Extracellular enzymatic activity (EEA) is performed by cell-associated and cell-free (i.e., “dissolved”) enzymes. This cell-free fraction is operationally defined as passing through a 0.22 μm filter. The contribution of cell-free to total EEA is comparable to the cell-associated counterpart, so it is critical to understand what controls the relative importance of cell-free versus cell-associated EEA. However, attempts to tease apart the contribution of EEAs in the so-called dissolved fraction (<0.22 μm) in general, and of the nanoparticle size fraction (0.020–0.20 μm) in particular, to the total EEA pool are lacking. Here we performed experiments with Northern and Southern Hemisphere coastal waters to characterize the potential contribution of that nanoparticle fraction to the total EEA fraction of alkaline phosphatase, beta-glucosidase and leucine aminopeptidase. We found a significant contribution (in both hemispheres) of the nanoparticle fraction to the total EEA pool (up to 53%) that differed depending on the enzyme type and location. Collectively, our results indicate that a significant fraction of the so-called “dissolved EEA” is not really dissolved but associated to nanoparticles, colloidal nanogels and/or viruses. Thus, the total marine EEA pool can actually be divided into a cell-associated, undissolved-cell-free (associated to nano-particle of different origins such as viruses and nanogels) and a dissolved-cell-free pools. Our results also imply that the dissolved EEA pool is more complex than thus far anticipated. Future research will be now needed to further characterize the factors controlling the relative importance of these different pools of EEA, which are key in the recycling of organic matter in the ocean.
Anthropogenic effects have created various risks for wild animals. Boat traffic is one of the most fatal risks for marine mammals. Individual behavioral responses of cetaceans, including diving behavior such as changing swimming direction and lengthing inter-breath interval, to passing boats is relatively well known; however, the social function of cetacean responses to boat traffic in a natural setting remains poorly understood. We focused on describing the behavioral responses of single and aggregated finless porpoises to boats passing at Misumi West Port, Ariake Sound, Japan, by using a drone characterized with a high-precision bird’s-eye angle. During the study period, we collected 25 episodes of finless porpoise responses to boats passing by. A mean (± SEM) of 5.1 ± 1.0 individuals were observed for each episode. The primary response to passing boats was avoidance by dive, which implies boat traffic is a substantial disturbance to finless porpoises that travel along the seawater surface daily. The diving duration decreased significantly with an increase in the number of aggregated individuals. The diving and floating reaction times were 10.9 ± 2.3 s and 18.7 ± 5.0 s, respectively. There was no significant difference between the reaction times indicating that each individual was motivated to keep the group cohesion consistent when floating even after the risk had dissolved, which is comparable to the behavior of porpoises that dive when riskier conditions are present, such as when a boat approaches an aggregation. Our findings provide new insights on the sociality of finless porpoises even though there were limitations, like an inability to identify a specific individual. The drone enabled us to observe the social behavior of finless porpoises and other cetaceans at an unprecedented resolution, which may lead to a better understanding of the evolutionary diversity of intelligence and sociality and the bridge to human evolution.
Marine ecosystems of temperate regions are highly modified by human activity and far from their original natural status. The North Sea, known as an intensively used area, has lost its offshore oyster grounds due to overexploitation in a relatively short time. Native oyster beds as a once abundant and ecologically highly important biogenic reef-type have vanished from the North Sea ecosystem in most areas of both their former distribution and magnitude. Worldwide, oyster stocks have been severely exploited over the past centuries. According to estimates, about 85% of the worldwide oyster reef habitats have been destroyed over the course of the last century. This loss of oyster populations has meant far more than just the loss of a valuable food resource. Oyster reefs represent a characteristic benthic community which offers a variety of valuable ecosystem services: better water quality, local decrease of toxic algal blooms, increase in nutrient uptake, increase of bentho-pelagic coupling, increase in species richness, increase of multidimensional biogenic structures which provide habitat, food, and protection for numerous invertebrate and fish species. The aim of oyster restoration is to promote redevelopment of this valuable missing habitat. The development of strategies, methods, and procedures for a sustainable restoration of the European oyster Ostrea edulis in the German North Sea is currently a focus of marine nature conservation. Main drivers for restoring this ecological key species are the enhancement of biodiversity and ecosystem services in the marine environment. Results of these investigations will support the future development and implementation of a large-scale and long-term German native oyster restoration programme to re-establish a healthy population of this once-abundant species now absent from the region.
