Data from: Differential recycling of coral and algal dissolved organic matter via the sponge loop

Corals and macroalgae release large quantities of dissolved organic matter
(DOM), one of the largest sources of organic matter produced on coral
reefs. By rapidly taking up DOM and transforming it into particulate
detritus, coral reef sponges are proposed to play a key role in
transferring the energy and nutrients in DOM to higher trophic levels via
the recently discovered sponge loop. DOM released by corals and algae
differs in quality and composition, but the influence of these different
DOM sources on recycling by the sponge loop has not been investigated.
Here, we used stable isotope pulse‐chase experiments to compare the
processing of naturally sourced coral‐ and algal‐derived DOM by three Red
Sea coral reef sponge species: Chondrilla sacciformis, Hemimycale arabica
and Mycale fistulifera. Incubation experiments were conducted to trace
13C‐ and 15N‐enriched coral‐ and algal‐derived DOM into the sponge tissue
and detritus. Incorporation of 13C into specific phospholipid‐derived
fatty acids (PLFAs) was used to differentiate DOM assimilation within the
sponge holobiont (i.e. the sponge host vs. its associated bacteria). All
sponges assimilated both coral‐ and algal‐derived DOM, but incorporation
rates were significantly higher for algal‐derived DOM. The two DOM sources
were also processed differently by the sponge holobiont. Algal‐derived DOM
was incorporated into bacteria‐specific PLFAs at a higher rate while
coral‐derived DOM was more readily incorporated into sponge‐specific
PLFAs. A substantial fraction of the dissolved organic carbon (C) and
nitrogen (N) assimilated by the sponges was subsequently converted into
and released as particulate detritus (15–24% C and 27–49% N). However,
algal‐derived DOM was released as detritus at a higher rate. The higher
uptake and transformation rates of algal‐ compared with coral‐derived DOM
suggest that reef community phase shifts from coral to algal dominance may
stimulate DOM cycling through the sponge loop with potential consequences
for coral reef biogeochemical cycles and food webs.