In order to demonstrate how scleractinian corals contribute to marine biodiversity by their host function, information on associated fauna was gathered during a biological survey at St. Eustatius, eastern Caribbean. This knowledge is especially urgent for a host coral such as Helioseris cucullata (Agariciidae), which has undergone strong declines in abundance at various Caribbean localities and has a poor record of associated fauna. New records of H. cucullata as host are presented for the coral gall crab Opecarcinus hypostegus (Cryptochiridae), the Christmas tree worm Spirobranchus giganteus (Serpulidae) and an unidentified serpulid tube worm of the genus Vermiliopsis. A second association record is reported for the coral barnacle Megatrema madreporarum (Pyrgomatidae). Coral-associated copepods were not found on H. cucullata despite a search for these animals. The new records were compared with previous records of other host coral species that showed elements of the same associated fauna. The present findings indicate that new discoveries concerning Caribbean coral reef biodiversity can still be made during field expeditions by targeting the assemblages of associated fauna of specific benthic host species.

Chemical composition of organic matter (OM) is a key driver for detritus consumption by macroinvertebrates and polyunsaturated fatty acid (PUFA) content is considered a candidate indicator of food palatability. Since traditionally used complex natural OM covaries in many quality attributes, it remains uncertain whether benthic invertebrates developed an actual preference for PUFA-rich food. Therefore we aimed to test the influence of the PUFA linoleic acid on OM consumption by aquatic macroinvertebrates using standardized surrogate substrates (decomposition and consumption tablet, DECOTAB) with added linoleic acid (PUFA) in comparison to consumption of DECOTAB containing only cellulose (Standard) or ground macrophytes (Plant). In microcosms, we observed a higher consumption rate of PUFA DECOTAB in comparison to Standard DECOTAB in two functionally distinct invertebrate species (Lumbriculus variegatus and Asellus aquaticus). This effect appeared to be overruled in the field due to unknown sources of natural variation. Although we observed higher consumption rates in species-rich ditches compared to species-poor ditches, consumption rates were comparable for all three types of DECOTAB deployed. Upon reduced food quality and palatability, results presented here hint that PUFA like linoleic acid may be a key OM attribute driving the performance of benthic macroinvertebrates and inherent functioning of aquatic ecosystems.