Marine environmental research最新文献

Artificial light at night (ALAN) is an escalating anthropogenic stressor that can affect ecological communities over a range of spatial scales by altering key ecological processes, such as predation and herbivory. Shallow subtidal reefs are highly diverse and productive habitats that are vulnerable to ALAN. We investigated rates of consumption by fish (predation and herbivory) under different light treatments (ALAN, dark and daylight conditions) using standardised bioassay methods, i.e. squidpops and Ulva pops in situ. We also used GoPros to record predator identity, number of strikes and time to strike in ALAN and daylight treatments. Contrary to previous studies, we found that predation and herbivory rates were significantly lower in ALAN treatments than in daytime and dark treatments. The highest predation and herbivory rates were observed in daytime treatments. The identity of predator species, time to strike and number of strikes also differed between daytime and ALAN treatments. Due to low light conditions, dark treatments were not filmed. Our findings suggest that ALAN can alter predation in unexpected ways, depending on the environmental conditions and species affected. Future coastal management strategies need to account for light pollution as a major stressor to preserve valuable ecological resources.

Small-scale fisheries, especially those from developing countries, are vital for millions. Understanding the impact of environmental and human factors on fish stocks and yields and how they might change is crucial to ensure the sustainable use of aquatic resources. We developed an ecosystem model using Ecopath and Ecosim (EwE) to investigate changes in target species biomass and ecosystem attributes over 83 years (2017-2100) caused by different scenarios of fishing pressure and ocean warming in the Brazilian Northeastern continental shelf. The simulations considered three IPCC climate change scenarios (RCP2.6 [0.42 °C], RCP4.5 [1.53 °C], and RCP8.5 [4.02 °C]) and four fishing pressure scenarios: two with increased pressure (10% and 30%) and two with decreased pressure (-10% and -30%). The Ecopath model indicated that the Brazilian Northeastern continental shelf ecosystem is a grazing-based system with high biomass in macroalgae and detritus compartments, supporting a diverse community of consumers. Our simulations projected overall reductions in the biomass of target species, mainly under extreme climate change. Increasing temperatures and fishing efforts reduced the biomass of large predatory species and the food web length in several scenarios. Although projected changes in ecological network and information metrics were of lower magnitude, results predicted declines in production/respiration ratio, material cycling, and ascendency (variable related to trophic specialization, internalization, and material cycling) with climate change. These declines were likely linked to increased respiration rates, metabolic costs, and lower trophic efficiency with elevated temperatures. Together, our results show how climate change and fishing pressure can change the structure of coastal ecosystems, potentially leading to undesirable alternative states for fisheries. Our approach demonstrates the effectiveness of ecosystem-based modeling in projecting likely trajectories of change, which can be especially useful for resource management in data-limited conditions.

Coastal bays link terrestrial and oceanic carbon reservoirs and play important roles in marine carbon cycles. Particulate organic carbon (POC) produced by phytoplankton is a major autochthonous carbon source in coastal bays. Previous studies on the fate of POC produced by phytoplankton mainly focused on the relationship between phytoplankton and zooplankton in classic food webs, while our knowledge on the roles of bacterioplankton is still limited, particularly in bays under highly intensive aquaculture activities. Here, we investigated bacterial community structure, and the influence of environmental factors and phytoplankton biomass and community structure based on samples collected in August 2022 from Sanggou Bay, a typical aquaculture bay in northern China. Environmental conditions, phytoplankton and bacterial community structure differed significantly between different aquaculture areas, showing higher relative abundance of Synechococcus sp. in the mixing area of shellfish and kelp culture (Area II) than the shellfish culture area (Area I). In contrast, Marivita cryptomonadis was more abundant in Area I, associated with elevated dissolved inorganic nitrogen (DIN), POC, POC/PN (the molar ratio of POC to particulate nitrogen) and sterol-derived total phytoplankton biomass. The strong correlation between total phytoplankton biomass and particle-associated bacteria indicated the important role of this bacterial fraction in processing organic compounds produced by phytoplankton. Significant correlations between bacterial community composition and POC/PN suggested more organic carbon potentially entering detrital biomass pools in Area I compared to Area II. Our results suggest that spatial distribution patterns of bacterial community structure were regulated by multiple abiotic and biotic factors and had a profound impact on the fate of organic carbon under highly intensive aquaculture activities in Sanggou Bay.

