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Ocean acidification, a decrease in the pH in marine waters associated with rising atmospheric CO2 levels, is a serious threat to marine ecosystems. In this paper, we determine the effects of long-term exposure to near-future levels of ocean acidification on the growth, condition, calcification, and survival of juvenile red king crabs, Paralithodes camtschaticus, and Tanner crabs, Chionoecetes bairdi. Juveniles were reared in individual containers for nearly 200 days in flowing control (pH 8.0), pH 7.8, and pH 7.5 seawater at ambient temperatures (range 4.4-11.9 °C). In both species, survival decreased with pH, with 100% mortality of red king crabs occurring after 95 days in pH 7.5 water. Though the morphology of neither species was affected by acidification, both species grew slower in acidified water. At the end of the experiment, calcium concentration was measured in each crab and the dry mass and condition index of each crab were determined. Ocean acidification did not affect the calcium content of red king crab but did decrease the condition index, while it had the opposite effect on Tanner crabs, decreasing calcium content but leaving the condition index unchanged. This suggests that red king crab may be able to maintain calcification rates, but at a high energetic cost. The decrease in survival and growth of each species is likely to have a serious negative effect on their populations in the absence of evolutionary adaptation or acclimatization over the coming decades.

Ocean acidification, a decrease in ocean pH with increasing anthropogenic CO 2 concentrations, is expected to affect many marine animals. To examine the effects of decreased pH on snow crab ( Chionoecetes opilio ), a commercial species in Alaska, we reared ovigerous females in one of three treatments: Ambient pH (~8.1), pH 7.8, and pH 7.5, through two annual reproductive cycles. Morphometric changes during development and hatching success were measured for embryos both years and calcification was measured for the adult females at the end of the 2-year experiment. Embryos and larvae analyzed in year one were from oocytes developed, fertilized, and extruded in situ , whereas embryos and larvae in year two were from oocytes developed, fertilized, and extruded under acidified conditions in the laboratory. In both years, larvae were exposed to the same pH treatments in a fully crossed experimental design. Starvation-survival, morphology, condition, and calcium/magnesium content were assessed for larvae. Embryo morphology during development, hatching success, and fecundity were unaffected by pH during both years. Percent calcium in adult females’ carapaces did not differ among treatments at the end of the experiment. In the first year, starvation-survival of larvae reared at Ambient pH but hatched from embryos reared at reduced pH was lowered; however, the negative effect was eliminated when the larvae were reared at reduced pH. In the second year, there was no direct effect of either embryo or larval pH treatment, but larvae reared as embryos at reduced pH survived longer if reared at reduced pH. Treatment either did not affect other measured larval parameters, or effect sizes were small. The results from this two-year study suggest that snow crabs are well adapted to projected ocean pH levels within the next two centuries, although other life-history stages still need to be examined for sensitivity and potential interactive effects with increasing temperatures should be investigated.

We used flow cytometry to determine if there would be a difference in hematology, selected immune functions, and hemocyte pH (pHi), under two different, future ocean acidification scenarios (pH = 7.50, 7.80) compared to current conditions (pH = 8.09) for Chionoecetes bairdi, Tanner crab. Hemocytes were analyzed after adult Tanner crabs were held for two years under continuous exposure to acidified ocean water. Total counts of hemocytes did not vary among control and experimental treatments; however, there were significantly greater number of dead, circulating hemocytes in crabs held at the lowest pH treatment. Phagocytosis of fluorescent microbeads by hemocytes was greatest at the lowest pH treatment. These results suggest that hemocytes were dying, likely by apoptosis, at a rate faster than upregulated phagocytosis was able to remove moribund cells from circulation at the lowest pH. Crab hemolymph pH (pHe) averaged 8.09 and did not vary among pH treatments. There was no significant difference in internal pH (pHi) within hyalinocytes among pH treatments and the mean pHi (7.26) was lower than the mean pHe. In contrast, there were significant differences among treatments in pHi of the semi-granular+granular cells. Control crabs had the highest mean semi-granular+granular pHi compared to the lowest pH treatment. As physiological hemocyte functions changed from ambient conditions, interactions with the number of eggs in the second clutch, percentage of viable eggs, and calcium concentration in the adult crab shell was observed. This suggested that the energetic costs of responding to ocean acidification and maintaining defense mechanisms in Tanner crab may divert energy from other physiological processes, such as reproduction.

