High levels of mercury in biota of a new Prairie irrigation reservoir with a simplified food web in Southern Alberta, Canada

Abstract

This study examined mercury levels in northern pike (Esox lucius) from the Twin Valley Reservoir in southern Alberta, 2 years after construction in 2003. The hypothesis was tested that mercury concentrations in pike from the reservoir are significantly higher than in pike from the nearby Oldman River. Mercury concentrations in muscle tissue (0.37-1.54 ppm) generally exceeded the consumption guideline of 0.5 ppm total mercury (THg), and were significantly higher (3.5-fold) than northern pike mercury concentrations in the Oldman River. In addition, these levels exceeded (up to 2-fold) previously published data from other reservoirs of the northern hemisphere. Gill-netting followed by stomach contents and stable isotope analysis revealed a very simple food web. No zooplanktivorous fish species were present, and the benthic fish community contained only few white sucker (Catostomus commersoni). Thus, the reservoir almost completely lacked forage fish, and the pike fed primarily on amphipods (Gammarus lacustris and Hyalella azteca), whose average mercury concentrations were 0.21 ppm. An observed low growth trajectory of northern pike in this reservoir may reflect low growth efficiency as a result of their invertebrate diet.

Reservoir Stratification Affects Methylmercury Levels in River Water, Plankton, and Fish Downstream from Balbina Hydroelectric Dam, Amazonas, Brazil

“…downstream from the Tucuruí Dam and Samuel Dam . Considering all piscivores, the concentrations observed in Cichla from Balbina were similar to those reported piscivores in several tropical, subtropical, and Canadian ,, reservoirs but higher than those observed in the Brazilian reservoir of Lago Manso, the Petit-Saut Reservoir, an artificial Amazonian lake, and some Canadian reservoirs that in general are younger than Balbina and/or have mercury contamination in their basin.…”

Biogeochemical analysis of ancient Pacific Cod bone suggests Hg bioaccumulation was linked to paleo sea level rise and climate change

“…A smaller-scale example of this process occurs when rivers are dammed to form hydroelectric reservoirs (Dmytriw et al, 1995). The large freshwater impoundments flood the land and lead to high levels of Hg in fish and other species (Brinkmann and Rasmussen, 2010). In this instance, we find high levels in an important subsistence species, Pacific Cod, suggesting a potential Hg exposure to prehistoric human populations not previously recognized.…”

Modulators of mercury risk to wildlife and humans in the context of rapid global change

“…For example, direct toxicity, changes in nutrient flow, and habitat loss can each result in losses of sensitive species and biodiversity, which affects food web structure (e.g., urban effluents (Wenger et al 2009 ; Holeton et al 2011 ); agricultural pesticides and fertilizers; forestry, (Richardson and Beraud 2014 )). The growth rates and bioenergetics of species shift as a result of changes in food supply, competition, and predation (Brinkmann and Rasmussen 2010 ). Losses in forest cover and permeable lands alter the timing and magnitude of water flow from terrestrial to aquatic systems (Sampaio da Silva et al 2009 ; Wenger et al 2009 ).…”