Dissolved organic matter uptake balances carbon budgets of Red Sea bivalves and ascidians.

In the Gulf of Aqaba (Red Sea), reef-derived dissolved organic carbon is the primary carbon source for bivalves, contributing 57% of body composition.

• Why it matters: Suspension feeders were thought to rely mainly on particulate organic matter, but reef-water planktonic carbon appears insufficient to meet metabolic oxygen demands.
• What they did: In situ oxygen uptake and concentration-dependent uptake of bulk DOC and fDOM were measured for Spondylus sp. and Polycarpa mytiligera, and δ13C mixing models used reef DOC (mean δ13C = -18.4 ± 0.7‰) to apportion sources.
• The result: DOC uptake may balance bivalve carbon budgets, while ascidians still rely primarily on POM (60–71%) with DOC as a supplementary source (23–29%).