Secular change in seaweed species composition and coverage of Sargassaceae on the artificial reef in Wakasa Bay, Japan.

The threat of declining seaweed beds has been a concern around the world. Seagrass and seaweed (brown algae) beds are essential habitats supporting fisheries. However, approximately 22% of these habitats have been lost in Japan due to increased coastal landfill sites and ports. This study aims to rehabilitate the depletion of these habitats by constructing an artificial reef in Wakasa Bay, Japan, and monitoring Sargassaceae succession in the second and fourth years after the construction was completed. In this study, we set up four sites on the artificial reef. Then we identified the seaweed species composition and coverage of the Sargassaceae using underwater visual observation by scuba divers. The seaweed coverage was already over approximately 80% in the second year after construction. The Sargassum horneri and S. confusum dominated during the first and second sampling in the second year after construction, and Myagropsis myagroides and S. patens during the third and fourth sampling in the fourth year after construction. Thus, the recovery of species composition takes longer than that of coverage. Therefore, observing species composition recovery is essential when constructing the artificial reef.

Impact of tidal fluctuations on bacterial community structure in Wuyuan Bay: A comparative analysis of waters inside and outside the tidal barrage.

The tidal barrage at Wuyuan Bay effectively mitigated the odor from the tidal flat during ebb tide, however, its effect on bacterial community structure in waters are still unclear. In this study, high-throughput sequencing was used to analyze the structure of the microbial community in waters inside and outside the tidal barrage during flood and ebb tides. Results showed bacterial diversity was higher in water outside the barrage during flood tide. The dominated species at phylum and genus levels were various in waters inside and outside the tidal barrage during flood and ebb tides. The water inside during ebb tide (E1) were dominated by two cyanobacterial genera, Cyanobium_PCC-6307 (42.90%) and Synechococcus_CC9902 (12.56%). The microbial function, such as porphyrin and chlorophyll metabolism and photosynthesis, were increased in E1. Norank_f__Nitriliruptoraceae was identified as differential microorganism in waters inside the barrage. Inorganic nitrogen and nonionic ammonia were significantly high in E1, and were negatively correlated with norank_f__Nitriliruptoraceae. These results suggest tidal barrage blocks water exchange, resulting in the accumulation of nutrients in Wuyuan Bay. Consequently, the environment became favorable for the growth of cyanobacteria, leading to the dominance of algae in the water inside the barrage and posing the risk of cyanobacterial bloom. Higher Nitriliruptoraceae inside the barrage might be a cue for the change of water quality.

Spatially Explicit Impact of Land Use Changes in the Bay Area on Anthropogenic Phosphorus Emissions and Freshwater Eutrophication Potential.

Land use changes significantly impact anthropogenic phosphorus (P) emissions, their migration to a water environment, and the formation of freshwater eutrophication potential (FEP), yet the spatiotemporally heterogeneous relationships at the regional scale have been less explored. This study combines land use classification, P-flow modeling, spatial analysis, and cause-effect chain modeling to assess P emissions and P-induced FEP at a fine spatial resolution in Guangdong-Hong Kong-Macao Greater Bay Area and reveals their dynamic responses to land use changes. We find that land conversion from cultivated land to impervious land corresponded to an increase in P emissions of 4.1, 1.8, and 0.5 Gg during 2000-2005, 2005-2010, and 2010-2015 periods, respectively, revealing its dominant but weakening role in the intensification of P emissions especially in less-developed cities. Expansion of aquacultural land gradually became the primary contributor to the increase in both the amount and intensity of P emissions. Land conversions from cultivated land to impervious land and from natural water bodies to aquacultural land led to 35.9% and 25.3% of the increase in FEP, respectively. Our study identifies hotspots for mitigating the environmental pressure from P emissions and provides tailored land management strategies at specific regional development stages and within sensitive areas.

Benthic foraminifera as bio-indicators of natural and anthropogenic conditions in Roscoff Aber Bay (Brittany, France).

