94 results found
McInnes AS, Laczka OF, Baker KG, et al., 2019, Live cell analysis at sea reveals divergent thermal performance between photosynthetic ocean microbial eukaryote populations, ISME JOURNAL, Vol: 13, Pages: 1374-1378, ISSN: 1751-7362
De Frond HL, van Sebille E, Parnis JM, et al., 2019, Estimating the mass of chemicals associated with ocean plastic pollution to inform mitigation efforts., Integr Environ Assess Manag
Plastic pollution in the marine environment is well documented. What remains less recognized and understood are the chemicals associated with it. Plastics enter the ocean with unreacted monomers, oligomers and additives, which can leach over time. Moreover, plastics sorb organic and inorganic chemicals from surrounding seawater, e.g., polychlorinated biphenyls (PCBs) and metals. Thus, interception and clean-up of plastics reduces the amount of chemical contaminants entering or re-entering the oceans, and removes those already present. Here, we estimate: 1) the mass of selected chemical additives entering the global oceans with common plastic debris items, and 2) the mass of sorbed chemicals (using PCBs as a case study) associated with microplastics in select locations. We estimate the mass of additives that entered the oceans in 2015 as constituents of seven common plastic debris items (bottles, bottle caps, expanded polystyrene containers, cutlery, grocery bags, food wrappers and straws/stirrers). We calculate that approximately 190 Tonnes of 20 chemical additives entered the oceans with these items in 2015. We also estimate the mass of PCBs associated with microplastics in two coastal (Hong Kong and Hawaii) and two open ocean (N. Pacific and S. Atlantic gyres) locations, as comparative case studies. We find that the mass of chemicals is related to the mass of plastics in a location, with greater mass of PCBs closer to the source (i.e., land), where there is more plastic per unit area compared to the open ocean. We estimate approximately 85,000 times more PCBs associated with plastics in an average 4.5 km stretch of beach in Hong Kong than from the same size transect in the N. Pacific gyre. In conclusion, continuing efforts for plastic interception and clean-up on shorelines effectively reduces the amount of plastic related chemicals entering and/or re-entering the marine environment. This article is protected by copyright. All rights reserved.
Lacerda ALDF, Rodrigues LDS, van Sebille E, et al., 2019, Plastics in sea surface waters around the Antarctic Peninsula, Scientific Reports, Vol: 9, ISSN: 2045-2322
Although marine plastic pollution has been the focus of several studies, there are still many gaps in our understanding of the concentrations, characteristics and impacts of plastics in the oceans. This study aimed to quantify and characterize plastic debris in oceanic surface waters of the Antarctic Peninsula. Sampling was done through surface trawls, and mean debris concentration was estimated at 1,794 items.km-2 with an average weight of 27.8 g.km-2. No statistical difference was found between the amount of mesoplastics (46%) and microplastics (54%). We found hard and flexible fragments, spheres and lines, in nine colors, composed mostly of polyurethane, polyamide, and polyethylene. An oceanographic dispersal model showed that, for at least seven years, sampled plastics likely did not originate from latitudes lower than 58°S. Analysis of epiplastic community diversity revealed bacteria, microalgae, and invertebrate groups adhered to debris. Paint fragments were present at all sampling stations and were approximately 30 times more abundant than plastics. Although paint particles were not included in plastic concentration estimates, we highlight that they could have similar impacts as marine plastics. We call for urgent action to avoid and mitigate plastic and paint fragment inputs to the Southern Ocean.
