Bioaccumulation of newly deposited mercury by fish and invertebrates: an enclosure study using stable mercury isotopes

Abstract

Enriched stable mercury (Hg) isotopes were added to four 10 m diameter enclosures in Lake 239 at the Experimental Lakes Area to increase inorganic Hg loading. Our main objectives were to (i) follow low-level additions (spikes) of isotope-enriched Hg through the biogeochemical cycle and into the food web and (ii) determine the relative contribution of newly deposited Hg to methyl Hg (MeHg) accumulation by fish and other biota. The experiment ran for two summers (2000, 2001), with different enriched Hg isotopes being added each year. Within 1 month of beginning additions in 2000, spike Hg was detected in water, zooplankton, and benthic invertebrates as MeHg, and in fish as total Hg (THg; the sum of inorganic and organic Hg). In 2001, concentrations in water of inorganic spike Hg added in 2000 were near detection limits, but concentrations of 2000 spike MeHg in water and biota remained unchanged or greater. Despite comparatively large increases in inorganic Hg loading, accumulation of ambient, non-spike MeHg predominated in all organisms, and spike MeHg never comprised more than 15%, even after 1 year. Our results suggest that changes in Hg loading will affect MeHg concentrations in fish and other biota, but that steady state may not be achieved for at least 10–30 years under conditions similar to our enclosures.

Whole-ecosystem study shows rapid fish-mercury response to changes in mercury deposition

“…5), indicating that the ecosystem is not yet in steady state. This may not happen for a decade or more (27). Thus, our data show that even the most responsive compartment of the catchment (the lake) was not yet at a new steady state, and the terrestrial compartments will take substantially longer to achieve such a state.…”

“…Zooplankton samples were taken and prepared for methylmercury analysis as described previously (34). H. azteca invertebrate samples were collected by kick-sampling and sweep-netting of epilimnetic sediments and prepared for analysis as described elsewhere (27). Yellow perch were collected using small-mesh gill nets (6-10 mm) set for short time periods (Ͻ15 min), and muscle samples were processed as described previously (27).…”

Differentiated availability of geochemical mercury pools controls methylmercury levels in estuarine sediment and biota

“…A significant recovery is expected only when a reduced atmospheric Hg loading have translated into a proportional decrease in catchment MeHg and Hg II runoff. The predicted time frame to reach such conditions is highly uncertain 5,25,40 .…”

“…Experiments have been conducted on whole-ecosystem 25 and mesocosm 38,40,47 scales where the MeHg concentration in biota has been related to increased simulated atmospheric Hg II loading rates (by addition of isotopically enriched Hg II tracers as labile complexes, presumably dominated by Hg(OH) 2 0 , to the water column). These studies consistently demonstrated that the added Hg II tracers were to a substantial extent (within days to weeks depending on system scale) methylated and incorporated in the aquatic food webs.…”

Avaliação da dinâmica do mercúrio (Hg) na Bacia do Rio Madeira nos ambientes lêntico e lótico

“…A grande propensão de aumento do Hg da água para os níveis tróficos superiores (HUDSON et al, 1994;PICKHARDT & FISHER, 2007), o fitoplâncton e zooplâncton exercem o papel intermediário no processo de bioacumulação e biomagnificação (BACK et al, 1995). O invertebrado é o elo entre os níveis tróficos intermediários e o topo da cadeia alimentar (BROWDER et al, 1994;STREEVER et al, 1996), podendo servir de alimento para peixes e pássaros (PONYI, 1994;PATERSON et al, 2006;EDMONDS et al, 2012). Os invertebrados fazem parte de várias cadeias alimentares e ocupa vários níveis tróficos, tornando-se assim importante biomarcador (BUCKLAND-NICKS et al, 2014).…”