Journal
POLAR BIOLOGY
Volume 39, Issue 6, Pages 1137-1153Publisher
SPRINGER
DOI: 10.1007/s00300-016-1932-z
Keywords
Climate change; Gadoids; Hypercapnia; Thermal window; Growth; Feed consumption; RCP 8.5
Categories
Funding
- German Federal Ministry of Education and Research (BMBF) [WP 4.1, WP 4.2, FKZ 03F0655B, FKZ 03F0728B]
- PACES (Polar Regions and Coasts in a Changing Earth System) program of the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI)
- project Polarisation (Norwegian Research Council) [214184/F20]
- RV Heincke (AWI) [AWI_HE408_00]
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Oceans are experiencing increasing acidification in parallel to a distinct warming trend in consequence of ongoing climate change. Rising seawater temperatures are mediating a northward shift in distribution of Atlantic cod (Gadus morhua), into the habitat of polar cod (Boreogadus saida), that is associated with retreating cold water masses. This study investigates the competitive strength of the co-occurring gadoids under ocean acidification and warming (OAW) scenarios. Therefore, we incubated specimens of both species in individual tanks for 4 months, under different control and projected temperatures (polar cod: 0, 3, 6, 8 A degrees C, Atlantic cod: 3, 8, 12, 16 A degrees C) and PCO2 conditions (390 and 1170 A mu atm) and monitored growth, feed consumption and standard metabolic rate. Our results revealed distinct temperature effects on both species. While hypercapnia by itself had no effect, combined drivers caused nonsignificant trends. The feed conversion efficiency of normocapnic polar cod was highest at 0 A degrees C, while optimum growth performance was attained at 6 A degrees C; the long-term upper thermal tolerance limit was reached at 8 A degrees C. OAW caused only slight impairments in growth performance. Under normocapnic conditions, Atlantic cod consumed progressively increasing amounts of feed than individuals under hypercapnia despite maintaining similar growth rates during warming. The low feed conversion efficiency at 3 A degrees C may relate to the lower thermal limit of Atlantic cod. In conclusion, Atlantic cod displayed increased performance in the warming Arctic such that the competitive strength of polar cod is expected to decrease under future OAW conditions.
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