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Flooding and environmental challenges for Venice and its lagoon : state of knowledge
Presenting scientific and technical synthesis of interdisciplinary research into the environmental threats to Venice and its lagoon, this text also looks at other cities under threat from rising sea levels, such as London and St. Petersburg.
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Characteristics, Restoration, and Enhancement of Southern California Lagoons
The successful enhancement and restoration of coastal lagoons requires a comprehensive understanding of the physical and biological conditions in each lagoon and the processes that influence the lagoon's performance. Since lagoons differ substantially from one location to another, the problems that affect lagoon performance differ as well. Coastal lagoons in Southern California (Figure 1) tend to be small with surface areas of a few hundred hectares or less and mean water depths of less than 2m. Careful monitoring studies of lagoons, together with historical reviews and data from previous studies, enable wetland scientists to recommend successful, cost-effective, environmentally sound plans for enhancement and restoration of Southern California lagoons. Recent understanding of the settings and physical processes controlling lagoon performance will enable us to produce improved schemes to enhance these systems. Usually the biological performance of a wetland depends on improvement of the physical parameters, such as tidal flushing, water quality, freshwater flow reduction, and channel and basin sedimentation. Other factors that should be taken into consideration are the impacts of the wetland on adjacent beaches, the response of the wetland to dry and wet periods, any possible or expected future climate changes, and biodiversity management. This paper discusses cases of environmental impacts on selected Southern California lagoons, together with proposed or existing projects to reduce or mitigate these impacts.
Journal Article
Assessment of Ecosystem Services Provided by Macrophytes in Southern Baltic and Southern Mediterranean Coastal Lagoons
The ecological importance of macrophytes is well known and reflected in nature protection law, for example, as a key biological quality element. However, the socio-economic role, such as the impact of macrophyte presence on recreational activities, is often overlooked. The purpose of this study was to assess the human benefits (or ecosystem services) provided by macrophytes. We developed a list of 25 macrophyte ecosystem services and 79 assessment indicators based on expert knowledge and literature data. First, hypothetical scenarios of coastal lagoons were developed to assess the impact of different ecological states (i.e., macrophyte coverage) and management measures (i.e., fisheries) on the ecosystem service provision. Scenario assessments were carried out by stakeholder workshops and literature search. Second, the ecosystem service potential of submerged and emergent macrophyte habitats were assessed by macrophyte experts and literature data. Results showed that cultural services are most important in terms of the overall actual provision of ecosystem services (scenario assessment) but also showing highest potential of the hypothetical ecosystem service provision (habitat assessment). Highest overall potential is shown for reeds and tall forb communities (83 out of maximum 125), followed by seagrass beds (71) and seaweed communities (61). Our ecosystem service assessment approaches (i.e., scenario and habitat-based) using socio-cultural data (i.e., stakeholders and experts-based) and biophysical data (i.e., indicators-based) can serve as supportive tools for coastal management and policy implementation visualizing the benefits of macrophytes to humans.
Journal Article
Heavy metal content and potential ecological risk assessment of sediments from Khnifiss Lagoon National Park (Morocco)
Coastal lagoons are important but sensitive environments, being transitional zones between land and sea. The Khnifiss lagoon is the most important desert wetland in Morocco, but little data have been produced concerning heavy metal geochemistry and enrichments in the sediments. Therefore, 26 surface sediments (15 intertidal and 11 subtidal) and 2 sediment cores were collected in 2016 and analyzed for a selection of heavy metals. The data were processed to assess the degree of contamination and the corresponding potential ecological risk, using several accumulation/enrichment indices, and the singular and multi-metal risk indices. Mean concentrations in the bottom layers of the two cores, dating from a pre-industrial age according to geochronological analysis, were used as the local geochemical background. The resulting values were on the whole lower than those reported for other areas of the northeastern coast of Morocco. Multivariate statistics were also applied to better understand relationships among variables (metals and other geochemical parameters) and to reveal similarities among sample groups. The results showed that, although the lagoon is not yet affected by significant anthropogenic influences, small enrichments can be recognized, especially for Ni and Cd. The cause may be related to the proximity to the main national highway, the vehicles and machinery used in the saltworks located in the area, and the small harbors used principally for fishing. In addition, industrial emissions from the Atlantic coast of Morocco and adjacent countries can be reasonably attributed as additional contributors to the enrichments. In terms of potential ecological risk, Cd shows the greatest impact compared to the other metals investigated.
