### MEMORANDUM

TO: DOCKET FOR TOXICS MACT FROM: CHRISTINE DAIVS , RISK AND BENEFITS GROUP SUBJECT: ECOSYSTEM EFFECTS FO R PROPOSED RULE DATE: 3/31/2011

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 communic ation materials . 

### 5.3 IMP AC T 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 environmental media with aquatic systems exper iencing the greatest exposures due to bioaccumulation. Bioaccumulation refers to the net uptake of a contaminant from all possible pathways and includes the accumulation that may occur by direct exposure to contaminated media as well as uptake from food. A tmospheric mercury enters freshwater ecosystems 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 enhance d in anaerobic and acidic environments, greatly increasing mercury toxicity and potential to bioaccumulate in aquatic foodwebs. A number of key biogeochemical controls influence the production of methylmercury in aquatic ecosystems. These include sulfur, p H, organic 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, elemental 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 accumulation in terrestrial ecosystems. 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 t errestrial species such as songbirds, bats, spiders, and amphibians that receive mercury deposition or fromaquatic systems near the forest areas they inhabit (Bergeron et al. 2010a, b; Cristol et al. 2008; Rimmer et al.

2005; Wada et al. 2009 & 2010). Num erous 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 designed studies. The body of work examinin g the effects of these exposures is growing but still incomplete given the complexities of the 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, con clusions 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 FIS H A review of the literature on effects of mercury on fish (Crump and Trudeau, 2009) reports results for numerous species including trout, bass (large and smallmouth), northern pike, carp, walleye, salmon and others from laboratory and field studies. The effects studied are reproductive and includ e 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 wate r 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 reproduc tive 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 information regarding the possible complementary effects of sulfur and mercury deposition. The ISA has concluded that there is a causal relationship between sulfur deposition and increased mercury methylation in wetlands and aquatic environments. This suggests that lowering the rate of sulfur deposition would also reduce mercury methylation thus allevi ating the effects of aquatic acidification as well as the effects of mercury on fish.

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, preservation, and protection groups have formed over the past few decades and have been instrumental in promoting conservation, education, monitoring, and research of breeding loons (McIntyreand Evers 2000, Evers 2006). Significant adverse effects o n breeding loons from mercury have been found to

occur, including behavioral (reduced nest

- sitting), physiological (flight feather asymmetry), and reproductive (chicks fledged/territorial pair) effects (Evers 2008, Burgess 2008) and reduced survival (Mitro , et al 2008). Additionally Evers et al. (2008) report that they believe that results from their study integrating the effects on the endpoints listed above and evidence from other studies the weight of evidence indicates that population

level effects nega tively impacting population viability occur in parts of Maine and New Hampshire, and potentially in broad areas of the loon’s range. Recently attention has turned to other piscivorous species such as the white ibis and great snowy egret. While considere d 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 have decrea sed foraging efficiency (Adams and Frederick 2008). Additionally ibises have been shown to exhibit decreased reproductive success and altered pair behavior at chronic exposure to levels of dietary MeHg commonly encountered by wild birds (Frederick and Jaya sena 2010). These effects include significantly more unproductive nests, male/male pairing, reduced courtship behavior (head bobbing and pair bowing) and lower nestling production by exposed males. In this study a worst

- case scenario suggested by the resul ts could involve up to a 50% reduction in fledglings 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 me rcury 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 possibly 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 exc ept the mountain west. Insectivorous birds have also been shown to suffer adverse effects due to current levels of mercury exposure. These songbirds such as Bicknell’s thrush, tree swallows and the great tit have shown reduced reproduction, survival, and c hanges in singing behavior. Exposed tree swallows produced fewer fledglings (Brasso 2008), lower survival (Hallinger 2010) and had compromised immune competence (Hawley 2009). The 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 effects were small and would likely have little effect on population viability in such a short

- lived species.

5.3.4 EFFECTS ON MAMMALSIn mammals adverse effects have been observed in mink and river otter collected in the wild in the

northeast where atmospheric deposition from municipal waste incinerators and electric utilities are the largest sources (USEPA 1999), both fish eating species. For o tter from Maine and Vermont maximum concentrations on Hg in fur nearly equal or exceed a concentration associated with mo rtality. C oncentration s in liver for mink in Massachusetts/Connecticut and the levels in fur from mink in Maine exceed concentrations a ssociated with acute mortality (Yates 2005). Adverse sub

- lethal effects may be associated with lower Hg concentrations and consequently be more widesprea d than potential acute effects. These effects may include increased activity, poorer maze performance, abnormal startle reflex, and impaired escape and avoidance behav

ior (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 expos ure levels . These effects range across species from fish to mammals and spatially 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 wil dlife and the effect on ecosystem 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.

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