Living benthic foraminifera, known as environmental bio-indicators of both natural and anthropogenic conditions in marine environments, were investigated in the coastal environment of Roscoff Aber Bay (Brittany, France). Eight sampling sites subject to natural variations (freshwater inputs, tides) and/or anthropogenic impacts (pollution, eutrophication) were studied over four seasons in 2021-2022 (November, February, May, August). We sought to understand the spatial distribution of foraminiferal populations within and between sampling sites over the different seasons and to identify sensitive species and those tolerant to anthropogenic impacts. To this end, sedimentary and biogeochemical characteristics of the sediments were examined by measuring grain size, temperature, oxygen, salinity, pH, environmental pigment concentration (chl a and phaeopigments), total organic carbon (TOC), isotopic ratios of carbon (δ13C), nitrogen (δ15N) and sulfide (δ34S), and chl a fluorescence. Considering these parameters as potential driving factors, four environments were distinguished among the sampling sites: open water, terrestrial, oligotrophic and eutrophic. These showed an increasing gradient of organic supply as well as very different microbial activities, highlighted by carbon and sulfide isotopic ratios. Foraminiferal population study revealed the dominant species characterising these main environments. The lowest abundance but highest diversity of foraminifera was found in the harbour site, associated with the dominance of Haynesina germanica, suggesting this species is tolerant to eutrophic environments and anthropogenic impacts. Open water was dominated by Ammonia beccarii and Elphidium crispum, while Quinqueloculina seminula was the most abundant species in the site with the greatest terrestrial influence. Interestingly, the observed organic enrichment of the harbour due to anthropogenic activities (fisheries, waste deposits, etc.) does not seem to significantly affect foraminiferal diversity. Overall, the benthic foraminiferal species in Roscoff Aber Bay appear to be an excellent proxy for marine environmental conditions under various natural and anthropogenic influences.

Participatory science methods to monitor water quality and ground truth remote sensing of the Chesapeake Bay.

Measurements by volunteer scientists using participatory science methods in combination with high resolution remote sensing can improve our ability to monitor water quality changes in highly vulnerable and economically valuable nearshore and estuarine habitats. In the Chesapeake Bay (USA), tidal tributaries are a focus of watershed and shoreline management efforts to improve water quality. The Chesapeake Water Watch program seeks to enhance the monitoring of tributaries by developing and testing methods for volunteer scientists to easily measure chlorophyll, turbidity, and colored dissolved organic matter (CDOM) to inform Bay stakeholders and improve algorithms for analogous remote sensing (RS) products. In the program, trained volunteers have measured surface turbidity using a smartphone app, HydroColor, calibrated with a photographer's gray card. In vivo chlorophyll and CDOM fluorescence were assessed in surface samples with hand-held fluorometers (Aquafluor) located at sample processing "hubs" where volunteers drop off samples for same day processing. In validation samples, HydroColor turbidity and Aquafluor in vivo chlorophyll and CDOM fluorescence were linear estimators of standard analytical measures of turbidity, chlorophyll and CDOM, respectively, with R2 values ranging from 0.65 to 0.85. Updates implemented in a new version (v2) of HydroColor improved the precision of estimates. These methods are being used for both repeat sampling at fixed sites of interest and ad-hoc "blitzes" to synoptically sample tributaries all around the Bay in coordination with satellite overpasses. All data is accessible on a public database (serc.fieldscope.org) and can be a resource to monitor long-term trends in the tidal tributaries as well as detect and diagnose causes of events of concern such as algal blooms and storm-induced reductions in water clarity.

MORPHOLOGICAL AND MOLECULAR CHARACTERIZATION OF DICHELYNE (NEOCULLANELLUS) DAKARENSIS N. SP. (NEMATODA: CUCULLANIDAE) PARASITIZING AN ECONOMICALLY IMPORTANT MARINE FISH, THE SOMPAT GRUNT, POMADASYS JUBELINI (PERCIFORMES: HAEMULIDAE), FROM HANN BAY IN DAKAR, SENEGAL.

Nematodes collected from the intestine of sompat grunt Pomadasys jubelini Cuvier, 1830 from Hann Bay in Dakar, Senegal represent a new species described herein as Dichelyne (Neocucullanellus) dakarensis n. sp., and investigated with the use of light and scanning electron microscopy. The new species differs from its congeners based on several characteristics, especially because the subgenus Neocucullanellus is the only 1 that has 2 ceca. In addition, the new species diagnosis is based on the number and arrangement of the caudal papillae as well as the size of the veil of spicules. Morphological data were supported by molecular analysis. Results obtained using SSU rDNA and COI distinguished the present specimens from other cucullanids. Molecular data indicated the close relatedness between the new species and Dichelyne cotylophora Ward and Magath, 1917.