Onink V, Wichmann D, Delandmeter P, et al., 2019, The role of ekman currents, geostrophy, and stokes drift in the accumulation of floating microplastic, Journal of Geophysical Research: Oceans, Vol: 124, Pages: 1474-1490, ISSN: 2169-9275
Floating microplastic in the oceans is known to accumulate in the subtropical ocean gyres, but unclear is still what causes that accumulation. We investigate the role of various physical processes, such as surface Ekman and geostrophic currents, surface Stokes drift, and mesoscale eddy activity, on the global surface distribution of floating microplastic with Lagrangian particle tracking using GlobCurrent and WaveWatch III reanalysis products. Globally, the locations of microplastic accumulation (accumulation zones) are largely determined by the Ekman currents. Simulations of the North Pacific and North Atlantic show that the locations of the modeled accumulation zones using GlobCurrent Total (Ekman+Geostrophic) currents generally agree with observed microplastic distributions in the North Pacific and with the zonal distribution in the North Atlantic. Geostrophic currents and Stokes drift do not contribute to large-scale microplastic accumulation in the subtropics, but Stokes drift leads to increased microplastic transport to Arctic regions. Since the WaveWatch III Stokes drift and GlobCurrent Ekman current data sets are not independent, combining Stokes drift with the other current components leads to an overestimation of Stokes drift effects and there is therefore a need for independent measurements of the different ocean circulation components. We investigate whether windage would be appropriate as a proxy for Stokes drift but find discrepancies in the modeled direction and magnitude. In the North Pacific, we find that microplastic tends to accumulate in regions of relatively low eddy kinetic energy, indicating low mesoscale eddy activity, but we do not see similar trends in the North Atlantic.
Duncan EM, Arrowsmith J, Bain C, et al., 2018, The true depth of the Mediterranean plastic problem: extreme microplastic pollution on marine turtle nesting beaches in Cyprus, Marine Pollution Bulletin, Vol: 136, Pages: 334-340, ISSN: 0025-326X
We sampled 17 nesting sites for loggerhead (Caretta caretta) and green turtles (Chelonia mydas) in Cyprus. Microplastics (<5 mm) were found at all locations and depths, with particularly high abundance in superficial sand. The top 2 cm of sand presented grand mean ± SD particle counts of 45,497 ± 11,456 particles m−3(range 637–131,939 particles m−3). The most polluted beaches were among the worst thus far recorded, presenting levels approaching those previously recorded in Guangdong, South China. Microplastics decreased with increasing sand depth but were present down to turtle nest depths of 60 cm (mean 5,325 ± 3,663 particles m−3. Composition varied among beaches but hard fragments (46.5 ± 3.5%) and pre-production nurdles (47.8 ± 4.5%) comprised most categorised pieces. Particle drifter analysis hindcast for 365 days indicated that most plastic likely originated from the eastern Mediterranean basin. Worsening microplastic abundance could result in anthropogenically altered life history parameters such as hatching success and sex ratios in marine turtles.
Kontopoulos D-G, van Sebille E, Lange M, et al., 2018, Phytoplankton thermal responses adapt in the absence of hard thermodynamic constraints, Publisher: Cold Spring Harbor Laboratory
<jats:p>To better predict how populations and communities respond to climatic temperature variation, it is necessary to understand how the shape of the response of fitness-related traits to temperature evolves (the thermal performance curve). Currently, there is disagreement about the extent to which the evolution of thermal performance curves is constrained. One school of thought has argued for the prevalence of thermodynamic constraints through enzyme kinetics, whereas another argues that adaptation can - at least partly - overcome such constraints. To shed further light on this debate, we perform a phylogenetic meta-analysis of the thermal performance curve of growth rate of phytoplankton - a globally important functional group -, controlling for potential environmental effects. We find that thermodynamic constraints have a minor influence on the shape of the curve. In particular, we detect a very weak increase of the maximum curve height with the temperature at which the curve peaks, suggesting a weak "hotter-is-better" constraint. Also, instead of a constant thermal sensitivity of growth across species, as might be expected from strong constraints, we detect phylogenetic signal in this as well as all other curve parameters. Our results suggest that phytoplankton thermal performance curves adapt to thermal environments largely in the absence of hard thermodynamic constraints.</jats:p>
