Organic matter assimilation and selective feeding by holothurians in the deep sea: some observations and comments

Carbon flows in the benthic food web of the Porcupine Abyssal Plain: The (un)importance of labile detritus in supporting microbial and faunal carbon demands

“…Only a few suspension feeders occur at the PAP (Iken et al 2001) and therefore suspension feeding is probably not an important feeding mode. Deposit feeders were split among surfacedeposit feeders and deposit feeders, with the former compartment feeding more selectivity on labile detritus as compared to semi-labile detritus, consistent with reports on the feeding strategies by the holothurians at PAP Ginger et al 2001;Wigham et al 2003). Macroand megabenthos that are classified as carnivores are mostly omnivores rather than mere predators.…”

“…The assimilation efficiency of semi-labile detritus was assumed to be lower by a factor of 2 (29-39% for Foraminifera and nematodes, 20-38% for macro-and megabenthos). These ranges match reasonably well with the assimilation efficiency of total organic matter for deposit-feeding holothurians, ranging between 15% and 22% at the Bay of Biscay (Khripounoff and Sibuet 1980) and between 16% to 46% at the PAP (Ginger et al 2001). Production rates were constrained for Foraminifera, nematodes, and macrobenthos based on Van Oevelen et al (2006), but were corrected for the low temperature with the Q 10 formulation.…”

“…To accommodate for this, feeding constraints were implemented that allowed predator feeding to range from omnivory (25% feeding through non-predation) to 100% predation. Although the feeding classifications may not always be strict, they are successfully used in many papers to gain additional insight in the trophic structure of the benthic community (Flach et al 1998), including the PAP (Iken et al 2001), and there is much information on feeding by holothurians Ginger et al 2001;Wigham et al 2003). This paper aimed to include specifically information on feeding types and isotope tracer studies to gain additional insights into the trophic structure of the benthic food web.…”

“…Both the deposit-and surface-deposit-feeding holothurians ingest organic matter with higher than the ambient Chl a and total hydrolyzable amino acid content (Ginger et al 2001;Witbaard et al 2001;Wigham et al 2003), suggesting that they selectively feed on organic matter of higher quality. However, the selectivity of the surfacedeposit feeders is stronger than that of the deposit feeders (Wigham et al 2003).…”

“…The Chl a content in the guts of the mobile surface-deposit feeder A. rosea (Wigham et al 2003) was between 525 and 781 times higher than in the sediment (sedimentary chlorophyll data from Witbaard et al 2000), suggesting strong selectivity for labile detritus. The Chl a content in guts of other holothurians, classified as deposit feeders, was between 2 and 18 times higher as compared to the sedimentary Chl a content (Ginger et al 2001;Wigham et al 2003Wigham et al , 2008. Since species other than A. rosea are also in the surface-deposit-feeding group, selectivity for surfacedeposit feeding was broadened to 50-1000 and selectivity for deposit feeders was set to 1-50 (Table 2).…”