Data from: Freshwater eutrophication drives sharp reductions in temporal beta diversity

Eutrophication has become one of the most widespread anthropogenic forces
impacting freshwater biological diversity. One potentially important
mechanism driving biodiversity changes in response to eutrophication is
the alteration of seasonal patterns of succession, particularly among
species with short, synchronous life cycles. We tested the hypothesis that
eutrophication reduces seasonally driven variation in species assemblages
by focusing on an understudied aspect of biodiversity: temporal beta
diversity . We estimated the effect of eutrophication on by sampling
benthic macroinvertebrate assemblages bimonthly for 2 years across 35
streams spanning a steep gradient of total phosphorus (P) and benthic
algal biomass (as chlorophyll). Two widely used metrics of β diversity
both declined sharply in response to increasing P and chl, regardless of
covariates. The most parsimonious explanatory model for included an
interaction between P and macroinvertebrate biomass, which revealed that
was lower when macroinvertebrate biomass was relatively high.
Macroinvertebrate biomass explained a greater amount of deviance in at
lower to moderate concentrations of P, providing additional explanatory
power where P concentration alone was unable to fully explain declines in.
Chl-explained similar amounts of deviance in comparison to the best P
model, but only when temperature variability, which was positively related
to, also was included in the model. Declines in suggest that nutrient
enrichment decreases the competitive advantage that specialists gain by
occupying particular temporal niches, which leads to assemblages dominated
by generalists that exhibit little seasonal turnover. The collapse of
seasonal variation in assemblage composition we observed in our study
suggests that treating dynamic communities as static assemblages is a
simplification that may fail to detect the full impact of anthropogenic
stressors. Our results show that eutrophication leads to more temporally
homogenous communities and therefore degrades a fundamental facet of
biodiversity.