Hart-Davis MG, Backeberg BC, Halo I, et al., 2018, Assessing the accuracy of satellite derived ocean currents by comparing observed and virtual buoys in the Greater Agulhas Region, REMOTE SENSING OF ENVIRONMENT, Vol: 216, Pages: 735-746, ISSN: 0034-4257
Fraser C, Morrison AK, Hogg AM, et al., 2018, Antarctica's ecological isolation will be broken by storm-driven dispersal and warming, NATURE CLIMATE CHANGE, Vol: 8, Pages: 704-+, ISSN: 1758-678X
Rodríguez-Zárate CJ, Sandoval-Castillo J, van Sebille E, et al., 2018, Isolation by environment in the highly mobile olive ridley turtle (Lepidochelys olivacea) in the eastern Pacific, Proceedings of the Royal Society B: Biological Sciences, Vol: 285, ISSN: 1471-2954
Spatial and temporal scales at which processes modulate genetic diversity over the landscape are usually overlooked, impacting the design of conservation management practices for widely distributed species. We examine processes shaping population divergence in highly mobile species by re-assessing the case of panmixia in the iconic olive ridley turtle from the eastern Pacific. We implemented a biophysical model of connectivity and a seascape genetic analysis based on nuclear DNA variation of 634 samples collected from 27 nesting areas. Two genetically distinct populations largely isolated during reproductive migrations and mating were detected, each composed of multiple nesting sites linked by high connectivity. This pattern was strongly associated with a steep environmental gradient and also influenced by ocean currents. These findings relate to meso-scale features of a dynamic oceanographic interface in the eastern tropical Pacific (ETP) region, a scenario that possibly provides different cost-benefit solutions and selective pressures for sea turtles during both the mating and migration periods. We reject panmixia and propose a new paradigm for olive ridley turtles where reproductive isolation due to assortative mating is linked to its environment. Our study demonstrates the relevance of integrative approaches for assessing the role of environmental gradients and oceanographic currents as drivers of genetic differentiation in widely distributed marine species. This is relevant for the conservation management of species of highly mobile behaviour, and assists the planning and development of large-scale conservation strategies for the threatened olive ridley turtles in the ETP.
Ardhuin F, Aksenov Y, Benetazzo A, et al., 2018, Measuring currents, ice drift, and waves from space: the Sea surface KInematics Multiscale monitoring (SKIM) concept, OCEAN SCIENCE, Vol: 14, Pages: 337-354, ISSN: 1812-0784
Phillips JS, Sen Gupta A, Senina I, et al., 2018, An individual-based model of skipjack tuna (Katsuwonus pelamis) movement in the tropical Pacific ocean, PROGRESS IN OCEANOGRAPHY, Vol: 164, Pages: 63-74, ISSN: 0079-6611
Bull CYS, Kiss AE, van Sebille E, et al., 2018, The Role of the New Zealand Plateau in the Tasman Sea Circulation and Separation of the East Australian Current, JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, Vol: 123, Pages: 1457-1470, ISSN: 2169-9275
The East Australian Current (EAC) plays a major role in regional climate, circulation, and ecosystems, but predicting future changes is hampered by limited understanding of the factors controlling EAC separation. While there has been speculation that the presence of New Zealand may be important for the EAC separation, the prevailing view is that the time‐mean partial separation is set by the ocean's response to gradients in the wind stress curl. This study focuses on the role of New Zealand, and the associated adjacent bathymetry, in the partial separation of the EAC and ocean circulation in the Tasman Sea. Here utilizing an eddy‐permitting ocean model (NEMO), we find that the complete removal of the New Zealand plateau leads to a smaller fraction of EAC transport heading east and more heading south, with the mean separation latitude shifting >100 km southward. To examine the underlying dynamics, we remove New Zealand with two linear models: the Sverdrup/Godfrey Island Rule and NEMO in linear mode. We find that linear processes and deep bathymetry play a major role in the mean Tasman Front position, whereas nonlinear processes are crucial for the extent of the EAC retroflection. Contrary to past work, we find that meridional gradients in the basin‐wide wind stress curl are not the sole factor determining the latitude of EAC separation. We suggest that the Tasman Front location is set by either the maximum meridional gradient in the wind stress curl or the northern tip of New Zealand, whichever is furthest north.
