Trophic effects of sponge feeding within Lake Baikal's littoral zone. 2. Sponge abundance, diet, feeding efficiency, and carbon flux

Abstract

Endemic freshwater demosponges in the littoral zone of Lake Baikal, Russia, dominate the benthic biomass, covering 44% of the benthos. We measured in situ sponge abundance and grazing and calculated sponge‐mediated fluxes of picoplankton (plankton <2 µm) for two common species, Baikalospongia intermedia and Baikalospongia bacillifera. By means of dual‐beam flow cytometry, we found retention efficiencies ranging from 58 to 99% for four types of picoplankton: heterotrophic bacteria, Synechococcus‐type cyanobacteria, autotrophic picoplankton with one chloroplast, and autotrophic picoplankton with two chloroplasts. By using a general model for organism‐mediated fluxes, we conservatively estimate that through active suspension feeding, sponges are a sink for 1.97 g C d−1 m−2, mostly from procaryotic cell types. Furthermore, grazing by these extensive sponge communities can create a layer of picoplankton‐depleted water overlying the benthic community in this unique lake.

Coral cavities are sinks of dissolved organic carbon (DOC)

“…Sponges can take up minute particles like viruses (Hadas et al 2006) and 0.1-mm sized beads from ambient water (Leys and Eerkes-Medrano, 2006). Pile et al (1996Pile et al ( , 1997 showed that the sponges used in their studies did not show selective feeding on any component of the plankton community. They suggested that the composition of the plankton community and the variability in the water column can affect sponge nutrition.…”

“…These findings may not be surprising because the cryptic biota is dominated by suspension feeders, particularly by sponges (e.g., Vasseur 1977;Richter and Wunsch 1999;Wunsch et al 2002). Sponges are very efficient filter feeders, especially in feeding on particles smaller than 2 mm, like bacterioplankton (e.g., Reiswig 1974;Pile et al 1996;Kö tter and Pernthaler 2002). Smaller differences between cavity and reef water DOC concentrations in Berau as compared to those in Curaçao could be explained by shorter residence times of water in the cavities of the Berau area.…”

Trait-mediated ecosystem impacts: how morphology and size affect pumping rates of the Caribbean giant barrel sponge

“…They efficiently process large volumes of water and thereby play important roles in benthic−pelagic coupling (Pile et al 1997, Bak et al 1998, organic matter cycling (Reiswig 1974, Yahel et al 2003 and nutrient element cycling (Southwell et al 2008, Fiore et al 2013. By modifying the biotic and abiotic properties ABSTRACT: Sponges are a dominant component of Caribbean coral reef suspension-feeding communities.…”

Flow cytometry as a tool for the study of phytoplankton

“…Vazquez-Dominguez et al (1999) pre-sented some succesful flow cytometric experiments to estimate grazing rates on bacteria with fluorescently labeled tracers, and Kuipers and Witte (1999) demonstrated the use of flow cytometry to obtain significant results in a study of the impact of microzooplankton community grazing on different size classes of algae. Pile et al (1997 ) studied trophic effects of sponge feeding on four types of picoplankton, and Monger et al (1999) examined the influence of cell-surface hydrophobicity. Gin et al (1999) studied seasonal and depth variation in microbial size spectra at the Bermuda Atlantic time series station, using dual-beam flow cytometry to generate concentration and biomass size spectra of bacteria and phytoplankton.…”