### MEMORANDUM

TO: DOCKET FOR TOXICS MACT

FROM: CHRISTINE DAVIS, RISK AND BENEFITS GROUP

SUBJECT: ECOSYSTEM EFFECTS FOR PROPOSED RULE

DATE: 5/24/2011

Due to space limitations, we were unable to include the full text for the ecosystem effects of
mercury deposition in the preamble for the RIA and the Appropriate and Necessary Finding for the Toxics MACT proposed rule. We provide this memo to the docket as documentation of the ecosystem effects to support the information in the communication materials.



### 5.3 IMPACT OF MERCURY ON ECOSYSTEMS AND WILDLIFE

5.3.1 INTRODUCTION

Deposition of mercury to waterbodies can also have an impact on ecosystems and wildlife. Mercury contamination is present in all environmen tal media with aquatic systems experiencing the greatest exposures due to bioaccumulation. Bi oaccumulation refers to the net uptake of a contaminant from all possible pathways and includ es the accumulation that may occur by direct exposure to contaminated media as well as uptake from food.

Atmospheric mercury enters freshwater ecosyste ms by direct deposition and through runoff from terrestrial watersheds. Once mercury deposits, it may be converted to organic methylmercury mediated primarily by sulfate-reducing bacteria. Methylation is enhanced in anaerobic and acidic environments, greatly increasing mercury toxicit y and potential to bioaccumulate in aquatic foodwebs. A number of key biogeochemical controls influence the production of methylmercury in aquatic ecosystems. These include sulfur, pH, orga nic matter, iron, mercury “aging”, and bacteria type and activity (Munthe et al., 2007).

Wet and dry deposition of oxidized mercury is a dominant pathway for bringing mercury to terrestrial surfaces. In forest ecosystems, elem ental mercury may also be absorbed by plants stomatally, incorporated by foliar tissues and released in litterfall (Ericksen et al., 2003). Mercury in throughfall, direct deposition in precipitation, and uptake of dissolved mercury by roots (Rea et al., 2002) are also important in mercury accu mulation in terrestri al ecosystems.2 Soils have significant capacity to store large quantities of atmospherically deposited mercury where it can leach into groundwater and surface waters. The risk of mercury exposure extends to insectivorous terrestrial species such as songbirds, bats, spiders, and amphibians that receive mercury deposition or from aquatic systems near the fore st areas they inhabit (Bergeron et al., 2010a, b; Cristol et al., 2008; Rimmer et al., 2005; Wada et al., 2009 & 2010).

Numerous studies have generated field data on the levels of mercury in a variety of wild species. Many of the data from these environmental studies are anecdotal in nature rather than representative or statistically de signed studies. The body of work examining the effects of these exposures is growing but still inco mplete given the complexities of th e natural world. A large portion of the adverse effect research conducted to date has been carried out in the laboratory setting rather than in the wild; thus, conclusions about overarching ecosystem health and population effects are
difficult to make at this time. In the sections that follow numerous effects have been identified at differing exposure levels.

5.3.2 EFFECTS ON FISH

A review of the literature on effects of merc ury on fish (Crump and Trudeau, 2009) reports results for numerous species including trout, ba ss (large and smallmouth), northern pike, carp, walleye, salmon and others from laboratory and field studies. The effects studied are reproductive and include deficits in sperm and egg formation, histopathological changes in testes and ovaries, and disruption of reproductive hormone synthesis. These studies were conducted in areas from New York to Washington and while many were conducted by adding MeHg to water or diet many were
conducted at current environmental levels. While we cannot determine at this time whether these reproductive deficits are affecting fish populations across the United States it should be noted that it is possible that over time reproductive deficits could have an effect on populations. Lower fish populations would conceivably impact the ecosystem services like recreational fishing derived from having healthy aquatic ecosystems quite apart from the effects of consumption advisories due to the human health effects of mercury.

The Integrated Science Assessment for Oxides of Nitrogen and Sulfur – Ecological Criteria (Final Report, 2008) presents info rmation regarding the po ssible complementary ef fects of sulfur and mercury deposition. The ISA has concluded that there is a causal relationship between sulfur deposition and increased mercury methylation in we tlands and aquatic envi ronments. This suggests that lowering the rate of sulfur deposition would also reduce mercur y methylation thus alleviating the effects of aquatic acidification as well as the effects of mercury on fish.3 5.3.3 EFFECTS ON BIRDS

