Seagrass meadows support key ecosystem services, via provision of food directly for herbivores, and indirectly to their predators. The importance of herbivores in seagrass meadows has been well-documented, but the links between food webs and ecosystem services in seagrass meadows have not previously been made explicit. Herbivores interact with ecosystem services – including carbon sequestration, cultural values, and coastal protection. Interactions can be positive or negative and depend on a range of factors including the herbivore identity and the grazing type and intensity. There can be unintended consequences from management actions based on a poor understanding of trade-offs that occur with complex seagrass-herbivore interactions. Tropical seagrass meadows support a diversity of grazers spanning the meso-, macro-, and megaherbivore scales. We present a conceptual model to describe how multiple ecosystem services are influenced by herbivore pressure in tropical seagrass meadows. Our model suggests that a balanced ecosystem, incorporating both seagrass and herbivore diversity, is likely to sustain the broadest range of ecosystem services. Our framework suggests the pathway to achieve desired ecosystem services outcomes requires knowledge on four key areas: (1) how size classes of herbivores interact to structure seagrass; (2) desired community and management values; (3) seagrass responses to top–down and bottom–up controls; (4) the pathway from intermediate to final ecosystem services and human benefits. We suggest research should be directed to these areas. Herbivory is a major structuring influence in tropical seagrass systems and needs to be considered for effective management of these critical habitats and their services.
To investigate the occurrence and distribution of microplastics in the southeastern coastal region of the United States, we quantified the amount of microplastics in sand samples from multiple coastal sites and developed a predictive model to understand the drift of plastics via ocean currents. Sand samples from eighteen National Park Service (NPS) beaches in the Southeastern Region were collected and microplastics were isolated from each sample. Microplastic counts were compared among sites and local geography was used to make inferences about sources and modes of distribution. Samples were analyzed to identify the composition of particles using Fourier transform infrared spectroscopy (FTIR). To predict the spatiotemporal distribution and movements of particles via coastal currents, a Regional Ocean Modeling System (ROMS) was applied. Microplastics were detected in each of the sampled sites although abundance among sites was highly variable. Approximately half of the samples were dominated by thread-like and fibrous materials as opposed to beads and particles. Results of FTIR suggested that 24% consisted of polyethylene terephthalate (PET), while about 68% of the fibers tested were composed of man-made cellulosic materials such as rayon. Based on published studies examining sources of microplastics, the shape of the particles found here (mostly fibers) and the presence of PET, we infer the source of microplastics in coastal areas is mainly from urban areas, such as wastewater discharge, rather than breakdown of larger marine debris drifting in the ocean. Local geographic features, e.g., the nearness of sites to large rivers and urbanized areas, explain variance in amount of microplastics among sites. Additionally, the distribution of simulated particles is explained by ocean current patterns; computer simulations were correlated with field observations, reinforcing the idea that ocean currents can be a good predictor of the fate and distribution of microplastics at the sites sampled here.
Wildlife tourism is often extolled for its contribution to conservation. However, understanding the effects of tourism activities on the health of target animals is required to fully assess conservation benefits. Shark tourism operators often use food rewards to attract sharks in close proximity to tourists, but nothing is known about the contribution of these food rewards to the energetic requirements of target species. In this study, hand feeding of bull sharks Carcharhinus leucas was directly observed on 36 commercial shark watching dives in the Shark Reef Marine Reserve (SRMR), Fiji. Mean number of tuna heads consumed per dive by focal individuals ranged from 1.3 to 3.7. Monitored bull sharks consumed an average of ~0.74 heads per provisioning day, and bioenergetics modelling suggests that some sharks might periodically be meeting their full energy requirement from provisioning at the SRMR. Knowing how much individual sharks consume at provisioning sites and how this relates to their energy requirements is crucial in order to better understand the effects of wildlife tourism and its contribution to conservation.