Ocean warming (OW) and acidification (OA) are expected to interactively impact key phytoplankton groups such as diatoms, but the underlying mechanisms, particularly under long-term acclimation, remain poorly understood. In this study, we investigated the responses of the toxic diatom Pseudo-nitzschia multiseries to combined changes in temperature (20 °C and 30 °C) and CO₂ concentration (pCO₂ 400 μatm and 1000 μatm) using a multi-omics approach over an acclimation period of at least 251 generations. Physiological data suggest that elevated temperature, either alone or in combination with CO₂, reduced the net photosynthesis and nitrate uptake rate, thus inhibiting P. multiseries growth. Conversely, elevated CO₂ alone stimulated P. multiseries growth. Comparative genome analysis revealed the phenotypic plasticity in response to temperature and pCO₂ variations, even after more than 251 generations acclimation period. Temperature was identified as the dominant environmental factor, showing stronger effects than CO₂. Transcriptomic profiles indicated that genes involved in stress- and intracellular homeostasis such as Hsps, ubiquitination process and antioxidant defense were mostly down-regulated under long-term warming acclimation. This study demonstrates that P.multiseries responds similarly to both short-term and long-term experimental selection, suggesting that short-term experiments can be used to predict long-term responses.

Dissolved organic nitrogen (DON) has recently been recognized as an important nitrogen source for marine phytoplankton. However, the composition, sources, and biogeochemical cycling of DON in coastal ecosystems remain poorly understood. This study investigates the spatial distribution and seasonal variability of DON in Daya Bay, a subtropical semi-enclosed bay in the northern South China Sea. We measured DON concentrations, the DIN:DIP ratio, and the spectral characteristics of dissolved organic matter (DOM), including a(350), SUVA₂₅₄, and fluorescence components. Our findings reveal clear seasonal differences in the controlling factors for DON distribution: in summer, land-based sources and biological activities dominate, whereas in winter, oceanic circulation and its associated water mass mixing play a predominant role. The combined spectral indexes suggest that the transformation of DON is significantly more active in summer than in winter. Additionally, most stations exhibited low DIN:DIP ratios (<16) and relatively high chlorophyll a concentrations (>2 μg/L) during the summer months, while DIP concentrations in Daya Bay remained generally low (<1 μmol L^-1). This suggests that phytoplankton may assimilate DON, potentially leading to algal blooms and changes in population structure. Overall, these findings highlight the potential role of DON in the coastal nitrogen budget and phytoplankton dynamics, emphasizing the need for further investigation.

Comprehensive understanding of environmental multiple stressors on calcification in marine calcifiers remains an important topic of study, especially under ocean global change associated with multiple stressors. We explore the impact of multiple stressor on pteropod calcification in the southern Salish Sea (Washington, U.S.), a coastal estuarine system that exhibits a high degree of spatial and temporal variability in multiple environmental parameters across sampling locations. We hypothesized that such variability is associated with differences in pteropod calcification. Shell thickness and shell density across pteropod life history stages was compared with high-resolution outputs from a realistic model of regional circulation and biogeochemistry to explore how the mean and variability of multiple stressors (aragonite saturation state (Ω_ar), temperature, food availability) influence calcification. We found that both the mean and variability in multiple stressors play a major role in calcification in pteropods, with a generalized linear model explaining more than 60% of the variance. We suggest two different modes of shell building: stable conditions of lower mean Ω_ar trigger the loss of shell thickness and density. In the more variable habitats, i.e., where the variability occurs over diel and seasonal scales, shell thickness increases at higher Ω_ar variability and greater food availability, which might partially compensate for the loss of shell density. This plastic response appears to be consistent across life stages and could represent a response mechanism that allows some compensatory calcification under less favourable conditions. However, compensation is very limited, as evident by lower shell growth resulting in shell sizes comparable to early life stages. These results substantially improve the understanding of the variability in multiple stressors on the calcification process under multiple stressors and provide a foundation for the development of two new proxies for calcification monitoring, and with implications for marine carbon dioxide removal strategies.

Decanted oily wastewater is the generated stream associated with vessel-based skimming operations during offshore oil spill response. It contains a large amount of persistent, bio-accumulative, carcinogenic, and mutagenic oil contaminants, so it is critical to find effective ways to treat it. This study targets the decanted oily wastewater treatment by developing an integrated sand and activated carbon-based filtration approach. Three activated carbons (AC-1, AC-2, AC-3) were evaluated for oil removal from the oil-water mixture. AC-1 demonstrated superior performance with the highest BET surface area (704 m²/g) and pore volume (0.231 cm³/g). Batch adsorption experiments with AC-1 examined the effects of activated carbon textural characteristics, adsorbent dosage, and contact time on the total oil concentration and removal efficiency of polycyclic aromatic hydrocarbons (PAHs). Column experiments with AC-1 further explored various parameters, including the flow rate, column bed height, oil type, and adsorbent media on the adsorption performance. The findings demonstrate that 34 ml/min flow rate, 4 cm column height, and a combination of sand and activated carbon as adsorbent media achieved the highest total crude oil (Tera-Nova) and PAH removal efficiency (both 99.9%). By integrating the sand with activated carbon in the filtration system, both dissolved and emulsified petroleum hydrocarbons can be effectively removed. This research provides valuable insights into optimizing activated carbon-based systems in oil-water separation, with practical applications in marine oil spill response and wastewater treatment.

