Christmas tree worms are polychaetes of the genus, Spirobranchus (Serpulidae). These reef- dwelling species live inside tubes that are usually embedded inside the skeletons of corals belonging to either the order Scleractinia (Anthozoa) or to the family Milleporidae (Hydrozoa) (Hoeksema and Ten Hove 2017, Perry et al. 2017). Extended Spirobranchus worms are visible because of their large, bright-colored branchiae, shaped as twin spirals, and a peduncle (stalk) with a calcified spiny operculum on top. Their colormorph variation and the presence of long spines on the tube may serve as protection against predators (Grassle 1973). When in danger, the worms are able to retract quickly inside their tube, while using their operculum as a shield (Hoeksema et al. 2016, Pezner et al. 2017).

Although little is known about predators of Spirobranchus spp. and no actual attacks have been documented (Kupriyanova et al. 2001), predation has been inferred from damaged and/or missing opercula in about 10% of the examined specimens [Nishi and Kikuchi 1996 for Spirobranchus corniculatus (Grube, 1862)]. 

The cryptobiontic (cavity-dwelling) sponges from 32 growth framework reef cavities were collected over the depth range 12 m to 43 m along the leeward side of Bonaire, Netherlands Antilles. Thc resulting sample of 1,245 specimens comprised 92 species, which showed a peak in species diversity at about 18m depth. Of the 79 species that show significant restriction of their depth rangcs in this study, most are known elsewhere to have different or greater depth ranges. However, 17 eryptobiontic sponge species in Bonaire appear to be depth restricted. This suggests that there may be a depth zonation of some cryptobiontic sponges, and opens up the possibility that with more study, cryptobiontic sponges may be of some use in ancient reefs as a paleoenvironmental tool. The presence of 10 species of endolithic sponge over a broad depth range shows that sponge erosion in the cavities is widespread, although it does not appear to be intensive. Based upon the amount of preservable skeletal material produced by sponges in these reef cavities, it appears that as much as 97% of the cryptobiontic sponge sample would be lost during fossilization, leading to the conclusion that the fossil record of cryptobiontic sponges may be a very poor representation of their actual importance in fossil reef cavity systems.

Recent exploratory research on poorly studied deep reefs in the Caribbean Sea has yielded substantial new information about the diversity of deep-reef fishes and some invertebrates, but the diversity of deep-reef cephalopods has not been assessed. Using images, videos, and specimens collected with the aid of a manned submersible, as well as DNA sequences derived from the specimens, we surveyed the cephalopod diversity of the mesophotic and rariphotic reef communities at Curacao, southern Caribbean. Among the 50 records comprising 15 specimens, 39 photos, and 15 videos, of which six specimens matched video records, we found Octopus hummelincki Adam 1937, Pteroctopus cf tetracirrhus Delle Chiaje 1830, Scaeurgus unicirrhus Delle Chiaje 1841, Paroctopus mercatoris Adam 1937, and Lepidoctopus joaquini Haimovici and Sales 2019. In addition, we found one group of octopods, with two specimens that did not correspond to any known species. We describe this as a new species. One specimen of Lepidoctopus joaquini was hectocotylized on two arms.

Large-scale distribution of a large, commercially significant gastropod, Strombus gigas (queen conch), was investigated in a II ,OOO-haregion of the Great Bahama Bank near Lee Stocking Island, Exuma Cays. Maps of depth and seagrass biomass, generated with Landsat thematic mapper data, and a 4-year survey of juvenile conch distribution showed that most of the juveniles were in aggregations located in 1.5-4.0-m water depth. Although general locations of juvenile conch aggregations remained the same between 1989 and 1992, their total surface area occupied only about 1.5% of the 8,300 ha of seagrass habitat available. Locations of only the most persistent long-term aggregations could be predicted on the basis of preferred seagrass biomass (30-80 g dry weight m-2); however, important conch nurseries were always located in tidal channels which brought clear, oligotrophic water from the Exuma Sound. Harmonic analysis of water temperature data from sites with and without juvenile aggregations showed that conch nurseries were subject to flushing with oceanic water on every tide, whereas non-conch sites reflected only diurnal heating and cooling of bank water. Relationships between circulation and juvenile conch distribution on the Great Bahama Bank may be related directly to larval recruitment, or indirectly to aspects of nutrient cycling and food production; evidence for both mechanisms exists. Although exact locations of conch aggregations shift from year to year, these shifts appear to occur within larger nursery habitats, the boundaries of which are set by a precise combination of physical and biological factors. Because most meadows are probably unsuitable for this severely ovcrfished species, critical nursery habitats should be identified and protected. 