Seaweed functional strategies, functional groups, and taxon dynamics through a 213-year historical series of Rio De Janeiro Bay.

From Darwin's visit to nowadays, we analyzed the changes in species- and genus-level richness and turnover, equity, diversity, composition, as well as functional group and functional strategy dynamics over a 213-year historical series of the seaweed assemblage from Rio de Janeiro Bay. We developed new analysis methods to serve as a protocol for worldwide functional and bioindicator assessment of seaweed assemblages. Over the two centuries of changes tracked, the integration of taxonomic, functional group, and functional strategy analyses unraveled a trajectory of seaweed assemblage restructuring under human disturbance. Our taxonomic analyses showed a high species and genus turnover and a decline in richness, with the local extinction of the Sargassum genus, responsible for warm temperate kelp forests in the Western Atlantic. Seaweed functional group data presented a trend of morphological simplification and miniaturization, with the decline of marine forest canopy and subcanopy-forming groups favoring filamentous and crustose algae dominance. Functional strategy data showed the historical decline of competitive structuring as an assemblage driver in favor of disturbance and stress-structuring, as highlighted by the competitive strategy decrease, coupled with stress-tolerant and ruderal strategies rise across metrics. These changes were successfully portrayed by the new ecological index we proposed, the C/SR index. It is the first quantitative index for seaweed assemblages, designed to be a trackable metric for conservation, monitoring, and restoration efforts.

Storms mobilize organophosphate esters, bisphenols, PFASs, and vehicle-derived contaminants to San Francisco Bay watersheds.

In urban to peri-urban watersheds such as those surrounding San Francisco Bay, stormwater runoff is a major pathway by which contaminants enter aquatic ecosystems. We evaluated the occurrence of 154 organic contaminants via liquid chromatography coupled to tandem mass spectrometry, including organophosphate esters (OPEs), bisphenols, per- and polyfluoroalkyl substances (PFASs), and a suite of novel urban stormwater tracers (SWCECs; i.e., vehicle-derived chemicals, pesticides, pharmaceuticals/personal care products, benzothiazoles/benzotriazoles). Time-averaged composite sampling focused on storms in highly developed watersheds over four wet seasons, with complementary sampling in less-urban reference watersheds, near-shore estuarine sites, and the open Bay. Of the targeted contaminants, 68 (21 SWCECs, 29 OPEs, 3 bisphenols, 15 PFASs) were detected in ≥10 of 26 urban stormwater samples. Median concentrations exceeded 500 ng L-1 for 1,3-diphenylguanidine, hexa(methoxymethyl)melamine, and caffeine, and exceeded 300 ng L-1 for 2-hydroxy-benzothiazole, 5-methyl-1H-benzotriazole, pentachlorophenol, and tris(2-butoxyethyl) phosphate. Median individual PFAS concentrations were <10 ng L-1, with highest concentrations for PFHxA (180 ng L-1), PFOA (110 ng L-1), and PFOS (81 ng L-1). In six of eight urban stormwater samples analyzed for 6PPD-quinone (a tire rubber-derived transformation product), concentrations exceeded coho salmon acute toxicity thresholds, suggesting (sub)lethal impacts for sensitive species. Observed concentrations were generally significantly higher in highly developed watersheds relative to reference watersheds, but not statistically different in near-shore estuarine sites, suggesting substantial transient exposure potential at stormwater outfalls or creek outflows. Results emphasized the role of stormwater in contaminant transport, the importance of vehicles/roadways as contaminant sources, and the value of monitoring broad multi-analyte contaminant suites to enable comprehensive source and toxicity evaluations.

Exploring the temporal toxicity signature: A baseline evaluation of the heavy metal concentration in estuarine core sediments in the coastal region of cauvery delta, bay of bengal.

