A growth cline in encrusting benthos along a latitudinal gradient within Antarctic waters

Growth and mortality of 3 species (Inversiula nutrix, Celleporella bougainvillei, Fenestrulina rugula) of encrusting bryozoans were examined from 5 Antarctic localities, along a latitudinal gradient. Typically, growth in marine invertebrates is, for ecological equivalents, slower or much slower in cold seas than warm waters. Contrary to the general trend, growth rates of 3 bryozoans were found to accelerate with increasing latitude in Antarctic waters. Population age structure also showed a dramatic change across the 5 study sites (from 54 to 68° S) through hugely increased mortality with increasing latitude. Reduction in inter-specific competition is theorised as explaining higher growth rates. Increased levels of ice scour are probably responsible for the differential mortality.