In situ feeding and element removal in the symbiont‐bearing sponge Theonella swinhoei: Bulk DOC is the major source for carbon

Abstract

The vast majority of organic matter in the world ocean is found in the dissolved pool. However, no evidence has been demonstrated for direct uptake of bulk dissolved organic matter (DOM) by organisms other than bacteria and some invertebrate larvae. The total organic carbon (TOC) is 10-30% higher in coral reefs than in adjacent open waters. The dissolved organic carbon (DOC) accounts for Ͼ90% of the TOC. Using a new in situ technique for clean sampling of the seawater inhaled and exhaled by benthic suspension feeders, we measured directly the removal of DOC in the symbiont-bearing reef sponge Theonella swinhoei. The sponge removed up to 26% (mean Ϯ SD: 12% Ϯ 8%) of the TOC (dissolved and particulate) from the water it filtered during a single passage through its filtration system. Most of the carbon gained by the sponge was from the dissolved pool (10 Ϯ 7 mol C L Ϫ1 ), an order of magnitude greater than the carbon gained from the total living cells (phytoplankton and bacteria) the sponge removed (2 Ϯ 1 mol C L Ϫ1). In T. swinhoei, over two-thirds of the sponge biomass consists of symbiotic bacteria, which likely play an important role in DOC uptake. Our findings indicate that the role of DOC in metazoan nutrition and the role of metazoans in DOC cycling may have been grossly underestimated.The total organic carbon (TOC) in the ocean is divided into two major compartments: particulate (POC) and dis-1 Corresponding author (gitai.yahel@huji.ac.il).

Osmotrophy in modular Ediacara organisms

“…As organisms increase in size, SA/V drops and osmotrophy alone becomes insufficient to meet nutrient demands. Thus, strictly osmotrophic organisms tend to be microscopic (e.g., bacteria), although some macroscopic animals, including sponges, corals, brachiopods, bryozoans, molluscs, and echinoderms, use osmotrophic feeding on DOC as a supplemental food source (22)(23)(24)(25)(26).…”

Depleted dissolved organic carbon and distinct bacterial communities in the water column of a rapid-flushing coral reef ecosystem

“…Corals may rapidly consume DOC and bacterioplankton (Sorokin, 1973), although many recent studies show corals to be sources, rather than sinks, for DOC (Ferrier-Pages et al, 1998;Van Duyl and Gast, 2001;Hata et al, 2002;Nakajima et al, 2009). Recent work has demonstrated the potential for sponges to consume both DOC and bacterioplankton at biogeochemically significant rates (Yahel et al, 2003;Van Duyl et al, 2006;de Goeij and Van Duyl, 2007;De Goeij et al, 2008). However, conspicuous sponge taxa, which exhibit the highest filtration rates (Southwell et al, 2008), are virtually absent from our study area, and even inconspicuous benthic sponges cover o1% of the reef benthos in Moorea on average (Adjeroud, 1997, http://mcr.…”

The Significance of Syncytial Tissues for the Position of the Hexactinellida in the Metazoa

“…Al− though typical sponges feed primarily on bacterial−sized parti− cles through the microvilli of their choanocytes (e.g., Reiswig 1971;Riisgård and Larsen 2000), in some cases (Leys and Eerkes−Medrano 2006) particle capture is through pseudo− podial extensions of these cells; larger particles (5-50 μm) are often captured by amoebocytes lining the incurrent canal walls (Reiswig 1971). There has also been an increasing apprecia− tion of the role of direct uptake of dissolved organic carbon (e.g., Reiswig 1981;Yahel et al 2003), but it is not yet clear to what extent symbiotic organisms are responsible for the up− take, and if the sponge itself is responsible, what is the mecha− nism of uptake. Other studies have also shown that sponge growth rate is independent of the supply of Dissolved Organic Carbon, suggesting a greater dependence on solid particle consumption (Koopmans and Wijffels 2008).…”