Globally, the concentration of heavy metals and sediment toxicity analysis are significant liabilities to aquatic environments. This scrutiny outlines the sediment textures, heavy metals and toxicity status associated with environmental pollution indices in the core sediment of the Cauvery and Vettar estuaries, East coast of India. The impact of rapid industrialization, urbanization, harbour activities and agricultural activities influences on the twain estuary is a significant concern to designate the environment. The contamination status of the sediments affects the potential biodiversity, ecological risks and human health. A total of two core sediments were recovered from the Cauvery and Vettar estuaries in March 2023 to decipher the environmental pollution status. Meticulous observation of the textural studies underscores the prevalence of sand content in Cauvery, and Vettar sediments consist of predominate clay content and minor silt contents. Furthermore, the organic matter is augmented in the Vettar River due to the higher input of waste disposal, seaweeds and algae due to the surrounding landmass. Twain core sediments argue that heavy metal concentration is decreasing in order as Fe > Zn > Ni > Pb > Cu > Cr by using portable X-ray fluorescence (pXRF) spectrometry. Remarkable results of environmental pollution indices such as Igeo, Ef, Cf, Cd and mCd state very highly polluted, extreme enrichments, high contamination and very high degree of contamination. Furthermore, the potential ecological risk indices such as PLI, SQGs, and PERI argue polluted, medium to high toxicity and moderate adverse ecological risk to the estuarine regions. Statistical analysis of the heavy metal affirms the enrichment of Fe metals may derive from lithogenic and/or anthropogenic influences, and the other studied metals such as Cu, Ni, Zn, Pb and Cr may be influenced by the anthropogenic activities in the aspect of point and non-point pollution sources. This could result from both estuaries undergoing higher pollution, in which the Vettar estuary is a considerable environmental risk zone compared to the Cauvery river due to the impact of industrial effluents and rapid urbanization activities. This finding underscores the urgent need for enhanced estuarine sediment quality study and comprehensive assessment of sediment toxicity, regulating the beneficial acumen for the government to follow the suitable remediation on the embellish policy of river and marine environments.

Assessment of water quality and identification of priority areas for intervention in Guanabara Bay basin, Rio de Janeiro, Brazil, using nonparametric and multivariate statistical methods.

The Guanabara Bay hydrographic region (GBHR) has served as a central hub for human settlement and resource utilization throughout Brazil's history. However, the region's high population density and intense industrial activity have come at a cost, leading to a significant decline in water quality. This work aimed to identify homogeneous regions in GBHR according to water quality parameters in dry and rainy periods. The following water quality monitoring variables were monitored at 49 gauge stations: total phosphorus (TP), nitrate (NO3-), dissolved oxygen (DO), hydrogenionic potential (pH), turbidity (Turb), thermotolerant coliforms (TCol), total dissolved solids (TDS), biochemical oxygen demand (BOD), water temperature (Tw), and air temperature (Ta). The statistical analysis consisted of determining principal components, cluster analysis, seasonal differences, and Spearman's correlation. The water quality parameter correlations were not expressively influenced by seasonality, but there are differences in the concentrations of these parameters in the dry and rainy periods. In the dry period, urban pressure on water quality is mainly due to fecal coliforms. The resulting clusters delimited areas under urban, agricultural, and forestry influence. Clusters located in areas with high demographic density showed high concentrations of TCol and TP, while clusters influenced by forestry and agriculture had better water quality. In the rainy season, clusters with urban influence showed problems with TCol and TP, in addition to some characteristics in each group, such as high TDS, NO3-, and BOD. Forested areas showed high DO, and clusters under agricultural influence had higher concentrations of TCol, BOD, and NO3- concerning forested regions. The troubling state of sanitation in GBHR occurs in metropolitan regions due to lack of a formal sanitation system.

Distribution characteristics, source analysis and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the western Honghai Bay of China.

The distribution characteristics and risk levels of PAHs in surface sediment in the Honghai Bay of China are studied in this paper. The results showed that the concentration of total PAHs in this area ranged from 100.65 ng·g-1 to 241.31 ng·g-1, with an average concentration of 158.83 ng·g-1. The tricyclic PAHs were the main components in the detected PAHs. PAH pollution levels in this region were low and moderate as compared with adjacent areas. Traceability results showed that the sediment PAHs mainly originate from coal and biomass combustion. PAHs concentrations at some stations were above the Environmental Quality Reference Level. The PAHs toxicity and ecological risk level in surface sediments in the area was determined to be low to moderate by toxicity equivalence testing and risk entropy value assessment.

