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
-
Publication Date
Version Number
1

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 2 m long Schindler Patalas trap (53um mesh) and with vertical tows (1 m above the bottom of the lake to the surface) using a Wisconsin net (80um mesh). Zooplankton samples are preserved in buffered formalin (up until the year 2000) or 80% ethanol (2001 onwards) 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. A minimum of 5 samples per lake-year are identified and counted. Sampling Frequency: fortnightly during ice-free season - every 6 weeks during ice-covered season. Number of sites: 7.
Core Areas
Dataset ID
37
Date Range
-
Maintenance
ongoing
Metadata Provider
Methods
Sample Collection: Schindler-Patalas Trap For LTER lakes use the 2-meter high, 45L Schindler-Patalas trap with 53um mesh net and cup. The volume of the trap used should be indicated on the Volume by Weight form. Collect samples from the target depths at the deep sampling station in each lake. Sample depths are measured from the middle of the trap. Target Depths: TR: 1, 3, 5, 7, 9, 15, 20, 27, 31 meters CRorBM: 1, 3, 5, 7, 9, 11, 13, 15, 18 meters SP: 1, 3, 5, 7, 9, 11, 13, 15, 17 meters ALorTB: 1, 3, 6 meters CB: 1 meter Take samples starting at the surface and working down. Lower the trap slowly so that it remains vertical in the water. Pause at the target depth long enough to allow both trap doors to close completely, and check when it reaches the surface that both did close. Drain the trap through the net and cup, swirling the cup until the liquid level is below the mesh windows. Remove the cup from the net and pull out the center pin to drain the sample into jar, then rinse cup and pin several times with 95percent EtOH into the sample jar. Sample Collection: Wisconsin Net Lower the net to the bottom sample depth. Pull it up slowly, at a rate of about 3 seconds per meter. A slow haul prevents the net from pushing water and plankton away from the mouth of the net. Drain the cup until the water level is below the lower window, then pour contents into the sample jar. Rinse the cup with 95percent EtOH several times, adding the rinse to the sample jar. Hypsometric Pooling Rationale and Definition In March 1986 the LTER Zooplankton Group decided to pool the discrete depth Schindler Patalas trap samples into one pooled sample per lake-date for counting. Counting pooled samples rather than all of the depth samples reduces the time to produce zooplankton count data. The group hoped to count pooled samples from the entire backlog of uncounted samples and eventually to count samples shortly after collection. Samples are pooled considering lake hypsometry and, therefore, represent the entire lake. Previously, unpooled samples (2-9 samples per lake-date) or samples pooled considering only a water column were counted. Hypsometric pooling allows us to consider the zooplankton community as representing the entire lake, as our other limnological methods do, instead of just a column of water. Lake hypsometry is a three dimensional image of a lake or basin. In a simplified example of hypsometry, a lake is similar to a cone filled with water. If the cone were divided into three layers by two equidistant horizontal planes, the volumes in those layers would be very different from each other. The uppermost layer would contain the most water. Similarly, the upper depths typically contain most of the volume of a lake. Pooling is the creation of a new sample from subsamples of the Schindler trap samples collected from one lake-date. The volume of each subsample used to make the pooled sample reflects the depth range the sample represents and the volume of water that range represents relative to the entire lake volume. Samples pooled in this manner are called HP samples, for hypsometrically pooled, and are referred to as volume weighted because the volume of lake water each depth sample represents determines the subsample size. In sum, the advantages to this method of pooling are quicker turnover time and representation of the entire lake in a volume weighted fashion. Disadvantages of this method include the time required to pool subsamples, errors introduced during pooling, and the loss of more specific depth information. Pooling Procedure Allow the sample jars to air dry for a day or two. Weigh the Wisconsin Net sample and record the weight on the Volume by Weight form. Mark the liquid level on the jar with a Sharpee brand permanent marker. Add 95percent EtOH to each Schindler trap sample to bring liquid volume up to a weight of 105g, measured by weighing the sample jar with lid on the balance. If sample jars already contain more than 105g of liquid, allow some of the volume to evaporate in the hood, and then bring up to 105g. Record the final weight of jar plus sample plus EtOH on the Volume by Weight form. Calculate the subsample volumes, called target volumes, using the hypsometric table for each lake. Record these volumes on the Volume by Weight form. Mix the first sample gently and thoroughly by tilting the jar from side to side. Measure the target volume into a plastic graduated cylinder. Pour the subsample quickly and smoothly because the plankton settle out quite rapidly. Choose the smallest size graduated cylinder that can measure the target volume in one aliquot. Add the subsample to the labeled HP jar. Repeat with all other depth samples. When all of the subsamples have been added to the HP sample, rinse each graduated cylinder into the HP jar with several small volumes of EtOH. Place the HP sample in the hood to evaporate the excess volume of EtOH. The final weight of the HP sample should be 105g. Mark the liquid level on the jar with a Sharpee brand permanent marker. If the samples are from the August quarterly, pour the remainder of each Schindler sample into a labeled jar for archival. For all other sample dates, discard what is left of the Schindler samples. Rinse and air dry the field sample jars. Sample Storage