Search

Macroalgae dominate nutrient dynamics and function as high-value foods for microbial, meio- and macrofaunal communities in coastal ecosystems. Because of this vital role, it is important to clarify the physiological information associated with environmental changes as it reflects their growth potential. To evaluate the effects of the changes in salinity and nutrients, the photosynthetic efficiency of a green macroalga Ulva fasciata from the Daya Bay was tested at a range of salinity (i.e., 31 to 10 psu) and nitrogen content (i.e., 5 to 60 µmol L−1). The results showed that cellular chlorophyll a (Chl a), carbohydrate and protein contents of U. fasciata were increased due to reduced salinity, and were decreased by interactive nitrogen enrichment. Within a short culture period (i.e., 18 h), the reduced salinity decreased the maximum photosynthetic efficiency (rETRmax and Pmax) derived from the rapid light response curve and photosynthetic oxygen evolution rate versus irradiance curve, respectively, as well as the saturation irradiance (EK). This reducing effect diminished with enlonged cultivation time and reversed to a stimulating effect after 24 h of cultivation. The nitrogen enrichment stimulated the rETRmax and Pmax, as well as the EK, regardless of salinity, especially within short-term cultivation period (i.e., < 24 h). In addition, our results indicate that seawater freshening lowers the photosynthetic efficiency of U. fasciata in the short term, which is mitigated by nitrogen enrichment, but stimulates it in the long term, providing insight into how macroalgae thrive in coastal or estuarine waters where salinity and nutrients normally covary strongly. [ABSTRACT FROM AUTHOR]

Transforming arid and semi-arid deserts into farmlands significantly alters soil moisture and fertility, affecting the trophic structure and functionality of soil fauna. Diversity and function of soil macrofaunal community can accurately reflect changes in soil quality and health during the succession of oasis farmlands. In this study, the assemblage of soil macrofauna and soil environmental factors in cultivated and abandoned croplands in the Zhangye Oasis of Gansu Province, were investigated using a hand-sorting method, and we analyzed the relationship between the trophic structure of soil macrofauna and the soil environment. Our results showed that: 1) Farmland cultivation increased the soil water content, soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP), while reducing pH. 2) The density, taxon richness, and Shannon-Wiener index of soil macrofauna in cultivated croplands were higher than in abandoned croplands, increasing with cultivation duration. The density of soil macrofauna in 100-year-old farmlands was 2.5, 1.5 and 1.4 times of that in 10-year-old, 30-year-old and 50-year-old farmlands; 3) the density and taxon richness of predatory, phytophagous, and other feeding types of soil macrofauna in cultivated croplands were higher than those of abandoned croplands. The observed increases in density and taxon richness are likely due to the improved soil conditions resulting from cultivation practices. The density-based ratio of predatory to phytophagous and other feeding types of soil macrofauna initially increases then decreases, inversely related to cultivation age. 4) changes in soil environment had little effect on the predatory soil macrofaunal community, and the explained variance by SOC, TP, and pH indicates the significant influence of these soil properties on the composition of the phytophagous soil macrofaunal community. SOC, TP, and pH explained 7.3 % of the variation in phytophagous soil macrofaunal community, while TN, TP, and pH explained 15.4 % of the variation in other feeding types of soil macrofauna. In conclusion, our findings highlight the positive impact of oasis farmland cultivation on soil quality and the enhancement of soil macrofauna diversity, which in turn could contribute to the resilience and productivity of these agricultural ecosystems. • The density and taxon richness of soil macrofauna in cultivated croplands were higher than in abandoned croplands. • The ratio of predatory to phytophagous soil macrofauna in abandoned croplands is lower than that in the cultivated farmlands. • Soil environmental factors have little effect on predatory soil macrofaunal communities but significantly influence the phytophagy and other feeding types. [ABSTRACT FROM AUTHOR]

