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Vulnerability of marine megafauna to global at-sea anthropogenic threats
No full textMarine megafauna species are affected by a wide range of anthropogenic threats. To evaluate the risk of such threats, species’ vulnerability to each threat must first be determined. We build on the existing threats classification scheme and ranking system of the International Union for Conservation of Nature (IUCN) Red List of Threatened Species by assessing the vulnerability of 256 marine megafauna species to 23 at-sea threats. The threats we considered included individual fishing gear types, climate-change-related subthreats not previously assessed, and threats associated with coastal impacts and maritime disturbances. Our ratings resulted in 70 species having high vulnerability (v > 0.778 out of 1) to at least 1 threat, primarily drifting longlines, temperature extremes, or fixed gear. These 3 threats were also considered to have the most severe effects (i.e., steepest population declines). Overall, temperature extremes and plastics and other solid waste were rated as affecting the largest proportion of populations. Penguins, pinnipeds, and polar bears had the highest vulnerability to temperature extremes. Bony fishes had the highest vulnerability to drifting longlines and plastics and other solid waste; pelagic cetaceans to 4 maritime disturbance threats; elasmobranchs to 5 fishing threats; and flying birds to drifting longlines and 2 maritime disturbance threats. Sirenians and turtles had the highest vulnerability to at least one threat from all 4 categories. Despite not necessarily having severe effects for most taxonomic groups, temperature extremes were rated among the top threats for all taxa except bony fishes. The vulnerability scores we provide are an important first step in estimating the risk of threats to marine megafauna. Importantly, they help differentiate scope from severity, which is key to identifying threats that should be prioritized for mitigatio
Seawater carbonate chemistry based carbon dioxide removal: towards commonly agreed principles for carbon monitoring, reporting, and verification
Full text linkCarbon Dioxide Removal (CDR) from the atmosphere is unavoidable if we are to meet the Paris Agreement’s goal of limiting global warming to 1.5°C, and almost certainly required to limit warming to 2°C. The ocean exchanges carbon dioxide (CO 2 ) with the atmosphere and is a large repository of carbon that could either be partially emptied to allow more CO 2 absorption or have its carbon storage capacity enhanced to allow it to remove additional CO 2 from the atmosphere. Early-stage techniques exist to utilise the ocean in atmospheric CO 2 removal, but typically, the atmospheric CO 2 removal these techniques stimulate happens downstream of their activity. Verifying the carbon removal associated with these techniques, while critical when evaluating the approaches and pricing the removal, is challenging. This study briefly reviews the challenges associated with verifying the carbon removal associated with non-biological (abiotic) engineered marine CDR approaches, specifically Ocean Alkalinity Enhancement and Direct Ocean Carbon Capture and Storage, and presents the findings from a workshop held with interested parties spanning industry to government, focused on their collective requirements for the Monitoring, Reporting, and Verification (MRV) of carbon removal. We find that it is possible to agree on a common set of principles for abiotic marine MRV, but identify that delivering this MRV with today’s understanding and technology could be prohibitively expensive. We discuss focal areas to drive down marine MRV costs and highlight the importance of specification of MRV criteria by an ultimate regulator to stimulate investment into the required work. High-quality MRV is important to correctly price any CO 2 removal, but we identify that accessibility and transparency in MRV approaches are also key in realising the broader benefits of MRV to society
Rising Tide to Silent Tsunami: Unveiling the role of plastics in driving antimicrobial resistance
Full text linkPollution caused by plastic production and waste has severe consequences on global economies, social inequalities, and ecosystems. Likewise, antimicrobial resistance (AMR) is one of the greatest One Health challenges. These threats are typically considered in isolation, but there is likely a complex interplay between the two. By adopting a systems approach and looking across the whole life cycle of plastics, we propose the range of ways in which plastic may influence AMR. Starting with raw material extraction processes where the leaching of potentially AMR co-selective chemicals used in pumping or piping of plastic feedstocks may influence AMR development in environmental microbial communities. Then, during production and manufacture, the use of plastic additives may impose selection for AMR. Finally, during use, collection or disposal, plastics can transport AMR biofilms in the community, clinical, agricultural, or aquatic settings. By linking these two important One Health threats, we may be better equipped and informed to combat them
