In the first decades of 2000s, several Italian sites affected by strong anthropogenic impact were recognized as Sites of National Interest (SINs) for a successive reclamation project, some of which also including marine sectors. These coastal areas are characterized by high complexity and diversity as regards the natural setting as well as for extent, history, type, and degree of contamination. For this, the Italian Ministry of Environment charged its scientific research Institute (earlier ICRAM, now ISPRA) with planning a flexible, adaptable, and large-scale environmental characterization. In this context, the investigation of marine sediments was identified as the primary target to assess the environmental status, because of their conservative capacity with respect to contaminants and their role in the exchange processes with other environmental matrices, such as water column and aquatic organisms. A multidisciplinary, chemical–physical, and ecotoxicological survey was identified as the most appropriate and objective criterion for assessing the sediment quality associated, when necessary, with integrative studies. The results derived from this multidisciplinary approach highlighted the main sources of contamination, together with size and extent of the environmental impact on the coastal marine areas, strictly correlated with the kind of anthropogenic activities and coastal morphology. In order to underline how the different environmental setting influences the degree of anthropogenic impact, four different case studies, selected among the more complex by geochemical and geomorphological viewpoints and more extensively studied, were considered. A comprehensive evaluation of these case studies allowed to deduce some general principles concerning the effects of anthropogenic impact, which can be applicable to other transitional and marine coastal areas.
Human Impacts on the Environment
Rapid urbanization leads to an accelerating decline of seagrass beds. The status of seagrass beds along the entire coastline of a rapidly urbanizing area, Guangdong Province, was examined to document the change in seagrass beds and to explore the determinants of seagrasses characteristics and their plasticity. Thirteen seagrass beds were newly discovered with a total area as 679.04 ha, whereas eleven known seagrass beds have decreased from 972.55 ha to 858.67 ha with seven of them having disappeared in recent decade primarily due to exacerbated construction of artificial shorelines and beach dams, increased nutrient inputs from fish caging and shrimp pond culture, oyster culture, mangrove planting and shellfish collection. The leaf nitrogen content of Halophila ovalis, which dominated the largest beds, increased from (2.09 ± 0.24)% in 2011 to (3.39 ± 0.18)% in 2017, indicating enhanced eutrophication. The optimum seawater dissolved inorganic nitrogen and dissolved inorganic phosphorus levels for Halophila beccarii were 40 μmol/L and 2.5 μmol/L, respectively. The standing stock and plant dimensions of H. beccarii were positively correlated with sediment mud content. Longer, wider leaves, and greater aboveground and belowground biomass were observed at lower salinities, indicating that H. beccarii prefers hyposaline habitats. High shoot density could induce intraspecific competition followed by self-thinning in H. beccarii, leading to reduced leaf area, aboveground and belowground biomass, and root length. Thus, long-term monitoring of seagrass beds along the rapidly urbanizing coastline of Guangdong Province is needed to unravel the mechanisms of decline and to develop effective management strategies.
Anthropogenic noise is a known threat to marine mammals. Decades of research have shown that harbor porpoises are particularly sensitive to anthropogenic noise, and geographic displacement is a common impact from noise exposure. Small, localized populations may be particularly vulnerable to impacts associated with displacement, as animals that are excluded from their primary habitat may have reduced foraging success and survival, or be exposed to increased threats of predation or bycatch. Seal bombs are underwater explosives used in purse seine fisheries to deter marine mammals during fishery operations. Pinnipeds are believed to be the primary target for seal bomb use, however there may be indirect impacts on harbor porpoises. Active purse seine fishing using seal bombs in the greater Monterey Bay area may, at times, span the entire range of the Monterey Bay harbor porpoise stock, which may lead to negative impacts for this population. In this contribution, we review anthropogenic noise as a threat to harbor porpoises, with a focus on the potential for impacts from seal bomb noise exposure in the Monterey Bay region.