• First insights into NE Pacific deep-sea macrofauna from the Bering Sea and Aleutian Trench (AT) and slope. • The Bering Sea differs from Aleutian slope and trench. • Depth is the most important driver of the assemblage composition in the North Pacific. • Adding 235 times more faunistic information to known data from GBIF and OBIS. • Hadal zones in the eastern AT show variable taxa richness. The deep sea, Earth's largest biome, harbors numerous unknown species. Prior to the AleutBio (Aleutian Trench Biodiversity Studies) expedition from July to September 2022, the Northeast (NE) Pacific at abyssal and hadal depths was virtually unexplored. Our study presents new findings from the AleutBio project on the macrofaunal composition of the Bering Sea (BS) and Aleutian Trench (AT) collected by means of an epibenthic sledge (EBS), comparing these results with data from the Kuril-Kamchatka Trench (KKT) and the Northwest (NW) Pacific. Additionally, we examine variations in macrofaunal composition and abundance across different regions and depths. A biogeographic gap analysis using data from the Ocean Biodiversity Information System (OBIS) and the Global Biodiversity Information Facility (GBIF) found that, out of 170,627 occurrence records from the North Pacific and Bering Sea, only 153 were from depths below 3,500 m. The AleutBio project addressed this gap by significantly expanding the dataset with 36,499 new records collected during the expedition using an EBS. Nearly 98% of the specimens were from five phyla: Arthropoda, Annelida, Mollusca, Echinodermata, and Nematoda, with Polychaeta, Copepoda, and Nematoda being the most abundant taxa. Although the number of individuals varied between stations, there was no significant decrease in abundance with increasing depth, and some hadal stations had similar numbers of invertebrates as abyssal stations. Regional differences were observed, with Polychaeta and Nematoda being dominant in the BS, and Copepoda more prevalent at western abyssal stations. Depth emerged as the key factor influencing macrofaunal distribution, with distinct patterns across bathyal, abyssal, and hadal depths. Comparisons with other NW Pacific regions, like the Sea of Japan and the Sea of Okhotsk, show that depth and water body isolation play crucial roles in shaping faunal communities. AleutBio's extensive sampling below 3,500 m has vastly increased available data, aiding in the understanding and conservation of deep-sea biodiversity. While certain taxa showed patchy distributions, no significant differences in faunal composition were found between geographic areas or depth zones. These findings underscore the dynamic nature of deep-sea ecosystems and highlight the importance of depth in shaping macrofaunal communities, emphasizing the need for continued research in these fascinating environments. [ABSTRACT FROM AUTHOR]

Oceanic hydrothermal vent systems represent some of the oldest habitats on Earth and serve as analogs for extraterrestrial environments. The Lost City Hydrothermal Field (LCHF) near the Mid-Atlantic Ridge is one such environment, and its large chimneys are unique in hosting actively venting hydrothermal fluids that are primarily controlled by serpentinization reactions in the subseafloor. Microbial communities within LCHF have been studied for insights into their functional adaptations to the warm, alkaline, and dissolved inorganic carbon-limited environment. Metagenomic and mineralogical data collected during a recent expedition to Lost City were analyzed to delineate associations between microbial populations and physical, chemical and biological characteristics of the chimneys. Bacterial 16S rRNA gene sequences show a high degree of putative microdiversity within the relatively dominant genera Desulfotomaculum, Sulfurovum, Thiomicrorhabdus, and Serpentinicella, which represent a large core of the overall LCHF vent bacterial community. This microdiversity relates to the compositional fraction of aragonite, brucite, and calcite minerals within chimney samples rather than just the composition of nearby vent fluids. Although many species are found in both chimneys and venting fluids, the overall microbial community structures in chimney biofilms remain distinct from the hydrothermal fluids that flow through them. Shotgun metagenomic analyses reveal differences among genes predicted to be involved in carbon, methane, nitrogen and sulfur cycling with respect to their correlations to the abundances of specific minerals. These data hint at microenvironmental complexity lost within standard bulk analyses. The findings of this study underscore the need to more closely examine microbe-mineral interactions in natural environments, critically informing not just population-level distributions, but also the functional underpinnings of these extremophile microbial communities. [ABSTRACT FROM AUTHOR]

