US Long-Term Ecological Research Network

North Temperate Lakes LTER: Trout Lake Spiny Water Flea 2014 - present

Abstract
Beginning in 2014, 30 meter vertical tows with a special zooplankton net were collected in Trout Lake specifically for the invasive Bythotrephes longimanus (spiny water flea). The net has a 400 micrometer mesh with a 0.5 meter diameter opening. Individuals are simply counted, and density is determined to be the number of individuals divided by the total water volume of each tow.
Additional Information
Related data set: North Temperate Lakes LTER: Zooplankton - Trout Lake Area 1992 - current (37)
Core Areas
Dataset ID
389
Date Range
-
Maintenance
on-going
Methods
Two 30-meter vertical tows (0.5m diameter, 400um mesh net) are collected at the deepest part of Trout Lake each time the lake is visited for routine LTER sampling during open water. On occasion, tows are collected on additional dates. Samples are visually scanned in their entirety for number of Bythotrephes present. The samples are not preserved or archived.

Publication Date
Version Number
2

North Temperate Lakes LTER: Pelagic Prey - Sonar Data 2001 - current

Abstract
Total pelagic fish abundance data were collected annually in mid-summer using sonar along a set of transects in each of eight lakes (Allequash, Big Muskellunge, Crystal, Sparkling, Trout, Mendota, Monona, and Fish), from 1981-1999, and in Lakes Monona and Fish from 1995-1999. This data is not available online (contact gahler@wisc.edu). No data was collected in 2000.