Journal Article
Framework for Regional to Global Extension of Optical Water Types for Remote Sensing of Optically Complex Transitional Water Bodies
Water quality indicator algorithms often separate marine and freshwater systems, introducing artificial boundaries and artifacts in the freshwater to ocean continuum. Building upon the Ocean Colour- (OC) and Lakes Climate Change Initiative (CCI) projects, we propose an improved tool to assess the interactions across river–sea transition zones. Fuzzy clustering methods are used to generate optical water types (OWT) representing spectrally distinct water reflectance classes, occurring within a given region and period (here 2016–2021), which are then utilized to assign membership values to every OWT class for each pixel and seamlessly blend optimal in-water algorithms across the region. This allows a more flexible representation of water provinces across transition zones than classic hard clustering techniques. Improvements deal with expanded sensor spectral band-sets, such as Sentinel-3 OLCI, and increased spatial resolution with Sentinel-2 MSI high-resolution data. Regional clustering was found to be necessary to capture site-specific characteristics, and a method was developed to compare and merge regional cluster sets into a pan-regional representative OWT set. Fuzzy clustering OWT timeseries data allow unique insights into optical regime changes within a lagoon, estuary, or delta system, and can be used as a basis to improve WQ algorithm performance.
Journal Article
Assessing the spatiotemporal transformation of a coastal lagoon inlet (1984–2019) using remote sensing and GIS: a study of Khenifiss Lagoon in Southern Morocco
Coastal lagoons are highly dynamic ecosystems that are continually changing in shape and size due to natural processes. This study used satellite imagery, remote sensing, and GIS mapping, along with historical wind and wave data, to comprehensively explore the long-term changes occurring at the Khenifiss Lagoon entrance and its downstream main channel, which is one of the most important wetlands protected by the Ramsar Convention in Morocco. By employing thorough image selection, rigorous corrections, and intricate processing and analysis techniques, this research shed light on the evolution of sediment deposition areas, eroded zones, vegetation coverage, and locations, where dune influence affected sedimentation in this dynamic coastal ecosystem. The investigation spanned from 1984 to 2019 and relied on the analysis of Landsat optical images gathered in 1984, 1990, 2000, 2009, and 2019. During the study period, the entrance to the Khenifiss Lagoon (Foum Agouitir) gradually enlarged, increasing from 1450 m in 1984 to 1650 m in 2019. Concurrently, vegetation coverage within the lagoon's entrance and main channel increased from 53.54 hectares in 2009 to 103.9 hectares in 2019, resulting in a significant decrease in total water body extent. Sediment deposition impacts 206 hectares, considerably surpassing the erosion-affected area of 99.14 hectares. This significant difference emphasizes the rising dominance of sedimentation over erosion at the Khenifiss Lagoon entrance zone. The processes of sedimentation within the lagoon are largely influenced by the dune's advance, which has resulted in silt deposition over an area of approximately 57.39 hectares. These findings highlight the lagoon's exposure to progressive closure and strongly support the need to start a monitoring program to evaluate the lagoon's changing condition, especially at the entrance and the main channel. This study puts forth several recommendations for implementing management strategies aimed at ensuring the sustainability of this coastal ecosystem.
Journal Article
How Sea Level Rise May Hit You Through the Backdoor: Changing Extreme Water Levels in Shallow Coastal Lagoons
Due to their choked geometry, coastal lagoons can attenuate extreme water levels compared to the open sea. However, this protective property is expected to decrease due to sea‐level rise. By studying idealized lagoons in a non‐dimensional parameter space, this study describes non‐linear interactions between tides, storm surges, freshwater fluxes into the lagoon, and sea‐level rise. The non‐dimensional numbers include lagoon geometry and forcing scales. The main objective is to provide an overview of potentially affected lagoons and to highlight the importance of attenuation changes due to sea‐level rise. Tidal and storm surge induced maximum water levels inside lagoons rise faster than sea‐level rise for most of the parameter space. Maximum water levels due to freshwater fluxes rise slower than sea‐level rise for strongly choked lagoons. For compound events, the response between rising faster or slower than sea‐level rise depends strongly on the lagoon geometry. Plain Language Summary Coastal lagoons are known to reduce extreme water levels compared to the open sea due to their narrow and shallow connections to the ocean. However, the rising mean sea level will decrease this protective property. In this study, we investigate lagoons using a simple box model to explore how combinations of tides, storm surges, river discharge, and sea‐level rise will change water levels inside lagoons. The study aims to provide an overview of potentially affected lagoons and to highlight the importance of these processes. Due to sea‐level rise, water from the ocean can more easily flow into the lagoon. Therefore, our results show that maximum water levels inside a lagoon can rise faster than sea‐level rise. On the other hand, river discharge can exit the lagoon more easily at the same time. For this case, water levels inside a lagoon rise slower than sea‐level rise. For events where tides, storm surges, and river discharge are all present, the maximum water level may rise either slower or faster than sea‐level rise, depending on the properties of the lagoon. Further studies are needed to understand the implications for coastal communities. Key Points Tides, storm surges, freshwater fluxes, and sea‐level rise interact non‐linearly on the water level in choked coastal lagoons Maximum water levels inside choked lagoons can increase faster than sea‐level rise due to non‐linear attenuation changes Maximum water levels due to freshwater fluxes increase slower than sea‐level rise
Journal Article