Preliminary Assessment of Mercury Accumulation in Massachusetts and Minnesota Seasonal Forest Pools

Abstract

Seasonal forest pools (SFPs) are common, widespread, and provide critical habitat for amphibians and invertebrates. The ephemeral hydrology of SFPs has been identified as an important factor in the production of biologically active methylmercury (MeHg). To investigate mercury (Hg) in SFPs, we collected water, fine benthic organic matter (FBOM), detrital materials, and faunal samples from 10 pools in Massachusetts and Minnesota, across a range of basin morphometry, water chemistry, canopy closure, and hydroperiod. Total Hg (THg) and MeHg concentrations were comparable to other small, lentic waters. MeHg was found in greater concentrations in fauna than in periphyton, detrital items, or FBOM. In spite of consistently lower pool acidity and higher THg deposition in Massachusetts, we found no significant differences in Hg concentrations between states. No significant relationship was found between MeHg concentration and canopy closure. A weak, positive relationship was identified between pool hydroperiod and the bioaccumulation of THg, suggesting that longer exposure may be a factor in increased Hg concentrations in basal resources, which is then propagated into consumer trophic levels. Further work on the mechanisms determining Hg trophic transfer and bioaccumulation is required to fully understand the influence of hydrogeochemical and landscape influences on Hg dynamics in SFPs.