Illegal, unreported and unregulated (IUU) fishing is a pervasive issue that affects economic, social, regulatory and environmental systems in all ocean basins. Research on the ecological impacts of IUU fishing has been relatively underrepresented, with minimal investigation into how IUU fishing may negatively affect populations of marine megafauna, such as sea turtles. To address this knowledge gap and identify priority areas for future research and management, we evaluated IUU fishing as a threat to a marine megafauna species group (sea turtles) in the Indian Ocean and Southeast Asia region (IOSEA). We designed and distributed an online survey to experts in the fields of sea turtle research, marine conservation, fisheries management, consulting and NGOs throughout IOSEA. Our results reveal that IUU fishing is likely to have potentially significant impacts on sea turtle populations in IOSEA through targeted exploitation and international wildlife trafficking. Addressing domestic IUU fishing needs to be actioned as a high priority within the study area, as does the issue of patrolling maritime borders to deter illegal cross-border transhipment. There is a demonstrable need to strengthen MCS and employ regional coordination to help build capacity in less-developed nations. Future research requirements include evaluating IUU fishing as a threat to sea turtles and other threatened marine species at multiple scales, further investigation into market forces throughout IOSEA, and examination of potential barriers to implementing management solutions. We advocate for introducing sea turtle-specific measures into IUU fishing mitigation strategies to help maximize the opportunity for positive outcomes in creating healthy ecosystems and stable communities.
Microplastics in the environment are a subject of intense research as they pose a potential threat to marine organisms. Plastic fibers from textiles have been indicated as a major source of this type of contaminant, entering the oceans via wastewater and diverse non-point sources. Their presence is also documented in terrestrial samples. In this study, the amount of microfibers shedding from synthetic textiles was measured for three materials (acrylic, nylon, polyester), knit using different gauges and techniques. All textiles were found to shed, but polyester fleece fabrics shed the greatest amounts, averaging 7360 fibers/m−2/L−1 in one wash, compared with polyester fabrics which shed 87 fibers/m−2/L−1. We found that loose textile constructions shed more, as did worn fabrics, and high twist yarns are to be preferred for shed reduction. Since fiber from clothing is a potentially important source of microplastics, we suggest that smarter textile construction, prewashing and vacuum exhaustion at production sites, and use of more efficient filters in household washing machines could help mitigate this problem.
Published research is reviewed to provide examples of both positive and negative interactions of contaminants and: climate change; habitat change; invasive and introduced species; and, eutrophication including harmful algal blooms. None of these stressor interactions results solely in negative effects. Research must shift from examining contaminants or other stressors in isolation to considering potential positive and negative effects of interactions, with the ultimate goal of providing the necessary information for the effective management of ecosystem services.
Plastic debris, specifically microplastic in the aquatic environment, is an escalating environmental crisis. Efforts at national scales to reduce or ban microplastics in personal care products are starting to pay off, but this will not affect those materials already in the environment or those that result from unregulated products and materials. To better inform future microplastic research and mitigation efforts this study (1) evaluates methods currently used to quantify microplastics in the environment and (2) characterizes the concentration and size distribution of microplastics in a variety of products. In this study, 50 published aquatic surveys were reviewed and they demonstrated that most (~80%) only account for plastics ≥ 300 μm in diameter. In addition, we surveyed 770 personal care products to determine the occurrence, concentration and size distribution of polyethylene microbeads. Particle concentrations ranged from 1.9 to 71.9 mg g−1 of product or 1649 to 31,266 particles g−1 of product. The large majority ( > 95%) of particles in products surveyed were less than the 300 μm minimum diameter, indicating that previous environmental surveys could be underestimating microplastic contamination. To account for smaller particles as well as microfibers from synthetic textiles, we strongly recommend that future surveys consider methods that materials < 300 μm in diameter.
