Mercury Contamination Across a Riverine Foodweb

Lakes and reservoirs are frequently monitored by researchers for elevated mercury concentrations in sportfish. Rivers and streams, especially those of smaller orders, are less frequently monitored for mercury contamination. Mercury contamination in the environment comes predominantly from anthropogenic sources like artisanal gold mining and the burning of coal. We address this gap by surveying mercury levels in a stream community in the Kiamichi River in southeastern Oklahoma sampling fish, aquatic insects, and freshwater mussels at ten sites in the river. We found elevated levels of mercury across taxa within the river including large individuals of sportfish populations having concentrations (2986 ±1053 ng/g) above the Environmental Protection Agency (EPA) limit. Furthermore, we observed high concentrations in darters and logperch (1133 ±464 ng/g), non-sportfish species found predominantly in rivers and streams. Our results indicate that mercury contamination can reach elevated concentrations in rivers and streams posing risks to both humans and wildlife.

Long-term effects of channelization on a cold-water stream community

Stream channelization is a common form of anthropogenic disturbance, whose impacts on cold-water biological communities have received little attention in comparison with the body of work demonstrating its negative effects on lowland, warm-water systems. Furthermore, it has been suggested that physical stream processes, given sufficient temporal scale, are capable of restoring channelized reaches to their natural state; however, empirical evidence of this is lacking. Here, we examine the effects of stream channelization on fish and invertebrate communities and their habitats in disturbed and undisturbed cold-water mountain streams in southern Alberta, 80 years postchannelization. Our results show that negative impacts associated with channelization, such as a significant reduction of deep pools and loss of flow refugia, remain prevalent along impacted reaches, inhibiting the reestablishment of native species across multiple trophic levels. While these findings are applicable for a range of cold-water salmonid populations, we suggest that they may be of special importance to the management of mountain whitefish (Prosopium williamsoni) populations, which may be more sensitive to channelization than other cold-water species.