Decreased lipid storage in juvenile Bering Sea crabs (Chionoecetes spp.) in a warm (2014) compared to a cold (2012) year on the southeastern Bering Sea

The decline of eastern Bering Sea snow (Chionoecetes opilio) and Tanner (Chionoecetes bairdi) crab has coincided with loss of spring sea ice extent and northward contraction of the 'cold pool,' a layer of cold (< 2 degrees C) summer bottom water. We measured temperature-associated growth and lipid storage of lab-reared Tanner crab, as well as the fatty acid content of field-collected juvenile Chionoecetes spp. Field collections occurred during a cold, high sea ice year (2012) and a warm, low ice year (2014), representative of cold and warm climate stanzas in the southeastern Bering Sea. Lab-reared Tanner crab maintained the lowest growth rates but highest lipids under cold conditions (2 degrees C). In the field, crabs contained higher fatty acids per wet weight (mg g(-1)) during 2012 than during 2014. Water column-integrated chlorophyll a (chla, an indicator of phytoplankton biomass) from large particles (> 10 mu m) such as diatoms was elevated in the colder year particularly over the central middle shelf. During the cold year, crab storage of diatom-sourced fatty acids (16:1n-7 to 16:0, r(2) = 0.72) as well as a station-specific relationship between large size-fraction integrated chla and crab total fatty acids (r(2) = 0.5) points to the potential importance of diatoms to juvenile crab nutrition. Our results suggest that continued warming and loss of sea ice across the Bering Sea may reduce juvenile crab lipid storage through both direct thermal effects as well as through the reduction of large-size phytoplankton delivered to the benthos.

Automated summary

The decline of eastern Bering Sea snow and Tanner crab is associated with loss of spring sea ice extent and northward contraction of the 'cold pool.' Lab-reared Tanner crab had the highest lipid content under cold conditions, while field-collected crabs had higher fatty acids during 2012 compared to 2014. Water column-integrated chlorophyll a from large diatoms was elevated in the colder year, indicating the potential importance of diatoms to crab nutrition.