The impact of small benthic passive suspension feeders in shallow marine ecosystems: the hydroids as an example

Benthic suspension feeders are abundant in littoral and shallow sub-littoral ecosystems, where they feed on the plankton and on organic matter suspended in the water column. Recent studies indicate that active suspension feeders with powerful water filtration mechanisms (e.g., bivalve molluscs) may exert an important influence on the abundance and production of phytoplankton, and probably zooplankton as well. Passive suspension feeders, such as hydrozoans, have received less attention, and their effect on shallow planktonic communities is poorly understood. This paper presents evidence that hydrozoans, which make only a minor contribution to benthic community biomass, capture large amounts of zooplankton and seston, and that they may play an important role in transferring energy from pelagic to benthic ecosystems over a wide range of latitudes.