The replacement of natural marine habitats with less structurally complex human infrastructure has been linked to the homogenisation of epibenthic assemblages and associated changes in fish assemblages. To mitigate these impacts, eco-engineering efforts have focussed on increasing the physical and biogenic complexity of artificial structures, in the form of crevices added to seawalls and the seeding of the substrate with habitat-forming organisms such as oysters. While these studies have assessed how these interventions affect epibenthic assemblages, the effect of these strategies on the behaviour, such as feeding and habitat use, of different functional groups of fish (e.g. cryptobenthic and pelagic) remains uncertain. To do this, we manipulated complexity on seawalls by adding concrete tiles with different physical (flat or structured with crevices and ridges) and biogenic (seeding with two common habitat-forming species or naturally recruited fouling) complexities. We assessed pelagic and cryptobenthic fish species composition, abundance, interaction time with the tiles and number of feeding bites on three occasions 8–12 months after deployment. Cryptobenthic fish interacted more with physically complex tiles than flat tiles, regardless of biogenic complexity. In contrast, cryptobenthic fish fed more from flat tiles compared to physically complex tiles, and also appeared to feed more from tiles seeded with oysters. Pelagic fish interacted and fed more from naturally fouled tiles compared to unfouled control tiles, regardless of physical complexity. This study showed that manipulating complexity at the scales used here affects behaviour of fish, but it does not affect fish community. Increasing physical complexity facilitated fish use of seawalls as habitat by providing refuge, while it also hindered fish feeding by providing refuge for their prey. Cryptobenthic fish are important trophic linkages in their ecosystems and we have shown that by changing habitat complexity, we can change the habitat use and feeding activity of these fish, allowing them to fulfil this essential ecosystem role.
We argue that there is a separation between studies of the biophysics of natural and “built” marine canopies. Here, by “built” we specifically refer to floating, suspended aquaculture canopies. These structures, combining support infrastructure and crop, exhibit several unique features relative to natural marine canopies, in that they take a particular species, suspend them in spatially structured, mono-cultured arrangement and then induce a systematic harvest cycle. This is in contrast to natural canopies that are irregular and variable in form, have natural recruitment and growth, and sustain some level of biodiversity and more exposed to climate extremes. We synthesize published work to identify the points of difference and similarity with natural canopy studies. This perspective article identifies four main themes relating to (i) key scales, (ii) structural configuration, (iii) connections between biology and physics and (iv) connecting natural and built canopy science. Despite clear differences between natural and built canopies, they have more in common than not and we suggest that both sub-fields would benefit from better connection across the divide.
Over the last decade there has been a global effort to eco-engineer urban artificial shorelines with the aim of increasing their biodiversity and extending their conservation value. One of the most common and viable eco-engineering approaches on seawalls is to use enhancement features that increase habitat structural complexity, including concrete tiles molded with complex designs and precast “flowerpots” that create artificial rock pools. Increases in species diversity in pits and pools due to microhabitat conditions (water retention, shade, protection from waves, and/or biotic refugia) are often reported, but these results can be confounded by differences in the surface area sampled. In this study, we fabricated three tile types (n = 10): covered tile (grooved tile with a cover to retain water), uncovered tile (same grooved tile but without a cover) and granite control. We tested the effects of these tile types on species richness (S), total individual abundance (N), and community composition. All tiles were installed at 0.5 m above chart datum along seawalls surrounding two island sites (Pulau Hantu and Kusu Island) south of Singapore mainland. The colonizing assemblages were sampled after 8 months. Consistent with previous studies, mean S was significantly greater on covered tiles compared to the uncovered and granite tiles. While it is implied in much of the eco-engineering literature that this pattern results from greater niche availability allotted by microhabitat conditions, we further investigated whether there was an underlying species-individual relationship to determine whether increases in S could have simply resulted from covered tiles supporting greater N (i.e., increasing the probability of detecting more species despite a constant area). The species-individual relationship was positive, suggesting that multiple mechanisms are at play, and that biodiversity enhancements may in some instances operate simply by increasing the abundance of individuals, even when microhabitat availability is unchanged. This finding underscores the importance of testing mechanisms in eco-engineering studies and highlights ongoing mechanistic uncertainties that should be addressed to inform the design of more biodiverse seawalls and urban marine environments.
Seawater desalination is increasingly being pursued to address freshwater shortages. In California, multiple coastal seawater desalination facilities have been proposed to diversify water portfolios and to increase reliability of water supply. This paper explores local residents support for a newly constructed desalination plant in Carlsbad, a small coastal community in Southern California. The plant is the first high-capacity desalination facility in California and started operation in December 2015. We found strong support for the desalination plant as 71.9% of residents reported support for the plant. Only 15.5% of respondents were undecided indicating that residents had a clear opinion on the plant. Perceptions about local water resources were significant predictors of support. Attitudes may change over time if the state of water resources and perceptions thereof change. Expected outcomes of the plant also predicted support. An increase in available drinking water was a positive predictor, while environmental and social impacts were negative predictors. Economic impacts in terms of an increase in the price of water did not influence local support. Ethnicity and age were the only socio-demographic variables that had an effect on support suggesting that the socio-demographic profile of a community may not be a good predictor of community support or rejection of this water supply technology.
