Can isolated wetlands come to the trophic rescue of surrounding ecosystems? Investigating new pathways for food web connectivity

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Food web subsidies occur when a productive “donor” habitat sends nutrients, energy and/or organic matter to an unproductive “recipient” habitat. This movement of materials can stabilize food webs and enable higher overall productivity, but can also deliver contaminants. These fluxes are challenging to study and to manage because they are at odds with conventional notions of ecosystem boundaries. ******There are more than 20 million small wetlands across the globe, and many of these are deemed inconsequential by humans because they are shallow, isolated from surrounding waterbodies, freeze or dry out entirely in the winter, and lack fish. As such, they are regularly viewed as simple sinks for waste, leaving them undervalued by society and often drained, filled or degraded. This research program challenges that notion, and instead examines them as important donor habitats, providing a significant foodweb subsidy via a large flux of winged organisms namely semi-aquatic (waterboatmen) and emergent (midges) insects. It is possible that this subsidy is responsible for maintaining fisheries production in rivers and lakes both in this region and in other cold or dry regions of the world, but little is known about its quality, including both healthy (omega-3 fatty acids) and harmful (mercury) compounds.******This program will test if these wetlands come to the trophic rescue of rivers, lakes and fields by evaluating the timing, magnitude, and nutritional quality of the subsidy. My team will examine how these fluxes change in different parts of North America, from northern Canadian environments where ice-cover is significant and the summer growing season is short, to arid environments in the southern United States where most wetlands dry completely in late summer. We will also determine if these insects deliver contaminants such as mercury from wetlands to rivers, because wetlands are known hotspots for mercury methylation. Finally, we will evaluate how changes in water quality affect insect community composition and whether wetland degradation from eutrophication and salinization favors migrant or non-migrant taxa. Together, this research could reveal new reasons to conserve wetlands in Canada and across the globe.