Cold seeps are areas characterised by specialized biological communities that rely on chemosynthesis for their nutrition. To date, research conducted on New Zealand's Hikurangi Margin seep communities has focused on communities at 650-1200 m water depth. Here, we characterize the macrofaunal nematode communities of New Zealand cold seeps for the first time, and at deeper (> 1200 m) seep locations (Maungaroa, Glendhu and Urutī South). There were no significant difference in nematode abundance, species richness, diversity and evenness among the seep areas, which may reflect the lack of difference in most sediment variables. However, a consistent spatial pattern in nematode abundance was observed within all the seep areas on the Hikurangi Margin: abundance was highest at or near the seep centre, decreased steeply away from the centre and was low in the periphery. These spatially consistent patterns reflect the influence of methane seepage, which appears limited to the inner 150-200 m radius of each area, on nematode abundance via input of chemosynthetic food sources. We found significant differences in nematode community structure among all three areas, with most of the heterogeneity in community structure between the shallow Urutī South area and deeper Maungaroa and Glendhu areas, and differences among nematode communities of high, medium and low abundance associated with site-specific gradients in methane seepage. Within area variability in nematode community structure was mainly correlated with food availability and sediment grain size. Consistent with previous investigations of seep nematodes, we did not find evidence of seep endemics. Although deposit feeders were generally the most abundant feeding group, there were differences in the relative abundances of different feeding groups such as microvores and epigrowth feeders among the seep areas, and as a function of distance from the centre of the seep areas. Impact on seep communities from gas hydrate extraction processes may occur via reduction or potentially cessation of free-gas methane supply to the seafloor, 'sand' production at the seafloor due to the physical degradation of the substrate structure, or alteration of the structural integrity of the seafloor substrate. Any spatial management options considered for managing these impacts should reflect the differences in benthic community structure between depths and locations on the Hikurangi Margin. [ABSTRACT FROM AUTHOR]

Settling aggregates transport organic matter from the ocean surface to the deep sea and seafloor. Though plankton communities impact carbon export, how specific organisms and their interactions affect export efficiency is unknown. Looking at 15 years of eDNA sequences (18S-V4) from settling and sedimented organic matter in the Fram Strait, here we observe that most phylogenetic groups were transferred from pelagic to benthic ecosystems. Chaetoceros socialis, sea-ice diatoms, Radiolaria, and Chaetognatha are critical components of vertical carbon flux to 200 m depth. In contrast, the diatom C. socialis alone is essential for the amount of organic carbon reaching the seafloor. Spatiotemporal changes in community composition show decreasing diatom abundance during warm anomalies, which would reduce the efficiency of a diatom-driven biological carbon pump. Interestingly, several parasites are also tightly associated with carbon flux and show a strong vertical connectivity, suggesting a potential role in sedimentation processes involving their hosts, especially through interactions with resting spores, which could have implications for pelagic-benthic coupling and overall ecosystem functioning. Examining 15 years of data in the Arctic, this study shows that plankton, including diatoms and parasites, play key roles in exporting carbon to the seafloor. Species like Chaetoceros socialis are crucial for carbon flux and pelagic-benthic coupling. [ABSTRACT FROM AUTHOR]

Marine hydrocarbon seeps typically harbor a relatively predictable microbiome, including anaerobic methanotrophic (ANME) archaea. Here, we sampled two cold seeps in Monterey Bay, CA – Clam Field and Extrovert Cliff – which have been known for decades but never characterized microbiologically. Many aspects of these seeps were typical of seeps worldwide, including elevated methane and sulfide concentrations, 13C-depleted dissolved inorganic carbon, and the presence of characteristic macrofauna. However, we observed atypical microbial communities: extremely few ANME sequences were detected in either 16S rRNA or mcrA gene surveys at Clam Field (< 0.1 % of total community reads), even after 6 months of incubation with methane in the laboratory, and only slightly more ANME sequences were recovered from Extrovert Cliff (< 0.3 % of total community reads). At Clam Field, a lack of ANME mcrA transcription, a lack of methane-dependent sulfate reduction, and a linear porewater methane profile were consistent with low or absent methanotrophy. Although the reason for the scarcity of ANME archaea is still unclear, we postulate that non-methane hydrocarbon release excludes anaerobic methanotrophs directly or indirectly (e.g., through competitive interactions with hydrocarbon-degrading bacteria). Our findings highlight the potential for hydrocarbon seeps without this critical biofilter and therefore greater methane emissions from sediments. [ABSTRACT FROM AUTHOR]

Grain size and beach slope are critical factors in coastal science and management. However, it is difficult to have information on their distribution everywhere in the world, as most of the coast has never been documented. For many applications, it is essential to have at least a rough estimate when local field measurements are not available. Here, we review the existing prediction formulas relating beach slope to grain size and wave conditions, using publicly available global datasets and comparing them with a benchmark dataset of ground measurements from different authors worldwide. Uncertainties arise from the input parameters, in particular coastal waves, a key parameter of all formulae, but also from empirical coefficients that are undocumented or inaccessible with the global dataset. Despite the recognized importance of tides, they are often overlooked in formulae relating beach slope to sediment grain size. We therefore present an improved formulation that incorporates tidal effects. Although satellites offer a promising alternative to predictive formulae for direct estimation of beach slope and grain size, the current accuracy and methodologies of satellite data are insufficient for global applications. Continued advances in satellite missions, including higher resolution and revisit frequency, as well as new sensors, are essential to improve predictive capabilities and facilitate wider implementation. [ABSTRACT FROM AUTHOR]