and Record Keeping Store samples in cardboard records boxes obtained from UW Stores, storing samples from each lake in a separate box. Approximately one year of samples will fit in one box. Fill out the forms for each sample and sample box, as noted below. Box Inventory Form: A record of box contents. It remains in the sample storage box. Volume by Weight Form: A record of samples collected for any one lake-date and their volumes, storage box number, and history of sample usage. Filed in 3-ring binders, one copy at the Zoology Museum and one copy with Corinna Gries. Samples Stored Form: A record of all samples collected and storage box number for each. Current forms are kept in a binder at Trout Lake; archived forms are kept in the UW Zoology Museum. The data are eventually entered into the electronic LTER Museum Catalog. When boxes become full, check the contents against the Inventory Form and Samples Stored Form, and transfer them to the sample storage room in the garage. LTER samples and related paperwork are eventually transferred to the Zoology Museum at UW-Madison. Zooplankton Counting Before removing a subsample from any zooplankton sample jar, weigh the sample to check for evaporation. If the weight is within 0.1 gram of the last weight recorded on the Volume by Weight sheet, no fluid replacement is necessary. If the weight is more than 0.1 gram low, add 95percent EtOH to the sample to bring it up to the correct volume. Mix the sample well by turning the jar on its side and tipping back and forth gently. We use a Hensen-Stempel pipet with a 5-ml plunger for subsampling zooplankton samples. After mixing the sample, take the subsample as quickly as possible to avoid biasing the subsample as organisms begin to sink. There should be no air bubbles inside the Hensen-Stempel pipet. If there are, replace the subsample into the jar, completely dry the pipet, and begin again with the mixing. When you have a bubble-free subsample, dry the outside of the pipet and dispense the subsample into a cup with 53µ mesh bottom. Rinse the pipet into the cup with RO water, and continue rinsing the sample in the cup, washing the ethanol out of the sample through the mesh. Rinse the subsample into the counting tray with RO water, washing the mesh thoroughly to transfer all organisms into the tray. After removing subsample(s) from the jar, weigh the sample jar, and record this weight in a new column of the Volume by Weight form. Record the balance used, your initials, and the date at the top of the column, and add a column header such as Column C minus subsamples removed for counting . Do not put the subsample back into the sample jar after counting. Mark the new liquid level on the jar with a permanent marker. Replace the sample jar into the proper storage box. Count copepods and cladocerans first, identifying individuals to species wherever possible, and staging all copepodids. Measure a subset of each species. Then add a few drops of Lugol s solution to the subsample to stain it, and count the rotifers and nauplii. Count two subsamples for copepods and cladocerans. Count one subsample for rotifers and nauplii. If there are less than 100 of the dominant rotifer in one subsample, count a second subsample for rotifers and nauplii. Add milli-RO water to the tray as necessary to keep the surface of the subsample level. If the surface becomes concave as the subsample evaporates, it is difficult to focus clearly, and measurements may become distorted. Count all eggs attached to any species. For copepods and cladocerans, keep track of the number of individuals with eggs as well as the total number of eggs. Total number of eggs is sufficient for rotifers. Measurements are done as follows: Measure copepods from the tip of the head to the end of the urosome, excluding the caudal rami. Measure cladocerans from the tip of the head to the posterior of the carapace, excluding tailspine. However, measure helmeted Daphnia species from the anterior edge of the eye to the posterior of the carapace. Rotifers are not routinely measured, but where they have been, the total body length excluding spines is measured. Body width rather than length is measured for Conochilus, Conochiloides, and Collotheca. Describe, measure, and draw any unknown species on a separate sheet of paper. If possible, take a photograph of the unknown.</p>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. Densities are contained in three database tables. The original data is in dbmaker.zoop_raw; an intermediate table is dbmaker.zoop_all_density; and the final table (the one this website extracts density from) is dbmaker.zoop_allnl_summary_snap. 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 table that was corrected in this case is dbmaker.zoop_all_density. The correction algorithm is as follows: Records from dbmaker.zoop_raw are first grouped to isolate each unique 3-tuple of lake, sample date, and species. Each group is subsequently treated independently. Multiplying the fields 'hp_factor' and 'no_per_l' results in a density value for that record. Density values are then summed within each unique replicate (sex stage is what varies within a replicate). These resultant sums are then averaged over all replicates, giving a density value for each lake, sample date, species, and depth combination. The result is written into field 'number_per_liter' in table dbmaker.zoop_all_density. Densities are subsequently summed over depth before being provided via the website. Records after 1989 were already valid and did not require any modification.</p>Taxonomic resolution: A genus-only designation could mean a different species than the otherwise named species, or it could mean that the person counting only identified it to genus.&nbsp; Within one sample (same lake and date) it may be assumed that a genus only individual is a different species than other SameGenus/Namedspecies in the same count.</p>
Short Name
NTLPL03
Version Number
37
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