Coastal communities experience a wide array of environmental and social changes to which they must constantly adapt. Further, a community's perception of change and risk has significant implications for a community's willingness and ability to adapt to both current and future changes. As part of a larger study focusing on the adaptive capacity of communities on the Andaman Coast of Thailand, we used Photovoice to open a dialogue with communities about changes in the marine environment and in coastal communities. This article presents the results of two exploratory Photovoice processes and discusses prospects for using the Photovoice method for exploring social and environmental change. Changes examined included a number of broader environmental and social trends as well as ecological specifics and social particularities in each site. Participants also explored the social implications of environmental changes, the impacts of macro-scale processes on local outcomes, and emotive and active responses of individuals and communities to change. Photovoice is deemed a powerful method for: examining social, environmental, and socio-ecological change, triangulating to confirm the results of other scientific methods, revealing novel ecological interactions, and providing input into community processes focusing on natural resource management, community development, and climate change adaptation.
Vulnerability and adaptation to climate change have become a dominant theme in development and conservation research and work. Yet coastal communities are facing a wider array of different stressors that affect the sustainability of natural resources and the adaptive capacity of local residents. The ability of communities and households to adapt is influenced by the nature, number, and magnitude of the changes with which they have to contend. In this paper, we present the range of 36 socio-economic (i.e. economic, social, governance and conflict) and biophysical (i.e. climate change and other environmental) stressors that emerged from qualitative interviews in seven coastal communities on the Andaman coast of Thailand. These stressors were then integrated into a quantitative survey of 237 households wherein participants were asked to rate the level of impact of these stressors on household livelihoods. Ratings showed that economic and some climate change stressors – extreme weather events and changes in rainfall patterns and seasons – were scored higher than other stressors. The paper also examines the relationships between community and various individual and household characteristics – such as gender, age, livelihoods, levels of social capital, and socio-economic status – and the perceived level of impacts of various stressors on household livelihoods. Overall, community and livelihoods had the most differentiated impacts on perceptions of stressors but few other prominent patterns emerged. In conclusion, this paper discusses the implications of the results for current climate change vulnerability and adaptation policy and practice in Thailand and elsewhere.
Increases in seawater temperature associated with global climate change are causing the mutualistic relationship between reef-building corals and the symbiotic dinoflagellates (genus Symbiodinium) that reside within their cells to break down. There is consequently an urgent need to develop tools for modeling coral biology in response to environmental shifts, an enterprise that is complicated by the fact that no pristine reefs remain on Earth. This work sought to 1) uncover the environmental factors that contribute most to observed spatio-temporal variation in coral physiology and 2) devise means of detecting anomalous behavior in field corals by analyzing a dataset from the Austral (French Polynesia) and Cook Islands of the South Pacific with a multivariate statistical approach. Upon employing this multi-tiered analytical platform, host genotype was found to be the most significant driver of variation in physiology of the pocilloporid coral colonies sampled across the two archipelagos. Furthermore, those colonies demonstrating the most extensive variation across the seven response variables assessed tended to deviate most significantly from the global mean response calculated across all samples, suggesting that high within-sample physiological variability may be one means of delineating aberrant coral behavior in the absence of data from pristine control reefs.
