Seagrass ecosystems of the Pacific Island Countries and Territories: A global bright spot

Seagrass ecosystems exist throughout Pacific Island Countries and Territories (PICTs). Despite this area covering nearly 8% of the global ocean, information on seagrass distribution, biogeography, and status remains largely absent from the scientific literature. We confirm 16 seagrass species occur across 17 of the 22 PICTs with the highest number in Melanesia, followed by Micronesia and Polynesia respectively. The greatest diversity of seagrass occurs in Papua New Guinea (13 species), and attenuates eastward across the Pacific to two species in French Polynesia. We conservatively estimate seagrass extent to be 1446.2 km², with the greatest extent (84%) in Melanesia. We find seagrass condition in 65% of PICTs increasing or displaying no discernible trend since records began. Marine conservation across the region overwhelmingly focuses on coral reefs, with seagrass ecosystems marginalised in conservation legislation and policy. Traditional knowledge is playing a greater role in managing local seagrass resources and these approaches are having greater success than contemporary conservation approaches. In a world where the future of seagrass ecosystems is looking progressively dire, the Pacific Islands appears as a global bright spot, where pressures remain relatively low and seagrass more resilient.

Seagrass ecosystem contributions to people's quality of life in the Pacific Island Countries and Territories

Seagrass ecosystems provide critical contributions (goods and perceived benefits or detriments) for the livelihoods and wellbeing of Pacific Islander peoples. Through in-depth examination of the contributions provided by seagrass ecosystems across the Pacific Island Countries and Territories (PICTs), we find a greater quantity in the Near Oceania (New Guinea, the Bismarck Archipelago and the Solomon Islands) and western Micronesian (Palau and Northern Marianas) regions; indicating a stronger coupling between human society and seagrass ecosystems. We also find many non-material contributions historically have been overlooked and under-appreciated by decision-makers. Closer cultural connections likely motivate guardianship of seagrass ecosystems by Pacific communities to mitigate local anthropogenic pressures. Regional comparisons also shed light on general and specific aspects of the importance of seagrass ecosystems to Pacific Islanders, which are critical for forming evidence-based policy and management to ensure the long-term resilience of seagrass ecosystems and the contributions they provide.

Mutremdamide A and koshikamides C-H, peptide inhibitors of HIV-1 entry from different Theonella species

A new sulfated cyclic depsipeptide, termed mutremdamide A, and six new highly N-methylated peptides, termed koshikamides C-H, were isolated from different deep-water specimens of Theonella swinhoei and Theonella cupola. Their structures were determined using extensive 2D NMR, ESI, or CDESI and QTOF-MS/MS experiments and absolute configurations established by quantum mechanical calculations, advanced Marfey's method, and chiral HPLC. Mutremdamide A displays a rare 2-amino-3-(2-hydroxyphenyl)propanoic acid and a new N(delta)-carbamoyl-beta-sulfated asparagine. Koshikamides C-E are linear undecapeptides, and koshikamides F-H are 17-residue depsipeptides containing a 10-residue macrolactone. Koshikamides F and G differ from B and H in part by the presence of the conjugated unit 2-(3-amino-5-oxopyrrolidin-2-ylidene)propanoic acid. Cyclic koshikamides F and H inhibited HIV-1 entry at low micromolar concentrations while their linear counterparts were inactive. The Theonella collections studied here are distinguished by co-occurrence of mutremdamide A, koshikamides, and theonellamides, the combination of which appears to define a new Theonella chemotype that can be found in deeper waters.

Paltolides A--C, anabaenopeptin-type peptides from the palau sponge Theonella swinhoei

Three new anabaenopeptin-like peptides, named paltolides A-C, were isolated from a deep-water specimen of the marine sponge Theonella swinhoei from Palau. Paltolides belong to a rare subgroup of sponge-derived anabaenopeptins that have in common a C-terminal tryptophan residue linked to the epsilon-amine of a lysine bearing a d configuration. The structures of paltolides A-C were determined by NMR and tandem MS techniques. Paltolide A is the first anabaenopeptin structure where a non-N-methylated amino acid precedes the C-terminal residue.

A global baseline for spawning aggregations of reef fishes

Species that periodically and predictably congregate on land or in the sea can be extremely vulnerable to overexploitation. Many coral reef fishes form spawning aggregations that are increasingly the target of fishing. Although serious declines are well known for a few species, the extent of this behavior among fishes and the impacts of aggregation fishing are not appreciated widely. To profile aggregating species globally, establish a baseline for future work, and strengthen the case for protection, we (as members of the Society for the Conservation of Reef Fish Aggregations) developed a global database on the occurrence, history, and management of spawning aggregations. We complemented the database with information from interviews with over 300 fishers in Asia and the western Pacific. Sixty-seven species, mainly commercial, in 9 families aggregate to spawn in the 29 countries or territories considered in the database. Ninety percent of aggregation records were from reef pass channels, promontories, and outer reef-slope drop-offs. Multispecies aggregation sites were common, and spawning seasons of most species typically lasted <3 months. The best-documented species in the database, the Nassau grouper (Epinephelus striatus), has undergone substantial declines in aggregations throughout its range and is now considered threatened. Our findings have important conservation and management implications for aggregating species given that exploitation pressures on them are increasing, there is little effective management, and 79% of those aggregations sufficiently well documented were reported to be in decline. Nonetheless, a few success stories demonstrate the benefits of aggregation management. A major shift in perspective on spawning aggregations of reef fish, from being seen as opportunities for exploitation to acknowledging them as important life-history phenomena in need of management, is urgently needed.

