Ocean acidification (OA) is predicted to be a major driver of ocean biodiversity change. At projected rates of change, sensitive marine taxa may not have time to adapt. Their persistence may depend on pre-existing inter-individual variability. We investigated individual male reproductive performance under present-day and OA conditions using two representative broadcast spawners, the sea urchins Lytechinus pictus and Heliocidaris erythrogramma. Under the non-competitive individual ejaculate scenario, we examined sperm functional parameters (e.g. swimming speed, motility) and their relationship with fertilization success under current and near-future OA conditions. Significant inter-individual differences in almost every parameter measured were identified. Importantly, we observed strong inverse relationships between individual fertilization success rate under current conditions and change in fertilization success under OA. Individuals with a high fertilization success under current conditions had reduced fertilization under OA, while individuals with a low fertilization success under current conditions improved. Change in fertilization success ranged from -67% to +114% across individuals. Our results demonstrate that while average population fertilization rates remain similar under OA and present-day conditions, the contribution by different males to the population significantly shifts, with implications for how selection will operate in a future ocean.

Global temperatures are rapidly changing, causing shifts in both biotic and abiotic environments. In the short term, physiological plasticity is likely to play an important role in the survival of species. We studied the association between temperature and reproductive investment in the common whelk Buccinum undatum, a North Atlantic gastropod exhibiting non-pelagic development. We calculated the number of eggs per capsule volume and egg energetic status (Carbon: Nitrogen (C: N) ratio) for egg masses from a temperate population of whelks from the Solent, UK over a four-year period (2009–2013). Data were compared with egg masses from a sub-Arctic population from Iceland collected in 2011. Results were compared to local seasonal water temperatures to examine the association between temperature and reproductive investment. In the Solent, average winter temperatures increased significantly between 2009 and 2013, the winter increase being significant. Both the number of eggs per capsule volume and the C:N ratio of eggs increased significantly between the initial and final spawning years. The number of eggs per capsule volume was significantly lower in eggs collected in Iceland, but C:N ratio was significantly higher. The results indicate that shifts in reproductive investment in B. undatum are associated with environmental temperature. B. undatum appears to show a high level of physiological plasticity in reproduction which may, in the short term, facilitate species survival as annual temperature shifts become more variable.

Persistent organic pollutants (POPs) such as dichlorodiphenyltrichloroethanes (DDTs), hexachlorobenzene (HCB), hexachlorocyclohexanes (HCHs), and polychlorinated biphenyls (PCBs) have been spreading to Antarctica for over half a century. Penguins are effective indicators of pelagic concentrations of POPs. We synthesized the literature on penguins to assess temporal trends of pelagic contamination in Antarctica, using fat and eggs to monitor changes from 1964 to 2011. DDT/DDE ratios suggest long-range atmospheric transport. Average DDT in fat (ww) increased from 44 ng g−1 in the 1960s, peaked at 171 ng g−1 in the mid-1980s, and then declined slowly to the present level of 101 ng g−1. Temporal trends in HCB contamination rose into the 1990s before declining. ∑HCHs in fat was ∼5 ng g−1 from 1960 to 1979, peaking at 33 ng g−1 during the period 1980–1989 before declining to ∼5 ng g−1 from 1990 to present. PCBs rose substantially from 1970 to 2009 in fat, varying more than DDTs and HCB in both fat and eggs. Antarctic penguins are good biological indicators of global DDT and HCB emissions, but the existing data are insufficient regarding HCHs and PCBs. Measurements of persistent organic pollutants in the fat and eggs of Antarctic penguins were synthesized to determine trends in the exposure of food webs in the Southern Ocean over the last half-century.

Significance
. For tens of millions of years, cold conditions have excluded shell-crushing fish and crustaceans from the continental shelf surrounding Antarctica. Rapid warming is now allowing predatory crustaceans to return. Our study of the continental slope off the western Antarctic Peninsula showed that abundant, predatory king crabs comprise a reproductively viable population at 841- to 2,266-m depth. Depth profiles of temperature, salinity, habitat structure, food availability, and predators indicate that there are no barriers to prevent king crabs from moving upward onto the outer shelf at 400–550 m. A cold-water barrier above 200 m could be breached within the next few decades. Emergence of king crabs on the shelf could have catastrophic consequences for the unique seafloor communities of Antarctica.

AbstractThe Antarctic fish fauna from outer continental shelf/upper slope depths is under-sampled compared to that of the inner shelf, and there are limited quantitative data available on absolute abundance and taxonomic change with depth. A photographic survey of demersal fishes was conducted along a depth-gradient of 400–2099 m on the outer shelf and upper slope west of Anvers Island, Palmer Archipelago. A total of 1490 fishes were identified at least to the family level. Notothenioids composed 52.7% of absolute abundance and non-notothenioids 47.3%. The most abundant families were Nototheniidae (39.4%), followed by Macrouridae (28.9%), Zoarcidae (16.9%), and Channichthyidae (12.1%). The most abundant species were the notothenioidsLepidonotothen squamifrons(30.5%) andChionobathyscus dewitti(11.7%), and the non-notothenioidMacrourusspp. (29.5%). The absolute abundance of all fishes peaked at 400–599 m. Depths of maximum abundance were 400–599 m forL. squamifrons, 700–1499 m forMacrourusspp. and 900–1499 forC. dewitti. At 700–999 m the abundance shifted from primarily notothenioids to the non-notothenioidsMacrourusspp. and zoarcids. Fishes of the outer shelf and upper slope are not provincialized like those of the inner shelf and are circum-Antarctic.