Monitoring and Assessment of Environmental Quality in Coastal Ecosystems, 4th Edition

Marine environmental quality is a complex and multifactorial concept that encompasses the assessment of the physical, chemical and biological status of a given marine environment as opposed to its natural state, as well as the measurement of the levels of contaminants present in water, sediments and organisms. To preserve the structure and function of marine ecosystems and their processes it is therefore pivotal to ensure their good environmental status. Coastal environments, in particular, are especially prone to degradation, fragmentation, pollution and destruction since these are worldwide human densely populated areas, where the anthropogenic pressure has been increasing for centuries. Also, as areas of intense exchange of energy and materials between the land and the oceans, they are especially sensitive and vulnerable to natural and anthropogenic disturbances [1]. Global climate changes and their multiple effects, such as ocean warming and acidification, rising sea-levels, and extreme storms and floods, impose additional threats to coastal environments. These several types of pressures act synergistically, increasing the detrimental effects beyond what would be anticipated from the addition of independent pressures [2].

Monitoring and assessment are fundamental components for effective marine management [3]. In fact, across the world there are several marine conventions and legislations (e.g., Cartagena Convention—Convention for the Protection of the Caribbean Sea; Water Framework Directive and Marine Framework Directive in the European Union; Clean Water Act in the USA) with monitoring and assessment programs aimed at defining ecological quality of marine ecosystems in an integrative way, by making use of several biological, physico-chemical and pollution elements [4]. Scientists have been developing distinct approaches to address those issues, with hydrological and sediment dynamics modeling, water quality monitoring and assessment, presence of pollutants and the development of ecological indicators, being some of the most common ones.

Continuous monitoring and management strategies driven by data collections are essential in the process of decision-making regarding coastal areas vulnerable to erosion [5]. Also, the development of structured frameworks that allow researchers to steer through the available technologies and datasets, according to their suitability to distinct monitoring scenarios and needs, is very important to support coastal management and improve the resilience of coastlines [6]. As such, developing new methodologies and technologies, or improving and integrating already existing ones, for monitoring and managing coastal erosion and other coastal hazards is crucial.

Multidisciplinary approaches that combine water quality, chemical contamination, and biological or ecological elements (e.g., 7, 8), are very useful for environmental monitoring and assessment, and become especially powerful tools when long-term datasets are available. The synergies obtained from the involvement of various expertise can help to deepen the understanding of environmental quality, which is fundamental for the protection of coastal ecosystems [7]. Furthermore, the combination of biological and chemical monitoring methods offers the comprehensive assessment currently needed, given the increasing anthropogenic impacts [8]. Finally, the use of integrated methods, such as multiple criteria analysis, that combine environmental, ecological, social and economic priorities, can help all parties involved to rationalize their views and create policies dependent on sound science [9]. As previously stated by [10], integration is the key to safeguarding beaches and their unique biodiversity, and to maintaining their benefits for the following generations through sustainable development: this statement was originally applied by those authors in reference to sandy beaches, but it can be further extended to all coastal ecosystems.

The fourth edition of the Special Issue on “Monitoring and Assessment of Environmental Quality in Coastal Environments” aimed to bring together contributions from several international experts focusing on the application of distinct tools and methods, in relation to diverse coastal environments with a varied geographical origin. After the rigorous peer review processes of Environments, twelve out of seventeen initial submissions were accepted for publication and inclusion in this Special Issue (eleven research articles and one review).

Contribution 1 reviewed the innovative remediation techniques available for dredged sediments in order to promote their multiple sustainable beneficial reuses, by turning them into valuable resources. The authors emphasize the integrated strategies and multidisciplinary approaches combining technological innovations that further improve sediment reuse to foster economic growth and environmental protection.

Several contributions explored the highly complex transition environments. Contributions 2 and 3 were focused on the iconic Venice Lagoon (Italy). Due to the relevance of the sediment load in sustaining tidal and subtidal habitats of the lagoon, contribution 2 analyzed the freshwater discharge and the sediment transport in two estuarine sections of the Dese River, the main tributary of this large wetland. The study highlighted that high-resolution monitoring of sediment delivery is critical for the protection of the estuarine areas of the Venice Lagoon, which has been facing an erosive trend in recent decades [11]. Major changes in the macroalgal assemblages of the Venice Lagoon in the last twenty years, caused by temperature increases, have been addressed in contribution 3. The authors concluded that the native cold-water taxa, mainly Phaeophyceae, are in sharp decline, while thermophilic species, namely non-indigenous Rhodophyceae species, are increasing and replacing the once dominant native taxa.

