DOI: 10.5061/dryad.z08kprr90
title: Which physicochemical variables should zooplankton ecologists measure when they conduct field studies?

description: Over the last century, a rich literature has developed describing how the
 physical and chemical environment influences zooplankton communities, but
 there is little guidance on the suite of limnological variables that
 should be measured by zooplankton ecologists. We performed a literature
 review to assess: 1) Which variables were measured most often by
 zooplankton ecologists; 2) Which of these variables were consistently
 related to zooplankton abundance and richness; and 3) Whether key
 variables were overlooked by investigators. Our results show that there is
 a core group of nine limnological variables that are measured most
 frequently, including lake surface area, pH, phosphorus, nitrogen,
 dissolved oxygen, conductivity, chlorophyll-a, maximum depth, and
 temperature. These variables were among those most often associated with
 variation in zooplankton, but several others, including dissolved organic
 carbon, alkalinity, and nitrate were sampled infrequently, despite showing
 promise as important explanatory variables. The selection of variables in
 past studies did not correlate with how often those variables were
 significant in the literature, but instead, might have been related to
 their ease of measurement. Neglecting to measure important variables could
 have implications for fundamental and applied studies that aim to
 understand the factors structuring zooplankton communities and their
 response to environmental change.
description: We performed a literature review to identify studies that
 investigated the environmental variables associated with zooplankton
 community structure in lakes or ponds using Google Scholar. For the
 purposes of our study, we defined community structure as either univariate
 metrics used to describe communities (richness, diversity, total
 abundance) or multivariate analyses such as principal component analysis,
 which summarizes relative species abundance. We considered studies
 published between 1970 to 2019 and used the following search terms to
 identify relevant studies 1) zooplankton distribution and abundance; 2)
 zooplankton abundance environmental factors; 3) zooplankton diversity
 environmental factors; 4) zooplankton richness environmental factors; and
 5) zooplankton lakes. Studies that collected data from fewer than three
 lakes or that included lakes with a salinity greater than 5 ‰ were
 excluded from our dataset. For each study, we extracted information on
 which physicochemical variables were measured and whether the
 investigators found a significant relationship between zooplankton
 communities and these variables. Where available, we also obtained the
 proportion of variation in zooplankton community structure explained by
 each variable in a study, as well as the mean, minimum, and maximum values
 measured for each environmental variable. When necessary, units of
 measurement were converted to ensure that all data were analyzed on the
 same scale.
description: There are three files in the dataset. 1)
 "main dbase for dryad.csv" contains the following
 columns: "Study" = the publication from which
 the data were obtained.
 "How.many.lakes.sites." = number of lakes examined in
 each study "Characteristics.measured" = the
 variables measured for each study
 "What.was.significant." = which variables were
 significantly related to zooplankton community structure
 "Percent.variation.explained" = the percent variance
 explained (when available from the manuscript)
 "Positive.or.negative" = the direction of the
 relationship between each significant predictor variable and the
 zooplankton community metric (when relevant)
 "Response" = the zooplankton community metric used in
 the study "Type.of.analysis" = the type of
 statistical analysis used to examine the relationship between predictor
 variables and zooplankton community structure. 2)
 "predictors spreadsheet for Dryad.csv" contains the following
 columns "Study" = the publication from which
 the data were obtained. "Characteristic
 measured" = the variables measured for each study
 "Minimum" = the minimum value of each variable for the
 associated study "Maximum" = the maximum
 value of each variable for the associated study
 "Units" = measurement units for each
 variable. 3) "places for Dryad.csv" contains
 the following columns: "Study" = the
 publication from which the data were obtained.
 "Latitude" = the approximate center latitude of the
 lakes sampled for the study "Longitude" = the
 approximate center longitude of the lakes sampled for the study