Cetina-Heredia P, van Sebille E, Matear RJ, et al., 2018, Nitrate Sources, Supply, and Phytoplankton Growth in the Great Australian Bight: An Eulerian-Lagrangian Modeling Approach, JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, Vol: 123, Pages: 759-772, ISSN: 2169-9275
Smith TM, York PH, Broitman BR, et al., 2018, Rare long-distance dispersal of a marine angiosperm across the Pacific Ocean, GLOBAL ECOLOGY AND BIOGEOGRAPHY, Vol: 27, Pages: 487-496, ISSN: 1466-822X
AimLong‐distance dispersal (LDD) events occur rarely but play a fundamental role in shaping species biogeography. Lying at the heart of island biogeography theory, LDD relies on unusual events to facilitate colonization of new habitats and range expansion. Despite the importance of LDD, it is inherently difficult to quantify due to the rarity of such events. We estimate the probability of LDD of the seagrass Heterozostera nigricaulis, a common Australian species, across the Pacific Ocean to colonize South America.LocationCoastal Chile, Australia and the Pacific Ocean.MethodsGenetic analyses of H. nigricaulis collected from Chile and Australia were used to assess the relationship between the populations and levels of clonality. Ocean surface current models were used to predict the probability of propagules dispersing from south‐east Australia to central Chile and shipping data used to determine the likelihood of anthropogenic dispersal.ResultsOur study infers that the seagrass H. nigricaulis dispersed from Australia across the entire width of the Pacific (c. 14,000 km) to colonize South America on two occasions. Genetic analyses reveal that these events led to two large isolated clones, one of which covers a combined area of 3.47 km2. Oceanographic models estimate the arrival probability of a dispersal propagule within 3 years to be at most 0.00264%. Early shipping provides a potential alternative dispersal vector, yet few ships sailed from SE Australia to Chile prior to the first recording of H. nigricaulis and the lack of more recent and ongoing introductions demonstrate the rarity of such dispersal.Main conclusionsThese findings demonstrate LDD does occur over extreme distances despite very low probabilities. The large number of propagules (100s of millions) produced over 100s of years suggests that the arrival of propagules in Chile was inevitable and confirms the importance of LDD for species distributions and community ecology.
McAdam R, van Sebille E, 2018, Surface connectivity and inter-ocean exchanges from drifter-based transition matrices, Journal of Geophysical Research: Oceans, Vol: 123, Pages: 514-532, ISSN: 2169-9275
Global surface transport in the ocean can be represented by using the observed trajectories of drifters to calculate probability distribution functions. The oceanographic applications of the Markov Chain approach to modelling include tracking of floating debris and water masses, globally and on yearly-to-centennial timescales. Here, we analyse the error inherent with mapping trajectories onto a grid and the consequences for ocean transport modelling and detection of accumulation structures. A sensitivity analysis of Markov Chain parameters is performed in an idealised Stommel gyre and western boundary current as well as with observed ocean drifters, complementing previous studies on widespread floating debris accumulation. Focusing on two key areas of inter-ocean exchange - the Agulhas System and the North Atlantic intergyre transport barrier - we assess the capacity of the Markov Chain methodology to detect surface connectivity and dynamic transport barriers. Finally, we extend the methodology's functionality to separate the geostrophic and non-geostrophic contributions to inter-ocean exchange in these key regions.
Bond T, Ferrandiz-Mas V, Felipe-Sotelo M, et al., 2018, The occurrence and degradation of aquatic plastic litter based on polymer physicochemical properties: A review, CRITICAL REVIEWS IN ENVIRONMENTAL SCIENCE AND TECHNOLOGY, Vol: 48, Pages: 685-722, ISSN: 1064-3389
Hennekam R, Zinke J, van Sebille E, et al., 2018, Cocos (Keeling) Corals Reveal 200 Years of Multidecadal Modulation of Southeast Indian Ocean Hydrology by Indonesian Throughflow, PALEOCEANOGRAPHY AND PALEOCLIMATOLOGY, Vol: 33, Pages: 48-60, ISSN: 2572-4517
Brach L, Deixonne P, Bernard M-F, et al., 2017, Anticyclonic eddies increase accumulation of microplastic in the North Atlantic subtropical gyre, MARINE POLLUTION BULLETIN, Vol: 126, Pages: 191-196, ISSN: 0025-326X
There are fundamental gaps in our understanding of the fates of microplastics in the ocean, which must be overcome if the severity of this pollution is to be fully assessed. The predominant pattern is high accumulation of microplastic in subtropical gyres. Using in situ measurements from the 7th Continent expedition in the North Atlantic subtropical gyre, data from satellite observations and models, we show how microplastic concentrations were up to 9.4 times higher in an anticyclonic eddy explored, compared to the cyclonic eddy. Although our sample size is small, this is the first suggestive evidence that mesoscale eddies might trap, concentrate and potentially transport microplastics. As eddies are known to congregate nutrients and organisms, this phenomenon should be considered with regards to the potential impact of plastic pollution on the ecosystem in the open ocean.
