Estuarine Coastal and Shelf Science最新文献

Many coastal regions around the globe experience land loss due to high relative sea level rise rates, declining sediment supply, and a host of other anthropogenic factors. To evaluate possible restoration strategies, we developed a computationally efficient Simplified Biophysical Model (SBM). The SBM includes hydrodynamic, morphodynamic, and marsh inundation components. The hydrodynamic and mineral sediment processes of the SBM are based on open source Delft3D models. The marsh inundation MATLAB module is a simplified vegetation response to salinity and inundation used to estimate annual organic accretion rates. Organic accretion is added annually to the morphodynamic calculations of mineral sediment. The typical run time for the SBM for an area of 4500 km² is ∼0.8, 2.5, and 4.7 days real time for one, three, and five decade simulations, respectively which is considered a computationally efficient for modeling decadal landscape evolution. The utility of the SBM was demonstrated through an application to assess the performance of a sediment diversion in the Barataria Basin in Louisiana, USA. The model results demonstrate the importance of incorporating the impact of salinity and inundation effects on the resilience of marshes subjected to high rates of relative sea level rise. Further, the sediment reduction analysis confirms the critical impact of the Mississippi River sediment decline on potential land building from sediment diversions where 1.5%, and 3% annual declining rates show a reduction in net land gain due to Mid-Barataria Sediment Diversion operation of 30% and 50 %, respectively. This highlights the importance of considering the Mississippi River sediment supply decline in restoration projects’ planning and specifically, sediment diversions.

A mass mortality event (MME) affected the endemic bivalve Pinna nobilis across the Mediterranean Sea in autumn 2016. This event affected specimens of all sizes, depth ranges and habitat types, resulting in a drastic decline in the species population close to 100%. Indeed, the consequences of a potential recovery, and therefore the viability of the populations of the species are unknown. To evaluate the likelihood of success when designing the reintroduction of the species in optimal areas, knowledge of population dynamics is essential. Here we compare two population subunits of Pinna nobilis from two areas with different environmental conditions, located in Cabrera National Park (protected area with low exposure to hydrodynamic activity) and San Telmo (unprotected area exposed to hydrodynamic activity), both in the Balearic Islands. A total of 259 individuals were tagged and monitored annually between 2011 and 2014, prior to the MME. Matrix population models were used to reduce the complexity of the age-structured population dynamics and assessing the degree of elasticity of the population. We showed that the subunit of San Telmo showed highly variable values of demographic rates, higher stochasticity and higher sensitivity to environmental variability than the population subunit of Cabrera National Park. The study shows the importance of the buffering effect of a large population as there are many adult individuals of many size classes in the population subunit of Cabrera National Park, as its age structure helps to cope with highly variable reproductive success. Therefore, these population subunits are more stable regardless of depth and would be a more suitable site for future reintroduction programs.

Water column nutrient concentrations and autotrophy in oligotrophic ecosystems are sensitive to eutrophication and other long-term environmental changes and disturbances. Disturbance can be defined as an event or process that changes the structure and response of an ecosystem to other environmental drivers. The role disturbance plays in regulating ecosystem functions is challenging because the effect of the disturbance can vary in magnitude, duration, and extent spatially and temporally. We measured changes in total nitrogen (TN), dissolved inorganic nutrient (DIN), total phosphorus (TP), soluble reactive phosphorus (SRP), total organic carbon (TOC), and chlorophyll-a (Chl-a) concentrations throughout the Everglades, Florida Bay, and the Florida Keys. This region has been subjected to a variety of natural and anthropogenic disturbances including tropical storms, fires, eutrophication, and rapid increases in water levels from sea-level rise and freshwater restoration. We hypothesized that the rate of change in water quality would be greatest in the coastal ecotone where disturbance frequencies and marine P concentrations are highest, and in freshwater marshes closest to hydrologic changes from restoration. We applied trend analyses on multi-decadal data (1996–2019) collected from 461 locations distributed from inland freshwater Everglades (ridge and slough) to outer marine reefs along the Florida Keys, USA. Total Organic Carbon decreased throughout the study area and was the only parameter with a systematic trend throughout the study area. All other parameters had spatially heterogeneous patterns in long-term trends. Results indicate more variability across a large spatial and temporal extent associated with changes in biogeochemical indicators and water quality conditions. Chemical and biological changes in oligotrophic ecosystems are important indicators of environmental change, and our regional ridge-to-reef assessment revealed ecosystem-specific responses to both long-term environmental changes and disturbance legacies.