Structural and mechanical properties of the decapod exoskeleton affect foraging, defense, and locomotion. Ocean acidification (OA) poses a threat to marine biomes and their inhabitants, particularly calcifying organisms. Vulnerability of the snow crab, Chionecetes opilio, a commercially important, high-latitude species, to OA has not been explored. Although all oceans are experiencing acidification, abiotic factors in high-latitude areas increase the rate of acidification. We examined the effect of long-term (2 year) exposure to decreased seawater pH (7.8 and 7.5, PCO2 ~ 760 and 1550 µatm, respectively) on exoskeletal properties in post-terminal-molt female C. opilio. Since the effects of OA vary among body regions in decapods, exoskeletal properties (microhardness, thickness, and elemental composition) were measured in five body regions: the carapace, both claws, and both third walking legs. Overall, adult C. opilio exoskeletons were robust to OA in all body regions. Decreased pH had no effect on microhardness or thickness of the exoskeleton, despite a slight (~ 6%) reduction in calcium content in crabs held at pH 7.5. In contrast, exoskeletal properties varied dramatically among body regions regardless of pH. The exoskeleton of the claws was harder, thicker, and contained more calcium but less magnesium than that of other body regions. Exoskeleton of the legs was thinner than that of other body regions and contained significantly greater magnesium concentrations (~ 2.5 times higher than the claws). Maintenance of exoskeletal properties after long-term OA exposure, at least down to pH 7.5, in adult C. opilio suggests that wild populations may tolerate future ocean pH conditions.

Data and insights from fishers are essential sources of information to advance understanding of fishery and ecosystem dynamics. Incorporating fisher and industry knowledge holds prospects for improving marine science and fisheries management. We address cooperative research in the context of collaboration between fishers, scientists, industries, universities, and agencies to develop applied research to understand marine ecosystems, inform fishery management, enhance sustainability, govern resource use, and investigate social-economic dynamics. We leverage the insights of more than 100 research scientists, fisheries managers, industry representatives, and fishers to outline actionable recommendations for effective approaches and mechanisms to integrate industry data, perspectives, and insights in fisheries science. We also highlight opportunities and address challenges and limitations to such collaboration.

Ocean acidification, a reduction in the pH of the oceans caused by increasing CO2, can have negative physiological effects on marine species. In this study, we examined how CO2-driven acidification affected the growth and survival of juvenile golden king crab (Lithodes aequispinus), an important fishery species in Alaska. Juveniles were reared from larvae in surface ambient pH seawater at the Kodiak Laboratory. Newly molted early benthic instar crabs were randomly assigned to one of three pH treatments: (1) surface ambient pH ~ 8.2, (2) likely in situ ambient pH 7.8, and (3) pH 7.5. Thirty crabs were held in individual cells in each treatment for 127 days and checked daily for molting or death. Molts and dead crabs were photographed under a microscope and measured using image analysis to assess growth and morphology. Mortality was primarily associated with molting in all treatments, differed among all treatments, and was highest at pH 7.5 and lowest at ambient pH. Crabs at pH 7.5 were smaller than crabs at ambient pH at the end of the experiment, both in terms of carapace length and wet mass; had a smaller growth increment after molting; had a longer intermolt period. Carapace morphology was not affected by pH treatment. Decreased growth and increased mortality in laboratory experiments suggest that lower pH could affect golden king crab stocks and fisheries. Future work should examine if larval rearing conditions affect the juvenile response to low pH.

Ocean warming and acidification are expected to influence the biology of the ecologically and economically important red king crab, Paralithodes camtschaticus . We investigated transcriptome responses of adult, larval and juvenile red king crab to assess sensitivity to reduced pH and elevated temperature. In adults, gill tissue (but not heart or cuticle) responded to reduced pH by differentially regulating many genes involved in metabolic, membrane and cuticular processes, but not ionic or acid/base regulation. In larval crabs, we found little evidence for a strong transcriptomic response to pH, but did observe large differences in the transcriptomes of newly hatched and one-week old larvae. In juvenile crabs, we found that there was a strong transcriptomic response to temperature across all pH conditions, but that only extreme low pH caused transcriptomic shifts. Most of the genes in juveniles that were differentially expressed were for cuticular and calcification processes. While inferences regarding the specific biological responses associated with changes in gene expression are likely to change as resources for red king crab genomics enabled studies continue to improve (i.e. better assemblies and annotation), our inferences about general sensitivities to temperature and pH across the life stages of red king crab are robust and unlikely to shift. Overall, our data suggest that red king crab are more sensitive to warming than acidification, and that responses to acidification at the transcriptomic level occur at different levels of pH across life stages, with juveniles being less pH sensitive than adults.

