Kratina, P., R. Mac Nally, W. J. Kimmerer, J. R. Thomson, and M. Winder. 2014. Human-induced biotic invasions and changes in plankton interaction networks. Journal of Applied Ecology. Doi: 10.1111/1365-2664.12266.
This study reports on how zooplankton species invasion affected multitrophic interaction network in the upper San Francisco Estuary over the last four decades.
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 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; intensi-fied 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. 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.