Wintering eiders acquire exceptional Se and Cd burdens in the Bering Sea: physiological and oceanographic factors

Abstract

During late winter (March) in the Bering Sea, levels of Se in livers and Cd in kidneys of spectacled eiders Somateria fischeri were exceptionally high (up to 489 and 312 µg g −1 dry mass, respectively). Comparison of organ and blood samples during late winter, early spring migration, and breeding suggests that the eiders' high Se and Cd burdens were accumulated at sea, with highest exposure during winter. High exposure may have resulted from high metabolic demands and food intake, as well as concentrations in food. In the eiders' remote wintering area, their bivalve prey contained comparable Se levels and much higher Cd levels than in industrialized areas. Patterns of chlorophyll a in water and sediments indicated that phytoplankton detritus settling over a large area was advected into a persistent regional eddy, where benthic prey densities were higher than elsewhere and most eider foraging occurred. Se and Cd assimilated or adsorbed by bloom materials apparently also accumulated in the eddy, and were incorporated into the bivalve prey of eiders. Atmospheric deposition of dust-borne trace elements from Asia, which peaks during the ice-edge phytoplankton bloom from March to May, may augment processes that concentrate Se and Cd in eider prey. Compared with freshwater birds, some sea ducks (Mergini) accumulate much higher concentrations of trace elements, even with the same levels in food, with no apparent ill effects. Nevertheless, the absolute and relative burdens of different elements in sea ducks vary greatly among areas. Our results suggest these patterns can result from (1) exceptional accumulation and tolerance of trace elements when exposure is elevated by high food intake or levels in food, and (2) atmospheric and oceanographic processes that concentrate trace elements in local benthic food webs.

Modeling spatial patterns of limits to production of deposit-feeders and ectothermic predators in the northern Bering Sea

“…Moreover, once the range of possible diets for component taxa are known, research emphasis might shift to understanding effects of major disturbances, dispersal timing and processes, and early survival of settling larvae as drivers of food web structure in different areas (Oliver et al, 1985;Hunt and Mullineaux, 2002;Conlon and Kvitek, 2005;Palumbi and Hedgecock, 2005). These stochastic processes also include abiotic factors that determine the timing, magnitude, and subsequent lateral advection of fresh microalgae settling from the water column (cf., Hunt et al, 2009;Brown and Arrigo, 2013;Lovvorn et al, 2013b). Although such abiotic processes might be mostly stochastic, trends in their frequency and intensity can perhaps result in directional change in food web structure and function.…”

“…One possible change is in organic matter supply. Such change could result from altered sea ice patterns which affect the timing, duration, or magnitude of microalgal blooms (ice algae and phytoplankton), or from shifts in wind-driven currents that redistribute settled bloom material Brown and Arrigo, 2013;Lovvorn et al, 2013b). Another expected change is increased water temperature, which could alter the species composition, abundance, or metabolic demands of predators or prey.…”

“…This region exhibits large spatial differences in sediment chlorophyll, grain size, and organic content (Grebmeier and Cooper, 1995;Grebmeier et al, 2006), and showed major shifts in the species, abundance, and dispersion of dominant deposit-feeders over four decades 2014). These patterns could reflect variations in deposition or subsequent lateral transport of organic matter and larvae, as well as varying abundance and impacts of predators (Cooper et al, 2002Cui et al, 2009Cui et al, , 2012Lovvorn et al, 2013b;Kolts et al, 2013aKolts et al, , 2014.…”

Variable wind, pack ice, and prey dispersion affect the long‐term adequacy of protected areas for an Arctic sea duck

“…We also found that the abundance and dispersion of species and sizes of bivalves had changed substantially over the preceding decade (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)). These changes probably resulted from wind-driven shifts in water movements that alter the grain size and organic content of sediments, advection and settlement of larvae, and possibly abundance of other predators that compete for the same prey (Kolts 2012, Lovvorn et al 2013). Thus, when projecting the adequacy of habitat in protected areas for bottom-feeding endotherms, one must consider not only trends in total ice extent, but also possible shifts in winds that can greatly alter both the dispersion of food and its accessibility relative to ice concentrations (Danielson et al 2011(Danielson et al , 2012.…”

“…Endangered Species Act (ESA), which requires delineation and protection of Critical Habitat for species that are listed. The wintering area of Spectacled Eiders, as well as the migration and molting areas in Norton Sound and the northeast Chukchi Sea, are designated Critical Habitat for this species (see Lovvorn et al 2009Lovvorn et al , 2013. The ESA, along with the Marine Mammal Protection Act (MMPA) and provisions for Essential Fish Habitat under the Magnuson-Stevens Act, are the main U.S. federal laws that mandate creation of protected areas, with a focus on particular species in certain places.…”