A statistical evaluation of nearly 10 years of high-resolution surface seawater carbon dioxide partial pressure (pCO2) time-series data collected from coastal moorings around O’ahu, Hawai’i suggest that these coral reef ecosystems were largely a net source of CO2 to the atmosphere between 2008 and 2016. The largest air-sea flux (1.24 ± 0.33 mol m−2 yr−1) and the largest variability in seawater pCO2 (950 μatm overall range or 8x the open ocean range) were observed at the CRIMP-2 site, near a shallow barrier coral reef system in Kaneohe Bay O’ahu. Two south shore sites, Kilo Nalu and Ala Wai, also exhibited about twice the surface water pCO2 variability of the open ocean, but had net fluxes that were much closer to the open ocean than the strongly calcifying system at CRIMP-2. All mooring sites showed the opposite seasonal cycle from the atmosphere, with the highest values in the summer and lower values in the winter. Average coastal diurnal variabilities ranged from a high of 192 μatm/day to a low of 32 μatm/day at the CRIMP-2 and Kilo Nalu sites, respectively, which is one to two orders of magnitude greater than observed at the open ocean site. Here we examine the modes and drivers of variability at the different coastal sites. Although daily to seasonal variations in pCO2and air-sea CO2 fluxes are strongly affected by localized processes, basin-scale climate oscillations also affect the variability on interannual time scales.
Atoll islands’ alongshore sediment transport gradients depend on how island and reef morphology affect incident wave energy. It is unclear, though, how potential atoll morphologic configurations influence shoreline erosion and/or accretion patterns, and how these relationships will respond to future sea-level rise (SLR). Schematic atoll models with varying morphologies were used to evaluate the relative control of individual morphological parameters on alongshore transport gradients. Incident wave transformations were simulated using a physics-based numerical model and alongshore erosion and accretion was calculated using empirical formulae. The magnitude of the transport gradients increased with SLR: initial erosion or accretion patterns intensified. Modeled morphologic parameters that significantly influenced alongshore transport were the atoll diameter, reef flat width, reef flat depth, and island width. Modeled atolls with comparably small diameters, narrow and deep reef flats with narrow islands displayed greater magnitudes of erosion and/or accretion, especially with SLR. Windward island shorelines are projected to accrete toward the island’s longitudinal ends and lagoon due to SLR, whereas leeward islands erode along lagoon shorelines and extend toward the island ends. Oblique island, oriented parallel to the incident deepwater wave direction, shorelines are forecast to build out leeward along the reef rim and toward the lagoon while eroding along regions exposed to direct wave attack. These findings make it possible to evaluate the relative risk of alongshore erosion/accretion on atolls due to SLR in a rapid, first-order analysis.
Small-scale fisheries (SSF) have long been overshadowed by the concerns and perceived importance of the industrial sector in fisheries science and policy. Yet in recent decades, attention to SSF is on the rise, marked by a proliferation of scientific publications, the emergence of new global policy tools devoted to the small-scale sector, and concerted efforts to tally the size and impacts of SSF on a global scale. Given the rising tide of interest buoying SSF, it's pertinent to consider how the underlying definition shapes efforts to enumerate and scale up knowledge on the sector—indicating what dimensions of SSF count and consequently what gets counted. Existing studies assess how national fisheries policies define SSF, but to date, no studies systematically and empirically examine how the definition of SSF has been articulated in science, including whether and how definitions have changed over time. We systematically analyzed how SSF were defined in the peer-reviewed scientific literature drawing on a database of 1,723 articles published between 1960 and 2015. We coded a 25% random sample of articles (n = 434) from our database and found that nearly one-quarter did not define SSF. Among those that did proffer a definition, harvest technologies such as fishing boats and gear were the most common characteristics used. Comparing definitions over time, we identified two notable trends over the 65-year time period studied: a decreasing proportion of articles that defined SSF and an increasing reliance on technological dimensions like boats relative to sociocultural characteristics. Our results resonate with findings from similar research on the definition of SSF in national fisheries policies that also heavily rely on boat length. We call attention to several salient issues that are obscured by an overreliance on harvest technologies in definitions of SSF, including dynamics along the wider fisheries value chain and social relations such as gender. We discuss our findings considering new policies and emerging tools that could steer scientists and practitioners toward more encompassing, consistent, and relational means of defining SSF that circumvent some of the limitations of longstanding patterns in science and policy that impinge upon sustainable and just fisheries governance.