A natural experiment was conducted to determine effects of a fossil-fueled power plant on home ranges of east Pacific green turtles Chelonia mydas in an urban foraging ground. The power plant, located in south San Diego Bay, California, USA, co-existed with a resident foraging aggregation of ~60 green turtles for ~50 yr. It was decommissioned during a long-term green turtle monitoring study, thus providing a rare opportunity to evaluate how the cessation of warm-water effluent affected turtle movements and habitat use in the area. During pre- and post-decommissioning of the power plant, 7 and 23 green turtles, respectively, were equipped with GPS-enabled satellite transmitters. Useful data were obtained from 17 turtles (4 for pre- and 13 for post-decommissioning). Core use areas (50% utilization distribution [UD]) increased from 0.71 to 1.37 km2 after the power plant decommissioning. Increase in post-power plant 50% UD was greater during nighttime (0.52 to 1.44 km2) than daytime (1.32 to 1.43 km2). Furthermore, UDs moved from the effluent channel to an area closer to seagrass pastures, a presumed foraging habitat of the turtles. The observed expansion of green turtle home ranges may increase turtle-human interactions, such as boat strikes, within the foraging ground; this underscores how seemingly innocuous human actions contribute to inadvertent consequences to wildlife. Possible management and conservation actions include increasing awareness of the public regarding turtle presence in the area through signage and education as well as legislating for a reduction in boat speeds in select areas of the bay.
Collisions with ships (ship strikes) are a pressing conservation concern for fin whales (Balaenoptera physalus) along western North America. Fin whales exhibit strong diel patterns in dive behavior, remaining near the surface for most of the night, but how this behavior affects ship-strike risk is unknown. We combined diel patterns of surface use, habitat suitability predictions, and ship traffic data to evaluate spatial and temporal trends in ship-strike risk to fin whales of the California Current System (CCS). We tested a range of surface-use scenarios and found that both increased use of the upper water column and increased ship traffic contribute to elevated ship-strike risk at night. Lengthening nights elevate risk during winter throughout the CCS, though the Southern California Bight experienced consistently high risk both day and night year-round. Within designated shipping lanes, total annual nighttime strike risk was twice daytime risk. Avoidance probability models based on ship speed were used to compare the potential efficacy of speed restrictions at various scales. Speed reductions within lanes may be an efficient remediation, but they would address only a small fraction (13%) of overall ship-strike risk. Additional speed restrictions in the approaches to lanes would more effectively reduce overall risk.
The whale-watching industry in Juneau, Alaska relies primarily on the presence of North Pacific humpback whales (Megaptera novaeangliae). To meet demands from the rapidly growing tourism industry, the number of whale-watching vessels in this region has tripled over the last 18 years. As a result, increased vessel presence could have negative effects on humpback whales, ranging from short-term behavioral disturbance to long-term impacts. The current humpback whale viewing regulations are outdated and may not be as effective as they were 18 years ago, when both the whale-watching industry and humpback whale population were smaller. The present study assessed how humpback whale movement and behavioral patterns were affected by (1) vessel presence and number of vessels present, and (2) time spent in the presence of vessels. The study also determined how humpback whale behavioral state transitions were affected by vessel presence. A total of 201 humpback whale focal follows were conducted during summer 2016 and 2017. Based on linear mixed effects models, whales in the presence (vs. absence) of vessels exhibited 38.9% higher deviation in linear movement (p = 0.001), 6.2% increase in swimming speed (p = 0.047) and a 6.7% decrease in inter-breath intervals (IBI) (p = 0.025). For each additional vessel present, deviation increased by 6.2% (p = 0.022) and IBI decreased by 3.4% (p = 0.001). As time spent in the presence of vessels increased, respiration rate increased (p = 0.011). Feeding and traveling humpback whales were likely to maintain their behavioral state regardless of vessel presence, while surface active humpback whales were likely to transition to traveling in the presence of vessels. These short-term changes in movement and behavior in response to whale-watching vessels could lead to cumulative, long-term consequences, negatively impacting the health and predictability of the resource on which the industry relies. Current formal vessel approach regulations and voluntary guidelines should be revisited to reduce vessel pressure and mitigate potential negative effects of this growing whale-watching industry.