Mesozooplankton plays a pivotal role within marine food webs. However, there is a paucity of studies examining the size-spectra and trophic efficiency of these communities in tropical neritic and oceanic waters. Here, normalised biovolume (NBSS) and normalised numbers size-spectra (NNSS) were fitted on zooplankton data from the southwestern tropical Atlantic. The spectra were compared to assess the trophic efficiency slope (NBSS) across different regions, the Shelf, the western boundary current system (WBCS), and the South equatorial current system (SECS) off oceanic islands. Zooplankton was collected from September to October 2015, at 34 stations using oblique hauls with a 300 μm mesh bongo net from 200 m depth to the surface during either day or night. Samples were analysed using a ZooScan. A total of 30 zooplankton taxa were recorded. Mean abundance and biovolume were 62.6 ind m^-3 and 36.2 mm³ m^-3, respectively. Zooplankton community structure differed significantly between areas, in abundance and biovolume. Copepoda was the most abundant group, representing 66% and 57% of the abundance in coastal areas and oceanic islands, respectively. Fish larvae, gelatinous plankton (mostly Chaetognatha, Thaliacea, and Siphonophora), and Decapoda were the main contributors in terms of biovolume. Overall, smaller organisms were found at the shelf, while larger organisms were found in the SECS. Total abundance was significantly higher on the shelf and in the WBCS than in the SECS, while individual biovolume was higher in the SECS. The NNSS and NBSS slopes were significantly steeper on the shelf than in the other areas. This can be attributed to the higher contribution of small copepods on the shelf and the higher contribution of large-sized copepods and other large organisms in oceanic waters. Flatter NBSS and NNSS slopes offshore reveal a higher trophic efficiency, illustrating the importance of large zooplankton, particularly chaetognaths and decapods, in contributing to the ecosystem secondary productivity in oligotrophic tropical pelagic marine ecosystems. The combination of both NNSS and NBSS provided a more comprehensive view of ecosystem structure and fluxes.

In this paper, the spatial and temporal distribution of chlorophyll-a (Chl-a) concentration in the South China Sea (SCS) and its major environmental regulator mechanisms were studied by using satellite remote sensing data sea surface temperature (SST), sea surface wind (SSW), and aerosol optical depth (AOD) spanning from January 2000 to December 2022. The results show that Chl-a in the SCS exhibit notable spatio-temporal variations: they peak in winter (∼0.234 mg m^-3) and autumn (∼0.156 mg m^-3), and decline in spring (∼0.144 mg m^-3) and summer (∼0.136 mg m^-3). Spatially, Chl-a near the coast and in upwelling areas are generally higher than those in offshore areas. A monthly average time series correlation analysis across the entire SCS shows that Chl-a significantly correlate with SST (R = -0.78, P < 0.01) and SSW (R = 0.78, P < 0.01), and moderately correlate with AOD (R = 0.29, P < 0.01). The regulator of environmental factors also shows seasonal differences: during the winter monsoon period, Chl-a has the highest partial correlation with SSW (R = 0.73, P < 0.01), followed by SST (R = -0.55, P < 0.01), and no significant partial correlation with AOD (R = 0.14, P > 0.05); during the summer monsoon period, Chl-a has the highest partial correlation with SST (R = -0.63, P < 0.01), followed by AOD (R = 0.40, P < 0.01), and no significant partial correlation with SSW (R = 0.12, P > 0.05). A comprehensive analysis indicates that the mixing and upwelling processes regulated by the winter monsoon and SST exert a greater influence on nutrient variations. The enhanced mixing caused by the winter monsoon and the cold environment promote the growth of phytoplankton, leading to higher Chl-a concentrations in winter compared to other seasons. In contrast, the increased temperature in the summer monsoon period significantly weakens the mixing effect of wind speed and nutrients influx from deep layers to surface layers. Consequently, the external nutrient sourced from aerosol becomes crucial in determining Chl-a distribution, especially in oligotrophic regions near the southern SCS and the basin. However, in regions where other nutrient sources significantly contribute, such as the coastal areas influenced by seasonal upwelling, the contribution of aerosols is negligible.