eポートフォリオ(ePortfolio)

Abstract Assessments of coral reef biodiversity generally focus on corals and fishes, although there is a variety of other taxa that live within the structure of coral reefs. Rubble cryptofauna includes sessile and motile species that inhabit dead coral and coral rubble and play critical roles in coral reef ecosystems. The examination of rubble cryptofauna can provide insights into the health and functioning of modern coral reefs. Here, we sampled rubble cryptofauna > 1 mm in size at 40 sites around the Palau archipelago (Western Micronesia) at outer reefs, channels, mangals, inner reefs, and the unique environment of enclosed Nikko Bay (Ngermid). Nine phyla, 174 families and 284 Lowest Identifiable Operational taxonomic units (hereafter LIOs) were identified from 4923 specimens. Outer reefs harboured the highest numbers of LIOs, followed by inner reefs, mangroves, channels and Nikko Bay. The nMDS analyses suggested that rubble cryptofauna communities of channels occupy an intermediate position between those of outer reefs and inner sites. As channels provide links between sites and are limited in number and area, they are important habitats to consider in future conservation planning. Finally, different taxonomic levels showed almost identical results, suggesting that analyses at higher taxonomic levels, while being easier to conduct with lower numbers of potential errors, have the potential of being useful for some habitat comparisons. However, this observation will need to be further verified with a larger variety of target specimens sizes and taxonomic levels in future research. The current dataset provides a rubble cryptofaunal baseline that can be compared to results of future examinations as coral reefs in Palau continue to be impacted by climate change.

ABSTRACT Environmental DNA metabarcoding has proven effective for local biodiversity assessment with relatively low sampling effort and cost. However, it is still necessary to evaluate whether it can capture changing community composition along with environmental parameters such as salinity. Salinity is a fundamental abiotic feature that defines suitable habitats for many creatures, mainly due to osmotic considerations. We comprehensively investigated environmental DNA collected from two environments with different salinities, oligohaline (greater than salinity 0.5) and limnetic (less than salinity 0.5), using metabarcoding at different taxonomic levels: 16S prokaryotic universal metabarcoding, 18S eukaryotic universal metabarcoding, and MiFish fish‐specific metabarcoding. These results showed that shared and unique genera in each salinity displayed different patterns at all taxonomic levels. An nMDS plot revealed that community composition is clearly segregated between salinity groups based on 16S analysis, but overlaps slightly when based on MiFish results. This may reflect osmotic tolerance, as fish communities change gradually, whereas bacterial communities change dramatically with sharp thresholds. PERMANOVA showed that these two salinity groups have significantly different community compositions at 16S, 18S, and MiFish levels. We further estimated taxa that differed in abundance in each salinity. Our results revealed that saltwater indicator bacteria such as Planococcaceae and Woeseiaceae were significantly more abundant in oligohaline sites, demonstrating that metabarcoding is capable of detecting halophilic bacteria, even though differences in salinity are relatively small. Several potentially harmful taxa, that is, fish‐borne fluke, Haplorchis taichui, or toxic bloom‐forming dinoflagellates, Karlodinium, were detected in limnetic and oligohaline sites, respectively. Considering Ishigaki Island's great biodiversity and in view of public health, further monitoring utilizing eDNA metabarcoding is necessary.

Abstract Symbiotic relationships between dinoflagellates of the family Symbiodiniaceae and other marine organisms support coral reef ecosystems. Reef-dwelling, large, benthic foraminifers contribute to reef substrate formation. Although foraminifera in the subfamily Soritinae host dinoflagellates of the family Symbiodiniaceae to form unique relationships, the diversity of these dinoflagellates and their spatial and population-level variation are not yet understood. Here, we investigated the diversity of the mutualistic dinoflagellate community in the foraminifer Amphisorus kudakajimensis collected from different depth at nine sites at three reef locations on Akajima Island, and from a single depth at one location on Okinawa Island, Okinawa, Japan. Next-generation sequencing technology and the SymPortal pipeline specific to analyses of the internal transcribed spacer 2 region of the ribosomal RNA gene of Symbiodiniaceae yielded 39 lineages in 154 specimens. Dominant lineages were the genera Cladocopium, Freudenthalidium, and Halluxium; the dinoflagellate community in one foraminifera comprised  multiple lineages. Halluxium was dominant in deep communities (> 9 m water depth) at Akajima, whereas it was not detected in shallow populations (< 2 m). Dinoflagellate genus richness was greater in the eight deep populations than in the two shallow populations. Specific combinations of Cladocopium and Freudenthalidium in A. kudakajimensis of the shallow reef suggest that symbiont communities converge in low-diversity combinations to accommodate large environmental fluctuations in shallow water with high UV light intensity. Our results provide insights into possible host–symbiont patterns for accommodating future climate change.

Abstract Background Marine benthic prokaryotic communities play crucial roles in material recycling within coastal environments, including coral reefs. Coastal sedimentary microbiomes are particularly important as potential reservoirs of symbiotic, beneficial, and pathogenic bacteria in coral reef environments, and therefore presumably play a core role in local ecosystem functioning. However, there is a lack of studies comparing different environments with multiple sites on the island scale, particularly studies focusing on prokaryotic communities, as previous investigations have focused mainly on a single site or on specific environmental conditions. In our study, we collected coastal sediments from seven sites around Okinawa Island, Japan, including three different benthic types; sandy bottoms, seagrass meadows, and hard substratum with living scleractinian corals. We then used metabarcoding to identify prokaryotic compositions and estimate enzymes encoded by genes to infer their functions. Results The results showed that the three substrata had significantly different prokaryotic compositions. Seagrass meadow sites exhibited significantly higher prokaryotic alpha-diversity compared to sandy bottom sites. ANCOM analysis revealed that multiple bacterial orders were differentially abundant within each substratum. At coral reef sites, putative disease- and thermal stress-related opportunistic bacteria such as Rhodobacterales, Verrucomicrobiales, and Cytophagales were comparatively abundant, while seagrass meadow sites abundantly harbored Desulfobacterales, Steroidobacterales and Chromatiales, which are common bacterial orders in seagrass meadows. According to our gene-coded enzyme analyses the numbers of differentially abundant enzymes were highest in coral reef sites. Notably, superoxide dismutase, an important enzyme for anti-oxidative stress in coral tissue, was abundant at coral sites. Our results provide a list of prokaryotes to look into in each substrate, and further emphasize the importance of considering the microbiome, especially when focusing on environmental conservation. Conclusion Our findings prove that prokaryotic metabarcoding is capable of capturing compositional differences and the diversity of microbial communities in three different environments. Furthermore, several taxa were suggested to be differentially more abundant in specific environments, and gene-coded enzymic compositions also showed possible differences in ecological functions. Further study, in combination with field observations and temporal sampling, is key to achieving a better understanding of the interactions between the local microbiome and the surrounding benthic community.

<jats:p>A new porcellanid species of the genus Enosteoides Johnson, 1970 is described on the basis of a single specimen collected from the burrow of an unidentified snapping shrimp of the genus Alpheus Fabricius, 1798, on the subtidal coarse sediment in Okinawa Island, Ryukyu Islands, southwestern Japan. Enosteoides lapis n. sp. is similar to E. melissa (Miyake, 1942) and E. philippinensis Dolorosa &amp; Werding, 2014 in the general morphology of the frontal region of the carapace, third thoracic sternite, and ambulatory legs, but is distinguished from both by the dorsal surface of the carapace being more strongly uneven, as well as by the absence of dense plumose setae on the lateral margins of the carapace, anterodorsal surfaces of the chelae, and anterior and posterior margins of the ambulatory meri.&#x0D;  </jats:p>