Data from: Compensatory dynamics of lotic algae break down nonlinearly with increasing nutrient enrichment

One important mechanism governing the temporal maintenance of biodiversity
is asynchrony in cooccurring competitors due to fluctuating environments
(i.e. compensatory dynamics). Temporal niche partitioning has evolved in
response to predictable oscillations in environmental conditions so that
species may offset competition, but we do not yet have a clear
understanding of how novel anthropogenic stressors alter seasonal patterns
of succession. Many primary producers are nutrient-limited, and enrichment
may decrease the importance of environmental fluctuations that govern
which species are effective competitors under naturally low nutrient
regimes. Consequently, elevated nutrient concentrations may synchronize
species responses to seasonality. By studying benthic algal assemblages
over two years from 35 streams that spanned a wide gradient of nutrient
enrichment, we found that compensatory dynamics characterizing seasonal
succession under natural nutrient regimes broke down at relatively low
levels of total phosphorus (P) enrichment (~ 25 μg L-1). With increasing P
more species were able to coexist at any given time, and seasonal
variation in assemblage composition was characterized by synchronous
swings in species biovolumes. We also observed much higher instability in
assemblage biovolumes with declines in compensatory dynamics, which
indicates that anthropogenic alteration of nutrient regimes can affect
community stability by changing the dominant mode of seasonal succession.
Our findings indicate that compensatory fluctuations of stream algae are
driven by seasonality, and provide insight about how nutrient enrichment
alters evolved drivers of species coexistence.