Long-term alterations of nutrient dynamics and phytoplankton communities in Daya Bay, South China Sea.

Dynamics of phytoplankton in coastal waters is a function of nutrient influx and the present study investigated the trend in nutrient dynamics and phytoplankton abundance of Daya Bay (DB), South China Sea, from 1986 to 2020. Dissolved inorganic nitrogen (DIN), Dissolved inorganic phosphate (DIP) and Silicates were measured. DIN concentration exhibited an increasing trend over the last decades, and it was above the threshold for the phytoplankton growth. DIP level showed a significant decreasing trend throughout the studied period, falling below the threshold for phytoplankton growth in the last decade, where harmful algal blooms were dominated by the dinoflagellates. Long-term anthropogenic influences severely change influx of DIN, DIP, and silicates which in turn shape the architecture of phytoplankton communities. Thus, the understanding of the complex interaction between nutrient influx, anthropogenic activities and dynamics of both water quality and biological elements are particularly important to decide criteria to manage coastal ecosystems.

Occurrence, characteristics and distribution of microplastics in commercial marine fishes of the Bay of Bengal.

The study aimed to assess and characterize microplastics (MPs) in muscles, guts, and gills of six commercially important marine fish from the Bay of Bengal. FTIR was utilized to identify MP's polymer compositions. A total 7085 MPs identified, where tuna exhibited the highest count and Bombay duck had the lowest. MPs abundance (MPs/g) was ranged from 1.56 ± 0.39 to 7.16 ± 1.36 in muscles, 1.91 ± 0.32 to 4.46 ± 0.75 in guts, and 2.36 ± 0.24 to 6.53 ± 1.58 in gills. The predominant MPs were 1-5 mm size (33.33-62.78 %), white/transparent color (18.45-54.63 %), filament shapes (75.00-94.71), and fiber types (73.21-94.71 %). FTIR revealed MPs 58.89 % polyethylene, 21.67 % polypropylene, 17.22 % polyester, and 2.22 % non-plastic compositions. Cluster analysis grouped two species with 50 % similarity, while PCA indicated significant variations among principal components (14-69.4 %) highlighting the dominance of fiber, particles, and 0.5-1.0 mm MPs in the fish tissues. The prevalence of MPs in seafood underscores measures to safeguard both the marine ecosystem and human health.

Low incidence of microplastics in coral reefs of Kane'ohe Bay, Hawai'i, USA.

This study investigated microplastic and other micro-debris pollution in sediment, seawater, sea cucumbers, and corals from fringing and patch reefs in Kane'ohe Bay, O'ahu, Hawai'i, USA. Microplastic pollution in Kane'ohe Bay Bay was low compared to other tropical coral reefs. Microplastics were detected in sediments (29 %), sea cucumbers (9 %), and coral (0-2 %) samples but were not quantifiable. Seawater had quantifiable microplastic (< 0.5 mm) and macroplastic (> 0.5 mm) pollution, with mean concentrations ranging from 0.0061 to 0.081 particles m-3. Most particles detected in seawater samples were larger, floating plastic debris consisting mostly of polyethylene, polypropylene fragments, and fibers. Across the other matrices, the most detected particles were polyester, polypropylene, and cotton fibers. These results provide baseline data for this important coral reef ecosystem, and further monitoring is recommended to understand the seasonal and long-term trends in microplastic pollution and its potential future impacts.

Variations in water exchange in the sub-areas of a bay following large-scale land reclamation.