Water clarity is an important indicator for the water quality of aquatic ecosystems and measured as Secchi disk depth (Z_SD). In this study, images from Landsat Thematic Mapper (TM), Enhanced Thematic Mapper Plus (ETM+), and Operational Landsat Imager (OLI) over the period from 1984 to 2022 are used to study the spatiotemporal variation in Jiaozhou Bay, a typical semi-enclosed bay in China, and to gain the insights into the drivers for the variation during the study period. The satellite images are first processed to obtain Z_SD, and corrected against the field measurements to ensure the Z_SD to be high-quality, and then the spatial and temporal distributions of Z_SD are analysed. The results show that the regional monthly average Z_SD over the study period are the highest in May and lowest in January. From long-term seasonal observation, it declines most significantly in Summer. In terms of inter-annual variation, the results clearly indicate that 2015 was a turning point, as the regional average Z_SD decreased significantly from 1984 to 2014 at a rate of approximately 0.022 m/year, but significantly increased from 2015 to 2022 with a rate of about 0.049 m/year. The turning trend of the water clarity in Jiaozhou Bay can be mainly attributed to the increasing sunshine duration during 2015–2022, as well as rapidly reduction emissions of industrial waste from Qingdao city during 2015–2016.

Estuarine behaviour is primarily controlled by the interaction of river discharge and tidal mixing. Transient increases in river discharge, which occur naturally during the wet season or can be managed in regulated basins, alter estuarine dynamics and reduce salt intrusion. Two characteristic times have been identified in the response to these river pulses: the adjustment time (the time required to adapt to the peak discharge) and the recovery time (the time required to return to steady state conditions). Previous work has analysed the effect of peak discharge and pulse duration in the adjustment process, focusing on long discharges (i.e. longer than the intrinsic estuarine timescale) and straight channels. This paper presents an idealised 3-dimensional model (Delft3D) to assess the effect of estuarine convergence on the response to short river pulses in tide dominated, well-mixed estuaries. The similarity between the tidal period, the estuarine timescale and the duration of the pulse led to the introduction of the time between tidal and river conditions as an additional parameter in the analysis. The results show that salt intrusion in convergent estuaries have a lower sensitivity to variations in river discharge compared to the behaviour of prismatic estuaries. Conversely, the influence of convergence on changes in salt intrusion due to the increased river discharge gains relevance in convergent estuaries. Seaward transport of salt is significantly enhanced by freshwater releases that occur between early and mid ebb, especially during spring tides. Increasing convergence reduces the asymmetry of the estuarine response, shortens the recovery time, and shifts the onset of maximum salt displacement and the minimum adjustment time. The results are particularly relevant for water management and salt intrusion control in regulated basins with limited resources, as the volume of fresh water used to reduce salt intrusion can be optimised considering the timing of the pulse release, which depends on the tidal conditions at the estuary.

Asian hard clams, Meretrix spp., are found in the coastal waters of the Indo-Pacific region, including Thailand. Climate change is a widespread and escalating global threat to biodiversity and ecosystems. This study aims to examine the current distribution of Meretrix in the Gulf of Thailand. Morphometric and genetic analyses were used for species identification and to understand intra- and interspecies shell variations of for all species we encountered. A genetic and morphometric study revealed the presence of two species of Meretrix. Meretrix meretrix was not found in the lower Gulf of Thailand, while M. astricta was not found in the eastern Gulf of Thailand. This is the first reporting of M. astricta in Thailand since 2010. Three and four genetic haplotypes were revealed for M. meretrix and M. astricta, respectively. The genetic distance within species ranged from 0.002 to 0.007 and 0.002–0.021 in M. meretrix and M. astricta, respectively. The BLAST results for M. astricta sequences showed over a 24% difference compared to related Meretrix species, while our M. meretrix sequences showed a high percentage of similarity with some M. meretrix sequences in the database. This study provides evidence of a recent decline in the species number of Meretrix in the Gulf of Thailand, which is part of the Pacific Ocean region. Species distributions and changes in community composition should be taken into account for management practices to ensure the sustainability of their ecosystems.