This literature review encompasses more than one-hundred and sixty worldwide studies on artificial reefs (ARs) in terms of their design, application, performance and management. Over the past three decades, research on ARs has increased remarkably, suggesting an increase in social and economic aspects of ARs. The scope of AR research has largely expanded from early AR design and deployment to improve fisheries to various additional purposes. In particular, recent research on ARs has had a tendency to focus on variations in the community structure or composition of ARs, suggesting that the purpose of AR research has shifted from improving fisheries as a resource to rehabilitation of marine ecosystems. Most countries are expected to make active use of AR functions, even if the objective of deployment might be different for each case. Consequently, AR research will most likely expand and evolve to span multiple purposes in the future.
The coastline of Qatar is a rich mosaic of productive and diverse ecosystems including mangrove forests, intertidal mudflats (sabkha), seagrass beds, and coral reefs. These ecologically interconnected ecosystems contain a substantial proportion of Qatar's total biodiversity, and support an estimated 97% of the >US$ 67 million in annual commercial fisheries, the highest value resource sector after petroleum. The extreme environmental conditions that characterize Qatar has led to fauna that are robust compared with other regions, but makes them highly sensitive to further pressure from anthropogenic stress. These vulnerable ecosystems have come under increasing pressure in recent decades as a result of dramatic expansion of coastal development, and threats to these ecosystems are likely to accelerate in the coming years as Qatar's economy and population continue to grow. Although environmental regulation had historically lagged behind the rapid pace of development, in recent years Qatar's leadership has aggressively expanded environmental management as a result of the growing awareness of the importance of coastal ecosystems. While these improvements are encouraging, management remains challenged by its current sectorial, project-driven focus. Ecosystem-based management (EBM) offers an opportunity to overcome these challenges by integrating impacts from across all major activities in multiple sectors and considering their cumulative effects on ecosystem services and products. While an EBM approach would require modest reprioritizing of existing processes and attention to addressing deficiencies in data needed to support decision making, it has the potential to greatly enhance the efficiency and effectiveness of coastal zone management. The article closes by summarizing a recently initiated research project on coral reefs and seagrass beds in Qatar which can serve as a model for development of the EBM approach for other coastal ecosystems in Qatar.
Coastal shoreline hardening is intensifying due to human population growth and sea level rise. Prior studies have emphasized shoreline-hardening effects on faunal abundance and diversity; few have examined effects on faunal biomass and size structure or described effects specific to different functional groups. We evaluated the biomass and size structure of mobile fish and crustacean assemblages within two nearshore zones (waters extending 3 and 16 m from shore) adjacent to natural (native wetland; beach) and hardened (bulkhead; riprap) shorelines. Within 3 m from shore, the total fish/crustacean biomass was greatest at hardened shorelines, driven by greater water depth that facilitated access to planktivore (e.g., bay anchovy) and benthivore-piscivore (e.g., white perch) species. Small-bodied littoral-demersal species (e.g., Fundulus spp.) had greatest biomass at wetlands. By contrast, total biomass was comparable among shoreline types within 16 m from shore, suggesting the effect of shoreline hardening on fish biomass is largely within extreme nearshore areas immediately at the land/water interface. Shoreline type utilization was mediated by body size across all functional groups: small individuals (≤60 mm) were most abundant at wetlands and beaches, while large individuals (>100 mm) were most abundant at hardened shorelines. Taxonomic diversity analysis indicated natural shoreline types had more diverse assemblages, especially within 3 m from shore, although relationships with shoreline type were weak and sensitive to the inclusion/exclusion of crustaceans. Our study illustrates how shoreline hardening effects on fish/crustacean assemblages are mediated by functional group, body size, and distance from shore, with important applications for management.
