Deep-sea Research Part Ii-topical Studies in Oceanography最新文献

Blooms of the toxic dinoflagellate Karenia brevis, also known as harmful algal blooms (HABs) or red tides, occur almost annually on the west coast of Florida, killing fish and other marine life, threatening public health and adversely impacting local economies. Mitigating such effects requires improved red tide forecast capabilities on the West Florida Shelf. A short-term Lagrangian trajectory forecast tool is developed to help federal, state, and local end users monitor and manage red tides on the west coast of Florida. The forecast products are based on the West Florida Coastal Ocean Model (WFCOM) and the Tampa Bay Coastal Ocean Model (TBCOM) nowcast/forecast systems. Observed K. brevis cell count data are uploaded daily into the models to generate 3.5-day forecasts of the bloom trajectories both on the shelf and in the estuaries. The tracking tool displays modeled bloom trajectories at the surface and near-bottom with five categories of cell concentrations (each approximately representing an order of magnitude difference in concentration). More general and user-friendly maps are also produced to provide red tide advisories along the coast, including those integrated with satellite imagery.

Vertical particle fluxes of particulate organic carbon (POC), chlorophyll a (Chl a) and biogenic silica (bSi) were measured on the productive shelf of southern Africa, the Agulhas Bank (AB), in March 2019. Sinking particulate material in the form of aggregates is hypothesized to form the benthic nepheloid layer (BNL) which is a turbid layer found near the seabed. This layer is known to affect the spawning success of squid as it is linked to high turbidity which reduces visibility during mating. To determine the distribution of fluxes and particle composition in the AB, we collected water samples below the surface mixed layer (‘export’) and near the seabed (‘bottom’) using a Marine Snow Catcher. POC export fluxes were significantly higher inshore than offshore (mean ± SD: 944.6 ± 302.0 & 461.1 ± 162.1 mg POC m⁻² d⁻¹, respectively). There was no significant difference in the cross-shelf distribution of Chl a and bSi export fluxes, however the inshore fluxes of Chl a and bSi were higher than offshore, suggesting a link between export fluxes and sinking organic matter derived from the more productive inshore surface waters. All bottom fluxes were significantly higher inshore, suggesting the contribution of sinking organic particles and resuspended bottom sediments to inshore fluxes. POC export efficiency (ratio of exported POC flux relative to net primary production (NPP)) was higher on the AB (range: 0.58–9.56) compared to the global shelf seas ratio of 0.18 and not related to NPP, suggesting an export of standing stock of carbon biomass, likely produced before the cruise. Transfer efficiency (i.e., the amount of exported flux that reaches the bottom) was also high (max: 0.99, 1.0 and 33.04 for POC, Chl a and bSi, respectively) but did not show a clear spatial pattern. We observed a significant positive correlation between bottom turbidity (a proxy for BNL presence) and export POC flux, suggesting the possibility that sinking organic matter is contributing to BNL formation on the AB.

Lobo-lobo are small fishes that are caught using fine mesh nets in the western Visayan Sea whose market extends outside of the Visayan Sea, and perhaps even outside of the country. With high consumer demands, it is targeted year-round. Catches of fine-meshed boat seines operating in the waters off Concepcion, Iloilo which target large amounts of small and early juvenile fishes were monitored daily from June to December 2016 and June 2020 to October 2021. Results showed that catches were comprised of several species and clearly show the selection for early juveniles by the lobo-lobo fishery. At least 53 families comprise the lobo-lobo catches, dominated by Engraulidae (78.5%) and Clupeidae (13.1%), and are mostly comprised of post-larvae and early juveniles with sizes ranging from 0.2 to 3.6 cm standard length. The estimated total annual catch of the local boat seine fleet during the study period ranged from 313.8 mt to 869.0 mt. The fishing operations are concentrated between Tago and Igbon Islands and appear to be consistent throughout the year, but the composition and proportion of catches differed seasonally. This area appears to be a critical habitat, supporting the growth and survival of several species. Protecting this area and restricting the use of fine-meshed nets targeting fry will likely have an overall positive impact on the local fish stocks.