The mesopelagic community is important for downward oceanic carbon transportation and is a potential food source for humans. Estimates of global mesopelagic fish biomass vary substantially (between 1 and 20 Gt). Here, we develop a global mesopelagic fish biomass model using daytime 38 kHz acoustic backscatter from deep scattering layers. Model backscatter arises predominantly from fish and siphonophores but the relative proportions of siphonophores and fish, and several of the parameters in the model, are uncertain. We use simulations to estimate biomass and the variance of biomass determined across three different scenarios; S1, where all fish have gas-filled swimbladders, and S2 and S3, where a proportion of fish do not. Our estimates of biomass ranged from 1.8 to 16 Gt (25–75% quartile ranges), and median values of S1 to S3 were 3.8, 4.6, and 8.3 Gt, respectively. A sensitivity analysis shows that for any given quantity of fish backscatter, the fish swimbladder volume, its size distribution and its aspect ratio are the parameters that cause most variation (i.e. lead to greatest uncertainty) in the biomass estimate. Determination of these parameters should be prioritized in future studies, as should determining the proportion of backscatter due to siphonophores.
Climate change and biological invasions are rapidly reshuffling species distribution, restructuring the biological communities of many ecosystems worldwide. Tracking these transformations in the marine environment is crucial, but our understanding of climate change effects and invasive species dynamics is often hampered by the practical challenge of surveying large geographical areas. Here, we focus on the Mediterranean Sea, a hot spot for climate change and biological invasions to investigate recent spatiotemporal changes in fish abundances and distribution. To this end, we accessed the local ecological knowledge (LEK) of small‐scale and recreational fishers, reconstructing the dynamics of fish perceived as “new” or increasing in different fishing areas. Over 500 fishers across 95 locations and nine different countries were interviewed, and semiquantitative information on yearly changes in species abundance was collected. Overall, 75 species were mentioned by the respondents, mostly warm‐adapted species of both native and exotic origin. Respondents belonging to the same biogeographic sectors described coherent spatial and temporal patterns, and gradients along latitudinal and longitudinal axes were revealed. This information provides a more complete understanding of the shifting distribution of Mediterranean fishes and it also demonstrates that adequately structured LEK methodology might be applied successfully beyond the local scale, across national borders and jurisdictions. Acknowledging this potential through macroregional coordination could pave the way for future large‐scale aggregations of individual observations, increasing our potential for integrated monitoring and conservation planning at the regional or even global level. This might help local communities to better understand, manage, and adapt to the ongoing biotic transformations driven by climate change and biological invaders.
Coral reef restoration is an increasingly important part of tropical marine conservation. Information about what motivates coral reef restoration as well as its success and cost is not well understood but needed to inform restoration decisions. We systematically review and synthesise data from mostly scientific studies published in peer‐reviewed and grey literature on the motivations for coral reef restoration, the variables measured, outcomes reported, the cost per hectare of the restoration project, the survival of restored corals, the duration of the project and its overall spatial extent depending on the restoration technique employed. The main motivation to restore coral reefs for the projects assessed was to further our ecological knowledge and improve restoration techniques, with coral growth, productivity and survival being the main variables measured. The median project cost was 400,000 US$ ha‐1 (2010 US$), ranging from 6,000 US$ ha‐1 for the nursery phase of coral gardening to 4,000,000 US$ ha‐1 for substrate addition to build an artificial reef. Restoration projects were mostly of short duration (1‐2 years) and over small spatial extents (0.01 ha or 108 m2). Median reported survival of restored corals was 60.9%. Future research to survey practitioners who do not publish their discoveries would complement this work. Our findings and database provide critical data to inform future research in coral reef restoration.
