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The objective of this study was to investigate whether populations inhabiting a contaminated environment are affected in terms of decreased genetic diversity due to selection of tolerant genotypes and if such effect carries a cost. Marine arctic amphipod populations (Orchomenella pinguis) were collected from sites within a contaminated fjord, as well as from sites outside the fjord on the west-coast of Greenland over three years (2006-2008). Impacts on genetic diversity, effects on resilience such as development of tolerance and cost were determined. AFLP-analysis was used to explore within and between population genetic diversity, and exposure studies were performed where the populations were subjected to known and unknown stressors to assess resilience. Populations collected at three contaminated sites all had reduced genetic diversity in 2007 compared to populations outside the fjord. This pattern was different in 2008 as all contaminated site populations increased in diversity, whereas a decrease in diversity occurred at the outer sites. However, tolerance, but even more so, cost, was related to contamination exposure in 2008, in spite of the shift in genetic diversity. We suggest that contamination rapidly induces effects that can be captured as tolerance and associated cost, whereas effects on genetic diversity can be difficult to separate from recent migration events that dilute eventual decreases in diversity due to contamination pressure. As long as impacted populations can be influenced by migration events that increase the genetic diversity and add health to an affected population, populations in contaminated areas may have enhanced probability of survival., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Phototoxicity of polycyclic aromatic hydrocarbons (PAHs) in the Arctic is important to study since the future PAH load is likely to increase. In combination with the increased UV-light penetration due to ozone layer thinning, phototoxicity may be a potential problem for arctic areas. The aim of this study was to evaluate effects of pyrene and phototoxicity of pyrene on natural algae and bacteria from arctic sediments. Sediments from a shallow-water marine baywere spiked with different pyrene concentrations. Microcosms containing the sediment were incubated under three light regimes, natural sunlight with UV-light, natural sunlight without UV-light, and dark. Significant effects were evident at low pyrene concentrations, particularly in presence of UV-light, indicating phototoxicity. The microalgae were especially sensitive to the phototoxicity of pyrene. Already atthe lowest pyrene concentration (Cfree: 4 nM) algal 14C-incorporation and chlorophyll a content were reduced. The toxic effects of pyrene on the microalgae probably led to the release of organic matter. In agreement with this, bacterial activity increased at high pyrene concentrations indicated by increased oxygen consumption and increased release of inorganic N and P from the sediment. This study indicates that phototoxicity of PAHs may be relevant for sediment communities from shallow marine arctic areas at environmentally relevant pyrene concentrations.

The phototoxicity potential of pyrene on natural algae and bacteria in an arctic sediment was evaluated and compared to that of pyrene treatment alone based on some functional and structural endpoints. Microcosms with arctic sediment from a shallow-water marine bay were incubated with pyrene under three different light regimes, natural sunlight with UV-light (Light(UV)), natural sunlight without UV-light (Light) and dark.Presence of pyrene directly affected the algal community measured as decreased (14)C-incorporation and decreased ammonium, nitrate and silicate uptake. These direct toxic effects from pyrene on the algae eventually led to indirect effects on the bacterial community observed as increased oxygen consumption. Besides the direct toxicity of pyrene to the benthic microbial community, indications of phototoxicity were found on the bacterial community detected as decreased oxygen consumption and increased bacterial diversity under Light(UV) compared to Light. No indication of phototoxicity of pyrene was found on the algae, which might be due to the high direct toxicity of pyrene. Our results indicate that shallow arctic marine areas might be affected by phototoxicity if concentrations of oil components in the sediments increase.