MEPS prepress abstract  -  doi: 10.3354/meps07365

ABSTRACT: The growth dynamics and survival of the sponge Corticium candelabrum (Demospongiae: Homosclerophorida) was surveyed in the northwestern Mediterranean for more than three years. Growth and regeneration rates, fission and fusion events, and survival were monitored monthly. Moreover, in situ punctual clearance experiments were conducted seasonally searching for possible relationships between food uptake and sponge dynamics. The monthly growth rates of C. candelabrum were low (0.19 ± 0.02 mean ± SE for the three study years), variable, and seasonal, with the highest values in summer. The cumulative survival function followed a stepped profile, with several consecutive months without mortality separated by shorter mortality events, which mainly occurred in cold months (winter-spring). However, an event of high mortality (76% of the monitored individuals died) took place in the particularly warm summer 2003. Fission events were frequent after previous damage (e.g. partial predation) and only one fusion event was recorded along the study period. The diet of C. candelabrum was highly heterogeneous. Differences in clearance rates among picoplankton types with season indicated that the sponge retained with different efficiency the several picoplankton types present in the water. Survival and growth rates were significantly different for small, medium, and large individuals (size-classes I, II, and III), with the small sponges showing the lowest survival (56.6% cumulative mortality for the two last study years) and the highest growth rates (0.18 ± 0.03 month^-1, mean ± SE). As a whole, the results indicate C. candelabrum is a slow growing but dynamic sponge.