In Southeast Asia, mangrove forest cover and biodiversity has shown a rapid decline in recent decades, despite extensive conservation efforts. Identifying and analysing discourses on biodiversity conservation improves our knowledge and understanding of stakeholder perspectives (including normative values and socially constructed viewpoints) on biodiversity conservation within a specific social-ecological context. Considering these perspectives in a decision-making context contributes to the long-term sustainability of resulting conservation approaches, thus contributing to continued biodiversity conservation efforts in the far future. We consider the urban City State of Singapore to identify and interpret stakeholder discourses -including values and socially constructed viewpoints-on (effective) mangrove biodiversity conservation and management in an urban context. Using the Q methodology, we: (i) delineate and describe mangrove conservation and management discourses in Singapore and (ii) extract consensual perspectives common to discourses as a basis for management recommendations. Areas of agreement and disagreement on motivation, prioritization and responsibilities related to mangrove conservation and management are described based on numerical (i.e. sorting of statements along an ordinal scale) and qualitative data (i.e. structured interviews). There was a large overlap between discourses, suggesting that disagreement between various stakeholders may not be a prominent inhibitor of future decision making regarding mangrove conservation and management. It seems stakeholders realise the urban context strongly limits the range of realistic conservation and management approaches of mangrove forests, resulting in the larger overlap between discourses. Generally, all participants agree no further loss of existing Singapore mangroves should be allowed. The most important recommendations to reach this ultimate objective include indefinite legal protection and increase of mangrove areas under national park and nature reserve status, as well as continued promotion of mangrove's cultural ecosystem services. The identified discourses can inform decision-making by deducing shared stakeholder objectives based on the consensus values and perspectives. These shared objectives can readily be incorporated in decision-making processes on mangrove conservation and management in an urban context.
Adapting fishing regulations in a highly uncertain environment remains a complex challenge for managers who have to deal with non-linear dynamics of fish population and harvest levels. In this research, a recent method of stochastic control is adapted to a general fishery management problem under multiples sources of uncertainty related to the dynamics of the fish population and the effect of fishing on its growth. The question is about adjusting permanently the management rule or to hold a fixed policy thus avoiding additional noise. The mathematical problem developed here, though oversimplified, represents an original approach to the fishery management issue inspired by the monetary policy challenge of a central bank (Brainard principle). It assumes that Control Variation Increases the level of Uncertainty (namely CVIU approach) under particular conditions, resulting in preferable inaction regions for managers. We specify these conditions to show that the management of a poorly known fishery is still possible by using a CVIU approach.
The need for management approaches based on ecosystem perspectives that thoroughly incorporate ecosystem considerations into marine planning has become increasingly urgent. In response, concepts such as ecosystem-based management (EBM), ecosystem-based approach (EBA) and ecosystem approach (EA) are increasingly being applied in marine/maritime spatial planning (MSP). The purpose of this article is to clarify potential differences and similarities between the three concepts and potential consequences of choosing one over the others. From a questionnaire and literature analysis, the findings showed vast disagreements on how the concepts are related, however the main perception is that the concepts overlap. Respondents agreed that a lack of clear definitions and understandings of the three concepts causes confusion and expect negative consequences for planning outcomes. Eleven principles for how the concepts are ideally performed were found, including; acknowledge interlinkages, see humans as a part of the ecosystem and consider cumulative impacts. While a complete overlap between EBM and EA principles were found, the weighting of each principle was different for each concept. Differences were also found in objectives of the concepts, where definitions of EBM were the only ones to include the objective of co-existence and definitions of EBA the only to include objectives of impact management and good environmental status. As this could have consequences in planning processes and thus in the outcomes, it is crucial that MSP practitioners and stakeholders are aware of different perceptions so that choosing between concepts does not lead to less ambitious or inadequate outcomes.