In addition to effects on fish, mercury also affects avian species. In previous reports (EPA 1997 and CAMR 2005) much of the focus has been on large piscivorous species, in particular the
common loon. The loon is most visible to the public during the summer breeding season on northern lakes and they have become an important symbol of wilderness in these areas (McIntyre and Barr 1997). A multitude of loon watch, preser vation, and protection grou ps have formed over the past few decades and have been instrumental in promoting conservation, education, monitoring, and research of breeding loons (M cIntyre and Evers 2000, Evers 2006) . Significant ad verse effects on breeding loons from mercury have been found to occu r, including behavioral (reduced nest-sitting), physiological (flight feather asymmetry), and reproductive (chicks fledged/territorial pair) effects (Evers 2008, Burgess 2008) and reduced survival (Mit ro et al., 2008). Additionally Evers et al. (2008) report that they believe that results from their st udy integrating the effects on the endpoints listed above and evidence from other studies the weight of evidence indicates that population-level effects negatively impacting population viability occu r in parts of Maine and New Hampshire, and potentially in broad areas of the loon’s range.

Recently attention has turned to other piscivor ous species such as the white ibis and great snowy egret. While considered to be fish-eating generally these wading birds have a diverse diet including crayfish, crabs, snails, insects and frogs. These species are experiencing a range of adverse effects due to exposure to mercury. The white ibis has been observed to ha ve decreased foraging efficiency (Adams and Frederick 2008). Additionally ibises have been show n to exhibit decreased reproductive success and altered pair behavior at chronic exposure to levels of dietary MeHg commonly encountered by wild birds (Frederick and Jayasena 2010). These effects include significantly more unproductive nests, male/male pairing, reduced courtship behavior (head bobbing and pair bowing) and lower nestling production by ex posed males. In this stud y a worst-case scenario suggested by the results could invo lve up to a 50% reduction in fl edglings due to MeHg in diet. These estimates may be conservative if male/male pairing in the wild resulted in a shortage of partners for females and the effect of homosexual breeding were magnified. In egrets mercury has been implicated in the decline of the species in south Florida (Sepulveda, et al. 1999) and Hoffman (2010) has shown that egrets experience liver and possi bly kidney effects. While ibises and egrets are
most abundant in coastal areas and these studies were conducted in south Florida and Nevada, the ranges of ibises and egrets extend to a large portion of the United States. Ibis territory can range inland to Oklahoma, Arkansas and Tennessee. Egret range covers virtually the entire United States except the mountain west. Insectivorous birds have also been shown to suffe r adverse effects due to4 current levels of mercury exposure. These songbird s such as Bicknell’s thrush, tree swallows and the great tit have shown reduced reproduction, surviv al, and changes in singing behavior. Exposed tree swallows produced fewer fledglings (Brasso 2008), lower survival (Hallinger 2010) and had compromised immune competence (Hawley 2009). Th e great tit has exhibited reduced singing behavior and smaller song repertoire in an area of high contamination in the vicinity of a metallurgic smelter in Flanders (Gorissen 2005). While these eff ects were small and would likely have little effect on population viability in su ch a short-lived species.

5.3.4 EFFECTS ON MAMMALS

In mammals adverse effects have been observed in mink and river otter collected in the wild
in the northeast where at mospheric deposition from municipal wa ste incinerators and electric utilities are the largest sources (USEPA 1999), both fish e ating species. For otter from Maine and Vermont maximum concentrations on Hg in fur nearly equal or exceed a concentration associated with mortality. Concentrations in liver for mink in Massachusetts/Connecticut and the levels in fur from
mink in Maine exceed concentr ations associated with acute mo rtality (Yates 2005). Adverse sublethal effects may be associated with lower Hg c oncentrations and consequently be more widespread than potential acute effects. These effects may incl ude increased activity, poorer maze performance,
abnormal startle refl ex, and impaired escape and avoidan ce behavior (Scheuhammer et al. 2007).
Conclusions

The studies cited here provide a glimpse of the scope of mercury effects on wildlife particularly reproductive and survival effects at current exposure levels. These effects range across species from fish to mammals and sp atially across a wide area of the United States. The literature is far from complete however. Much more research is required to establish a link between the ecological effects on wildlife and the effect on ec osystem services (services that the environment provides to people) for example recreational fishing, bird watching and wildlife viewing. EPA is not, however, currently able to quantify or monetize the benefits of reducing mercury exposures affecting provision of ecosystem services.5 5.3.5 REFERENCES Adams, Evan M., and Frederick, Peter C. Effects of methylmercury and spatial complexity on foraging behavior and foraging efficiency in juvenile white ibises (Eudocimus albus). Environmental Toxicology and Chem istry. Vol 27, No. 8, 2008.
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Bergeron, CM., Bodinof, CM., Unrine, JM., Hopk ins, WA. (2010b) Bioaccumulation and maternal transfer of mercury and selenium in amphibi ans. Environmental Toxi cology and Chemistry 29(4), 989-997.
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