Abstract
Zooplankton in Antarctic maritime lakes face challenges imposed by anthropogenic chemicals. Studies on temperate species suggest that lipophilic chemicals will accumulate in dormant embryos of Antarctic zooplankton and decrease hatching success, thereby threatening centuries of accumulated genetic diversity that would increase population resilience in the face of climate change. We evaluated the potential for lakes to act as sinks for legacy pollutants in the maritime Antarctic by testing sediments for polychlorinated biphenyls (PCBs) previously identified in soil, flora and fauna of lake catchments. Direct tests of embryo permeability to chemicals are confounded by potential adhesion of chemicals to the embryo surface and limited biomass available. Therefore, in order to assess the potential for lipophilic chemicals to penetrate and passively accumulate in dormant embryos of Antarctic lacustrine zooplankton, we evaluated the effect of anoxia on post-diapause development in the calanoid copepod, Boeckella poppei, and then used chemical anoxia induced by rotenone as a reporter for permeability of these embryos to moderately lipophilic chemicals. The data presented demonstrate that embryos of B. poppei from Antarctic lake sediments will passively accumulate moderately lipophilic chemicals while lying dormant in anoxic sediments. Implications for legacy POPs in sediments of Antarctic maritime lakes are discussed.
Highlights
To maintain the population in harsh and variable environments, inland and coastal zooplankton on all seven continents produce embryos capable of surviving decades to centuries in a cryptobiotic state[1,2,3,4], and this life-history strategy makes them uniquely susceptible to anthropogenic chemical influence
We propose that development after dormancy is the key stage where the impacts of anthropogenic chemicals will manifest in species like B. poppei, because zooplankton embryos are preloaded in utero with chemicals that bioaccumulate in the food web[10,11] and sit for years in bottom sediments where passive accumulation of chemicals continues[9,12]
Zooplankton of coastal and inland waters produce an “egg bank” that can provide resilience for a population by maintaining the genetic diversity required to deal with environmental change[2,36,49], but the embryos that make up these sediment egg banks are threatened by anthropogenic activities
Summary
To maintain the population in harsh and variable environments, inland and coastal zooplankton on all seven continents produce embryos capable of surviving decades to centuries in a cryptobiotic state[1,2,3,4], and this life-history strategy makes them uniquely susceptible to anthropogenic chemical influence. Because seabirds act as vectors that transport POPs to terrestrial environments around lakes[26,34,35], and meltwater containing POPs enters lakes during the austral summer, it is reasonable to predict that POPs are present in maritime lakes which support relatively isolated populations of zooplankton Despite these facts, neither lakes nor maritime lacustrine zooplankton are discussed in reviews of chemical pollution in Antarctica. Dormant embryos may lack the metabolic capacity required to breakdown or export such toxicants, and these embryos often lie in sediments devoid of light and oxygen that would otherwise facilitate chemical breakdown by oxidative processes Unless they possess a specialized barrier to lipophilic compounds, dormant embryos of B. poppei will passively bioaccumulate lipophilic compounds. The results demonstrate that embryos of B. poppei found in Antarctic lake sediments depend on anoxia to maintain the dormant population, and that the protective cyst wall of these embryos is permeable to moderately lipophilic chemicals
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