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Arctica islandica (ocean quahog), a commercially-important, long-lived bivalve species, is abundant on much of the northeastern United States continental shelf. Several recent studies have noted increases in growth rates of these clams over the last 200 years at some locations in the southern Mid-Atlantic Bight region whereas growth rates at sites farther north have remained constant through time. It has been suggested that these changes in growth rate are related to warming in the more southerly sites. However, a direct comparison between site-specific bottom-water temperatures and A. islandica growth rates has not been done. We present oxygen isotope data measured in Arctica islandica shells, a proxy for seawater temperature, paired with simulated temperature from high-resolution ocean model output to investigate the relationship between A. islandica shell growth rate and bottom water temperatures throughout the northeastern United States continental shelf. The relationship between oxygen isotopes and growth rate in A. islandica is assessed at several locations, including the continental shelf offshore New Jersey and Long Island, and the Georges Bank region. Bottom water temperature trends at these locations are further assessed using the VIKING20X ocean model, which uses JRA55-do (55-year Japanese Atmospheric Reanalysis for driving ocean-sea-ice models) atmospheric forcing from 1958 to present and nests a 1/20° Atlantic Ocean in a 1 ⁄ 4° global domain. The results of this work have implications for the ocean quahog fishery, in particular as water temperatures off the eastern coast of the United States are predicted to continue to increase in response to global climate change. Additionally, this research lends insights into the use of A. islandica growth as a paleoclimate proxy for bottom water temperature. 

Microorganisms are central to the functioning of coral reef ecosystems, but their dynamics are unstudied on most reefs. We examined the microbial ecology of shallow reefs within the Federated States of Micronesia. We surveyed 20 reefs surrounding 7 islands and atolls (Yap, Woleai, Olimarao, Kosrae, Kapingamarangi, Nukuoro, and Pohnpei), spanning 875053 km 2 . On the reefs, we found consistently higher coral coverage (mean ± SD = 36.9 ± 22.2%; max 77%) compared to macroalgae coverage (15.2 ± 15.5%; max 58%), and low abundances of fish. Reef waters had low inorganic nutrient concentrations and were dominated by Synechococcus, Prochlorococcus, and SAR11 bacteria. The richness of bacterial and archaeal communities was significantly related to interactions between island/atoll and depth. High coral coverage on reefs was linked to higher relative abundances of Flavobacteriaceae, Leisingera, Owenweeksia, Vibrio, and the OM27 clade, as well as other heterotrophic bacterial groups, consistent with communities residing in waters near corals and within coral mucus. Microbial community structure at reef depth was significantly correlated with geographic distance, suggesting that island biogeography influences reef microbial communities. Reefs at Kosrae Island, which hosted the highest coral abundance and diversity, were unique compared to other locations; seawater from Kosrae reefs had the lowest organic carbon (59.8-67.9 µM), highest organic nitrogen (4.5-5.3 µM), and harbored consistent microbial communities (>85% similar), which were dominated by heterotrophic cells. This study suggests that the reef-water microbial ecology on Micronesian reefs is influenced by the density and diversity of corals as well as other biogeographical features.