In 2001, collection resumed on Crystal, Sparkling, and Trout. In 2005, collection resumed on Lake Mendota. This data is included in this dataset as CSV files. The data represent lake-wide density estimates for abundant pelagic prey species in each lake. The sampling on each lake was conducted in depths greater than 5 meters to avoid hazards to equipment. In addition, because of the near field acoustic effects, the upper 2 meters of the water column is not represented in the data. Although they were rare, large targets representing predatory species were excluded from the density estimation for pelagic prey species using the proportion of large targets identified during single target analysis on each lake. Densities for Sparkling, Crystal and Mendota are for the entire basin of each lake. The data shown for Trout Lake represent densities in only the south basin. Number of sites: 4
Core Areas
Dataset ID
115
Date Range
-
LTER Keywords
Maintenance
ongoing
Metadata Provider
Methods
Sonar Sampling Protocol and Data Generation From 1981-1994, pelagic fish abundance data were collected along a set of transects in each of six lakes (Allequash, Big Muskellunge, Crystal, Sparkling, Trout, Mendota) using a Simrad 70 khz EY-M echosounder. The transducer was attached to a 4 aluminum towbody suspended in front of the boat and deployed at a speed of approximately 3-4 knots. Transects were run on two nights and two days in late summer in each year such that they intersected the deepest portions of each lake. The returning acoustic signal was recorded on audio tape (until ~ 1989) or DAT tapes (from ~ 1989-1994), as well as on paper charts. The recorded signal was analyzed with the deconvolution program developed by C.S. Clay (Rudstam et al. 1987, Stanton and Clay 1986, Jacobson et al. 1990) and with the HADAS post processing package by Torfinn Lindem (Lindem 1993, Rudstam et al. 1988) to estimate fish densities, by size, for each discrete depth in the lake. Most of the information collected from 1981 to 1989 was collected without recording the gain setting on the audio tapes and some tapes were recorded with too low gain resulting in too high signal to noise ratios. This made post processing difficult, however some data could be recovered by using the target strength of the dominant fish species to scale the recordings. Lars Rudstam analyzed data prior to 1989 using target strength estimated from fish caught in gillnets to calibrate the sonar information. Data and information was published on Trout Lake for 1983 and 1985 (Jacobson et al. 1990), Trout and Muskellunge Lakes for 1981 (Rudstam et al. 1987), on Mendota for 1981 to 1989 (Rudstam et al. 1993) and expanded to 1991 in DeStasio et al. (1995). For Crystal Lake, Rudstam generated data from 1981-1988 while Hrabik analyzed information from 1989-1995 (Sanderson et al. 1999). In 1995, the Simrad EY-M echosounder ceased to work reliably. In 1996, the LTER project purchased an HTI Model 241 echosounder with a 120 kHz split beam configuration. This echosounder was deployed in the manner described above on (Allequash, Big Muskellunge, Crystal, Sparkling, Trout, Mendota, Monona, and Fish Lakes). Ecoscape post-processing software, produced by HTI, was used to post-process data. Data were archived in the output format from HTI sounder software v. 1.0 and raw acoustic signals were stored on digital audio tapes. Prior to post processing of all HTI data, however, the computer containing the Ecoscape software ceased to work. No computer was purchased to replace it and the analysis, in 1998-9, also ceased. However, all the raw acoustic information is archived on digital audio tapes and processed on the HTI sounder software output files. After the laptop that operated the HTI system failed, there were no funds offered to replace it. No information was collected in 2000 because there was no laptop. Thus, there have been two major changes in analysis methods over time. The first was a change in single beam methods from the C.S. Clays deconvolution method to T. Lindems HADAS system. Rudstam et al (1988) found the two methods comparable. The second change involved switching from single beam analysis to split beam, from a 70kHz frequency to 120kHz and from Simrad to HTI and later Biosonics. Rudstam et al. (1999a) compared the single beam HADAS analysis using 70kHz (Simrad EYorM, HADAS analysis), split beam 70kHz (Simrad EY500, EP500 analysis) and split beam 120 kHz (Simrad EY500, EP500 analysis) for rainbow smelt in Lake Erie. Differences in density estimates and average target strengths were not large although there was a bias in the HADAS approach to single beam derived average target strength of 0.8dB (Rudstam et al. 1999a). Rudstam et al (1999b) reviewed the single beam methods in general and Mason and Schaner (2001) has compared data from the Biosonics, Simrad, and HTI units for smelt in Lake Champlain. From 2001-2003, sonar data was collected on Trout, Sparkling and Crystal Lakes using a Biosonics DT-6000 Echosounder with a 120kHz split beam transducer (T. Hrabik). Post-processing was performed using Echoview (SonarData Inc.) analysis software. In 2004, a Biosonics DT-X echosounder with a 70 kHz split beam transducer was used on Trout and Sparkling Lakes (T. Hrabik). No information was collected on Crystal Lake (the generator made too much noise in 2003 and caused a response from Law Enforcement). The information collected by Hrabik between 2001 and 2004 is currently being analyzed to generate aggregated lake-wide and 200 m transect-level fish size and density estimates (which can be converted into biomass and biomass by species using gillnet information) as well as transect-level data stratified at a 1m vertical depth resolution.Data Correction:December 2013: an error was detected for data from Sparkling Lake for the year 2004. Erroneous data have been replaced with corrected data in the metadata version 10 and data version v3.January 2014: an error was detected for data from Trout Lake for the year 2012. Erroneous data have been replaced with corrected data in the medatadata version 11 and data version v4. Literature cited DeStasio, B. J., L. G. Rudstam, A. Haning, P. Soranno, and Y. Allen. 1995. An in situ test of the effects of food quality on Daphnia population growth. Hydrobiologia 307:221-230. Jacobson, P. T., C.S. Clay, and J.J. Magnuson. 1990. Size, distribution, and abundance of pelagic fish by deconvolution of single beam acoustic data. Rapp. P.-v. Reun. Cons. int. Explor. Mer 189:304-311. Lindem, T. 1983. Successes with conventional in situ determination of fish target strength. FAO Fish. Rep. 300:104-111. Lindem, T. 1990. Hydro acoustic data acquisition system HADAS. Instruction manual. Lindem data acquisition Lda, Oslo. Lindem, T., and D. A. Houari. 1988. Hydro acoustic data acquisition system HADAS. mimoegraphed report. Lindeman, R. L. 1942. The trophic dynamic aspect of ecology. Ecology 23:157-176. Mason, D. M., and T. Schaner. 2001. Final report to the Great Lakes Fisheries Commisison for the acoustics intercalibration exercise in 1999. Rudstam, L. G., C. S. Clay, and J. J. Magnuson. 1987. Density and size estimates of cisco, Coregonus artedii using analysis of echo peak a single transducer sonar. Canadian Journal of Fisheries and Aquatic Sciences 44:811-821. Rudstam, L. G., S. Hansson, T. Lindem, and D. W. Einhouse. 1999. Comparison of target strength distributions and fish densities obtained with split and single beam echo sounders. Fisheries Research 42:207-214. Rudstam, L. G., T. Lindem, and S. Hansson. 1988. Density and in situ target strength of herring and sprat: a comparison between two methods of analyzing single beam sonar data. Fisheries Research 6:305-315. Rudstam, L. G., T. Lindem, and G. LaBar. 1999. The single beam analysis. Pages 6-13 in E. Ona, editor. Methodology for target strength measurements (with special reference to in situ techniques for fish and micronekton). International Council for the Exploration of the Sea, Copenhagen. Sanderson, B. L., T. R. Hrabik, et al. 1999. Cyclic dynamics of a yellow perch (Perca flavescens) population in an oligotrophic lake: evidence for the role of intraspecific interactions. Canadian Journal of Fisheries and Aquatic Sciences 56: 1534-42. Stanton, T. K., and C. S. Clay. 1986. Sonar echo statistics as a remote-sensing tool: volume and seafloor. IEEE Journal of Oceanic Engineering OE-11:79-96.
Short Name
NTLFI04
Version Number
32