Greening of grey and murky harbours: enhancing biodiversity and ecosystem functioning on artificial shorelines
No full textShoreline armouring in coastal cities can cause habitat degradation and biodiversity loss, often exacerbated by common anthropogenic stressors. Boulders are used as riprap to create revetments walls; but the homogenous surface and absence of shelter reduces intertidal biodiversity and ecosystem functioning. Eco-engineering can mitigate habitat loss through the addition of water retention and other microhabitats. We deployed four eco-engineered designs in a degraded harbour riprap for 18 months. Two units with site-specific designs combined multiple microhabitat types, attracting the highest species diversity. All four designs generally increased within-site β diversity and fish diversity compared to nearby unmanipulated ripraps. Suspension-feeding species and more species within key functional groups colonised eco-engineered units at patch and site scale. Tailored, site-specific eco-engineering shows great potential to rehabilitate degraded ripraps into functional, novel ecosystems. Combining eco-engineering with anthropogenic stress reduction to enable recovery can enhance biodiversity and ecosystem functioning in coastal citie
Monitoring Impacts of the Gulf Stream and its Rings on the Physics, Chemistry, and Biology of the Middle Atlantic Bight Shelf and Slope from CMV Oleander
No full textSustained observation is key to measuring physical and ecological variability in the Northwest Atlantic. Here we illustrate how a partnership with a merchant marine container vessel in service between New Jersey and Bermuda twice per week gives scientists a unique window into upper ocean currents, water properties, and marine ecology. Scientific observations collected from CMV Oleander, operated by Bermuda Container Line/Neptune Group, enable cross-disciplinary research, complement satellite measurements, and contribute to global observing programs—including the Global eXpendable BathyThermograph (XBT) Network, the Surface Ocean CO2 Atlas (SOCAT), and the Continuous Plankton Recorder (CPR) Survey. Recent co-located measurements along the Oleander Line document that fronts in temperature, salinity, and carbon dioxide concentrations align with the (sub)mesoscale circulation patterns. The sustained observations show warming and shrinking of the Slope Sea, a northward shift of the Gulf Stream, and warming of the “18°C water” (subtropical North Atlantic mode water) to 19°
Seasonal and spatial patterns of adult Antarctic krill at the Antarctic Peninsula: insights from a 41 year data analysis
Full text linkLocating the spawning grounds of Antarctic krill Euphausia superba is key to understanding their population dynamics and managing the commercial krill fishery. In the shelf waters of the Antarctic Peninsula where krill and their fishery are concentrated, a recent relaxation of fishing quotas has meant that locally successful spawning grounds could become increasingly targeted. This study revisits the existing paradigm that in summer, larger adult krill migrate away from these shelf-based fishing grounds, out towards oceanic waters to spawn off the shelf break (>1000 m). Our findings support a seasonal on-shelf division of adult krill, with smaller krill closer inshore. However, contrary to current understanding, our results suggest that 85% of the largest and most fecund >50 mm krill remain on-shelf during the summer spawning season. All adults (>30 mm) were strongly concentrated over the shelf throughout the whole spring-summer-autumn transition, with no evidence for any summer redistribution off-shelf. The Western Antarctic Peninsula (WAP) has strong on-shelf-off-shelf gradients in chlorophyll a and sea surface temperature, and based on generalised additive models, our study suggests that the high food requirement of adult krill, coupled with an oligotrophic off-shelf environment, contributes to the distribution of krill observed at the Antarctic Peninsula. The concentration of large, nutritious krill over the shelf throughout the season may be advantageous to land-based predators but raises concern for the management of fisheries that are becoming increasingly concentrated within the key adult krill habitat along the northern shelf of the WAP
Diapycnal Nutrient Fluxes and a Practical Assessment of the Biological Nutrient Trap in the North and South Atlantic Subtropical Gyres
Full text linkDiapycnal mixing supplies nutrients to the euphotic zone, which in oligotrophic regions may
substantially support rates of new production. However, the consensus view that diapycnal nutrient fluxes
support new production within the entire euphotic zone is challenged by deep living autotrophs that likely
consume some, if not all, of the diapycnal flux at depth. Quantifying how much of the diapycnal nitrate flux is
trapped by biological consumption immediately above the nitracline remains challenging and the implications
of nutrient trapping for comparisons of cross‐nitracline diapycnal fluxes with euphotic zone integrals of new
production remains unclear. It is increasingly important therefore to determine where in the euphotic zone the
diapycnal flux has impact. In this study, a simple assessment is presented of the strength of the “nutrient trap,”