Egg masses of Strombus gigas, S. costatus, and S. pugilus were gathered from depths of 3 to 18 m in the western part of the Los Roques Archipelago, Venezuela. S. gigas spawns from early July through mid-November. S. costatus begins spawning in November, and continues until May. S. pugilus egg masses were first discovered on March 29. Eggs were hatched in the laboratory and veligers fed enriched natural cultures of phytoplankton. Juveniles were fed various species of algae which grew naturally on the sides of the tanks, plus algae growing on rocks, which were introduced into the tanks. Preliminary growth data show S. gigas reaching a length of 31.7 mm in 171 days after hatching. After 175 days, S. costatus reached 42.7 mm. S. pugilus attained a mean length of 20.9 mm after 121 days. Mariculture potential and some aspects of the ecology of the three species, especially the juveniles, are discussed.

Rehabilitating populations of Caribbean coral species that have declined in recent decades has become a management priority throughout the region, stimulating the development of new methodologies to arti cially reseed degraded reefs. Rearing lar- vae of ecologically important coral species appears a particularly attractive method to aid the recovery of degraded populations because genetic recombination could yield new genotypes better capable of coping with the altered conditions on modern Caribbean reefs. Well-developed elkhorn coral (Acropora palmata Lamarck, 1816) populations form dense thickets that contribute to the maintenance of healthy and productive reefs by providing shelter to a variety of other reef organisms (Gladfelter and Gladfelter 1978). After >95% of A. palmata populations were decimated by a disease beginning in the mid-1970s, this species was listed as critically endangered under the Red List of threatened Species (IUCN 2013) and restoration e orts were initiated throughout the region to assist its recovery (Young et al. 2012). In 2011, we collected gametes from eight A. palmata colonies in situ o Curaçao, which were subsequently cross-fertilized to generate larvae. Competent larvae were settled on clay tiles (Panel A) and reared in a ow-through land-based nursery for one year (Panels B–C), after which they were outplanted to a breakwater at 2–5 m depth (Panel D) [refer to Chamberland et al. (2015) for details on methodology]. Seven out of nine outplanted colonies survived and continued to grow in situ (Panels D–E), reaching a size of 30–40 cm diameter and 20–30 cm height after 4 yrs (Panel F). On 8 and 10 September, 2015, nine and 11 d after the full moon, two colonies were ob- served releasing gametes between 155 and 175 min after sunset (Panels G–H). is is the rst time that an endangered Caribbean Acropora coral species was raised from larvae and grown to sexual maturity in the eld. Indeed, only one other study has documented age and colony size at reproductive onset in a broadcast spawning scler- actinian coral reared from larvae (Baria et al. 2012). e relatively short time until onset of spawning (≤4 yrs) observed for A. palmata shows that recovery of degraded coral populations by enhancing natural recruitment rates may be practicable if out- planted colonies are able to rapidly contribute to the natural pool of larvae. 

Christmas tree worms, Spirobranchus spp. (Serpulidae), are known for their wide range of stony host corals, being either scleractinians or milleporids. Apparently, octocorals overgrowing scleractinians act as secondary hosts for Spirobranchus worms.