Humpback whales rely on acoustic communication to mediate social interactions. The distance to which these social signals propagate from the signaller defines its communication space, and therefore communication network (number of potential receivers). As humpback whales migrate along populated coastlines, they are likely to encounter noise from vessel traffic which will mask their social signals. Since no empirical data exist on baleen whale hearing, the consequences of this are usually assumed, being the modelled reduction in their communication space. Here, the communication space and network of migrating humpback whales was compared in increasing wind-dominated and vessel-dominated noise. Behavioural data on their social interactions were then used to inform these models. In typical wind noise, a signaller's communication space was estimated to extend to 4 km, which agreed with the maximum separation distance between groups that socially interacted. An increase in vessel noise reduced the modelled communication area, along with a significant reduction in group social interactions, probably due to a reduction in their communication network. However, signal masking did not fully explain this change in social behaviour, implying there was also an additional effect of the physical presence of the vessel on signaller and receiver behaviour. Though these observed changes in communication space and social behaviour were likely to be short term and localized, an increase in vessel activity due to tourism and coastal population growth may cause more sustained changes along the humpback whale migration paths.
To better understand the threats posed by human activities on cetaceans, we compiled published studies and determined where, how, and by whom the research on this subject has been conducted in Brazil. We also determined which cetacean species were mostly investigated in these studies. We gathered the available scientific literature published from 1986 to 2016 that contained search terms in English that depicted major cetacean threats. Then, we developed a collaboration network among the authors' institutions and generated a distribution map of the investigated threats and study areas. From the 1047 compiled publications, we selected 103 studies that precisely addressed cetacean threats. The selected studies were carried out by 82 institutions from 12 countries. Most of these institutions were universities (n = 55), followed by non-governmental organizations (n = 15) and research institutes (n = 12). Among the two cetacean suborders, odontocetes were the most representative, with Sotalia guianensis and Pontoporia blainvillei present in 50 and 38 publications, respectively. For mysticetes, publications on Megaptera novaeangliae (n = 6) and Eubalaena australis (n = 5) were the most common. Among the addressed threats, more than half (54.4%) of the publications focused on pollution, followed by bycatch (19.4%) and vessel traffic (10.7%). Most of the study areas took place in the states of Rio de Janeiro (22.4%), São Paulo (19.7%), and Rio Grande do Sul (12.9%). Six institutions were the most prevalent in the collaboration networks, and their location corresponded to hotspots of cetacean diversity. Our findings may contribute to identifying research priorities and guide the conservation of cetacean species in Brazil.
Species conservation, river rehabilitation, stock enhancement, environmental impact assessment and related planning tools require indicators to identify significant impacts but also mitigation success. Since river systems are shaped by disturbances from floods and droughts, typical riverine fish species should have evolved life history traits providing resilience against such disturbances. This study compiled and analyzed resilience traits of European lampreys and fish species to derive a novel sensitivity classification of species to mortality. We assembled life history traits like maximum length, migration type, mortality, fecundity, age at maturity, and generation time of 168 species and created a novel method to weigh and integrate all traits to generate a final sensitivity score from one (low sensitivity) to three (high sensitivity) for each species. Large-bodied, diadromous, rheophilic and lithophilic species such as sturgeons, sea trout, and Atlantic salmon usually appeared to have high sensitivity to additional adult fish mortality, whereas small-bodied, limnophilic and phytophilic species with fast generation cycles were of low sensitivity. The final scoring and classification of 168 European lampreys and fish species according to their sensitivity can be easily regionalized by selecting the most sensitive candidates according to the local species pool. This sensitivity classification has major implications for advancing impact assessment, allowing better targeting of species for conservation measures, benchmarking progress during rehabilitation and enhancing the objective evaluation of the success of restoration projects.
The increasing use of tracking devices, such as the Vessel Monitoring System (VMS) and the Automatic Identification System (AIS), have allowed, in the last decade, detailed spatial and temporal analyses of fishing footprints and of their effects on environments and resources. Nevertheless, tracking devices usually allow monitoring of the largest length classes composing different fleets, whereas fishing vessels below a regulatory threshold (i.e., 15 m in length-over-all) are not mandatorily equipped with these tools. This issue is critical, since 36% of the vessels in the European Union (EU) fleets belong to these “hidden” length classes. In this study, a model [namely, a cascaded multilayer perceptron network (CMPN)] is devised to predict the annual fishing footprints of vessels without tracking devices. This model uses information about fleet structures, environmental characteristics, human activities, and fishing effort patterns of vessels equipped with tracking devices. Furthermore, the model is able to take into account the interactions between different components of the fleets (e.g., fleet segments), which are characterized by different operating ranges and compete for the same marine space. The model shows good predictive performance and allows the extension of spatial analyses of fishing footprints to the relevant, although still unexplored, fleet segments.