Bull CYS, Kiss AE, Jourdain NC, et al., 2017, Wind Forced Variability in Eddy Formation, Eddy Shedding, and the Separation of the East Australian Current, JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, Vol: 122, Pages: 9980-9998, ISSN: 2169-9275
van Sebille E, Griffies SM, Abernathey R, et al., 2017, Lagrangian ocean analysis: fundamentals and practices, Ocean Modelling, Vol: 121, Pages: 49-75, ISSN: 1463-5003
Lagrangian analysis is a powerful way to analyse the output of ocean circulation models and other ocean velocity data such as from altimetry. In the Lagrangian approach, large sets of virtual particles are integrated within the three-dimensional, time-evolving velocity fields. Over several decades, a variety of tools and methods for this purpose have emerged. Here, we review the state of the art in the field of Lagrangian analysis of ocean velocity data, starting from a fundamental kinematic framework and with a focus on large-scale open ocean applications. Beyond the use of explicit velocity fields, we consider the influence of unresolved physics and dynamics on particle trajectories. We comprehensively list and discuss the tools currently available for tracking virtual particles. We then showcase some of the innovative applications of trajectory data, and conclude with some open questions and an outlook. The overall goal of this review paper is to reconcile some of the different techniques and methods in Lagrangian ocean analysis, while recognising the rich diversity of codes that have and continue to emerge, and the challenges of the coming age of petascale computing.
Goddijn-Murphy L, Peters S, Van Sebille E, et al., 2017, Concept for a hyperspectral remote sensing algorithm for floating macro plastics, MARINE POLLUTION BULLETIN, Vol: 126, Pages: 255-262, ISSN: 0025-326X
There is growing global concern over the chemical, biological and ecological impact of plastics in the ocean. Remote sensing has the potential to provide long-term, global monitoring but for marine plastics it is still in its early stages. Some progress has been made in hyperspectral remote sensing of marine macroplastics in the visible (VIS) to short wave infrared (SWIR) spectrum. We present a reflectance model of sunlight interacting with a sea surface littered with macro plastics, based on geometrical optics and the spectral signatures of plastic and seawater. This is a first step towards the development of a remote sensing algorithm for marine plastic using light reflectance measurements in air. Our model takes the colour, transparency, reflectivity and shape of plastic litter into account. This concept model can aid the design of laboratory, field and Earth observation measurements in the VIS-SWIR spectrum and explain the results.
Lange M, van Sebille E, 2017, Parcels v0.9: prototyping a Lagrangian Ocean Analysis framework for the petascale age, Geoscientific Model Development Discussions, Vol: 10, Pages: 4175-4186, ISSN: 1991-9611
As ocean general circulation models (OGCMs)move into the petascale age, where the output of single simulationsexceeds petabytes of storage space, tools to analysethe output of these models will need to scale up too. Lagrangianocean analysis, where virtual particles are trackedthrough hydrodynamic fields, is an increasingly popular wayto analyse OGCM output, by mapping pathways and connectivityof biotic and abiotic particulates. However, the currentsoftware stack of Lagrangian ocean analysis codes isnot dynamic enough to cope with the increasing complexity,scale and need for customization of use-cases. Furthermore,most community codes are developed for stand-aloneuse, making it a nontrivial task to integrate virtual particles atruntime of the OGCM. Here, we introduce the new Parcelscode, which was designed from the ground up to be suffi-ciently scalable to cope with petascale computing. We highlightits API design that combines flexibility and customizationwith the ability to optimize for HPC workflows, followingthe paradigm of domain-specific languages. Parcelsis primarily written in Python, utilizing the wide range oftools available in the scientific Python ecosystem, while generatinglow-level C code and using just-in-time compilationfor performance-critical computation. We show a worked-outexample of its API, and validate the accuracy of the codeagainst seven idealized test cases. This version 0.9 of Parcelsis focused on laying out the API, with future work concentratingon support for curvilinear grids, optimization, effi-ciency and at-runtime coupling with OGCMs.
