Deep-sea corals are widespread throughout Alaska, including the continental shelf and upper slope of the Gulf of Alaska, the Aleutian Islands, the eastern Bering Sea, and extending as far north as the Beaufort Sea. Decreases in oceanic pH and resulting decreases in calcium carbonate saturation state could have profound effects on corals dependent on the extraction of calcium carbonate from seawater for skeletal building. Corals will be affected differently depending on their skeletal composition (aragonite vs. calcite), geographical location, and depth. The aragonite and calcite saturation horizons are already quite shallow in areas of the North Pacific Ocean and are predicted to become shallower in the near future. The skeletal composition is known for only a few Alaskan coral species and may be composed of aragonite, calcite, high-magnesium calcite, or amorphous carbonate hydroxylapatite. Skeletons composed of high magnesium-calcite are the most soluble and consequently corals with high-magnesium calcite skeletons, particularly those residing at depths deeper than the saturation horizon, are most at risk to decreases in oceanic pH. At the completion of this project we will be able to provide a comprehensive risk assessment for all corals in Alaskan waters.
This OAP project represents the first contribution of OAP to sustained coastal Alaska OA monitoring through three years (2015-2017) of maintenance of two previously established OA mooring sites located in critical fishing areas. In FY2015, It also supported a 19 day OA survey cruise along the continental shelf of the Gulf of Alaska in summer of 2015, designed to fill observing gaps that have made it difficult to quantify the extent of OA events. This support has been critical for continuing OA research in Alaska, as the initial infrastructure funding was not sufficient or intended for long-term operation.
These OAP-sponsored monitoring and observing activities support a number of cross-cutting research efforts. Firstly, the data itself will provide new insights into the seasonal progression of OA events caused by the progressive accumulation of anthropogenic CO2 into the region's coastal seas. The mooring and cruise data can also be used as an early warning system for stakeholders around the state, as well as to provide information for other types of OA research. Other projects within the OAP Alaska Enterprise focus on laboratory based evaluation of the impact of OA on commercially and ecologically important Alaskan species, especially during the vulnerable larval and juvenile life stages. This environmental monitoring informs those studies by describing the intensity, duration, and extent of OA events and providing a baseline for projecting future conditions. Finally, this observational data is used to validate new OA models that are currently being developed for the Gulf of Alaska and Bering Sea, and are applied in bio-economic models of crab and pollock abundance forecasts (e.g., Punt et al., 2014; Mathis et al., 2014).
To date many studies of the effects of ocean acidification on fishes have suggested that fish are somewhat resilient to effects on factors such as growth and survival. However, these experiments have generally not included potential interactive stressors which may increase the sensitivity to acidification stress. Further, experiments on some species have demonstrated the OA stress has significant potential to disrupt sensory and behavioral systems in fishes which could compromise survival in natural settings. In this project we will focus on examining the potential for behavioral disruptions due to OA and the interactive stresses of OA and nutritional state on critical Alaskan groundfishes.
The aim of this project was to forecast effects of ocean acidification on the commercially important Alaska crab stocks including the Bristol Bay red king crab (BBRKC) fishery, which is part of a modern fisheries management program, the Bering Sea and Aleutian Islands (BSAI) crab rationalization program. To investigate the biological and economic impacts of OA, a linked bioeconomic model was developed that a) integrates predictions regarding trends over time in ocean pH, b) separates life-history stages for growth and mortality of juveniles and adults, and c) includes fishery impacts by analyzing catch and effort in both biological and economic terms. By coupling a pre-recruitment component with post-recruitment dynamics, the BBRKC bioeconomic model incorporates effects of OA on vulnerable juvenile crabs in combination with effects of fishing on the BBRKC population as a whole. Many types of projections under management strategies can be made using linked bioeconomic models.
In 2010 and 2011, Alaska Fisheries Science Center (AFSC) scientists at the Kodiak Laboratory in Alaska tested the effects of lower pH due to increased carbon dioxide (CO2) on the survival, condition, and growth of red king crab (Paralithodes camtschaticus). Commercially important shellfish are a priority for AFSC research related to ocean acidification because of their economic value and because calcifying species are likely to suffer direct effects due to increased acidity (and a decrease in calcium carbonate saturation state) of our oceans.
The multi-year project objectives are to test the effects of CO2 enrichment (which leads to decreasing pH and lower saturation state) across a range of commercially important crab species and life stages (embryo, larvae, juveniles, and adults). The response variables currently measured include mortality, condition, growth, and calcification of the shell.