Heterogeneity of Fish Taxonomic and Functional Diversity Evaluated by eDNA and Gillnet along a Mangrove-Seagrass-Coral Reef Continuum.

The effective and reliable monitoring of fish communities is important for the management and protection of marine ecosystems. Environmental DNA (eDNA) metabarcoding is a relatively new method that has been widely used in recent years, while traditional sampling via fish catching (i.e., gillnets) is one of the most common and reliable fish monitoring methods used to date. We compared the taxonomic and functional diversity of fish detected within a mangrove-seagrass-coral reef continuum using both survey methods. One liter seawater and gillnet samples were collected in August 2021 from mangrove forests, seagrass meadows and coral reef habitats (n = 3 each) in Hainan, China. Surveys using eDNA and gillnets identified 139 genera belonging to 66 families and 58 genera belonging to 42 families, respectively. Regardless of the survey method, fish detected in mangrove, seagrass and coral reef habitats were heterogeneous in their communities; however, the shared species between habitats suggest some degree of connectivity. There were no significant differences between habitats in terms of taxonomic and functional diversity, but a higher taxonomic diversity was detected using eDNA. Both methods were able to distinguish fish assemblages between different habitats; however, gillnet surveys performed better than eDNA surveys for distinguishing mangrove from seagrass assemblages. Therefore, the concurrent use of eDNA and gillnet survey methods provides a more comprehensive approach to understanding the heterogeneity of fish taxonomic and functional diversity along mangrove-seagrass-coral reef continuums.

Seagrass habitat suitability model for Redang Marine Park using multibeam echosounder data: Testing different spatial resolutions and analysis window sizes.

Integrating Multibeam Echosounder (MBES) data (bathymetry and backscatter) and underwater video technology allows scientists to study marine habitats. However, use of such data in modeling suitable seagrass habitats in Malaysian coastal waters is still limited. This study tested multiple spatial resolutions (1 and 50 m) and analysis window sizes (3 × 3, 9 × 9, and 21 × 21 cells) probably suitable for seagrass-habitat relationships in Redang Marine Park, Terengganu, Malaysia. A maximum entropy algorithm was applied, using 12 bathymetric and backscatter predictors to develop a total of 6 seagrass habitat suitability models. The results indicated that both fine and coarse spatial resolution datasets could produce models with high accuracy (>90%). However, the models derived from the coarser resolution dataset displayed inconsistent habitat suitability maps for different analysis window sizes. In contrast, habitat models derived from the fine resolution dataset exhibited similar habitat distribution patterns for three different analysis window sizes. Bathymetry was found to be the most influential predictor in all the models. The backscatter predictors, such as angular range analysis inversion parameters (characterization and grain size), gray-level co-occurrence texture predictors, and backscatter intensity levels, were more important for coarse resolution models. Areas of highest habitat suitability for seagrass were predicted to be in shallower (<20 m) waters and scattered between fringing reefs (east to south). Some fragmented, highly suitable habitats were also identified in the shallower (<20 m) areas in the northwest of the prediction models and scattered between fringing reefs. This study highlighted the importance of investigating the suitable spatial resolution and analysis window size of predictors from MBES for modeling suitable seagrass habitats. The findings provide important insight on the use of remote acoustic sonar data to study and map seagrass distribution in Malaysia coastal water.

Biogeographic structure of fungal communities in seagrass Halophilia ovalis across the Malay Peninsula.

Distributed across both the tropical Atlantic and Pacific oceans, the seagrass Halophilia ovalis stabilizes coastal sediment, thereby preventing shoreline erosion and is also an important food source for megaherbivores such as dugongs. However, seagrass meadows globally are under severe duress due to both climate change and anthropogenic activities. We characterized the mycobiome of Halophilia ovalis at seven sites in the Malay Peninsula using ITS1 rDNA amplicon sequences and investigated differences in fungal community structure. We found that geographic location was a significant factor shaping fungal communities and that marine sediment harboured significantly higher diversity when compared to H. ovalis leaves, roots and rhizomes. Taken together, it is likely that locality rather than specific plant structure determines fungal community structure in H. ovalis. Because the plant mycobiome is known to exert a strong effect on plant health, to maximize the success of future seagrass transplantation and restoration work we propose that these efforts consider the importance of seagrass mycobiomes at all stages.

An updated checklist of the marine fish fauna of Redang Islands, Malaysia.