which is attributed to picoeukaryotes, a widely distributed group of autotrophic picoplankton found in the
subtropical and tropical ocean. This study finds significant potential for the total consumption of diapycnal
nutrient fluxes within a few meters of the nitracline, thus largely negating the significance of vertical diffusive
fluxes for processes occurring at shallower depths. These results suggest that the significance of diapycnal
nutrient fluxes for integrated productivity estimates is lower than generally assumed. Yet, although diapycnal
fluxes cannot be entirely discounted from nutrient budgets due to seasonality in the consumption of such fluxes
at depth, this likely makes harder current modeling efforts to constrain future ocean productivity where
predictions of increased stratification generally favor greater reliance upon the diapycnal pathway to support
production
Cooperative agreement between countries of the North Atlantic Ocean reduces marine plastic pollution but with unequal economic benefits
Full text linkPlastic pollution in the world’s oceans threatens ecosystems and biodiversity. The connected nature of the marine environment suggests that coordinated actions by countries sharing an ocean border may provide more effective pollution control than unilateral actions by any one country. However, countries often fail to cooperate, even when joint economic benefits would be higher under cooperation. Here we present a modelling framework to determine the potential economic benefits of cooperative marine plastic pollution management. The framework integrates an estimated plastic transfer matrix from a particle tracking model with game theory to derive the economic benefits of international cooperation for 16 countries bordering the North Atlantic Ocean. Subject to modelling uncertainties, a fully cooperative agreement yields aggregate annual net benefits of around $36 billion and a 64% reduction in emissions. The net benefits of cooperation persist over alternative scenarios and considering the impact of uncertainties but vary in magnitude and distribution
The influence of subtidal Laminaria canopies on local environmental conditions and the structure of understorey communities
No full textUnderstanding the role of species interactions (e.g. competition and facilitation) in structuring communities is a fundamental goal of ecology. It is well established that large canopy-forming seaweeds (e.g. kelps and fucoids) exert a strong influence on community structure, by offering biogenic habitat, altering environmental conditions and interacting with other species. While many studies have manipulated the density of seaweeds to causatively examine their effects on the local environment and associated communities, they are biased towards certain regions and canopy-forming species. We conducted a manipulative experiment at two subtidal sites characterised by mixed Laminaria canopies, in southwest England, UK. Three treatments were established in multiple replicate circular plots (area of 7.1 m2): 0% kelp removal (i.e. unmanipulated control), 50% kelp removal (i.e. thinning), and 100% removal. Within each plot, temperature, light levels and sedimentation rates were monitored over 3 months, and after 5 months the density of juvenile kelp recruits, the biomass of understorey macroalgae and the abundance of recruiting fauna were quantified. We found kelp canopies had no impact on temperature or sedimentation rates but their removal led to marked increases in light availability, juvenile kelp recruitment and understorey macroalgal biomass. Overall, our study shows that physical disturbance to Laminaria canopies alters resource availability (i.e. light and space), leading to increased abundances of kelp recruits and understory algae. Significant reductions in kelp canopy density, driven by storm disturbance, harvesting or decreased water quality for example, would lead to shifts in community structure and ecological functionin
Plant-like heliotropism in a photosymbiotic animal
No full textAs in plants, photosynthesis also represents a key energy source in photosymbiotic cnidarians bearing microalgae. We observed that the cnidarian sea anemone Anemonia viridis, commonly known as the snakelocks anemone, displayed heliotropism or solar tracking in their natural habitats. When exposed to sunlight, A. viridis point their tentacles towards the sun while remaining sessile, facing east at dawn and west at dusk as they track the sun's relative position through the day. This phenomenon was previously only observed in plants. Solar tracking movements in A. viridis are driven by peak wavelengths that prompt photosynthesis in their endosymbionts. The heliotropic response was absent in both bleached (aposymbiotic) A. viridis and in symbiotic A. viridis with chemically inhibited photosynthesis. We revealed a direct correlation between heliotropism and symbiont oxygen production in A. viridis and showed how photosymbiotic A. viridis utilises this mechanism to modulate exposure to solar irradiation. Our study exemplifies how photosynthetic organisms such as plants and symbiotic sea anemones, display similar behaviour in response to similar environmental pressure