Populations of Acropora palmata and Orbicella faveolata, two important reef-building corals, have declined precipitously across the Caribbean region since at least the 1970s. Recruitment failure may be limiting population recovery, possibly due to lack of suitable settlement habitat. Here, we examine the effects of algal turfs and algal turfs + sediment, two widely abundant substrate types across the Florida Keys, on the settlement of these two ecologically-important species. We show that sedimentsignificantly impedes coral settlement, reducing settlement 10- and 13-fold for A. palmata and O. faveolata, respectively, compared to turf algae alone. This result is corroborated by our field survey data that showed a strong, negative relationship between the abundance of turf + sediment and the abundance of juvenile corals. Turf algae alone did not reduce coral settlement. Our results suggest that sediment-laden turf algae are detrimental to settling corals, but that turf algae alone may be relatively benign.
Primary considerations for adopting an ecosystem approach to fisheries management (EAFM) as a management approach will involve an expanded scope of fisheries management over conventional approaches; specifically, EAFM will involve a broader scale of management. Development of a sub-regional EAFM plan can complement local, national, and regional fisheries management priorities, as well as help to catalyze management action at multiple levels that may not otherwise occur. A sub-regional EAFM policy planning approach has been undertaken for the Sulu-Sulawesi Seascape (SSS), a sub-region of Southeast Asia. This sub-regional policy planning approach illustrates how “scaling up” EAFM can support relevant international, regional, and other sub-regional fisheries management plans and environmental initiatives, while “scaling down” EAF can support relevant national, provincial/state, and local fisheries management plans in Indonesia, Malaysia and the Philippines.
Low-Elevation Coastal Zones in Central and South America are exposed to climate-related hazards (sea-level rise, climate variability and storms) which threaten the assets (people, resources, ecosystems, infrastructure, and the services they provide), and are expected to increase due to climate change. A non-systematic review is presented focusing on vulnerability elements, impacts, constraints to adaptation, and their possible strategies. The analysis emphasises the Intergovernmental Panel on Climate Change Reasons for Concern (e.g., threatened systems, extreme events, aggregated impacts, and critical thresholds), particularly on sea-level rise, degradation of mangroves, and invasive alien species in Central and South America focusing on case studies from Uruguay and Venezuela. Despite recent advances in coastal adaptation planning in Central and South America, there is an adaptation deficit in the implementation of measures and strategies against climate-related hazards, such as sea-level rise. Adaptation constraints are linked with poverty, resource allocation, lack of political will, and lack of early warning systems for climate-related hazards. Non-structural adaptation measures such as community-based adaptation and ecosystem-based adaptation are not fully mainstreamed into national plans yet. Government-level initiatives (e.g. National Adaptation Programmes of Action) are being developed, but a few are already implemented. In addition to specific thematic measures, the implementation of non-structural approaches, National Adaptation Programmes of Action and early warning systems, based on the reasons for concern, should foster adaptive capacity in coastal areas.
In this study, a general methodology that is based on numerical models and statistical analysis is developed to assist in the definition of marine litter cleanupand mitigation strategies at an estuarine scale. The methodology includes four main steps: k-means clustering to identify representative metocean scenarios; dynamic downscaling to obtain high-resolution drivers with which to force a transport model; numerical transport modelling to generate a database of potential litter trajectories; and a statistical analysis of this database to obtain probabilities of litter accumulation. The efficacy of this methodology is demonstrated by its application to an estuary along the northern coast of Spain by comparing the numerical results with field data. The necessary criteria to ensure its applicability to any other estuarywere provided. As the main conclusion, the developed methodology successfully assesses the litter distribution in estuaries with minimum computational effort.