Lange M, van Sebille E, 2017, Parcels v0.9: prototyping a Lagrangian ocean analysis framework for the petascale age, GEOSCIENTIFIC MODEL DEVELOPMENT, Vol: 10, Pages: 4175-4186, ISSN: 1991-959X
Koelmans AA, Kooi M, Law KL, et al., 2017, All is not lost: deriving a top-down mass budget of plastic at sea, ENVIRONMENTAL RESEARCH LETTERS, Vol: 12, ISSN: 1748-9326
Understanding the global mass inventory is one of the main challenges in present research on plastic marine debris. Especially the fragmentation and vertical transport processes of oceanic plastic are poorly understood. However, whereas fragmentation rates are unknown, information on plastic emissions, concentrations of plastics in the ocean surface layer (OSL) and fragmentation mechanisms is available. Here, we apply a systems engineering analytical approach and propose a tentative 'whole ocean' mass balance model that combines emission data, surface area-normalized plastic fragmentation rates, estimated concentrations in the OSL, and removal from the OSL by sinking. We simulate known plastic abundances in the OSL and calculate an average whole ocean apparent surface area-normalized plastic fragmentation rate constant, given representative radii for macroplastic and microplastic. Simulations show that 99.8% of the plastic that had entered the ocean since 1950 had settled below the OSL by 2016, with an additional 9.4 million tons settling per year. In 2016, the model predicts that of the 0.309 million tons in the OSL, an estimated 83.7% was macroplastic, 13.8% microplastic, and 2.5% was < 0.335 mm 'nanoplastic'. A zero future emission simulation shows that almost all plastic in the OSL would be removed within three years, implying a fast response time of surface plastic abundance to changes in inputs. The model complements current spatially explicit models, points to future experiments that would inform critical model parameters, and allows for further validation when more experimental and field data become available.
Axelsson C, van Sebille E, 2017, Prevention through policy: Urban macroplastic leakages to the marine environment during extreme rainfall events., Marine Pollution Bulletin, Vol: 124, Pages: 211-227, ISSN: 0025-326X
The leakage of large plastic litter (macroplastics) into the ocean is a major environmental problem. A significant fraction of this leakage originates from coastal cities, particularly during extreme rainfall events. As coastal cities continue to grow, finding ways to reduce this macroplastic leakage is extremely pertinent. Here, we explore why and how coastal cities can reduce macroplastic leakages during extreme rainfall events. Using nine global cities as a basis, we establish that while cities actively create policies that reduce plastic leakages, more needs to be done. Nonetheless, these policies are economically, socially and environmentally cobeneficial to the city environment. While the lack of political engagement and economic concerns limit these policies, lacking social motivation and engagement is the largest limitation towards implementing policy. We recommend cities to incentivize citizen and municipal engagement with responsible usage of plastics, cleaning the environment and preparing for future extreme rainfall events.
Cózar A, Martí E, Duarte CM, et al., 2017, The Arctic Ocean as a dead end for floating plastics in the North Atlantic branch of the Thermohaline Circulation., Science Advances, Vol: 3, ISSN: 2375-2548
The subtropical ocean gyres are recognized as great marine accummulation zones of floating plastic debris; however, the possibility of plastic accumulation at polar latitudes has been overlooked because of the lack of nearby pollution sources. In the present study, the Arctic Ocean was extensively sampled for floating plastic debris from the Tara Oceans circumpolar expedition. Although plastic debris was scarce or absent in most of the Arctic waters, it reached high concentrations (hundreds of thousands of pieces per square kilometer) in the northernmost and easternmost areas of the Greenland and Barents seas. The fragmentation and typology of the plastic suggested an abundant presence of aged debris that originated from distant sources. This hypothesis was corroborated by the relatively high ratios of marine surface plastic to local pollution sources. Surface circulation models and field data showed that the poleward branch of the Thermohaline Circulation transfers floating debris from the North Atlantic to the Greenland and Barents seas, which would be a dead end for this plastic conveyor belt. Given the limited surface transport of the plastic that accumulated here and the mechanisms acting for the downward transport, the seafloor beneath this Arctic sector is hypothesized as an important sink of plastic debris.
