Floating oil, plastics, and marine organisms are continually redistributed by ocean surface currents. Prediction of their resulting distribution on the surface is a fundamental, long-standing, and practically important problem. The dominant paradigm is dispersion within the dynamical context of a nondivergent flow: objects initially close together will on average spread apart but the area of surface patches of material does not change. Although this paradigm is likely valid at mesoscales, larger than 100 km in horizontal scale, recent theoretical studies of submesoscales (less than ∼10 km) predict strong surface convergences and downwelling associated with horizontal density fronts and cyclonic vortices. Here we show that such structures can dramatically concentrate floating material. More than half of an array of ∼200 surface drifters covering ∼20 × 20 km2 converged into a 60 × 60 m region within a week, a factor of more than 105 decrease in area, before slowly dispersing. As predicted, the convergence occurred at density fronts and with cyclonic vorticity. A zipperlike structure may play an important role. Cyclonic vorticity and vertical velocity reached 0.001 s−1 and 0.01 ms−1, respectively, which is much larger than usually inferred. This suggests a paradigm in which nearby objects form submesoscale clusters, and these clusters then spread apart. Together, these effects set both the overall extent and the finescale texture of a patch of floating material. Material concentrated at submesoscale convergences can create unique communities of organisms, amplify impacts of toxic material, and create opportunities to more efficiently recover such material.
Biodiversity compensation policy programs such as offsetting are increasingly being expanded to the marine realm. We reviewed the literature on biodiversity offsets and related compensatory policy to determine where marine offset policies occur. We also identified the most important differences between marine and terrestrial systems that are likely to have implications for how offsetting is conducted. We found that 77 nations had compensatory policies that enabled the use of offsets in the marine environment. Two important differences between marine and terrestrial offsets emerged: (1) biophysical differences, such as greater marine connectivity, lower likelihood of restoration success, and data paucity, and (2) social or governance differences, such as a lack of private ownership and a greater probability of leakage. We conclude that without better evaluation and innovation, it is premature to conclude that marine offsets can be effective. The lessons learned from the development of terrestrial offsets provide an opportunity to improve their application to marine ecosystems.
Marine Protected Areas (MPAs) have become recognized as important management tools for marine and coastal ecosystems in the last few decades. However, the theoretical underpinnings of MPA regimes have arguably not yet received sufficient attention. This paper attempts to remedy this by exploring how the Cultural Theory initiated by Dame Mary Douglas can provide a theoretical foundation for the current debates about the design of MPA regimes. It does so by firstly noting that the various types of MPA governance discussed in the literature correspond to the ways of organizing, perceiving and justifying social relations recognized in Cultural Theory. The article continues by setting out how Cultural Theory helps to explain when and why MPA regimes succeed or fail to reach their goals. In particular, the article highlights the practical importance of accommodating all ways of organizing and perceiving social relations in any MPA management plan. Finally, the paper suggests that further systematic, empirical work for assessing MPAs needs to be undertaken so as to corroborate the arguments advanced in this paper.
The escape of Atlantic Salmon (Salmo salar) from aquaculture facilities can result in both negative genetic and ecological interactions with wild populations, yet the ability to predict the associated risk to wild populations has remained elusive. Here we assess the potential of a spatiotemporal database of aquaculture facility locations, production estimates and escape events to predict the distribution of escaped farmed salmon and genetic impacts on wild populations in the Northwest Atlantic. Industry production data, reported escape events, and in-river detections of escaped farmed salmon were collected from across the Northwest Atlantic. Genetic estimates of impact were obtained using single nucleotide polymorphisms (95 loci) representing aquaculture and wild salmon throughout the region (30 populations, 3048 individuals). Both the number of escaped farmed salmon detected at counting facilities and the magnitude of genetic impacts were positively correlated with a cumulative spatial measure of aquaculture production. Our results suggest that the risk of escapees and genetic introgression from wild-farmed salmon interactions can be assessed using information on farm production characteristics. This represents a first step in predicting the impact of existing cage-based farms on wild Atlantic salmon.
More non-native species (NNS) are reported from harbors, estuaries and protected embayments than in wave-exposed, open-coast habitats. In California (USA), hundreds of NNS have become established in international ports, and dozens are known from smaller estuaries. In contrast, only 22 NNS are reported from the state’s 1350 km of open coast. As a result, the perception that open-coast habitats are not vulnerable to invasions has persisted. Management and monitoring focuses on ports and estuaries; the last major monitoring effort on the open coast occurred in 2004. Much of the species-rich Central California coast is now part of a network of marine protected areas (MPAs). We surveyed 12 wave-swept rocky intertidal and eight subtidal sites (from 37°53′40N 122°42′30W to 36°31′16N 121°56′22W) for NNS. At least one NNS was detected at half of the sites surveyed, but most were not widespread or abundant. One exception, a bryozoan in the Watersipora spp. complex, known primarily from ports and estuaries, was found at multiple sites, and was abundant at some. Another non-native, the alga Caulacanthus ustulatus, was abundant at a single site. MPAs were just as likely as sites outside of MPAs to have NNS. For subtidal sites, proximity to a harbor was correlated with the abundance of non-natives. Our findings suggest that our study area is still relatively uninvaded, but the success of Watersipora within some of these highly diverse rocky shore sites underscores the potential vulnerability of high-value open-coast systems to invasions.