This final manuscript in the special issue on “Funding for ocean conservation and sustainable fisheries” is the result of a dialogue aimed at connecting lead authors of the special issue manuscripts with relevant policymakers and practitioners. The dialogue took place over the course of a two-day workshop in December 2018, and this “coda” manuscript seeks to distil thinking around a series of key recurring topics raised throughout the workshop. These topics are collected into three broad categories, or “needs”: 1) a need for transparency, 2) a need for coherence, and 3) a need for improved monitoring of project impacts. While the special issue sought to collect new research into the latest trends and developments in the rapidly evolving world of funding for ocean conservation and sustainable fisheries, the insights collected during the workshop have helped to highlight remaining knowledge gaps. Therefore, each of the three “needs” identified within this manuscript is followed by a series of questions that the workshop participants identified as warranting further attention as part of a future research agenda. The crosscutting nature of many of the issues raised as well as the rapid pace of change that characterizes this funding landscape both pointed to a broader need for continued dialogue and study that reaches across the communities of research, policy and practice.
Beaches are economically and socially important to coastal regions. The intensive use of beaches requires active management to mitigate impacts to natural habitats and users. Understanding the patterns of beach use can assist in developing management actions designed to promote sustainable use. We assessed whether remotely piloted aerial systems (commonly known as drones) are an appropriate tool for quantifying beach use, and if beach activities are influenced by environmental conditions. Novel drone-based methods were used to quantify beach use. Drone flights recorded 2 km of beach, capturing video footage of the beach from the dune to water interface and the breaker zone. Flights were undertaken during three school holiday periods at four popular beaches in New South Wales, Australia. These videos were later analysed in the laboratory to categorise beach users. Of the total users sampled, 45.0% were sunbathing, 22.8% swimming, 21.2% walking, 10.6% surfing, and less than 0.5% were fishing. Participation in walking, surfing and fishing was similar throughout the sampling periods. However, sunbathing and swimming significantly increased during the austral spring and summer sampling periods. Usage patterns varied significantly among beaches, and during the different sampling periods, suggesting that adaptive management strategies targeted to specific areas are the most appropriate way to protect beach habitats and users. Furthermore, we demonstrate that drones are an effective assessment tool to improve coastal management decisions.
Marine protected areas (MPAs) have become an increasingly important tool to protect and conserve marine resources. However, there remains much debate about how effective MPAs are, especially in terms of their ability to protect mobile marine species such as teleost and chondrichthyan fishes. We used satellite and acoustic tags to assess the ability of a large oceanic MPA, the British Indian Ocean Territory MPA (BIOT MPA), to protect seven species of pelagic and reef-associated teleost and chondrichthyan fishes. We satellite-tagged 26 animals from six species (Blue Marlin, Reef Mantas, Sailfish, Silky Sharks, Silvertip Sharks, and Yellowfin Tuna), producing 2,735 days of movement data. We also acoustically tagged 121 sharks from two species (Grey Reef and Silvertip Sharks), which were monitored for up to 40 months across a large acoustic receiver array spanning the MPA. We found that the activity spaces of all satellite-tagged animals, including pelagic species, were much smaller than the area of the BIOT MPA, even taking into account errors associated with position estimates. Estimates of space use of acoustically tagged sharks, based on dynamic Brownian Bridge Movement Models (dBBMM), were also much smaller than the size of the MPA. However, we found important limitations when using dBBMM and demonstrate its sensitivity to both study duration and array design. We found that Grey Reef Sharks should be monitored for at least 1 year and Silvertip Sharks for 2 years before their activity space can be effectively estimated. We also demonstrate the potentially important role that intraspecific variability in spatial ecology may play in influencing the ability of MPAs to effectively protect populations of mobile species. Overall, our results suggest that, with effective enforcement, MPAs on the scale of the BIOT MPA potentially offer protection to a variety of pelagic and reef species with a range of spatial ecologies. We suggest that animals need to be tagged across seasons, years, and ontogenetic stages, in order to fully characterize their spatial ecology, which is fundamental to developing and implementing effective MPAs to conserve the full life history of target species.
