Data from: Human-induced biotic invasions and changes in plankton interaction networks

1.Pervasive and accelerating changes to ecosystems due to human activities
remain major sources of uncertainty in predicting the structure and
dynamics of ecological communities. Understanding which biotic
interactions within natural multitrophic communities are threatened or
augmented by invasions of non-native species in the context of other
environmental pressures is needed for effective management. 2.We used
multivariate autoregressive models with detailed time-series data from
largely freshwater and brackish regions of the upper San Francisco Estuary
to assess the topology, direction and strength of trophic interactions
following major invasions and establishment of non-native zooplankton in
the early 1990s. We simultaneously compared the effects of fish and clam
predation, environmental temperature, and salinity intrusion using
time-series data from > 60 monitoring locations and spanning more
than three decades. 3.We found changes in the networks of biotic
interactions in both regions after the major zooplankton invasions. Our
results imply an increased pressure on native herbivores; intensified
negative interactions between herbivores and omnivores; and stronger
bottom-up influence of juvenile copepods but weaker influence of
phytoplankton as a resource for higher trophic levels following the
invasions. We identified salinity intrusion as a primary pressure but
showed relatively stronger importance of biotic interactions for
understanding the dynamics of entire communities. 4.Synthesis and
applications. Our findings highlight the dynamic nature of biotic
interactions and provide evidence of how simultaneous invasions of exotic
species may alter interaction networks in diverse natural ecosystems over
large spatial and temporal scales. Efforts to restore declining fish
stocks may be in vain without fully considering the trophic dynamics that
limit the flow of energy to target populations. Focusing on multitrophic
interactions that may be threatened by invasions rather than a limited
focus on responses of individual species or diversity is likely to yield
more effective management strategies.