Mercury Cycling and Effects in Freshwater Wetland Ecosystems

Abstract

This literature review borrows from diverse fields because of the paucity of freshwater wetland studies on mercury cycling and effects. Peat cores provide an excellent means of dating mercury deposition temporal patterns. Conclusions about cycling suggest that a biogeochemical model would prove useful for evaluating wetland processes of mercury transformation and accumulation. Mercury methylation and the association of mercury with organic matter require additional research. Wetlands trap and release mercury, and its association with organic matter seems to affect the release rate. At high exposure, usually associated with laboratory studies or waste discharges, a variety of biotic toxic responses are observed. Predator species accumulate mercury predictably, and residue-effect relationships seem useful for an index of ecologic damage. More definitive conclusions require additional research to define the ecosystem properties that affect mercury transfer to wetland predators. 5-30 22"-76" ~ ~ aEstimated by assuming net of leaching vs. uptake from deeper levels is zero and peat production rate is 0.4 kg/m2/yr [56,10,55].

Sediment-adsorbed total mercury flux through Yolo Bypass, the primary floodway and wetland in the Sacramento Valley, California

“…This is an important omission because it is the largest source of flow, sediment, and THg derived Sacramento Basin (Domagalski, 2001;Singer and Aalto, 2009). Overall, there is a lack of long-term analyses on mercury mass balance within the Yolo Bypass, where higher rates of methylation are expected because of the organic carbon-rich, stagnant wetland environments that occur there (Rudd, 1995;Zilloux et al, 1993).…”

High levels of mercury contamination in multiple media of the Carson River drainage basin of Nevada: implications for risk assessment.

“…Of greatest concern are the organomercury species, which are lipophilic and bioaccumulate in the food chain (3). The best-documented cases of mercury affecting human health occurred at Minamata and Niigata in Japan (4) and in Iraq (5).…”

“…The data indicate that the three-to fourfold mercury increment in these areas during the last 100-150 years comes from the atmosphere via wet and dry deposition (1,9). Understanding the transport, transformation, and fate of mercury in the environment is critical, given the element's potential for methylation and subsequent biomagnification in the food chain (3,10). Unfortunately, measuring trace levels of mercury is complicated by the fact that it is ubiquitous in nature, and ultraclean sampling and analytical protocols are required to prevent inadvertent contamination (1).…”

“…Accordingly, many features of mercury transport, fate, food chain contamination, and effects on the biosphere are better addressed in areas such as the Carson River Drainage Basin (CRDB) where mercury contamination is high and the duration of exposure is long. The duration of exposure is important because biomagnification is time dependent, and long exposures are likely to result in mercury-specific responses in sensitive organisms (3). These responses include accommodation at the physiologic or biochemical level, genetic adaptation at the population level, and behavioral avoidance mechanisms at the species level (3).…”

“…The duration of exposure is important because biomagnification is time dependent, and long exposures are likely to result in mercury-specific responses in sensitive organisms (3). These responses include accommodation at the physiologic or biochemical level, genetic adaptation at the population level, and behavioral avoidance mechanisms at the species level (3).…”