Abstract
This study was designed to evaluate prey selection (type and size) by the octocoral Carijoa riisei at Porto de Galinhas beach, Northeast Brazil, relating prey availability in plankton with the content inside polyps. Diatoms and cyanophytes were the predominant items found in both polyp gastric cavity and plankton. A correlation between prey abundance in the plankton and in the gastric cavity of C. riisei polyps was observed. Mastogloia sp. showed the highest positive electivity index (0.99). Benthonic items were found, with 0.51% of total consumed preys. The size amplitude of prey items in the plankton was similar to those found inside the polyps, although the mean prey size in the polyps (112.7 µm) was significantly lower than the value found in the plankton (240.5 µm). Thus, the study indicates some size selectivity in this species or at least size limitation. From the results, we concluded that the octocoral C. riisei is an opportunistic polyphagous species in the Brazilian northeast coast, showing suspensivorous passive filtering feeding habit with a preference for small prey items and evidencing its important ecological role in the reefal ecosystem as responsible for bidirectional energy transference between pelagic zones and the benthos.
Highlights
Specific physical properties of the sea water allow living organisms and organic matter to remain suspended in the water column creating a feeding niche for suspensivorous animals, an advantage over
Despite the evidences that the feeding ecology of suspensivorous animals is important to the understanding of coastal ecosystems, the knowledge on their natural diet and feeding rates is still poor (Ribes et al 2003)
This study recorded a correlation between prey abundance in the water column and its occurrence in the gastrovascular content of the octocoral C. riisei, demonstrating an opportunistic behavior
Summary
Specific physical properties of the sea water allow living organisms and organic matter to remain suspended in the water column creating a feeding niche for suspensivorous animals, an advantage overDespite the evidences that the feeding ecology of suspensivorous animals is important to the understanding of coastal ecosystems, the knowledge on their natural diet and feeding rates is still poor (Ribes et al 2003). According to Rossi et al (2004), studies of the effects of benthonic suspension consumers on plankton abundance in coastal ecosystems have focused mainly on phytoplankton. Many studies and reviews show the importance of these organisms in marine food webs, emphasizing the role of cnidarians (hydroids and octocorals) in shallow water environments (Gili et al 1997, Gili and Coma 1998, Genzano 2005, Tsounis et al 2005). These organisms could outstandingly act in the energy transference from plankton to benthos
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