MEPS 485:91-103 (2013)  -  DOI: https://doi.org/10.3354/meps10316

ABSTRACT: Temperate marine ecosystems exhibit a marked seasonal variation in environmental conditions that strongly affects the bioenergetics and population dynamics of benthic organisms. As benthic suspension feeders, sponges are subjected to seasonal changes in the supply of their food in the water column. In this study, we examined the temporal variation in the concentration of the picoplanktonic food particles present in the water column and their retention by 3 common demosponges (Crella incrustans, Haliclona venustina and Strongylacidon sp.) from the south coast of Wellington, New Zealand. We sampled 3 times each year over a 2 yr period to examine temporal variation in particle retention efficiency and in the number of particles retained by each species relative to the abundance of particles in the water column. Our results showed that the picoplanktonic species composition and abundance in the water column changed seasonally and between years, as did sponge retention efficiencies and amounts of the available picoplanktonic organisms retained. Averaged across a year, the consumption of non-photosynthetic bacteria is likely to provide the study species with between 20 and 40 times more carbon than the consumption of Synechococcus and Prochlorococcus (marine cyanobacteria). Although the concentration of food particles in the water column positively correlated with the amount of particles retained across all species, we found that retention efficiency did not change with particle concentration. This suggests that retention efficiency is independent of ambient particle concentration, and sponges are unable to increase their particle capture efficiency when food concentrations are lower (e.g. during winter months) and are therefore likely to be susceptible to low levels of food availability.

KEY WORDS: Sponges · Picoplankton · Seasonal · Retention · Carbon · Temperate