Ocean acidification (OA) threatens marine crustaceans, particularly those at high latitudes where conditions are rapidly changing. Red king crab (RKC) support important fisheries in Alaskan waters. RKC early life stages are sensitive to OA when exposure occurs as embryos and juveniles. However, in a supporting study, RKC were surprisingly tolerant of varying OA conditions (pH 7.5, 7.8, & 8.0) when reared long-term from larval hatching to the first crab stage (C1). Here, we examined gene expression in the C1 juveniles to characterize transcriptional activity of these OA-tolerant crabs. Expression of nearly half of all genes (44%) correlated with OA treatment, suggesting a strong molecular response to OA, contrary to the phenotypic results. Downregulated functions were numerous in response to OA, and included reduced energy production, biosynthesis, immune function, and notably lipid and carbohydrate metabolic processes, which suggest a shift in metabolic strategy to protein catabolism, possibly to reduce CO 2 production and facilitate acid/base regulation. Only a handful of functions were enriched in OA-induced genes, which were related to transcription regulation, control of growth and cell death, and signaling activity. Transposon activity was high in OA-reared crab, many of which were upregulated at consistent levels, suggesting that transposon mobilization may be a component of the RKC OA-response system. Genetic composition did not differ among OA treatments indicating that transcriptional differences in OA-reared crab were more likely attributed to phenotypic plasticity than selective mortality. Our results suggest that OA-reared RKC have a narrowed, possibly optimized, set of gene functions that enables OA-tolerance through the early juvenile stage. OA-exposure from hatch may benefit RKC and related species by “hardening” them against OA through physiological reprogramming. Future studies should test OA-hardened crabs in additional challenges, as metabolic and immune limitations may ultimately make them more vulnerable to infection or secondary stressors.

Walleye pollock (Theragra chalcogramma) perform diel vertical migration (DVM) as juveniles, but have an increasing tendency to be associated with the bottom with age. We studied the DVM of a local population of adult pollock in the northern Gulf of Alaska in August and November 2003. There was no relationship between the depth of pollock and the isolume (line of equal light intensity) necessary for visual foraging in August. Pollock passed through the thermocline at this time. In November there was a significant relationship between pollock biomass above/below the 200 m isobath and the isolume necessary for visual foraging. It is hypothesized that in August pollock ignore the isolume and thermocline, simply tracking the movements of their prey (euphausiids) to feed upon them near the surface at night. In November, relatively denser pollock shoals migrate up and down with the isolume necessary for visual foraging to feed on decapods.

Abundance and distribution of fish biomass were surveyed around a Steller sea lion (Eumetopias jubatus) haulout (nonbreeding) and rookery (breeding) site in the Gulf of Alaska to test the hypothesis that seasonal occupation of either site was related to the availability of prey. The haulout and rookery are located 30 nmi (55.56 km) apart at Long Island and Marmot Island in the Central Gulf of Alaska region where the Steller sea lion population is slowly recovering from a severe decline. Surveys conducted in May and November of 2002 (just before and after the breeding season) showed significantly higher prey energy density (total fish biomass density × energy content; kJ nmi^sup -2^) around the Long Island haulout than around the Marmot Island rookery. A survey conducted in July of 2002 (during breeding season) showed prey energy densities that were not significantly different between Long Island and Marmot Island but that were more concentrated in a single area by Marmot Island. Major prey species groups in all surveys were arrowtooth flounder, walleye pollock, cod, and soles; all are known prey of Steller sea lions in this area. Steller sea lion counts at Long Island during nonbreeding seasons from 2000 to 2004 correlated significantly with midwater prey energy densities. Steller sea lion counts at Marmot Island over the same period did not correlate with midwater prey energy densities in either breeding or nonbreeding seasons. The results of the study indicate that prey availability may be an important factor in the choice of haulout sites by Steller sea lions, and the higher prey availability at rookery sites provides some advantage. [PUBLICATION ABSTRACT]