Little Rock Lake Experiment at North Temperate Lakes LTER: Zooplankton count 1983 - 2000

Abstract
The Little Rock Acidification Experiment was a joint project involving the USEPA (Duluth Lab), University of Minnesota-Twin Cities, University of Wisconsin-Superior, University of Wisconsin-Madison, and the Wisconsin Department of Natural Resources. Little Rock Lake is a bi-lobed lake in Vilas County, Wisconsin, USA. In 1983 the lake was divided in half by an impermeable curtain and from 1984-1989 the northern basin of the lake was acidified with sulfuric acid in three two-year stages. The target pHs for 1984-5, 1986-7, and 1988-9 were 5.7, 5.2, and 4.7, respectively. Starting in 1990 the lake was allowed to recover naturally with the curtain still in place. Data were collected through 2000. The main objective was to understand the population, community, and ecosystem responses to whole-lake acidification. Funding for this project was provided by the USEPA and NSF. Zooplankton samples are collected from the treatment and reference basins of Little Rock Lake at at two to nine depths using a 30L Schindler Patalas trap (53um mesh). Zooplankton samples are preserved in buffered formalin and archived. Data are summed over sex and stage and integrated volumetrically over the water column to provide a lake-wide estimate of organisms per liter for each species. Sampling Frequency: varies - Number of sites: 2
Core Areas
Dataset ID
251
Date Range
-
LTER Keywords
Maintenance
completed
Metadata Provider
Methods
We collect zooplankton samples at the deepest part of the lake using two different gear types. We take one vertical tow with a Wisconsin Net (80um mesh), and a series of Schindler Patalas (53um mesh) samples spanning the water column. All samples are preserved in cold 95percent EtOH. After collection we combine subsamples of the individual Schindler Patalas trap samples to create one hypsometrically pooled sample for each lakeordate. The individual depth samples are discarded after pooling except from one August sampling date per year. The Hypsometrically Pooled sample and the Wisconsin Net sample are archived in the UW Zoology museum. We count zooplankton in one or two subsamples, each representing 1.8L of lake water, of the hypsometrically pooled samples to calculate zooplankton abundance. We count one sample date per month from the open water season, and the February ice cover sample. We identify individuals to genus or species, take length measurements, and count eggs and embryos. Protocol log: 1981-May1984 -- a 0.5m high, 31L Schindler Patalas trap with 80um mesh net was used. Two Wisconsin Net tows were collected. Preservative was 12percent buffered formalin. June1984 -- changed to 53um mesh net on Schindler trap. July1986 -- began using the 2m high, 45L Schindler Patalas trap. Changed WI Net collection to take only one tow. 2001 -- changed zooplankton preservative from 12percent buffered formalin to 95percent EtOH. The number of sample dates per year counted varies with lake and year, from 5 datesoryear to 17 datesoryear. 1981-1983 -- pooled samples are of several types: Total Pooled (TP) were created using equal volume subsamples of the Schindler samples. Epi, Meta, Hypo pooled used equal volume subsamples from the Schindler samples collected from each of the thermal strata. Strata Pooled used equal volume subsamples from the Epi, Meta, Hypo pooled samples to create an entire lake sample. Hypsometrically Pooled (HP) is our standard, which uses subsample volumes weighted to represent the hypsometry of the lake.
Short Name
LRZOOP1
Version Number
3

