Using next-generation sequencing techniques to assess adaptive capacity and illuminate mechanisms underlying the effects of high pCO2 on Alaskan crab and fish species

Why we care
Many economically important crab and fish species are negatively affected by exposure to ocean acidification predicted to occur throughout their ranges in the coming decades. Ocean acidification results in decreased growth, altered development, weaker exoskeletons, increased energy outputs, altered immune systems, altered behavior, and increased mortality in some of these species. Other stressors such as increased temperature can have interactive negative effects when combined with ocean acidification. Traditional laboratory experiments cannot duplicate the gradual changes that will affect species populations over multiple life-history stages and generations, so using next-generation genetic approaches provide insight into effects beyond specific life stages.

What we are doing 
This study will use next-generation sequencing techniques to identify specific alterations in the molecular, metabolic, and physiological pathways of individuals exposed to ocean acidification. This is a way to identify pathways that impart tolerance to ocean acidification and warming. This project determines the effect of ocean acidification and thermal stress on gene expression in Pacific cod larvae and juvenile Tanner crab and identifies genetic markers indicating ocean acidification resilience. 

Benefits of our work
Investigators will identify the cellular pathways that impart tolerance to ocean acidification. By comparing individuals that demonstrate low sensitivity to ocean acidification and with the general population, we enhance the ability to predict how adaptation will alter the species’ response to future ocean conditions. This research will inform the fishing industry and coastal, fisheries-dependent Alaskan communities about potential effects of ocean change on commercially important species. Outcomes can be used to drive future responses and adaptations in these industries regarding affected fisheries.

Alaska is expected to experience ocean acidification faster than any other United States coastal waters, primarily due to its colder water which absorbs more carbon dioxide than warmer waters. With seafood industry job incomes over $1.5 billion annually and a communities that rely on healthy oceans for subsistence, nutrition, and culture, increased ocean acidification is expected to have significant implications. Research on the potential impact to salmon has emerged as one of the top priorities, identified during a 2016 statewide workshop and stakeholder survey. Despite the economic importance of salmon, little research has been done on the effects of ocean acidification on salmon and the fishing industry and communities that depends on salmon. Acidification has been shown to impair coho salmon’s ability to smell and detect their prey. It has also been shown to reduce pink salmon growth rates. In addition, future ocean acidification is expected to affect salmon prey species, which is expected to affect Pacific salmon survival, abundance and productivity. This project will investigate the implication of ocean acidification thresholds and major ecosystem shifts in the Gulf of Alaska on salmon. Integrated human-ecological models will be developed to simulate management scenarios to assess the benefits of pre-emptive adaptation planning and policy making. The information from modeling these scenarios will help create decision tools for salmon managers.

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.

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.