Estuary

Pollution characteristics, distribution, risk and sources of 7 heavy metals in sediments of Yangtze River Estuary were investigated. Total concentration ranges of As, Cr, Cu, Cd, Pb, Zn and Ni were [0, 16.5], [1.48, 51.3], [2.66, 318], [0, 0.99], [35.6, 992], [8, 91.3] and [1.88, 108] mg/kg, respectively. Based on the potential ecological risk index and Geoaccumulation index, it was determined that Pb is the most polluted heavy metal. According to class I standard of "Marine sediment quality" of China, mean baseline levels multiples were Pb (8...

This study describes the development of the CHANnelized Optical System II (CHANOS II), an autonomous, in situ sensor capable of measuring seawater dissolved inorganic carbon (DIC) at high frequency (up to ∼1 Hz). In this sensor, CO2 from acidified seawater is dynamically equilibrated with a pH-sensitive indicator dye encapsulated in gas-permeable Teflon AF 2400 tubing. The pH in the CO2 equilibrated indicator is measured spectrophotometrically and can be quantitatively correlated to the sample DIC. Ground-truthed field data demonstrate the sensor's capabilities in both time-series measurements and surface mapping in two coastal sites across tidal cycles...

A comprehensive study was conducted to assess heavy elemental pollution in the Savannah River, which flows through diverse landscapes encompassing agricultural, industrial, and commercial zones in South Carolina and Georgia. The investigation focused on the impacts of various anthropogenic activities on the river, potentially harming human health and aquatic ecosystems. Thirty samples, collected from the beginning of the Savannah River at Lake Hartwell to the Savannah River estuary near the Atlantic Ocean, were analyzed using Instrumental Neutron Activation Analysis...

The Arab region is located in an arid environment and suffers from water scarcity and poor water quality which are expected to become more severe in coming years due to global warming. In this study, the groundwater quality of 205 wells in Qatar was investigated. The physical parameters of pH, electrical conductivity (EC), total dissolved solids (TDS), salinity, inorganic carbon (IC), and organic carbon (OC) were determined. The study characterized the concentrations of major anions of Cl, F, Br, NO3 , PO4 , and SO4 , and major cations of Ca, K, Mg, and Na...

Microbial mediated nitrogen (N) transformation is subject to multiple controlling factors such as prevailing physical and chemical conditions, and little is known about these processes in sediments of wet-dry tropical macrotidal systems such as Darwin Harbour in North Australia. To understand key transformations, we assessed the association between the relative abundance of nitrogen cycling genes with trophic status, sediment partition and benthic nitrogen fluxes in Darwin Harbour. We analysed nitrogen cycling gene abundance using a functional gene microarray and quantitative PCRs targeting the denitrification gene (nosZ) and archaeal ammonia oxidation (AOA...

Atlantic bottlenose dolphins are extensively studied, though little has been published regarding their occurrence patterns in the large and highly urbanized estuary of the Chesapeake Bay, USA. To address this knowledge gap, the Chesapeake DolphinWatch project was initiated in the summer of 2017. Utilizing a citizen science (also known as volunteer science) methodology, members of the public were encouraged to report dolphin sightings through a specialized mobile (iOS and Android) and web-based (https://chesapeakedolphinwatch...

Manganese (Mn) is a vital micronutrient and participates in multiple biochemical reactions and enzyme catalytic activities. Its cycling is tightly connected with iron (Fe) and nitrogen (N). Although coastal sediments are recognized as an important source of dissolved Mn to marine waters, this contribution remains inadequately quantified. In the summer of 2019 and 2020, we investigated benthic fluxes of dissolved Mn, Fe and ammonia (NH4 + ) in the Changjiang Estuary and East China Sea shelf using the 224 Ra/228 Th disequilibrium approach...

The Reloncaví estuary in southern Chile is famous for its aquaculture. However, recurring harmful algal blooms have adversely affected mussel production. Therefore, regular monitoring of algal toxins is urgently needed to better understand the contamination status of the estuary. In this study, we quantified 15 types of lipophilic shellfish toxins in Metri Bay in the Reloncaví estuary on a biweekly basis for 4 years. We identified algal species using microscopy and metabarcoding analysis. We also measured water temperature, salinity, chlorophyll-a, and dissolved oxygen to determine the potential relationships of these parameters with algal toxin production...

The St. Lawrence Estuary (SLE) beluga (Delphinapterus leucas) population is highly exposed to an array of contaminants that were identified as one of the causes to the non-recovery of this endangered and declining population. In the last decade, an increasing number of parturition-associated complications and calf mortality has been reported in this population. It was suggested that elevated exposure to organohalogens (e.g., the halogenated flame retardants polybrominated diphenyl ethers [PBDEs]) and stress could play a role in this phenomenon by perturbing thyroid hormones...

Benthic microbial communities play a crucial role in maintaining the stability and function of estuarine ecosystems. However, their organization and response to multiple stresses in severely disturbed coastal areas remains to be elucidated. In this study, we revealed the presence of contrasting benthic bacterial and fungal communities in the Liaohe (LH) and Yalujiang (YLJ) estuaries, which are located at similar latitudes and are characterized by similar climates but are subjected to different levels of anthropogenic pressure...