Marine mammals are in many situations one of the most studied component of marine ecosystems. Their habitat requirements may be used to detect and describe the impacts of changes in the environmental conditions or in the human-induced pressures affecting the area where they live. The aim of this study is to investigate the distribution patterns of the most frequent cetacean species occurring in the area of the Pelagos Sanctuary (Northwestern Mediterranean Sea) and their potential correlations with both environmental and anthropogenic drivers of changes. Two different types of data were used: sighting data from ship-board surveys and strandings data collected along the Ligurian coast by the Italian Stranding Network, spanning from 1986 to 2014. Sighting data were collected during summer surveys conducted from June to September, between 1990 and 2014 in an area of approximately 29,000 km2, within the Pelagos Sanctuary for over 115,000 km surveyed under favorable conditions. A total of 4,683 sightings of the five most common cetacean species were collected: 3,305 (70.5%) striped dolphins, 814 (17.3%) fin whales, 169 (3.6%) Risso's dolphins, 347 (7.4%) sperm whales and 48 (1.02%) Cuvier's beaked whales. The species time series of both encounter and stranding rates have been investigated in the light of potential drivers of changes. The results suggest that the area may be suffering from some ecosystem change which is causing the observed changes in the distribution pattern of the five species. Potential disturbance from human activities, namely fishery and maritime traffic, could not be excluded.
In modeling biological and ecological processes from data, it is essential to deal with data selection bias properly in order to obtain reliable and reasonable predictions. To incorporate the mechanism of selection bias into a statistical analysis, a propensity score (PS) is widely employed as an inverse probability weight in order to obtain a consistent estimation of a binary response variable of interest. However, the estimation performance often becomes unstable due to the mis-estimation of the PS. In order to obtain a consistent estimation as well as to stabilize the estimation performance, we propose a new regression model that incorporates the PS as an explanatory variable. Moreover, we show that the proposed model has a the property of double robustness, which enables us to obtain a consistent estimation of the response without suffering from selection bias if either the PS model or the proposed model is correctly specified. The robust bias correction model also accommodates heterogeneity of data distributions based on an asymmetric logistic model, which in turn improves model fitting and prediction accuracy. The PS in our regression model enables us to estimate consistently the global fish stock status even if the information of the stock status available is biased.
In this work, we describe and discuss the current status, trends, and gaps for aquatic invasion research in South America, and we reveal the current state of multinational collaborations on these matters across the continent. First, to measure temporal change in the magnitude of invasion research for South America, we replicated a survey performed in 2001 for marine exotic species, using identical methods used back then to search publications in the Aquatic Science and Fisheries Abstracts database. Second, to compare the South America invasion research effort, in terms of the production of scientific literature on aquatic invasion biology, across time (years), countries, aquatic (freshwater, estuarine, and marine) environments, themes, and taxonomic groups, we performed a more comprehensive search of publications using multiple databases (Scielo, ASFA, Scopus and Google Scholar). This exhaustive survey included articles in international, regional and local peer reviewed journals on aquatic (freshwater, marine and estuarine) exotic species of SA that were published between 2004 and 2014 in the three dominant languages of South America. We found that the research effort for marine exotic species research in South America increased 9-fold between the two time periods (1997–2001 vs. 2002–2014), with most (90%) of recent research occurring in the Atlantic (vs. Pacific) coast. This disparity in research effort between coasts is consistently evident for individual environments (including freshwater, estuarine, and marine waters) and countries. While the focus of publications is unevenly distributed among research themes and taxa, the paucity of comparative analyses among countries is especially striking. Despite the general increment in research effort within the discipline, we consider there is an urgent need for more solid and concerted multinational efforts to address (financially, scientifically and socially) the conspicuous gaps in aquatic invasion research. Failing to make these efforts is probably the major threat hampering the development of successful long term programs and strategies directed to prevent, manage and/or control the introduction of exotic species and their many impacts in the continent.
A fisheries management model that identifies the economic optimal management of fisheries under the influence of nutrients is presented. The model starts from the idea that growth in fish biomass increases with increasing availability of nutrients owing to higher food availability up to a peak, after which growth falls due to eutrophication. The model is applied to Swedish and Danish cod fisheries in the Western Baltic Sea and identifies the welfare contribution of the fisheries, measured as the sum of resource rent and producer surplus. In 2010, the welfare contribution was −28% of the landing value. Maximizing the model with respect to effort alone and additionally over nitrogen concentration increases the contribution to 11% of the landing value in 2010. The analysis shows that the welfare effect of reducing fishing effort through management reforms is large, but that the effect of incorporating nitrogen in fisheries policy is small.