Climate change and human disturbance threatens coral reefs across the Pacific, yet there is little consensus on what characterizes a “healthy” reef. Benthic cover, particularly low coral cover and high macroalgae cover, are often used as an indicator of reef degradation, despite uncertainty about the typical algal community compositions associated with either near-pristine or damaged reefs. In this study, we examine differences in coral and algal community compositions and their response to human disturbance and past heat stress, by analysing 25 sites along a gradient of human disturbance in Majuro and Arno Atolls of the Republic of the Marshall Islands. Our results show that total macroalgae cover indicators of reef degradation may mask the influence of local human disturbance, with different taxa responding to disturbance differently. Identifying macroalgae to a lower taxonomic level (e.g. the genus level) is critical for a more accurate measure of Pacific coral reef health.
Regional fisheries management organizations (RFMOs) are key bodies responsible for managing fisheries on the high seas and also in areas of the ocean under national jurisdiction. The performance of RFMOs has, however, become the focus of broad-based criticism in the context of increasing fishing effort, the scale, and sophistication of illegal, unregulated and unreported fishing, and concerns over the wider environmental impacts of fishing activities. In response to these criticisms, the United Nations General Assembly has called on RFMOs to carry out performance reviews (PRs) to assess their record in fisheries management. PRs can provide the opportunity to assess the strengths and weaknesses of past actions by specific RFMOs. There is, however, limited information and analysis available on the progress made by RFMOs after PRs have been carried out. To fill this gap, this paper assesses the performance of five RFMOs that have undergone PRs on two occasions. The paper assesses the performance of these five RFMOs against a scoring system that analyses improvements made after the first PR based on the recommendations made in the second PR. This analysis is encouraging, as all five RFMOs demonstrated significant improvement in their performance in the period after their initial PR, especially in “conservation and management” and “international cooperation” activities.
Aquaculture has been identified to have potentials for adapting climate impacts, and it is being leveraged upon in some developing tropical African countries for food production, employment, food security and poverty eradication. However, it is also vulnerable to climate impacts, linked with certain ecological challenges and competition from anthropogenic factors. This chapter utilized secondary and primary data from various sources to address review questions bordering on the vulnerability of tropical Africa to impact of climate change, potentials of utilizing aquaculture for enhanced climate impact adaptation and food security, aquaculture-related ecological issues and the required management, policy and regulatory actions for its sustainable utilization in this regard. The study revealed that tropical Africa is vulnerable to climate change; aquaculture has viable elements for climate impact adaptation and food security but could contribute to environmental challenges. Aquaculture however has capacity to adjust to the environmental claims, achievable through adequate monitoring, control and surveillance for adherence to ecological considerations. There is the need to specifically formulate policies and provide a strong institutional framework to cater for the nuances of aquaculture, climate impact adaptation and food security. And to ensure for sustenance, it is necessary to strengthen policies and management frameworks with human and financial capacity, within the implementing agencies at local, national and regional levels in tropical Africa.
Although the existence of zooxanthellate corals in mesophotic coral ecosystems (MCEs; light-dependent coral ecosystems from 30 to 150 m in depth) has been known since the nineteenth century and focused scientific exploration of MCEs began over 50 years ago, more than 70% of all research on MCEs has been published only within the past seven years. MCEs represent approximately 80% of potential coral reef habitat worldwide, yet very little is known about them in comparison to shallow reefs. Many MCE species new to science have been discovered in the past decade, and many more await discovery. The term MCEs has been widely adopted by the scientific community since its 2008 inception; however, there is considerable inconsistency in how it is subdivided into “upper” and “lower” (and sometimes “middle”) zones. Moreover, doing so may lead to artificial boundaries when habitats and ecological communities at different depth zones may blend together. Growing evidence suggests that MCEs harbor proportionally more geographically endemic species than their shallow-water counterparts, and initial indications are that major biogeographic patterns described for shallow reef organisms may not apply to MCEs. Although MCEs may serve as refugia for some shallow species, they are increasingly recognized as unique ecosystems, important in their own right. Future research on MCEs should aim to address gaps in our understanding of the basic physical and biological characteristics of MCEs including geography, taxonomic composition, depth distribution, ecology, physiology, and connectivity. Improving knowledge of MCEs would benefit from combining different technologies to leverage the strengths of each.