Mitigating the negative impacts of invasive lionfish (Pterois volitans/milescomplex) is a top priority for marine reef fisheries management, with human removals considered the most viable approach to population control. Control efforts via diver spearfishing removals have annually removed tens of thousands of lionfish throughout their invasive range, but the effectiveness of removal efforts to remove 100% or achieve target lionfish densities in a given reef system has not been fully evaluated. Accounting for detection and removal efficacy is necessary for developing and evaluating lionfish management targets, as population- and community-level effects of lionfish removals may be diminished by undetected lionfish remaining in the system. This study quantified lionfish detection, catchability, and removal efficiency to evaluate the effectiveness of lionfish surveys and removal efforts on northern Gulf of Mexico (nGOM) artificial and natural reefs. Detection was assessed during crepuscular and midday time periods via diver and remotely operated vehicle (ROV) video surveys, with covariates for time of day and survey methodology assessed using generalized linear mixed models. Catchability and removal efficiency were estimated via depletion models based on serial removals via spearfishing on 6 artificial reefs and 9 natural reefs. A priori, we had expected lionfish detection to be higher during crepuscular periods given lionfish in the Caribbean and in their native range have been shown to forage more actively away from reefs then. However, we found lionfish detection was not significantly different between midday and crepuscular periods. Survey methodology affected detection, with 24% fewer lionfish being detected via ROV surveys versus diver surveys at artificial reefs and 72% fewer lionfish detected via ROV surveys at natural reefs. Therefore, density estimates on nGOM natural reefs, which constitute of >99% of the region’s habitat, may be higher than previously reported and problematic for lionfish management. Mean catchability for spearfishing lionfish was 0.88 on artificial reefs and 0.69 on natural reefs standardized for area. Mean removal efficiency for the first removal event was 87% on artificial reefs and 67% on natural reefs, higher than removal efficiency computed for Caribbean reefs (47%). Incomplete detection and <100% removal efficiency, in concert with density-dependent processes, may explain recent findings that sustained lionfish removal efforts had no discernible positive impacts on native reef fish communities.
Micro(nano)plastics, as emerging contaminants, have attracted worldwide attention. Nowadays, the environmental distribution, sources, and analysis methods and technologies of micro(nano)plastics have been well studied and recognized. Nevertheless, the role of micro(nano)plastic particles as vectors for attaching organisms is not fully understood. In this paper, the role of micro(nano)plastics as vectors, and their potential effects on the ecology are introduced. Micro(nano)plastics could 1) accelerate the diffusion of organisms in the environment, which may result in biological invasion; 2) increase the gene exchange between attached biofilm communities, causing the transfer of pathogenic and antibiotic resistance genes; 3) enhance the rate of energy, material and information flow in the environment. Accordingly, the role of microplastics as vectors for organisms should be further evaluated in the future research.
Environmental Impact Assessment (EIA) is an important process for evaluating the effects of development, and to assist decisions to effectively manage potential deep-sea mining (DSM). However, although EIA is a widely used and accepted approach, there has been considerable debate over its effectiveness. In this paper, we summarise some of the key problems raised by previous EIA reviews, as well as examining several EIAs carried out in recent years for DSM, and highlight issues identified by management agencies. Scientific shortcomings are discussed, and recommendations provided on ways to improve performance. These include inadequate baseline data, insufficient detail of the mining operation, insufficient synthesis of data and the ecosystem approach, poor assessment and consideration of uncertainty, inadequate assessment of indirect impacts, inadequate treatment of cumulative impacts, insufficient risk assessment, and consideration of linkages between EIA and other management plans. The focus of the paper is on scientific limitations, but we also consider some aspects of their application to elements of process and policy.
Designation of large expanses of the ocean as Marine Protected Area (MPA) is increasingly advocated and realised. The effectiveness of such MPAs, however, requires improvements to vessel monitoring and enforcement capability. In 2014 commercial fishing was excluded from the Ascension Island Exclusive Economic Zone (EEZ). In 2015, through updated regulations, a licenced fishery re-opened in the northern half of the EEZ while the southern half remained closed. To assess compliance with these closures and regulations, several promising satellite technologies (Satellite Automatic Identification System (S-AIS), Synthetic Aperture Radar (SAR), Vessel Monitoring System (VMS) of two vessels), were trialled alongside at-sea patrols. Use of SAR enabled assessment of ‘dark’ (non-AIS transmitting) vessels, the scope of whose activities are hardest to gauge. The high level of compliance with regulations observed, suggests the MPA may prove effective, yet a need for vigilance remains. Vessels aggregate near the EEZ border and a quarter of vessels tracked across three years exhibited S-AIS transmission gaps and present a heightened compliance risk. Use of remote, rather than local, expertise and infrastructure provide a blue-print and economies of scalefor replicating monitoring across similarly sized MPAs; particularly for large (>~ 25 m) vessels with metallic superstructures conducive to SAR detection. Funding ongoing monitoring in Ascension is challenged by current levels of license uptake, which provides insufficient offsetting revenue. Satellite-derived intelligence, can be used to set risk thresholds and trigger detailed investigations. Planning long-term monitoring must, however, incorporate adequate resources for follow-up, through patrols and correspondence with flag-states and fisheries management organisations.