Anthropogenic plastic pollution is a global problem. In the marine environment, one of its less studied effects is the transport of attached biota, which might lead to introductions of non-native species in new areas or aid in habitat expansions of invasive species. The goal of the present work was to assess if the material composition of beached anthropogenic litter is indicative of the rafting fauna in a coastal area and could thus be used as a simple and cost-efficient tool for risk assessment in the future. Beached anthropogenic litter and attached biota along the 200 km coastline of Asturias, central Bay of Biscay, Spain, were analysed. The macrobiotic community attached to fouled litter items was identified using genetic barcoding combined with visual taxonomic analysis, and compared between hard plastics, foams, other plastics and non-plastic items. On the other hand, the material composition of beached litter was analysed in a standardized area on each beach. From these two datasets, the expected frequency of several rafting taxa was calculated for the coastal area and compared to the actually observed frequencies. The results showed that plastics were the most abundant type of beached litter. Litter accumulation was likely driven by coastal sources (industry, ports) and river/sewage inputs and transported by near-shore currents. Rafting vectors were almost exclusively made up of plastics and could mainly be attributed to fishing activity and leisure/ household. We identified a variety of rafting biota, including species of goose barnacles, acorn barnacles, bivalves, gastropods, polychaetes and bryozoan, and hydrozoan colonies attached to stranded litter. Several of these species were non-native and invasive, such as the giant Pacific oyster (Crassostrea gigas) and the Australian barnacle (Austrominius modestus). The composition of attached fauna varied strongly between litter items of different materials. Plastics, except for foam, had a much more diverse attached community than non-plastic materials. The predicted frequency of several taxa attached to beached litter significantly correlated with the actually observed frequencies. Therefore we suggest that the composition of stranded litter on a beach or an area could allow for predictions about the corresponding attached biotic community, including invasive species.
Wind energy is considered one of the most promising clean technologies for power generation. For the sustainable development of this industry, it is essential that planning integrate spatial zoning with estimates of installed capacity and energy production. A Geographic Information System-based methodology was developed to propose planning for wind farms from a spatial perspective in the extreme south of Brazil. Through multi-criteria evaluation, the feasibility of the study area for this activity was analyzed according to suitability and constraint criteria. The assessment of suitability was based on wind energy exploitation, while the constraint analysis was based on the environmental legislation, social aspects and exclusion areas. In the suitability analysis, importance weights were assigned to the variables according to the unprecedented combination of the Delphi, linear and geometric Analytic Hierarchy Process methods. Constraint and suitability maps were established for the wind farms. The integration of both aspects allowed the generation of a spatial zoning map. Based on this zoning, installed capacity was calculated according to technical characteristics of a reference wind turbine. Finally, energy production of the suitable zones was estimated. The proposed spatial planning aims to contribute to the licensing processes in southern Brazil. Furthermore, the methodology developed can be replicated in other similar case studies.
Climate change is a threat to marine ecosystems and the services they provide, and reducing fishing pressure is one option for mitigating the overall consequences for marine biota. We used a minimally realistic ecosystem model to examine how projected effects of ocean warming on the growth of Antarctic krill, Euphausia superba, might affect populations of krill and dependent predators (whales, penguins, seals, and fish) in the Scotia Sea. We also investigated the potential to mitigate depletion risk for predators by curtailing krill fishing at different points in the 21st century. The projected effects of ocean warming on krill biomass were strongest in the northern Scotia Sea, with a ≥40% decline in the mass of individual krill. Projections also suggest a 25% chance that krill biomass will fall below an established depletion threshold (75% of its unimpacted level), with consequent risks for some predator populations, especially penguins. Average penguin abundance declined by up to 30% of its unimpacted level, with up to a 50% chance of falling below the depletion threshold. Simulated krill fishing at currently permitted harvest rates further increased risks for depletion, and stopping fishing offset the increased risks associated with ocean warming in our model to some extent. These results varied by location and species group. Risk reductions at smaller spatial scales also differed from those at the regional level, which suggests that some predator populations may be more vulnerable than others to future changes in krill biomass. However, impacts on predators did not always map directly to those for krill. Our findings indicate the importance of identifying vulnerable marine populations and targeting protection measures at appropriate spatial scales, and the potential for spatially-structured management to avoid aggravating risks associated with rising ocean temperatures. This may help balance tradeoffs among marine ecosystem services in an uncertain future.
