Changes in aquatic communities resulting from interactions between climate change and invasive aquatic plants in the Adirondack Park, New York

Background/Question/Methods

Invasive species of plants and animals represent one of the principal threats to aquatic ecosystems. Climate change in the form of increases in water temperatures and resulting changes in energy and nutrient dynamics may impede or promote the competitive advantage and spread of these invasive species. In this study we evaluated the relationships between increases in water temperature; growth, survival and invasive potential of invasive aquatic plants; and resulting changes in ecosystems structure. Our focal plant species were Eurasian water milfoil, Myriophyllum spicatum, an invasive species in the United States, and northern water milfoil, M. sibericum, a native species with similar life history traits. Experiments were conducted in artificial mesocosms (1000-gallon cattle tanks), with water heaters used to simulate climate change. We monitored growth, survival, and invasive potential (represented by the number of growing fronds present in the tank at the conclusion of the study) of the two milfoil species during a 10-week field season. We also documented the abundance of zooplankton and algal biofilm in each tank at the conclusion of the study.

Results/Conclusions

Our results showed that temperature did not directly affect milfoil, with the invasive species, M. spicatum, demonstrating higher growth, survival, and invasive potential when compared to the native milfoil species, M. sibericum. Temperature did directly affect algae growth with more algae at higher temperatures. Zooplankton density was affected by both milfoil species and temperature: Zooplankton in mesocoms with the M. spicatum did not increase with temperature whereas zooplankton in mesocosms with M. spicatum increased rapidly with higher temperatures. Based on these results, we conclude that climate change is unlikely to influence competitive dominance of the invasive species, M. spicatum. When considering the aquatic community in general, however, and particularly the strong relationships between milfoil species and zooplankton densities, our results indicate that invasive species and climate change may act synergistically with the potential to alter ecosystem structure and function.