Dissolved organic carbon (DOC) release of three algal and two coral species was determined at three light intensities (0, 30–80, and 200–400 μmol photons m−2 s−1) in ex situ incubations to quantify the effect of light availability on DOC release by reef primary producers. DOC release of three additional algal species was quantified at the highest light intensity only to infer inter-specific differences in DOC release. For species tested at different light intensities, highest net release of DOC occurred under full light (200–400 μmol photons m−2 s−1). DOC released by benthic algae under full light differed (up to 16-fold) among species, whereas DOC release by scleractinian corals was minimal (Orbicella annularis Ellis and Solander, 1786) or net uptake occurred (Madracis mirabilis Duchassaing and Michelotti, 1860) independent of light availability. DOC concentrations and light intensities were also measured in situ near seven benthic primary producers, sediment, and in the water column at nine sites evenly distributed along the leeward coast of Curaçao. In situ DOC concentrations increased with light availability, although the magnitude of this positive effect differed among species and bottom types tested. In situ DOC concentrations were on average lower in November–December [87 (SD 45) μmol L−1] compared to May–June [186 (SD 136) μmol L−1], which can, at least partly, be explained by the lower light availability in the latter period. Our results suggest that DOC release by Caribbean benthic primary producers varies considerably among species and depends on light availability in reef algae. 

Curaçao, Dutch Caribbean, is home to three species of gall crabs belonging to Cryptochiridae, a family obligatorily associated with a wide range of scleractinian host species. Gall crabs are reliant on their host coral; females are sedentary and never leave their dwelling (van der Meij 2014a). One of the three Atlantic gall crab species is Opecarcinus hypostegus (Shaw and Hopkins, 1977), which inhabits corals of the genus Agaricia. Corals of this genus are abundant in the photic zone (<30 m), but also in the mesophotic zone (30–150 m), where they predominantly belong to Agaricia grahamae Wells, 1973 and Agaricia lamarcki Milne- Edwards and Haime, 1851. The latter was found to be most abundant at depths of 25–60 m (Bongaerts et al. 2013). 

During a survey on 31 March, 2014, with the manned CuraSub submersible launched from Substation Curaçao (12°05 ́04.14 ̋N, 68°53 ́53.16 ̋W), a colony of A. lamarcki was observed at approximately 60 m depth (Panel B) exhibiting the characteristic tunnel formed by O. hypostegus. The shape of this tunnel is virtually identical to those found with O. hypostegus crabs in A. lamarcki at shallower depths (Panel A: Slangenbaai, Curaçao). Hence, we contend that this is strong evidence of O. hypostegus at mesophotic depth. 

The present finding is relevant in the light of the “deep reef refugia” hypothesis, which states that mesophotic reefs may act as a refuge in the face of global reef decline (Bongaerts et al. 2010), as it furthers our knowledge on the communities that presently thrive on these deep reefs. 

Although little fisheries data exist for red hind, Epinephelus guttatus (Linnaeus, 1758) on the Saba Bank, Netherlands Antilles, spawning aggregation characteristics from other populations can be used to assess the health of a red hind spawning population previously undocumented there. In December 2005, a spawning aggregation site for red hind was surveyed on Saba Bank at 17°33.6´N, 63°17.7´W. Red hind aggregated on the northeast edge of the bank, in an area of 0.053 km2 . Spawning occurred in January 2006 during the week prior to and possibly after the full moon. Reproductively developed males and females were collected from December through February, however, in January average fish density increased from 1.46 ± 0.26 fish 100 m–2 to 34.27 ± 2.20 fish 100 m–2 and the M:F sex ratio shifted from 4:1 to unity. Fish were observed exhibiting little territorial or haremic behavior. Gonadosomatic indices in females reached high daily averages in January and February of 15.86 ± 5.4 and 6.93 ± 2.40 respectively, one day prior to the full moon. Average daily water temperature dropped throughout the study period, and during the week prior to the full moon in January, ranged from 26.7 °C to 26.5 °C. Current direction was dominated by tidal fluctuations but during the spawning period was predominantly directed to the southwest. Comparison of spawning population characteristics across red hind aggregation sites in the eastern Caribbean under varying degrees of protection suggests that the Saba Bank aggregation is moderately exploited and should be monitored and more closely managed.