Coastal reclamation is the gain of land from the sea or coastal wetlands for agricultural purposes, industrial use or port expansions. Large-scale coastal land reclamation can have adverse effects on the coastal environment, including loss of marine habitats and deterioration of coastal water quality. In recent decades, coastal land reclamation has occurred extensively to meet the increasing needs of rapid economic development and urbanization in China. The overall objective of this study is to understand the coastal reclamation status of China from 1979 to 2014 and analyzed its driving factors for mitigating negative ecological effects. The data of coastal reclamation were done with the ERDAS Imagine V9.2 platform and ArcGIS software based on remote images including Landsat, SPOT, ZY-2 and ZY-3. Potential driving factors for sea reclamation were selected based on statistics bulletins and the knowledge of experts in coastal management. In order to understand the relationships among possible impact factors and coastal reclamation, the Partial Least-Squares Regression models was constructed. The analysis results indicated that the total area of reclamation was 11162.89 km2 based on remote sensing images between 1979 and 2014. Shandong Province is the largest reclamation area, reaching 2736.54 km2, and the reclamation is mainly concentrated in Zhejiang, Jiangsu and Liaoning, where the reclamation areas were all more than 1000 km2. According to the remote sensing images, there are three coastal reclamation hotspot regions including Bohai bay (in which is located Liaoning, Tianjin and Hebei), Jiangsu province coastal area and Hangzhou bay (in Zhejiang province). A large scale land reclamation plan of more than 5880 km2 has been made by local government and 2469 km2 has approved by the State Council. From the analyzed results, there is a significant collinearity between these indicators, and no significant correlation between the area of reclamation and selected indicators. Economic development and employees in marine industries have weak positive correlation and correspondingly, the area of cultivated land (ACL) had a negative correlation. Because of the weak correlation, there is an assumption that economic development, outcome of coastal reclamation and population growth were not only was the direct driving factor, but also the outcome of coastal reclamation and population growth was not the direct driving indicator. Construction land quota and huge economic returns to local government may be the direct driving factors according to our field investigation. To resolve the contradiction between the need for land and coastal wetland conservation, it is recommended that China should establish a special management agency and coordination mechanisms, reconsidered the implementation of the reclamation plans and projects that have been approved, enhance law enforcement and increase penalties and strengthen public participation in reclamation management.
Coastal zones are exposed to natural hazards in the context of global change and the concentration of human activities, which justifies the interest in assessing at-risk territories. This paper proposes a reproducible method to identify the erosion risk territories on the basis of an exposure index creation. An assessment of the building exposure to shoreline retreat is conducted along 350 km of the Atlantic French coast (Pays de la Loire regional administrative division) including rocky coasts, coastal barriers and sand spits, estuaries, bays, and coasts with protection structures. The segmentation of a 100-m landward strip is carried out with 30*100 m boxes. Three geoindicators are computed within each box: (i) the shortest shoreline-building distance (ii) the building footprint of the first row (iii) the coastal erosion along sandy coasts. The aggregation of these geoindicators within each box leads to the creation of an exposure index. Thus, this spatial framework provides a reproducible method to improve the synthetic knowledge of the erosion risk in the Pays de la Loire Region. The whole of the risk situation is detected at 1/5000 scale, which is original and significant progress. The accuracy of this study is due to the generic data used and the 30*100 m segmentation. This spatial resolution leads to finer results than previous studies. This new method can detect all the exposures in order to anticipate crises management through the deployment of a real operational alert system.
Nearshore ecosystems are increasingly recognized as critical habitats for fish of cultural, ecological and economic significance. These ecosystems are often densely inhabited by juvenile fish, highly productive and refuges from predation, leading ecologists to characterize them as nurseries. However, nearshore ecosystems are being transformed globally to support demands of growing coastal populations. Many shorelines are modified by armouring (e.g. seawalls, riprap) that minimizes erosion, and overwater structures (e.g. piers, docks) that facilitate waterfront use. These modifications affect the ecology of nearshore systems by restructuring, eliminating and shading shallow waters.
Here, we review literature examining effects of armouring and overwater structures on coastal and estuarine fishes, and discuss how research and management can coordinate to minimize negative effects.
Along armoured shorelines, fish assemblages differed from unarmoured sites, fish consumed less epibenthic and terrestrial prey, beach spawning was less successful and fish were larger. Under large overwater structures, visually oriented fish were less abundant and they fed less. Shade from overwater structures also interrupted localized movements of migratory fish. Thus, shoreline modifications impaired habitats by limiting feeding, reproduction, ontogenetic habitat shifts from shallow to deeper waters and connectivity.
Research suggests that restoring shallow waters and substrate complexity, and minimizing shading underneath overwater structures, can rehabilitate habitats compromised by shoreline modifications.
Synthesis and applications. Shoreline armouring and overwater structures often compromise fish habitats. These threats to nearshore fish habitats will become more severe as growing coastal populations and rising sea levels increase demands for shoreline infrastructure. Our ability to assess and rehabilitate nearshore fish habitats along modified shorelines will be enhanced by: focusing research attention on metrics that directly indicate fish habitat quality; implementing and evaluating shoreline features that repair compromised habitat functions within human-use constraints; collating natural history knowledge of nearshore ecosystems; and embracing the socio-ecological nature of habitat improvements by educating the public about conservation efforts and fostering appreciation of local nearshore ecosystems. Actions to reduce impacts of shoreline modifications on fish are particularly feasible when they align with societal goals, such as improving flood protection and providing spaces that facilitate recreation, education, and connections between people and nature.