North Temperate Lakes LTER: Zooplankton - Madison Lakes Area 1997 - current

Abstract
Zooplankton samples for the 4 southern Wisconsin LTER lakes (Mendota, Monona, Wingra, Fish) have been collected for analysis by LTER since 1995 (1996 Wingra, Fish) when the southern Wisconsin lakes were added to the North Temperate Lakes LTER project. Samples are collected as a vertical tow using an 80-micron mesh conical net with a 30-cm diameter opening (net mouth: net length ratio = 1:3) consistent with sampling conducted by the Wisconsin Dept. Natural Resources in prior years. Zooplankton tows are taken in the deep hole region of each lake at the same time and location as other limnological sampling; zooplankton samples are preserved in 70% ethanol for later processing. Samples are usually collected with standard tow depths on most dates (e.g., 20 meters for Lake Mendota) but not always, so tow depth is recorded as a variate in the database. Crustacean species are identified and counted for Mendota and Monona and body lengths are recorded for a portion of each species identified (see data protocol for counting procedure); samples for Wingra and Fish lakes are archived but not routinely counted. Numerical densities for Mendota and Monona zooplankton samples are reported in the database as number or organisms per square meter without correcting for net efficiency. [Net efficiency varies from a maximum of about 70% under clear water conditions; net efficiency declines when algal blooms are dense (Lathrop, R.C. 1998. Water clarity responses to phosphorus and Daphnia in Lake Mendota. Ph.D. Thesis, University of Wisconsin-Madison.)] Organism densities in number per cubic meter can be obtained by dividing the reported square-meter density by the tow depth, although adjustments for the oxygenated depth zone during the summer and early fall stratified season is required to obtain realistic zooplankton volumetric densities in the lake's surface waters. Biomass densities can be calculated using literature formulas for converting organism body lengths reported in the database to body masses. Sampling Frequency: bi-weekly during ice-free season from late March or early April through early September, then every 4 weeks through late November; sampling is conducted usually once during the winter (depending on ice conditions). Number of sites: 4 Note: for a period between approximately 2011 and 2015, a calculation error caused density values to be significantly greater than they should have been for the entire dataset. That issue has been corrected.
Core Areas
Dataset ID
90
Date Range
-
Maintenance
ongoing
Metadata Provider
Methods
We collect zooplankton samples at the deepest part of the lake using two different gear types. We take one vertical tow with a Wisconsin Net (80um mesh), and a series of Schindler Patalas (53um mesh) samples spanning the water column. All samples are preserved in cold 95percent EtOH.After collection we combine subsamples of the individual Schindler Patalas trap samples to create one hypsometrically pooled sample for each lakeordate. The individual depth samples are discarded after pooling except from one August sampling date per year. The Hypsometrically Pooled sample and the Wisconsin Net sample are archived in the UW Zoology museum.We count zooplankton in one or two subsamples, each representing 1.8L of lake water, of the hypsometrically pooled samples to calculate zooplankton abundance. We count one sample date per month from the open water season, and the February ice cover sample. We identify individuals to genus or species, take length measurements, and count eggs and embryos.Protocol log: 1981-May1984 -- a 0.5m high, 31L Schindler Patalas trap with 80um mesh net was used. Two Wisconsin Net tows were collected. Preservative was 12percent buffered formalin.June1984 -- changed to 53um mesh net on Schindler trap.July1986 -- began using the 2m high, 45L Schindler Patalas trap. Changed WI Net collection to take only one tow.2001 -- changed zooplankton preservative from 12percent buffered formalin to 95percent EtOH.The number of sample dates per year counted varies with lake and year, from 5 datesoryear to 17 datesoryear.1981-1983 -- pooled samples are of several types: Total Pooled (TP) were created using equal volume subsamples of the Schindler samples. Epi, Meta, Hypo pooled used equal volume subsamples from the Schindler samples collected from each of the thermal strata. Strata Pooled used equal volume subsamples from the Epi, Meta, Hypo pooled samples to create an entire lake sample. Hypsometrically Pooled (HP) is our standard, which uses subsample volumes weighted to represent the hypsometry of the lake.
Short Name
NTLPL06
Version Number
31