Semi-enclosed bays often have weak water exchange capacities, leading to frequent environmental pollution, particularly localized pollution. This study examines the local effects of changes in local factors on water circulation within Bohai Bay after land reclamation. To address the limitations of previous methods in measuring sub-regional water exchange, we introduce the concept of Local Average Influence Time (LAIT) to qualitatively and quantitatively analyze the impact of land reclamation on water exchange between sub-regions in semi-enclosed bays. Results indicate that land reclamation can enhance the self-purification capacity of sub-regions with significant shoreline changes in Bohai Bay, but this improvement is closely linked to dynamic factors such as wind, tide, and runoff. The degree of water exchange between sub-regions shows significant spatial heterogeneity, with land reclamation influencing the primary direction of water transport. This is largely due to the obstruction caused by newly constructed artificial headlands, making the neighbor area new high-risk zones for pollution. Wind can promote water circulation within the bay, but its effects are spatially heterogeneous and sensitive to shoreline topography changes. River discharge can enhance local water exchange but is weakened by obstruction from artificial headlands. Tide promotes water exchange between the bay mouth and inner bay areas, while their impact on sub-regional water exchange is also spatially heterogeneous and sensitive to changes in shoreline and topography. This study provides a quantitative method for assessing water exchange between regions and offers insights into the impact of land reclamation on water circulation within semi-enclosed bays.

Description and pathology of a new genus and species of fish blood fluke (Digenea: Aporocotylidae Odhner, 1912) infecting white mullet, Mugil curema Valenciennes, 1836 (Mugiliformes: Mugilidae) in Mobile Bay (northern Gulf of Mexico) with a phylogenetic analysis.

Three fish blood flukes (Aporocotylidae Odhner, 1912) infect mullets (Mugiliformes: Mugilidae): Cardicola mugilis Yamaguti, 1970 and Plethorchis acanthus Martin, 1975 infect striped mullet, Mugil cephalus Linnaeus, 1758 in the Central Pacific Ocean (Hawaiian Islands) and Brisbane River (Australia), respectively; Cardicola brasiliensis Knoff & Amato, 1992 infects Lebranche mullet, Mugil liza Valenciennes, 1836 from the Southwestern Atlantic Ocean (Brazil). White mullets were cast-netted from the mouth of Deer River, a coastal saltmarsh of Mobile Bay, in the north-central Gulf of Mexico and examined for blood fluke infections. Specimens of Mugilitrema labowskiae Warren & Bullard n. gen., n. sp. were found infecting the endocardial surface and inter-trabecular spaces of the atrium, ventricle, and bulbous arteriosus. The new genus and species differ from all other aporocotylids by having the combination of two post-caecal testes, a uterus with straight ascending and descending portions, and a common genital pore. The 28S analysis recovered the new species and P.acanthus as sister taxa and Aporocotylidae as monophyletic. Carditis associated with intense infections comprised endocardial hyperplasia, resulting in a thickened cardiac endothelium. Probable dead or deteriorating eggs in the myocardium were encapsulated by granulomas composed of epithelioid histiocytes. Live eggs infected the afferent artery of gill filaments and were associated with varied hyperplasia of the overlying epithelium and haemorrhaging from the afferent artery in high-intensity infections. The new species is the first aporocotylid infecting a mullet from the northwestern Atlantic Ocean and only the second description of demonstrable endocarditis attributed to an adult fish blood fluke infection.

Marine fungal community composition and diversity across a polluted site in the south Mediterranean coast: the Monastir Bay, Tunisia.

Marine fungi communities play a crucial role in the recycling of nutrients, restoration of biological systems, and the overall functioning of ecosystems. While aquatic fungal communities do react to pollution, there is a significant lack of information regarding the changes in the fungal community's structure, caused by marine pollution. In this study, we aim to address this gap in knowledge by investigating the range and makeup of fungal species present in marine environments in a polluted bay in Tunisia, spanning a biodiversity hotspot (Monastir Bay). Sequence analysis of the internal transcribed spacer region from culturable mycobiome and physicochemical parameters were investigated at seven sites in the bay. A total of 32 fungal taxa were identified at the genus and/or species levels and were assigned to four major groups (Aspergillacae 37.5%, Dothiomyceta 21.87%, Sordariamyceta 28.12%, and Yeasts 12.5%) with a remarkable predominance of Aspergillus genus. Assessment of the Shannon-Wiener diversity index and the Simpson dominance index revealed that the highest species diversity index (0.84) was recorded at the Kheniss site. Our results suggest the existence of diverse fungal communities, can be considered a useful community model for further ecological and evolutionary study of fungi in the bay.

Image-derived indicators of phytoplankton community responses to Pseudo-nitzschia blooms.

