DOES SEA ICE COVER AFFECT GROWTH IN JUVENILE STAGES OF THE ANTARCTIC SCALLOP, ADAMUSSIUM COLBECKI?
To test the hypothesis, the first 50 mm of growth from 5 BOS and 5 EC specimens (all adults >50 mm) were photographed at 25x magnification. Increments between discernable striae were measured along the axis of maximum growth using the iSolution Lite imaging system. Mean increment width was calculated to homogenize winter and summer growth (means for each specimen and each site) and to isolate peak summer growth (largest 10% of increments for each site). If higher productivity leads to faster growth, BOS specimens should have higher mean increment widths for both homogenized growth and for peak summer growth.
Juvenile A. colbecki from BOS and EC showed no difference in mean striae increment width for homogenized growth (t=-0.215, df=7.989, p=0.83). Mean increment width for each site was equal (0.24 mm). Peak summer growth was slightly higher for BOS (0.49 mm) than EC (0.47 mm), but the difference was not statistically significant (t=-1.44, df=145.6, p=0.15). If juvenile striae represent fortnightly growth, these results indicate that growth rates do not differ between EC and BOS, despite different ice regimes. EC may have additional nutrient sources, possibly from sea ice algae. Alternatively, nutrient availability may not be a primary determinant of growth rate in A. colbecki.