Ocean warming, primarily resulting from the escalating levels of greenhouse gases in the atmosphere, leads to a rise in the temperature of the Earth's oceans. These gases act as heat-trapping agents, contributing to the overall phenomenon of global warming. In order to gain a comprehensive understanding of how ocean warming impacts marine ecosystems, a thorough literature review was conducted over a span of three decades, involving 2484 initial publications. The systematic literature review screening was facilitated by utilizing Abstrackr's web-based application to efficiently select relevant abstracts, resulting in a final list of 797 publications aligned with the study's objectives. Since the advent of the industrial revolution, greenhouse gas emissions have witnessed an exponential surge, leading to a cumulative increase in atmospheric temperatures at an average rate of 0.08 °C (0.14 °F) per decade since 1880. Over the past 50 years, the ocean has emerged as a primary heat reservoir, absorbing and distributing the majority of the Earth's warming, with more than 90% of the heat gain occurring within its waters. Between 1950 and 2020, the global sea surface temperature (SST) increased by 0.11 °C (0.19 °F). The consequences of ocean warming extend significantly to the environment and climate. It induces the expansion of the ocean, alters its stratification and currents, diminishes oxygen availability, elevates sea levels, and intensifies hurricanes and storms. It also affects marine species' physiology, abundance, distribution, trophic interactions, survival, and mortality and can also cause stress and consequences for human societies that depend on impacted marine resources. Ocean warming is projected to increase from 2 to 4 and 4–8 times under climate scenarios Shared Socioeconomic Pathways 1–2.6 and Shared Socioeconomic Pathways 5–8.5, respectively, with an additional 0.6–2.0 °C added by the end of the century. We summarize its impacts and detailed negative or positive responses on marine taxonomic groups. We also provide critical information to help stakeholders, scientists, managers, and decision-makers to mitigate and adapt while improving biodiversity conservation and sustainability of marine ecosystems.

Algae form prolific coastal habitats and contribute the largest carbon dioxide (CO₂) flux globally. Most of the algal biomass is transported to the coastal ocean as particulate organic matter (OM), of which the contribution of carbon occurs mainly in depositional environments. Identifying the algal contribution alongside other major sources of organic carbon (OC) is crucial for determining allochthonous and autochthonous contributions in blue carbon habitats. In this study, we identified the algal contribution to OC storage in the seagrass meadow of Tanjung Adang Shoal (Johor, Malaysia) using dual-stable isotope measurements (δ¹³C and δ¹⁵N) and environmental DNA (eDNA) analysis. Stable isotope analysis showed that mangrove plants are the largest contributor to organic carbon pool in the sediments, followed by seston, macroalgae, epiphytes and seagrasses. The combined proportions of sestonic, macroalgal and epiphytic inputs as algal-derived organic matter had contributed a cumulative of 41.4–55.4% of organic matter in the bulk sediment. The eDNA method was used to examine bulk sediments and determine the types of algae present in the seagrass meadow at the genus/family level. Results showed that the main macroalgae present were from member of Coralinalles, Cladophoraceae and Ulvaceae, while diatoms were the predominant microalgae found in the sediment. These findings shed light on the importance of algae in carbon sequestration in the seagrass ecosystem. Understanding the role of algae in carbon storage and their interactions with sediment is crucial in the face of global and local environmental changes.

The Wallaby-Cuvier Escarpment is a 700 km long, NW-SE trending linear geological feature that marks the southern boundary of the Cuvier Plateau. The Plateau rises from the adjacent 5500 m deep abyssal plain to a topographical high of 3000 m, approximately 450 km off the coast of Western Australian. In 2021, a 50 km long segment of the escarpment, covering an area of 1700 km², was mapped by a high-resolution full-ocean depth multibeam echosounder. The habitat of the study area was explored during two video surveys undertaken using the crewed submersible Limiting Factor. Using Benthic Terrain Modeler (BTM), we classified the seabed into five geomorphological classes; flat plains, depressions, broad slopes, steep slopes, and crest. Video footage was used to classify habitat types and to record benthic megafauna occurrences which revealed highly heterogeneous and rapidly changing habitats. Six habitats were proposed based on the nature of geomorphology, slope, and substrate textures. A total of 202 organisms comprising 52 morphotaxa were scored during 198 min of survey that included at least eight phyla and 29 families. Despite a high number of morphotaxa, the total abundance of organisms is considered low which we attribute to oligotrophic surface waters. However, the distribution of organisms and their feeding strategies were well-aligned with habitat type. This study documents faunal distribution and habitat diversity of a rarely explored type of deep-sea geomorphological feature, and in a largely unexplored area and depth of the Indian Ocean.