One of the largest lagoons in Europe, the Oder/Szczecin Lagoon in the Baltic Sea region, was analyzed in contributions 4 and 5. Using a combination of monitoring data from the last 40 years and 3D ecosystem modeling, contribution 4 evaluated changes in phytoplankton abundance and diversity on distinct temporal scales, from short-term effects to long-term trends. The authors concluded that, while phytoplankton biomass and composition presented pronounced interannual and short-term variability, the average annual phytoplankton biomass and the long-term species composition did not change significantly. However, heat- and cold waves did not show consistent immediate effects. In contribution 5, 3D ecosystem model simulations over a 10-year period, complemented with socio-economic data, to assess the ecosystem services of the Oder/Szczecin Lagoon were performed and analyzed. Model simulations revealed that nitrogen retention was the lagoon’s most important ecosystem service, with the highest economic income, and that commercial fisheries had been diminishing its economic significance in the lagoon. According to their conclusions, the authors highlighted that ecosystem services and potential changes derived from the implementation of human interventions (e.g., channel deepening) should be considered in environmental impact assessments.

The morphology, the drainage density and drainage efficiency of three distinct marsh landscapes of the Ashepoo, Combahee, and Edisto (ACE) Basin, of the southeastern North American coastal plain in South Carolina (USA), were explored in contribution 6, using high-resolution digital elevation models. The findings of those authors suggest that drainage density and drainage efficiency should be considered separately, with drainage efficiency being mostly influenced by the structure and spatial arrangement of creek networks within a marsh.

Contribution 7 analyzed the sand dune ponds of the wetlands of Doñana National Park (in southwestern Spain), which is one of the most important wetlands in Europe, recognized as a UNESCO World Heritage Site and a Ramsar Wetland of International Importance. This study aimed to characterize the thermal regime of surface water and groundwater on those environments to identify potential trends related to the rising temperatures and the decreasing precipitation over an eight-year time series, as well as to study patterns in groundwater flow dynamics. The findings of this contribution warrant the analyses of the sensitivity of those wetlands to global environmental change and grant the characterization of recharge and discharge flows in this coastal aquifer.

In the coastline of the Gulf of Trieste (Adriatic Sea, Italy), contribution 8 analyzed the spatial distribution, the seasonal patterns and the temporal trends of toxic phytoplankton, together with physico-chemical parameters, nutrient concentrations and precipitation, along four selected shellfish farming sites on a long-term dataset. The results demonstrated that the spatial distribution of toxic phytoplankton presented significant gradients and that nutrients and the physico-chemical parameters varied seasonally. Therefore, the study provides a valuable basis for further approaches with the aim of analyzing the impact of climate variability in the dynamics of toxic phytoplankton at the Gulf of Trieste.

Within the context of coastal erosion monitoring, contribution 9 proposes a novel multi-platform methodology, integrating field-based measurements with online Earth Observation data, to create a comprehensive and accessible toolkit for quantifying beach morphodynamical characteristics. The methodology was tested with real conditions using beaches of the Bocas del Toro Archipelago, on the Caribbean coast of Panama, as case study. The use of the multi-platform toolkit revealed to be advantageous in capturing multiscale dynamics, deepening the understanding of coastal morphodynamics, which is especially relevant for remote tropical beaches that often lack essential baseline data.

A mangrove monitoring program across 18 countries over the wider Caribbean, on a long-term temporal series and focused on the dominant mangrove species Rhizophora mangle, was performed under the Caribbean Coastal Marine Productivity (CARICOMP) program and two decades of those results were presented by contribution 10 of this Special Issue. The main objective of this contribution was to reveal the spatial and temporal variability of the monitored mangroves across the region and investigate potential drivers of change on these coastal ecosystems. The results revealed high variability in mangrove structure and productivity across the study region and a lack of consistency among sites in long-term trends of mangrove productivity, suggesting that local-level drivers of forest structure, productivity and change are important. Also, according to the authors, conservation and management strategies should be site-specific and reinforced by the monitoring of local environmental events.

Aimed at analyzing the risks of biological invasion in mangrove ecosystems caused by port activities in their vicinity, contribution 11 presents the opportunities and challenges faced by Latin America’s largest and most important port complex, the Port of Santos (Brazil), regarding its activities and transport flows and the potential for technological use to mitigate environmental conflicts. The results revealed that the intense and constant flow of international vessels into the Port of Santos leads to a persistent threat of biological invasion, reinforcing the role of ships as vectors for the transport of exotic species. Also, the authors highlight that control measures, mediated by effective policies, regulations and technologies, should be implemented in the short term to avoid destabilizing the adjacent mangrove ecosystems and causing socio-economic losses.

Finally, in light of the rapidly warming rates faced by Antarctica and their effects on seawater temperature and salinity at intertidal environments, contribution 12 investigated the combined effects of salinity fluctuations and temperature rise on the health status and physiology of the Antarctic intertidal macroalga Adenocystis utricularis. The findings demonstrated that warming temperature had a negative effect on A. utricularis oxidative response at a control salinity (33 psu), but that an altered stress response to salinity fluctuations arises under thermal stress, revealing an interactive effect between salinity and temperature.