BACKGROUND: Redang Islands Marine Park consists of nine islands in the state of Terengganu, Malaysia. Redang Island is one of the largest off the east coast of Peninsular Malaysia, which is famous for its crystal-clear waters and white sandy beaches. The ichthyofauna of the Redang archipelago was surveyed by underwater visual observations between August 2016 and May 2018. Census data were compiled with existing records into the checklist of the marine fish of the Redang archipelago presented herein. A total of 314 species belonging to 51 families were recorded. The most speciose families (Pomacentridae, Labridae, Scaridae, Serranidae, Apogonidae, Carangidae, Gobiidae, Chaetodontidae, Lutjanidae, Nemipteridae and Siganidae) were also amongst the most speciose at the neighbouring Tioman archipelago (except Chaetodontidae). The coral fish diversity index value for the six families of coral reef fishes (Chaetodontidae, Pomacanthidae, Pomacentridae, Labridae, Scaridae and Acanthuridae) of the study sites was 132. We estimated that there were 427 coral reef fish species in the Redang archipelago. According to the IUCN Red List, eight species are Near Threatened (Carcharhinus melanopterus, Chaetodon trifascialis, Choerodon schoenleinii, Epinephelus fuscoguttatus, E. polyphekadion, Plectropomus leopardus, Taeniura lymma and Triaenodon obesus), eleven are Vulnerable (Bolbometopon muricatum, Chaetodon trifasciatus, Chlorurus sordidus, Dascyllus trimaculatus, Epinephelus fuscoguttatus, E. polyphekadion, Halichoeres marginatus, Heniochus acuminatus, Nebrius ferrugineus, Neopomacentrus cyanomos and Plectropomus areolatus) and three are Endangered (Amphiprion clarkia, Cheilinus undulatus and Scarus ghobban) in the Redang archipelago. NEW INFORMATION: Five species are new records for Malaysia (Ctenogobiops mitodes, Epibulus brevis, Halichoeres erdmanni, H. richmondi and Scarus caudofasciatus) and 25 species are newly recorded in the Redang archipelago.

Seagrass-associated fungal communities show distance decay of similarity that has implications for seagrass management and restoration.

Marine fungal biodiversity remains vastly understudied, and even less is known of their biogeography and the processes responsible for driving these distributions in marine environments. We investigated the fungal communities associated with the seagrass Enhalus acoroides collected from Singapore and Peninsular Malaysia to test the hypothesis that fungal communities are homogeneous throughout the study area. Seagrass samples were separated into different structures (leaves, roots, and rhizomes), and a sediment sample was collected next to each plant. Amplicon sequencing of the fungal internal transcribed spacer 1 and subsequent analysis revealed significant differences in fungal communities collected from different locations and different structures. We show a significant pattern of distance decay, with samples collected close to each other having more similar fungal communities in comparison with those that are more distant, indicating dispersal limitations and/or differences in habitat type are contributing to the observed biogeographic patterns. These results add to our understanding of the seagrass ecosystem in an understudied region of the world that is also the global epicenter of seagrass diversity. This work has implications for seagrass management and conservation initiatives, and we recommend that fungal community composition be a consideration for any seagrass transplant or restoration programme.

Purification and identification of novel cytotoxic oligopeptides from soft coral Sarcophyton glaucum.

Globally, peptide-based anticancer therapies have drawn much attention. Marine organisms are a reservoir of anticancer peptides that await discovery. In this study, we aimed to identify cytotoxic oligopeptides from Sarcophyton glaucum. Peptides were purified from among the S. glaucum hydrolysates produced by alcalase, chymotrypsin, papain, and trypsin, guided by a methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay on the human cervical cancer (HeLa) cell line for cytotoxicity evaluation. Purification techniques adopted were membrane ultrafiltration, gel filtration chromatography, solid phase extraction (SPE), and reversed-phase high-performance liquid chromatography (RP-HPLC). Purified peptides were identified by de novo peptide sequencing. From papain hydrolysate, three peptide sequences were identified: AGAPGG, AERQ, and RDTQ (428.45, 502.53, and 518.53 Da, respectively). Peptides synthesized from these sequences exhibited cytotoxicity on HeLa cells with median effect concentration (EC50) values of 8.6, 4.9, and 5.6 mmol/L, respectively, up to 5.8-fold stronger than the anticancer drug 5-fluorouracil. When tested at their respective EC50, AGAPGG, AERQ, and RDTQ showed only 16%, 25%, and 11% cytotoxicity to non-cancerous Hek293 cells, respectively. In conclusion, AERQ, AGAPGG, and RDTQ are promising candidates for future development as peptide-based anticancer drugs.