Zooplankton form an integral component of epi- and mesopelagic ecosystems, and there is a need to better understand their role in ocean biogeochemistry. The export and remineralisation of particulate organic matter at depth plays an important role in controlling atmospheric CO₂ concentrations. Pelagic mesozooplankton and micronekton communities may influence the fate of organic matter in a number of ways, including: the consumption of primary producers and export of this material as fast-sinking faecal pellets, and the active flux of carbon by animals undertaking diel vertical migration (DVM) into the mesopelagic. We present day and night vertical biomass profiles of mesozooplankton and micronekton communities in the upper 500 m during three visits to an ocean observatory station (P3) to the NW of South Georgia (Scotia Sea, South Atlantic) in austral spring, alongside estimates of their daily rates of ingestion and respiration throughout the water column. Day and night community biomass estimates were dominated by copepods >330 μm, including the lipid-rich species, Calanoides acutus and Rhincalanus gigas. We found little evidence of synchronised DVM, with only Metridia spp. and Salpa thompsoni showing patterns consistent with migratory behaviour. At depths below 250 m, estimated community carbon ingestion rates exceeded those of metabolic costs, supporting the understanding that food quality in the mesopelagic is relatively poor, and organisms have to consume a large amount of food in order to fulfil their nutritional requirements. By contrast, estimated community rates of ingestion and metabolic costs at shallower depths were approximately balanced, but only when we assumed that the animals were predominantly catabolising lipids (i.e. respiratory quotient = 0.7) and had relatively high absorption efficiencies. Our work demonstrates that it is possible to balance the metabolic budgets of mesopelagic animals to within observational uncertainties, but highlights the need for a better understanding of the physiology of lipid-storing animals and how it influences carbon budgeting in the pelagic.

Ensemble models, statistical analysis and machine learning (ML) can be used to predict novel conditions in a rapidly changing ocean. Traditionally, ML has been understood as a purely data-driven approach and has been used on both observational and model data to forecast Sea Surface Temperature (SST) anomalies. Here we use ML trained only on climate model simulations to predict regional SST variations, thereby suggesting a novel role for ML as an ensemble model interpolator. We propose a measure of the predictability provided by different ML implementations as well as by standard time series analysis methods. Weighting each forecast by this predictability measure computed on model data only, provides a significant improvement in forecast skill. We demonstrate the performance of this approach for regions around Australia, the Nino3.4 region (central-eastern equatorial Pacific) and in the eastern equatorial Pacific. These analyses show that SST predictability varies as a function of geographical location, area size, seasonality, proximity to the coast and model data quality.

Analysis of the Tortonian sediments in the northeast Indian Ocean from NGHP–01–17A drilled at Andaman Basin shows 22 silicoflagellate taxa belonging to the genera Bachmannocena, Dictyocha, Distephanopsis, Paramesocena and Stephanocha. This study records the first evidence of Tortonian silicoflagellates from the offshore of northeast Indian Ocean. Two Partial Range zones namely Dictyocha varia, and Dictyocha extensa and one Subzone i.e. Bachmannocena elliptica have been proposed. In the present study, it has been observed that the transition of D. varia to D. extensa took place within the Tortonian. Fossil records of double skeletons in the silicoflagellate taxa are rare; however, we have documented double skeletons in three silicoflagellate taxa i.e. Dictyocha calida, Dictyocha fibula subspecies ausonia and Stephanocha speculum (6-sided). Ratio of Dictyocha and Stephanocha based on the combined abundance of all the taxa of the two genera reveals that there was substantial dominance of Dictyocha over Stephanocha throughout the studied sequence. The Dictyocha/Stephanocha palaeotemprature proxy indicated prevalence of warmer climate during the Tortonian (9.86 Ma to 7.39 Ma) with a cooling minimum in the Bachmannocena elliptica Subzone during 8.104 Ma – 8.088 Ma corresponding with nutrient rich condition.

A wide variety of coral communities are found in the Ryukyu Archipelago in southern Japan. Although reports of coral diseases and lesions in this region have increased since the 2000's, the variations of coral diseases among islands are somewhat limited. In this study, we conducted surveys to reveal the coral lesion assemblage and patterns in the marine national park area of Kerama Island and the quasi-national park on Yoron Island. Both sites are located 150 km away apart in the Ryukyu Archipelago. In total, 12 gross lesions were found in 30 coral genera. Corals in Yoron Island had 22% greater gross lesion abundance than Kerama Island (13.40 ± 1.36%) with an overall mean lesion abundance of 16.83 ± 1.66% (mean ± SE). Each Island shows a distinct pattern and group of coral lesion compositions. The disease lesion group of 7.21 ± 1.37% was dominated by White Syndrome (WS) and Black Band Disease (BBD), which severely infected various coral genera in Yoron Island. Corals in Kerama Island were predominantly affected by non-disease group lesion (9.76 ± 1.33%), such as Chalinula nematifera (CN) sponge overgrowing on the coral surface. Corals in the genus Pachyseris were highly susceptible (17.79%) to the diseases on Yoron Island, while Acroporid corals were the most susceptible (8.32%) to the diseases on Kerama Island. In addition, Porites were affected by disease and non-disease lesions from all sites in both Kerama and Yoron. These findings highlight the emergence of potential threats to coral communities in these national/quasi-national marine parks in Kerama and Yoron Island, which may be a factor limiting the survival and growth of key Scleractinian coral taxa. In addition, immediate consideration of environmental monitoring may be required to prevent coral disease outbreaks in the future.