In an era of accelerated biodiversity loss and limited conservation resources, systematic prioritization of species and places is essential. In terrestrial vertebrates, evolutionary distinctness has been used to identify species and locations that embody the greatest share of evolutionary history. We estimate evolutionary distinctness for a large marine vertebrate radiation on a dated taxon-complete tree for all 1,192 chondrichthyan fishes (sharks, rays and chimaeras) by augmenting a new 610-species molecular phylogeny using taxonomic constraints. Chondrichthyans are by far the most evolutionarily distinct of all major radiations of jawed vertebrates—the average species embodies 26 million years of unique evolutionary history. With this metric, we identify 21 countries with the highest richness, endemism and evolutionary distinctness of threatened species as targets for conservation prioritization. On average, threatened chondrichthyans are more evolutionarily distinct—further motivating improved conservation, fisheries management and trade regulation to avoid significant pruning of the chondrichthyan tree of life.
Managing natural resources in an era of increasing climate impacts requires accounting for the synergistic effects of climate, ecosystem changes, and harvesting on resource productivity. Coincident with recent exceptional warming of the northwest Atlantic Ocean and removal of large predatory fish, the American lobster has become the most valuable fishery resource in North America. Using a model that links ocean temperature, predator density, and fishing to population productivity, we show that harvester-driven conservation efforts to protect large lobsters prepared the Gulf of Maine lobster fishery to capitalize on favorable ecosystem conditions, resulting in the record-breaking landings recently observed in the region. In contrast, in the warmer southern New England region, the absence of similar conservation efforts precipitated warming-induced recruitment failure that led to the collapse of the fishery. Population projections under expected warming suggest that the American lobster fishery is vulnerable to future temperature increases, but continued efforts to preserve the stock's reproductive potential can dampen the negative impacts of warming. This study demonstrates that, even though global climate change is severely impacting marine ecosystems, widely adopted, proactive conservation measures can increase the resilience of commercial fisheries to climate change.
Aquatic invasive species (AIS) are biological pollutants that cause detrimental ecological, economic, and human-health effects in their introduced communities. With increasing globalization through maritime trade, ports are vulnerable to AIS exposure via commercial vessels. The Cuban Port of Mariel is poised to become a competitive transshipment hub in the Caribbean and the intent of this study was to evaluate present and potential impacts AIS pose with the likely future increase in shipping activity. We utilized previous assessment frameworks and publicly accessible information to rank AIS by level of threat. Fifteen AIS were identified in Cuba and one, the Asian green mussel Perna viridis (Linnaeus, 1758), had repeated harmful economic impacts. Five species associated with trade partners of Port Mariel were considered potentially detrimental to Cuba if introduced through shipping routes. The results presented herein identify species of concern and emphasize the importance of prioritizing AIS prevention and management within Cuba.
Although anthropogenic oil spills vary in size, duration and severity, their broad impacts on complex social, economic and ecological systems can be significant. Questions pertaining to the operational challenges associated with the tactical allocation of human resources, cleanup equipment and supplies to areas impacted by a large spill are particularly salient when developing mitigation strategies for extreme oiling events. The purpose of this paper is to illustrate the application of advanced oil spill modeling techniques in combination with a developed mathematical model to spatially optimize the allocation of response crews and equipment for cleaning up an offshore oil spill. The results suggest that the detailed simulations and optimization model are a good first step in allowing both communities and emergency responders to proactively plan for extreme oiling events and develop response strategies that minimize the impacts of spills.
The ecological effects of tuna fish farms are largely undocumented. This study confirmed their high capacity to attract surrounding wild fish. The aggregation effect persisted year round, without detectable seasonal differences. Farm impact was restricted to close proximity of the sea cages, and was more prominent over the bottom than in the water column strata. Tuna fish farms proved to be high energy trophic resources, as indicated by the enhanced fitness status of two focal species, bogue and seabream. Under abundant food supply, seabream appear to allocate the majority of energy reserves to gonaddevelopment. Farm associated bogue had greater parasite loads, with no detrimental effect on fitness status. Overall, tuna fish farms can be regarded as population sources for aggregated wild fish, and under the no fishing conditions within the leasehold areas, can serve as functional marine protected areas.