Abstract
We investigated how establishment of invasive dreissenid mussels impacted the structure and energy sources of the littoral benthic food web of a large temperate lake. We combined information about pre- and postdreissenid abundance, biomass, and secondary production of the littoral benthos with results of carbon and nitrogen stable isotope analysis of archival (predreissenid) and recent (postdreissenid) samples of all common benthic taxa. This approach enabled us to determine the importance of benthic and sestonic carbon to the littoral food web before, and more than a decade after dreissenid establishment. Long term dreissenid presence was associated with a 32-fold increase in abundance, 6-fold increase in biomass, and 14-fold increase in secondary production of the littoral benthos. Dreissenids comprised a large portion of the post-invasion benthos, making up 13, 38, and 56% of total abundance, biomass, and secondary production, respectively. The predreissenid food web was supported primarily by benthic primary production, while sestonic material was relatively more important to the postdreissenid food web. The absolute importance of both sestonic material and benthic primary production to the littoral benthos increased considerably following dreissenid establishment. Our results show drastic alterations to food web structure and suggest that dreissenid mussels redirect energy and material from the water column to the littoral benthos both through biodeposition of sestonic material as well as stimulation of benthic primary production.
Highlights
The establishment of invasive organisms is a threat facing aquatic ecosystems world wide [1,2,3]
Biomass, Estimated Production Abundance, biomass, and estimated production (EP) of the nearshore benthos were much higher in 2007–2008 than in 1993, the year immediately preceding dreissenid establishment in Lake Simcoe
The results of isotope mixing models and the large increases in biomass and production of the benthos imply that the absolute contribution of both sestonic and benthic material to the food web increased dramatically following dreissenid establishment (Fig. 3)
Summary
The establishment of invasive organisms is a threat facing aquatic ecosystems world wide [1,2,3]. Among the most significant– but often most difficult to quantify–ecological impacts of species invasions are alterations to food web structure and energy flow patterns [3]. Stable isotope analysis (SIA) of carbon and nitrogen in constituents of the food web offers a way to untangle the complex effects of species invasions and other perturbations on the trophic structure of ecosystems. Nitrogen isotopic composition changes predictably with movement up the food web, allowing the determination of consumer trophic level if the nitrogen isotopic composition of basal resources in known [6], [7]. C and N stable isotopes have been used to characterize the effects of invasive organisms on the flow of energy through ecosystems [8], [9], food web length [10], and resource partitioning [11]
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