Impacts of global climate change on coral reefs are being amplified by pulse heat stress events, including El Niño, the warm phase of the El Niño Southern Oscillation (ENSO). Despite reports of extensive coral bleaching and up to 97% coral mortality induced by El Niño events, a quantitative synthesis of the nature, intensity, and drivers of El Niño and La Niña impacts on corals is lacking. Herein, we first present a global meta-analysis of studies quantifying the effects of El Niño/La Niña-warming on corals, surveying studies from both the primary literature and International Coral Reef Symposium (ICRS) Proceedings. Overall, the strongest signal for El Niño/La Niña-associated coral bleaching was long-term mean temperature; bleaching decreased with decreasing long-term mean temperature (n = 20 studies). Additionally, coral cover losses during El Niño/La Niña were shaped by localized maximum heat stress and long-term mean temperature (n = 28 studies). Second, we present a method for quantifying coral heat stress which, for any coral reef location in the world, allows extraction of remotely-sensed degree heating weeks (DHW) for any date (since 1982), quantification of the maximum DHW, and the time lag since the maximum DHW. Using this method, we show that the 2015/16 El Niño event instigated unprecedented global coral heat stress across the world's oceans. With El Niño events expected to increase in frequency and severity this century, it is imperative that we gain a clear understanding of how these thermal stress anomalies impact different coral species and coral reef regions. We therefore finish with recommendations for future coral bleaching studies that will foster improved syntheses, as well as predictive and adaptive capacity to extreme warming events.
Climate change research is advancing to more complex and more comprehensive studies that include long-term experiments, multiple life-history stages, multi-population, and multi-trait approaches. We used a population of the barnacle Balanus improvisus known to be sensitive to short-term acidification to determine its potential for long-term acclimation to acidification. We reared laboratory-bred individuals (as singles or pairs), and field-collected assemblages of barnacles, at pH 8.1 and 7.5 (≈ 400 and 1600 μatm pCO2 respectively) for up to 16 months. Acidification caused strong mortality and reduced growth rates. Acidification suppressed respiration rates and induced a higher feeding activity of barnacles after 6 months, but this suppression of respiration rate was absent after 15 months. Laboratory-bred barnacles developed mature gonads only when they were held in pairs, but nonetheless failed to produce fertilized embryos. Field-collected barnacles reared in the laboratory for 8 months at the same pH’s developed mature gonads, but only those in pH 8.1 produced viable embryos and larvae. Because survivors of long-term acidification were not capable of reproducing, this demonstrates that B. improvisus can only partially acclimate to long-term acidification. This represents a clear and significant bottleneck in the ontogeny of this barnacle population that may limit its potential to persist in a future ocean.
Free or subsidised mosquito net (MN) distribution has been an increasingly important tool in efforts to combat malaria in recent decades throughout the developing world, making great strides towards eradicating this hugely detrimental disease. However, there has been increasing concern in the natural resource management and healthcare communities over alternative use of MNs, particularly in artisanal fisheries where it has been suggested they pose a threat to sustainability of fish stocks. So far, little evidence has been presented as to the global prevalence and characteristics of MN fishing, limiting global management initiatives and incentives for action across disciplines. We conducted a rapid global assessment of mosquito net fishing (MNF) observations from expert witnesses living and/or working in malarial zones using an internet survey. MNF was found to be a broadly pan-tropical activity, particularly prevalent in sub-Saharan Africa. MNF is conducted using a variety of deployment methods and scales including seine nets, scoop/dip nets, set nets and traps. MNF was witnessed in a broad range of marine and freshwater habitats and was seen to exploit a wide range of taxa, with capture of juvenile fish reported in more than half of responses. Perceived drivers of MNF were closely related to poverty, revealing potentially complex and arguably detrimental livelihood and food security implications which we discuss in light of current literature and management paradigms. The key policies likely to influence future impacts of MNF are in health, regarding net distribution, and natural resource management regarding restrictions on use. We outline critical directions for research and highlight the need for a collaborative, interdisciplinary approach to development of both localised and broad-scale policy.
