A cup half full: the first assessment on the distribution, ecology and need for conservation of the threatened Neptune's cup sponge, Cliona patera, in the Gulf of Thailand.

The Neptune's cup sponge is an iconic species found in marine soft sediment habitats in the Indo-West Pacific, with a history of overharvesting and extreme population declines. Access to SCUBA diving surveys has allowed for its rediscovery at Singapore, its type locality; however, with fewer than ten living individuals documented in the twenty-first century, the species is believed to be in need of conservation. Here, we share the results from surveys across the Gulf of Thailand, allowing for a documentation of 29 additional individuals, with information on their ecology and distribution. Of the 29 individuals, extensive damage or mortality caused by marine debris is recorded for six individuals, and one further individual is believed to be lost due to an unknown cause. Documented threats from the Gulf of Thailand differ from those in Singapore; however, low population sizes and poor connectivity remain a significant concern for the survival of the species.

Influence of thermal stress and bleaching on heterotrophic feeding of two scleractinian corals on pico-nanoplankton.

The feeding strategies of Montipora digitata and Porites lutea, two dominant corals in the Okinawan reefs, were investigated. The focus was on pico- and nanoplankton feeding efficiencies, using 6-h incubations. Although healthy M. digitata consumed from 72% to 87% more pico-nanoplankton cells than P. lutea, feeding rates of bleached corals of both species were similarly low at heat stress (33 °C). Heterotrophic carbon acquisition with respect to dark respiration varied from 3% to 65% in M. digitata and from 7% to 68% in P. lutea. A decrease in the feeding efficiency of bleached M. digitata under heat stress shows its vulnerability to water heating events. Feeding rates of P. lutea were low under all conditions and treatments; therefore, this species is less vulnerable to heat stress due to the strategy of meeting metabolic costs by using translocated organic matter from endoliths and selecting pico-nanoplankton cells with a high C/N ratio.

13C and 15N assimilation and organic matter translocation by the endolithic community in the massive coral Porites lutea.

Corals evolved by establishing symbiotic relationships with various microorganisms (the zooxanthellae, filamentous algae, cyanobacteria, bacteria, archaea, fungi and viruses), forming the 'coral holobiont'. Among them, the endolithic community is the least studied. Its main function was considered to be translocation of photo-assimilates to the coral host, particularly during bleaching. Here, we hypothesize that (i) endolithic algae may show similar primary production rates in healthy or bleached corals by changing their pigment ratios, and therefore that similar production and translocation of organic matter may occur at both conditions and (ii) diazotrophs are components of the endolithic community; therefore, N2 fixation and translocation of organic nitrogen may occur. We tested these hypotheses in incubation of Porites lutea with 13C and 15N tracers to measure primary production and N2 fixation in coral tissues and endoliths. Assimilation of the 13C atom (%) was observed in healthy and bleached corals when the tracer was injected in the endolithic band, showing translocation in both conditions. N2 fixation was found in coral tissues and endolithic communities with translocation of organic nitrogen. Thus, the endolithic community plays an important role in supporting the C and N metabolism of the holobiont, which may be crucial under changing environmental conditions.