Water temperature and dissolved oxygen are two important parameters which affect the ecosystem functions which estuaries provide. As such, we need to understand the long-term change of these parameters in English estuaries to better understand those areas which may be vulnerable in the present and future. Detecting these trends in monitoring data is difficult however, since temporally and spatially heterogeneous sampling has the potential to obscure any long-term component of change. In this study, we use a generalized additive model (GAM) approach to isolate the inter-annual change of water temperature and dissolved oxygen in spot sampled monitoring data across English estuaries. This technique can account for the potentially non-linear variability caused by temporal and spatial variations in sampling throughout the day and year. We find that water temperature in all modelled estuaries has warmed, with an average warming of 0.037 °C/yr between 1990 and 2022, in line with temperature change in rivers and the sea surface around England. For the same period, dissolved oxygen has increased for roughly half of modelled estuaries and decreased for the other half. The variation across English estuaries in these two conditions is best explained by the geographical location of an estuary. Many of the estuaries warming at the greatest rate are those where sea surface temperature increase has also been greatest. We suggest the observed distribution of changes in dissolved oxygen can be explained by three processes: (1) temperature driven change, (2) dissolved oxygen improvement (e.g., reduced nutrient inputs through wastewater management regulation) and (3) changes in the number of primary productivity-induced super saturation events. This study provides a comprehensive look at temperature and dissolved oxygen change across English estuaries over the past ∼30 years, which may provide information on the processes behind how these water quality parameters have changed and will continue to do so.

A large number of artificial wetlands have replaced natural wetlands along waterbird migration routes to supply breeding, resting and feeding grounds for waterbirds. Effective identification of potential artificial wetlands that could serve as suitable habitats for waterbirds can provide important reference for field investigation and waterbird conservation. In this study, the habitat suitability of the Pied Avocet in the Yellow River Delta (YRD), China was simulated with the optimized MaxEnt model based on its occurrence records and environmental variables. The results showed that the MaxEnt model could well predict the habitat suitability of the Pied Avocet (Recurvirostra avosetta) in the YRD. The suitable habitats were distributed in the specific areas of the coastal zone, and artificial wetlands such as salt pans and mariculture ponds were the main components in the high-suitability area. The top three environmental factors affecting habitat selection were the land use and land cover (LULC), distance to the coastline and normalized difference vegetation index (NDVI). This paper emphasizes the role of artificial wetlands in providing suitable habitat for waterbirds. In order to better protect the habitat of waterbirds and alleviate human-bird conflict in the YRD, some targeted suggestions were put forward for the management gap of artificial wetlands. This study has strong practical significance for the protection and habitat management of waterbirds in the YRD. The methodology we employed is transferable to other wetlands, where efficient management is inhibited due to a lack of comprehensive field investigations.

Anthropogenic pressures exerted on coastal areas, combined with climate change, and accelerated sea level rise, result in the loss of natural habitats. At the same time, the number of coastal protection and defense structures have increased considerably and may become the dominant habitat in many intertidal regions. In this study we characterize the epibiota of artificial substrates (granite blocks) from coastal defense structures used to contain the effects of rising sea levels, and the same type of artificial substrate found in contact with coastal reefs located on Serrambi beach, northeast of Brazil. We mapped, measured, and photographed 45 artificial granite blocks and their surroundings in the field. A gradient was found for the number of taxa on the blocks, from high coverage by macroalgae to extensive non-colonized areas. However, it was observed that the closer to the natural reef the greater the taxonomic richness. Our results also indicate that the factor that best explains the colonization of blocks is the coverage of their surroundings, thus, few organisms were found on blocks whose surrounding unconsolidated sediment area was very extensive. In our wind and sun exposure simulation, granite rock demonstrated a more accelerated and greater level of heating (up to 3 °C) compared to fragments of natural substrate, although the variation in the slightly lighter colored and smaller granite block resembles the variation in the reef fragment. We suggest that the use of lighter-colored granite blocks at mid-coastal levels can increase the colonization rate of these substrates.

In this paper, one- and two-dimensional statistical analyses of significant storm parameters were conducted along natural and protected coasts of the Dziwnów Spit, based on quantiles and concentration ellipses. In the one-dimensional analysis, the quantiles of 0.9, 0.99 and 0.999 erosion magnitude D, sea level F, significant wave height H and storm duration T were determined, and these quantiles correspond to significant storm occurrence once every 10, 100 and 1000 years, respectively. To account for the influence of other variables on the erosion magnitude, log-linear models describing the linear dependence of log(D) on F and log(D) on F and H were built. Based on these models, the corresponding quantiles for the erosion magnitude D were also determined. In the multivariate case, using the 2-dimensional normal distribution, (log(D), F), (log(D), H), and (log(D), T) concentration ellipses were determined for the above pairs of parameters for probabilities of 0.9, 0.99 and 0.999, respectively. The application of one-dimensional distribution results in the lowest values of eroded material of dune, while the use of concentration ellipses estimates the highest values of dune erosion. Moreover, the developed log-linear models better predict the values of eroded material of dune along natural coast than on protected one.