To describe, model and assess the relative importance of environmental and climatic factors likely influencing the regional distribution of coral cover and assemblages with contrasting life histories and susceptibilities to bleaching.
We compiled the first comprehensive empirical dataset for coral communities in the south-eastern Indian Ocean (SEIO), incorporating information from 392 sites along the western coast of Australia and offshore atolls/islands across ~19° of latitude.
We assessed hard coral cover and community composition to genus using point-intercept transects or point-count analysis of digital images taken along transects. We explored spatial variation in environmental conditions and in composition of corals with contrasting life histories. After de-trending the temporal patterns, we assessed the relative importance of environmental metrics to coral cover, life histories and bleaching susceptibility using a full subsets model-selection approach with generalized additive mixed models, accounting for both temporal and among site variation.
The distribution of temperature, light, the frequency of temperature anomalies and tropical cyclones appear to be drivers of coral community structure. Functional diversity of low- to mid-latitude coral communities may convey some resilience to thermal stress, while higher latitude communities dominated by Competitive and Bleaching-Susceptible taxa may lack this functional resilience. These patterns likely reflect varying historical exposure to cyclones and temperature anomalies.
As evident in recent years, changing background conditions and regimes of disturbance in coming decades will shift the distribution, functional diversity and resilience of coral reefs throughout the SEIO. The rate and magnitude of environmental change will ultimately determine the future of the tropical reefs and whether the higher latitude reefs provide some refuge from climate change. Our study highlights the need to quantify the distributional properties of key environmental metrics to better understand and predict reef condition through coming decades.
The record and ever-present danger of overfishing of living resources requires there to be a legal framework for the international management of these oceanic resources. The chapter opens with a history of the legal fisheries regime as it has developed since the late nineteenth century when the negative impact of overfishing on stocks was first noticed, highlighting how the remedial measures have had limited success because they have been biologically rather than economically grounded, including the pivotal concept, maximum sustainable yield. It then turns to an examination of the fisheries regime in the 1982 UN Convention on the Law of the Sea, both in the exclusive economic zone, where the bulk of fisheries take place, and on the high seas. The following section then deals with six major innovations by which the 1995 UN Fish Stocks Agreement attempts to overcome these problems for stocks that straddle the boundary between national zones and the high seas or are highly migratory; this is complemented by the 1993 FAO Compliance Agreement covering some of the same ground. Non-economic uses have in recent decades become dominant as regards marine mammals. The framework for these is briefly introduced. Finally, a concluding section on current issues and future developments concentrates on the perennial problem of allocation among States of limited participatory rights in international fisheries and on the composite concept of illegal, unreported and unregulated fishing, which, because it is usually treated as a single undifferentiated phenomenon, threatens to obscure the important distinction between fishing that is unlawful and fishing that is merely unregulated.
Oceans and seas are adversely affected by a large number of anthropogenic pressures. The need to better integrate the policies of different sectors, which impact the oceans is generally seen. Different countries strive to implement a more integrated approach for the management and protection of their marine areas. Important tools which can support this process are marine spatial planning and marine protected areas. If a single administrative body is made responsible for the entire task of sustainable marine use and conservation, this could help to bundle responsibilities. Existing approaches often do not meet expectations. Reasons for this are diverse, ranging from insufficient governmental and scientific resources, lack of political will or a federal political system that complicates cooperation and coordination.