Marine lake ecosystem dynamics illustrate ENSO variation in the tropical western Pacific

Understanding El Niño/Southern Oscillation (ENSO) and its biological consequences is hindered by a lack of high-resolution, long-term data from the tropical western Pacific. We describe a preliminary, 6 year dataset that shows tightly coupled ENSO-related bio-physical dynamics in a seawater lake in Palau, Micronesia. The lake is more strongly stratified during La Niña than El Niño conditions, temperature anomalies in the lake co-vary strongly with the Niño 3.4 climate index, and the abundance of the dominant member of the pelagic community, an endemic subspecies of zooxanthellate jellyfish, is temperature associated. These results have broad relevance because the lake: (i) illustrates an ENSO signal that is partly obscured in surrounding semi-enclosed lagoon waters and, therefore, (ii) may provide a model system for studying the effects of climate change on community evolution and cnidarian-zooxanthellae symbioses, which (iii) should be traceable throughout the Holocene because the lake harbours a high quality sediment record; the sediment record should (iv) provide a sensitive and regionally unique record of Holocene climate relevant to predicting ENSO responses to future global climate change and, finally, (v) seawater lake ecosystems elsewhere in the Pacific may hold similar potential for past, present, and predictive measurements of climate variation and ecosystem response.

Cytotoxic Macrolides from a New Species of the Deep-Water Marine Sponge Leiodermatium

Chemical investigation of a new species of the deep-water marine sponge Leiodermatium, collected by manned submersible at a depth of 740 feet in Palau, resulted in the isolation of two cytotoxic macrolides, leiodolides A (1) and B (2). The leiodolides represent the first members of a new class of 19-membered ring macrolides, incorporating several unique functional groups including a conjugated oxazole ring, a bromine substituent, and an alpha-hydroxy-alpha-methyl carboxylic acid side-chain terminus. The structures of these new metabolites were established by spectroscopic analysis, chemical modification, and degradation. The relative and absolute stereochemistries at most chiral centers were assigned on detailed interpretation of spectroscopic data, coupled with chemical degradation and application of the modified Mosher ester method. Leiodolide A showed significant cytotoxicity (average GI(50) = 2.0 microM) in the National Cancer Institute's 60 cell line panel with enhanced activity against HL-60 leukemia and OVCAR-3 ovarian cancer cell lines.

Identity and diversity of coral endosymbionts (zooxanthellae) from three Palauan reefs with contrasting bleaching, temperature and shading histories

The potential of corals to associate with more temperature-tolerant strains of algae (zooxanthellae, Symbiodinium) can have important implications for the future of coral reefs in an era of global climate change. In this study, the genetic identity and diversity of zooxanthellae was investigated at three reefs with contrasting histories of bleaching mortality, water temperature and shading, in the Republic of Palau (Micronesia). Single-stranded conformation polymorphism and sequence analysis of the ribosomal DNA internal transcribed spacer (ITS)1 region was used for genotyping. A chronically warm but partly shaded coral reef in a marine lake that is hydrographically well connected to the surrounding waters harboured only two single-stranded conformation polymorphism profiles (i.e. zooxanthella communities). It consisted only of Symbiodinium D in all 13 nonporitid species and two Porites species investigated, with the remaining five Porites harbouring C*. Despite the high temperature in this lake (> 0.5 degrees above ambient), this reef did not suffer coral mortality during the (1998) bleaching event, however, no bleaching-sensitive coral families and genera occur in the coral community. This setting contrasts strongly with two other reefs with generally lower temperatures, in which 10 and 12 zooxanthella communities with moderate to low proportions of clade D zooxanthellae were found. The data indicate that whole coral assemblages, when growing in elevated seawater temperatures and at reduced irradiance, can be composed of colonies associated with the more thermo-tolerant clade D zooxanthellae. Future increases in seawater temperature might, therefore, result in an increasing prevalence of Symbiodinium phylotype D in scleractinian corals, possibly associated with a loss of diversity in both zooxanthellae and corals.

Cytotoxic beta-carbolines and cyclic peroxides from the Palauan sponge Plakortis nigra

Four beta-carbolines, plakortamines A-D, two cyclic peroxides, epiplakinic acids G and H, and two related gamma-lactones, (2S,4R)- and (2R,4R)-2,4-dimethyl-4-hydroxy-16-phenylhexadecanoic acid 1,4-lactones, were isolated from the deep-water sponge Plakortis nigra from Palau. The structures of the eight new metabolites were elucidated by interpretation of spectroscopic data. Most of the metabolites inhibited the HCT-116 human colon tumor cell line.

Redistribution of fallout radionuclides in Enewetak Atoll lagoon sediments by callianassid bioturbation

The lagoon sediments of Enewetak Atoll in the Marshall Islands contain a large selection of fallout radionuclides as a result of 43 nuclear weapon tests conducted there between 1948 and 1958. Studies of the burial of fallout radionuclides have been conducted on the islands and in several of the large craters, but studies of their vertical distribution have been limited to about the upper 20 cm of the lagoon sediments. We have found elevated fallout radionuclide concentrations buried more deeply in the lagoon sediments and evidence of burrowing into the sediment by several species of callianassid ghost shrimp (Crustacea: Thalassinidea) which has displaced highly radioactive sediment. The burrowing activities of callianassids, which are ubiquitous on the lagoon floor, facilitate radionuclide redistribution and complicate the fallout radionuclide inventory of the lagoon.