DOI: 10.5061/dryad.3bk3j9kkz
title: Zooplankton recovery from a whole‐lake disturbance: Examining roles of abiotic factors, biotic interactions, and traits

description: Community assembly following disturbance is a key process in determining
 the composition and function of the future community.  However,
 replicated studies of community assembly at whole ecosystem scales are
 rare.  Here, we describe a series of whole-lake experiments in
 which the recovery of zooplankton communities was tracked following an
 ecosystem-scale disturbance, i.e., application of the piscicide,
 rotenone.  Using a BACI design, fourteen lakes in eastern
 Washington were studied: seven lakes were treated with rotenone, while
 seven lakes acted as reference systems.  Each lake was monitored
 up to six months before and one to two years after the rotenone
 treatments.  Zooplankton samples and environmental measurements
 were collected approximately monthly from each lake. Community responses
 following disturbance were assessed using metrics of abundance, diversity,
 and community composition, as well as taxonomic group abundance. 
 Zooplankton recovery was also assessed using species traits related to
 habitat, feeding mode, trophic level, body size, and life
 history.  In addition to patterns of recovery, potential
 mechanisms were explored relating to abiotic conditions, biotic
 interactions, and traits. There were steep declines in the abundance
 (average across years: 99%) and diversity (average across years: 75%) of
 the zooplankton community following rotenone treatment.  Although
 abundance had recovered by the second year of the study, community
 diversity had not fully recovered after two years.  Communities
 from rotenone lakes appeared to be compositionally recovered within about
 eight months following disturbance. Cyclopoid copepods were typically the
 first group to recover, and remained dominant for a few months, whereas
 cladocerans recovered more slowly, typically within ~6-7 months following
 rotenone. Calanoid copepods were not fully recovered two years after
 rotenone treatment. Traits related to body size and feeding mode were
 associated with the zooplankton communities following rotenone treatment.
 We failed to observe significant spatial synchrony in recovery patterns of
 zooplankton across lakes, though we did observe significant synchrony of
 zooplankton taxonomic groups within lakes.  These findings
 suggest that traits related to ecological function, and to a lesser
 extent, biotic and abiotic factors, as well as characteristics of the
 disturbance itself, may be important in helping to understand recovery
 processes. 
description: Data were collected between 2014 and 2016 in a set of 14 lakes in
 eastern Washington state.  Seven lakes served as references, while seven
 lakes were treated with rotenone in either fall 2014 or fall 2015. 
 Monthly samples were collected for water quality parameters (water
 temperature, dissolved oxygen, specific conductance, pH, Secchi depth; the
 first four parameters at 1-m intervals from the deepest spot in the lake)
 and crustacean zooplankton (vertical integrated tows from the bottom to
 the surface; from three locations). In July of each sampling year, an
 integrated water sample of the epilimnion was collected for nutrient
 analysis.  Crustacean zooplankton samples from each date-lake combination
 were combined, weighting by volume of net tows, and were identified and
 enumerated using microscopy.  See paper for additional details.  Fish
 stocking densities were obtained from the Washington Department of Fish
 and Wildlife. Zooplankton were analyzed with several
 metrics, including abundance, taxonomic group abundance (calanoids,
 cyclopoids, cladocerans), Shannon-Wiener diversity, adult species density,
 and trait composition. Surface measurements of dissolved oxygen, specific
 conductance, and pH were used in analyses. Lakes that
 were treated with rotenone in 2014 and 2015 were analyzed in separate
 models (referred to as 2014 rotenone and 2015 rotenone), in order to
 account for the differences in treatment years.  Two linear mixed effects
 (LME) models were run for 2014 rotenone lakes: year one and year two
 following treatment.  The 2014 rotenone year one model contrasted the four
 rotenone lakes with the seven reference lakes from June 2014 to September
 2015; whereas the year two model again used pre-impact data from June to
 September 2014 contrasted with post-impact data from October 2015 to
 September 2016.  Samples from reference lakes could therefore be
 classified as both “after treatment” (2014 treatment, year 1) but also
 “before treatment” (2015 treatment, year 1).
description: When monthly samples were not taken, an empty line of NA values
 are included so that figures show gaps appropriately. A
 README file is included that describes the R scripts and associated
 datasets.