The salt marsh harvest mouse (Reithrodontomys raviventris) is an endangered species, endemic to the San Francisco Bay Estuary, that co-occurs with the more broadly distributed species, the western harvest mouse (Reithrodontomys megalotis). Despite their considerable external morphological similarities, the northern subspecies of salt marsh harvest mice have relatively longer and thicker tails than do western harvest mice, which may be related to their abilities to climb emergent marsh vegetation to avoid tidal inundation...

Estuaries are vulnerable to oceanic and atmospheric climate change. Much of the research investigating climate change impacts on estuaries is focused on saltwater intrusion within surface water due to drought and rising sea levels, with implications for ecosystems and humans. Groundwater and soil near estuaries may also be influenced, as estuary salinity and hydraulic head changes can impact soils and aquifers not previously at risk of salinization. This study was conducted to address knowledge gaps related to present and future groundwater salinity distribution in a groundwater system connected to a macro-tidal estuary that experiences a tidal bore due to its hydraulic connection to the Bay of Fundy in Nova Scotia, Canada...

The massive use of antibiotics has led to the escalation of microbial resistance in aquatic environment, resulting in an increasing concern regarding antibiotic resistance genes (ARGs), posing a serious threat to ecological safety and human health. In this study, surface water samples were collected at eight sampling sites along the Yangtze River Estuary. The seasonal and spatial distribution patterns of 10 antibiotics and target genes in two major classes (sulfonamides and tetracyclines) were analyzed. The findings indicated a high prevalence of sulfonamide and tetracycline resistance genes along the Yangtze River Estuary...

UNLABELLED: Phytoplankton are important drivers of aquatic ecosystem function and environmental health. Their community compositions and distributions are directly impacted by environmental processes and human activities, including in the largest estuary in North America, the Chesapeake Bay. It is crucial to uncover how planktonic eukaryotes play fundamental roles as primary producers and trophic links and sustain estuarine ecosystems. In this study, we investigated the detailed community structure and spatiotemporal variations of planktonic eukaryotes in the Chesapeake Bay across space and time for three consecutive years...

Understanding of the photochemical ozone (O3 ) pollution over the Pearl River Estuary (PRE) of southern China remains limited. We performed an in-depth analysis of volatile organic compounds (VOCs) data collected on an island (i.e., the Da Wan Shan Island, DWS) located at the downwind of Pearl River Delta (PRD) from 26 November to 15 December 2021. Abundances of O3 and its precursors were measured when the air masses originated from the inland PRD. We observed that the VOCs levels at the DWS site were lower, while the mixing ratio of O3 was higher, compared to those reported at inland PRD, indicating the occurrence of photochemical consumption of VOCs during the air masses transport, which was further confirmed by the composition and diurnal variations of VOCs, as well as ratios of specific VOCs...

Agricultural run-off in Australia's Mackay-Whitsunday region is a major source of nutrient and pesticide pollution to coastal and inshore ecosystems of the Great Barrier Reef. While the effects of run-off are well documented for the region's coral and seagrass habitats, the ecological impacts on estuaries, the direct recipients of run-off, are less known. This is particularly true for fish communities, which are shaped by the physico-chemical properties of coastal waterways that vary greatly in tropical regions...

Understanding heavy metals in rivers is crucial, as their presence and distribution impact water quality, ecosystem health, and human well-being. This study examined the presence and levels of nine heavy metals (Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn) in 16 surface water samples along the Chao Phraya River, identifying Fe, Mn, Zn, and Cr as predominant metals. Although average concentrations in both rainy and dry seasons generally adhered to WHO guidelines, Mn exceeded these limits yet remained within Thailand's acceptable standards...

Under global warming, heat stress can induce the excessive production of reactive oxygen species, causing irreversible damage to aquatic animals. It is essential to predict potentially harmful impacts on aquatic organisms under heat stress. Eriocheir sinensis, a typical crustacean crab, is widely distributed in China, American and Europe. Parent E. sinensis need migrate to the estuaries to reproduce in winter, and temperature is a key environmental factor. Herein, we performed a comprehensive transcriptomic and proteomic analysis in the hepatopancreas of E...

Although saltmarshes are critical coastal ecosystems they are threatened by human activities and sea-level rise (SLR). Long-term restoration and management strategies are often hampered by an insufficient understanding of the past, present, and future processes that influence tidal wetland functionality and change. As understanding vegetation distribution in relation to elevation and tidal hydroperiod is often the basis of restoration and management decisions, this study investigated the relationships between micro-topography, tidal hydroperiod, and the distribution of saltmarshes, mangroves, and unvegetated flats in a tropical estuary situated within a Great Barrier Reef Catchment in North Queensland, Australia...

This study investigates the sedimentation behaviors of microplastics (MPs) within a typical meso-scale river estuary, the Yalu River Estuary (YRE) and its riverine reservoir. It analyzes sediment cores in two habitats of Yalu River, revealing changing MPs abundance over time. Results highlight significant differences in riverine and estuarine MPs deposition. Reservoir sample contains more MPs in fragments. Color variations are notable in estuarine samples but minimal in reservoir sample. After 1980, estuarine cores show an increase in coarser MPs, likely due to growth of aquaculture activities...