton Migration paper
    (2020-11-05) Austin, Jay A; jaustin@d.umn.edu; Austin, Jay A; University of Minnesota Duluth, Large Lakes Observatory
    In a recent manuscript, zooplankton are shown to change their migratory behavior due to a change in stratification regime. This submission includes data and MATLAB scripts sufficient to recreate the four figures in the paper.
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    Seasonal community and food web dynamics of planktonic and benthic organisms in temperate lakes, with emphasis on winter
    (2022-10) Shchapov, Kirill
    Lakes of temperate regions are experiencing shortening of the winter period and reductions in the ice-cover duration. Despite these changes, winter ecological and biological processes are still not well understood due to the relatively small number of studies occurring during the ice-on period. However, recent studies showed that the winter season can play an important role for lower trophic level organisms, like zooplankton and benthic communities, in terms of their reproduction, succession, and food availability. With the ongoing changes in winter conditions, lower trophic level organisms could experience changes in abundances and nutritional qualities, which will consequently affect higher trophic level consumers like fish. Further, such disturbances could affect whole food web energy transfer and trophic level interactions of the lake ecosystem. Therefore, lake studies including winter could help to better understand the complete picture of intra-annual lake ecosystem processes. To better understand seasonal changes in lower trophic level organisms' population, community, and trophic dynamics during winter, I conducted research across lakes of different size classes and trophic states with a focus on the wintertime. The objectives of my research were: a) to assess seasonal variations in seston, zooplankton and benthic organisms abundances and environmental drivers affecting them; b) to determine seasonal changes in food sources and trophic positions of planktonic and benthic organisms using carbon and nitrogen stable isotopes; and c) to evaluate nutritional status of the lower-level organisms using fatty acid analysis.Here, I present the results of two studies distributed among four chapters. In the first study, I compared summer and winter environmental parameters and zooplankton communities across 13 lakes in Minnesota and Wisconsin. In the second study, I described the full-year seasonal changes in abundance and nutritional quality of seston, zooplankton, and benthos of Lake Superior, with emphasis on winter. In Chapter 1, I investigated parameters associated with changes in crustacean zooplankton densities, community composition, and their food sources between winter and summer across lakes of varying trophic status. I found that eutrophic lakes had higher zooplankton densities under the ice than dystrophic and oligotrophic lakes. Zooplankton communities were more similar across lakes during winter than during the open water period. Carbon and nitrogen stable isotopes suggested that zooplankton have higher lipid content in winter. In Chapter 2, I conducted a comprehensive full-year study of crustacean zooplankton and the effect of environmental parameters shaping zooplankton communities throughout the year in five nearshore regions of Lake Superior. My results suggested that zooplankton are still active during winter and vary greatly in densities between seasons, with greater variability at shallow than deep stations. I also found that water temperature and food availability were key drivers of total zooplankton abundance and the densities of the main taxonomic groupsthroughout the year. In Chapter 3, I provide the results of a survey study of coarse-level benthic organism seasonal changes across five locations of Lake Superior. This study showed relatively stable benthos abundances across all sampled locations, suggesting a continuous availability of littoral food sources for benthivorous fish throughout the year, including winter. I also found that the benthos diversity index was the highest in fall, while the species richness was similar across all seasons. In Chapter 4, I used stable isotope and fatty acid analysis to assess the origin of energy sources and nutritional values throughout the year in planktonic and benthic organisms. This information was intended to better assess and understand food availability for higher trophic level organisms. My results indicate low zooplankton abundances during winter but higher lipid content of total and essential fatty acids (EFA). Conversely, selected benthic organisms had higher total lipid content in summer than in winter. However, I found that concentrations of EFA (e.g., DHA, EPA, -ALA) in benthic organisms were low despite the high benthos densities throughout the year. This study suggests that different elements of the lower-level food web may vary in their importance as energy and nutrition sources for higher-level organisms like fish throughout the year. Together these four chapters provide important information on the seasonal dynamics of lower trophic level organisms across small and large lake ecosystems. These results help to address the winter ecology knowledge gap in seasonally frozen lakes and contribute to a better understanding of the effect of changing environmental conditions on lower trophic level organisms across a broad range of lake ecosystems. Additionally, the results of these studies provide new insights into the seasonality of freshwater organisms of the lower food web and their importance for higher-level consumers like fish. The detailed information provided in this research on temporal and spatial distribution along with nutritional conditions of seston, zooplankton, and benthic organisms can have important implications for fish productivity and distribution research and management. This study helps to identify future research efforts to charachterize the effect of climate change on food web dynamics in northern temperate lakes.