DOI: 10.5061/dryad.kd51c5bh9
title: Invasive crayfish: drivers or passengers of degradation in freshwater ecosystems?

description: Invasive species, e.g. the freshwater crayfish Procambarus clarkii,
 reportedly negatively influence the abundance of various aquatic species.
 Moreover, these invaders are increasingly linked to ecological degradation
 of aquatic ecosystems, since invaded habitats show increased levels of
 turbidity, nitrogen and organic matter concentration. P. clarkii has,
 among other impacts, been associated with eutrophication in invaded
 habitats. However, observations indicate that the presence of P. clarkii
 is often not accompanied by ecosystem degradation, begging the question
 whether they are drivers of degradation, or function as passive passengers
 along for the ride driven by other stressors. To test these contrasting
 hypotheses, we conducted a full factorial experiment in 24 mesocosms with
 P. clarkii and nutrient pollution (specifically N, P, K), a ubiquitous
 stressor on aquatic ecosystems. Here we assessed the effects on community
 compositions of morphologically identified macrophytes and chironomids,
 and of compositions of bacteria, phytoplankton and diatoms identified
 using environmental DNA (eDNA) metabarcoding. Nutrient pollution induced
 significant shifts in macrophyte biomass, and in the composition of the
 bacterial, diatom and phytoplankton communities. All microbial communities
 treated with nutrient pollution diverged from the control initially, after
 which the bacterial and phytoplankton communities converged back to the
 control in the final weeks. In contrast, we found only marginal effects of
 P. clarkii, rendering it unlikely as a significant short- to medium-term
 driver of the tested biodiversity. Since microbial communities respond
 quickly to changes in the environmental conditions, these results signify
 that the utilized mesocosms were relatively stable in spite of P.
 clarkii's presence. The studied crayfish density and timeframe may be
 leveraged as threshold values in the design and execution of freshwater
 management strategies that aim to avert potential negative impacts of P.
 clarkii on ecosystem structure. Ultimately, the importance of nutrient
 pollution is reinforced as a driver of environmental change in aquatic
 ecosystems.
description: Raw output of NGS runs. Methods of sample collection and
 processes were performed as described in the corresponding
 manuscript.
description: **Invasive crayfish: drivers or passengers of degradation in freshwater
 ecosystems? - raw NGS data** This dataset includes paired end
 metabarcoding results (Illumina Miseq v3) using distinct primer sets for
 bacteria, phytoplankton, and diatoms. Sequences have been demultiplexed
 and organized per sample and per taxonomic group (bacteria, phytoplankton,
 and diatoms) as .gz files in FASTQ format. A .csv file has been included
 to refer sample name to the corresponding sampling time (represented by
 the calendar week; ranging between weeks 18-30 in 2019) and applied
 treatment (N, Cr, CrN, C). *Abbreviations used in the dataset:* ALG: The
 phytoplankton data BACT: The bacterial data DIAT: The diatom data X01-X12:
 Negative controls N: Nutrient pollution treatment Cr: Crayfish treatment
 CrN: Combined nutrient pollution + crayfish treatment C: Control
 treatment