Phytoplankton populations in the natural environment interact with each other. Despite rising global concern with Pseudo-nitzschia blooms, which can produce the potent neurotoxin domoic acid, we still do not fully understand how other phytoplankton genera respond to the presence of Pseudo-nitzschia. Here, we used a 4-year high-resolution imaging dataset for 9 commonly found phytoplankton genera in Narragansett Bay, alongside environmental data, to identify potential interactions between phytoplankton genera and their response to elevated Pseudo-nitzschia abundance. Our results indicate that Pseudo-nitzschia tends to bloom either concurrently with or right after other phytoplankton genera. Such bloom periods coincide with higher water temperatures and lower salinity. Pseudo-nitzschia image abundance tends to increase the most from March-May and peaks during May-Jun, whereas the image-derived biovolume and width of Pseudo-nitzschia chains increase the most during Jan-Feb. For most phytoplankton genera, their relationship with Pseudo-nitzschia abundance is noticeably different from their relationship with Pseudo-nitzschia image features. Despite the complexity in the phytoplankton community, our analysis suggests several ecological indicators that may be used to determine the risk of harmful algal blooms.

Identification of the nitrate pollution in surface water of Dongshan Bay based on stable isotope technology.

Identifying and quantifying water nitrate pollution is crucial for managing aquatic environment of a bay. Dongshan Bay, a significant semi-enclosed bay in the southeastern coastal area of Fujian Province, features mangrove and coral reef ecosystems at its estuary and bay mouth, respectively. Dongshan Bay is impacted by human activities such as mariculture. We quantified and analyzed nitrate pollution status in the surface waters of Dongshan Bay by measuring physicochemical parameters, stable isotopes (δ15N-NO3-, δ18O-NO3- and δ15N-NH4+) of the surface waters, and using statistical methods including the MixSIAR isotope mixing model. The results showed that the concentrations of chlorophyll a and dissolved inorganic nitrogen in the surface waters exhibited a noticeable gradient change, decreasing from the estuary of the Zhangjiang River to the mouth of Dongshan Bay. The maximum concentrations of chlorophyll a, NH4+, NO3- and NO2- were 45.2 µg·L-1, 52.67 µmol·L-1, 379.2 µmol·L-1 and 3.93 µmol·L-1, respectively. The nitrogen and oxygen isotope values of NH4+ and NO3- in the surface waters showed significant spatial variations. According to the MixSIAR model results, nitrogen sources in the surface waters of Dongshan Bay were mainly freshwater inputs of the Zhangjiang River estuary, aquaculture wastewater, and groundwater. The freshwater input from the Zhangjiang River estuary contributed the most (25.2%), while aquaculture wastewater, groundwater and urban sewage accounted for 24.6%, 19.0%, and 15.1%, respectively. It is evident that freshwater input from the Zhangjiang River estuary is the primary source of nitrate in the surface waters of Dongshan Bay.

[Impact of road infrastructure on ecological networks in the Guangdong-Hong Kong-Macao Greater Bay Area, China]. / 粤港澳大湾区道路基础设施对生态网络的影响.

The construction of road infrastructure has resulted in the degradation of wildlife habitat and the decrease of ecological network connectivity and stability. Studying the impacts of road infrastructure on wildlife life and migration is significant for regional wildlife conservation and ecological network optimization. We assessed the impacts of road infrastructure on habitat suitability using the MaxEnt model based on wildlife occurrence point data in the Guangdong-Hong Kong-Macao Greater Bay Area. We constructed the ecological networks and identified ecological breakpoints using the minimum cumulative resistance model, and compared the ecological network connectivity of different scenarios with the landscape connectivity index and graph theory index. The results showed that railway and motorway significantly affected habitat suitability, causing a decrease in wildlife habitat suitability. Affected by road infrastructure, the fragmentation of ecological sources intensified, the resistance of ecological corridors increased, and the ecological network connectivity and stability significantly decreased. A total of 536 ecological breakpoints were identified, which were concentrated in the area adjacent to ecological sources. The results would provide important scientific references for wildlife habitat conservation and ecological restoration in the Guangdong-Hong Kong-Macao Greater Bay Area.