North Temperate Lakes LTER: Zooplankton - Trout Lake Area 1982 - current

Abstract
Zooplankton samples are collected from the seven primary northern lakes (Allequash, Big Muskellunge, Crystal, Sparkling, and Trout lakes and bog lakes 27-02 [Crystal Bog], and 12-15 [Trout Bog]) at two to nine depths using a 2m long Schindler Patalas trap (53um mesh) and with vertical tows using a Wisconsin net (20cm diameter, 80um mesh). Zooplankton samples are preserved in buffered formalin (until 2001) or 95% ethanol (2001 onwards). Subsamples of the individual Schindler trap samples are combined to create a hypsometrically pooled sample which is counted for copepods, cladocerans, and rotifers. Data are summed over sex and stage to provide a lake-wide estimate of organisms per liter for each species. A minimum of 5 samples per lake-year are counted. The data set also contains length measurements for copepods and cladocerans. The Wisconsin net sample and the pooled sample are archived in the UW Zoology museum. Each year one complete set of Schindler Patalas depth samples collected in August is also archived. From 1981 to August 1986 - used a 0.5m high Schindler Patalas trap. Sampling Frequency: every two weeks during ice-free season, every 5 weeks during ice-cover. Number of sites: 7
Core Areas
Dataset ID
37
Date Range
-
Maintenance
ongoing
Metadata Provider
Methods
Schindler-Patalas trap samples are collected with a 2-meter high, 45L Schindler-Patalas trap with 53um mesh net at the deepest part of the lake. Samples are collected from specified target depths to include most or all of the water column, every two weeks during open water and every five weeks during ice cover. In addition, a vertical tow taken with an 80um mesh Wisconsin net is collected from the same location. Samples are preserved in the field with cold 95 percent EtOH.
For zooplankton counting, a hypsometrically pooled sample is created from subsamples of the individual Schindler Patalas samples. Subsample volumes are calculated using the hypsometric data for each lake, so that each subsample volume is proportional to the volume of lake water represented by the trap sample. A portion of the pooled sample is counted for copepods, cladocerans, and rotifers, identifying individuals to species or genus. All eggs are counted and length measurements are taken on copepods and cladocerans. Taxonomic resolution: A genus-only designation may mean a different species than the otherwise named species in that lake, or it may mean that the person counting only identified it to genus in that sample. Within one sample (same lake and date) it may be assumed that a genus only individual is a different species than other SameGenus/Named species in that count.
All records from 1981-1989 were modified in March 2015 to correct an error in how density had been calculated. Density values in many cases are significantly reduced. The table that was corrected in this case is dbmaker.zoop_all_density. Density values are modified from the original to final tables as they are summed or averaged over other variables (sample depth, replicate, and sex stage). The final table, where this website extracts density from, is dbmaker.zoop_allnl_summary_snap. Records after 1989 were already valid and did not require any modification.
Short Name
NTLPL03
Version Number
37
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