The methane seeps on the Pacific margin of Costa Rica support extensive animal diversity and offer insights into deep-sea biogeography. During five expeditions between 2009 and 2019, we conducted intensive faunal sampling via 63 submersible dives to 11 localities at depths of 300–3600 m. Based on these expeditions and published literature, we compiled voucher specimens, images, and 274 newly published DNA sequences to present a taxonomic inventory of macrofaunal and megafaunal diversity with a focus on invertebrates. In total 488 morphospecies were identified, representing the highest number of distinct morphospecies published from a single seep or vent region to date. Of these, 131 are described species, at least 58 are undescribed species, and the remainder include some degree of taxonomic uncertainty, likely representing additional undescribed species. Of the described species, 38 are known only from the Costa Rica seeps and their vicinity. Fifteen range extensions are also reported for species known from Mexico, the Galápagos seamounts, Chile, and the western Pacific; as well as 16 new depth records and three new seep records for species known to occur at vents or organic falls. No single evolutionary narrative explains the patterns of biodiversity at these seeps, as even morphologically indistinguishable species can show different biogeographic affinities, biogeographic ranges, or depth ranges. The value of careful molecular taxonomy and comprehensive specimen-based regional inventories is emphasized for biodiversity research and monitoring. [ABSTRACT FROM AUTHOR]

Introduction: Power plants discharge thermal and cold effluents that significantly alter marine environments, impacting various organisms, including benthic communities. While thermal discharge has received considerable research attention, the impacts of cold discharge remain underexplored. This systematic review synthesizes existing research on the effects of power plant discharges on marine benthic ecosystems. Methods: A systematic literature search was conducted using Scopus, PubMed, and Web of Science, following PRISMA guidelines, covering studies from 1974 to 2024. A total of 58 articles were included in this review. CiteSpace was used to visualize trends, and statistical analysis was conducted to assess relationships between environmental parameters and changes in benthic abundance. Results: A significant negative correlation was observed between temperature differentials, ambient temperature, and benthic abundance. Thermal discharge generally led to reduced benthic diversity and abundance, with occasional increases under low ambient temperatures. Cold discharge effects remain less documented, with evidence primarily focused on phytoplankton and fish. Additionally, dissolved oxygen, pH, and bottom sediment composition were significantly altered by power plant discharge. Detection and mitigation measures are crucial to managing these impacts. Mitigation measures include distributed discharge for cold effluents, advanced heat recovery systems, and careful site selection to minimize impacts on sensitive ecosystems. Long-term management and adaptive strategies are essential to reduce adverse effects and maintain ecological balance. Discussion: Thermal discharges adversely impact marine benthic organisms by decreasing biodiversity and changing community structure, largely due to elevated temperatures and reduced oxygen levels. Cold discharges present unique challenges that require further research to fully understand their ecological impacts. Mitigation measures, such as distributed discharge for cold effluents and advanced heat recovery systems for thermal discharges, are essential to minimize the environmental impact of power plant operations. [ABSTRACT FROM AUTHOR]

Salt marshes are globally important blue carbon ecosystems, providing essential services such as coastal protection, carbon sequestration, nutrient cycling, and biodiversity support. Among their key inhabitants, macrofauna play critical roles in sustaining ecosystem health and resilience through processes like bioturbation, nutrient cycling, organic matter turnover, and trophic interactions, which in turn support ecosystem services such as fisheries and coastal community livelihoods. Despite their contributions, no comprehensive review has yet focused exclusively on the diverse roles and services of salt marsh macrofauna. This review aims to address this gap by synthesizing current research, supported by a bibliometric analysis revealing significant growth in studies since the year 2000, especially those addressing ecosystem services and climate resilience. We provide an in-depth assessment of macrofaunal functions in bioturbation, nutrient cycling, organic matter dynamics, greenhouse gas regulation, primary and secondary production, and food web interactions. Additionally, we examine the ecosystem services provided, such as provisioning, regulating, and cultural services, and explore the impact of environmental stressors on macrofaunal communities. Finally, this review identifies significant knowledge gaps, offering strategic insights for future research and serving as a vital reference for advancing coastal management and salt marsh conservation strategies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025 Elsevier Ltd. All rights reserved.)