Everett JD, van Sebille E, Taylor MD, et al., 2017, Dispersal of Eastern King Prawn larvae in a western boundary current: New insights from particle tracking, Fisheries Oceanography, Vol: 26, Pages: 513-525, ISSN: 1054-6006
Patterns in larval transport of coastal species have important implications for species connectivity, conservation, and fisheries, especially in the vicinity of a strengthening boundary current. An Ocean General Circulation Model for the Earth Simulator particle tracking model was used to assess the potential dispersal of Eastern King Prawn (EKP) larvae Melicertus (Penaeus) plebejus, an important commercial and recreational species in Eastern Australia. Particles were exposed to a constant natural mortality rate, and temperature-dependent growth (degree-days) was used to determine the time of settlement. Forward and backward simulations were used to identify the extent of larval dispersal from key source locations, and to determine the putative spawning regions for four settlement sites. The mean dispersal distance for larvae was extensive (~750–1,000 km before settlement), yet the northern spawning locations were unlikely to contribute larvae to the most southern extent of the EKP range. There was generally great offshore dispersal of larvae, with only 2%–5% of larvae on the continental shelf at the time of settlement. Our particle tracking results were combined with existing site-specific reproductive potentials to identify the relative contributions of larvae from key source locations. Although mid-latitude sites had only moderate reproductive potential, they delivered the most particles to the southern coast and are probably the most important sources of larval EKP for the two southern estuaries. Our modelling suggests that mesoscale oceanography is a strong determinant of recruitment success of the EKP, and highlights the importance of both larval dispersal and reproductive potential for understanding connectivity across a species’ range.
Turney CSM, Fogwill CJ, Palmer JG, et al., 2017, Tropical forcing of increased Southern Ocean climate variability revealed by a 140-year subantarctic temperature reconstruction, CLIMATE OF THE PAST, Vol: 13, Pages: 231-248, ISSN: 1814-9324
Occupying about 14 % of the world's surface, the Southern Ocean plays a fundamental role in ocean and atmosphere circulation, carbon cycling and Antarctic ice-sheet dynamics. Unfortunately, high interannual variability and a dearth of instrumental observations before the 1950s limits our understanding of how marine–atmosphere–ice domains interact on multi-decadal timescales and the impact of anthropogenic forcing. Here we integrate climate-sensitive tree growth with ocean and atmospheric observations on southwest Pacific subantarctic islands that lie at the boundary of polar and subtropical climates (52–54° S). Our annually resolved temperature reconstruction captures regional change since the 1870s and demonstrates a significant increase in variability from the 1940s, a phenomenon predating the observational record. Climate reanalysis and modelling show a parallel change in tropical Pacific sea surface temperatures that generate an atmospheric Rossby wave train which propagates across a large part of the Southern Hemisphere during the austral spring and summer. Our results suggest that modern observed high interannual variability was established across the mid-twentieth century, and that the influence of contemporary equatorial Pacific temperatures may now be a permanent feature across the mid- to high latitudes.
Krüger L, Ramos JA, Xavier JC, et al., 2017, Identification of candidate pelagic marine protected areas through a seabird seasonal-, multispecific- and extinction risk-based approach, Animal Conservation, Vol: 20, Pages: 409-424, ISSN: 1367-9430
With increasing pressure on the oceans from environmental change, there has been a global call for improved protection of marine ecosystems through the implementation of marine protected areas (MPAs). Here, we used species distribution modelling (SDM) of tracking data from 14 seabird species to identify key marine areas in the southwest Atlantic Ocean, valuing areas based on seabird species occurrence, seasonality and extinction risk. We also compared overlaps between the outputs generated by the SDM and layers representing important human threats (fishing intensity, ship density, plastic and oil pollution, ocean acidification), and calculated loss in conservation value using fishing and ship density as cost layers. The key marine areas were located on the southern Patagonian Shelf, overlapping extensively with areas of high fishing activity, and did not change seasonally, while seasonal areas were located off south and southeast Brazil and overlapped with areas of high plastic pollution and ocean acidification. Non-seasonal key areas were located off northeast Brazil on an area of high biodiversity, and with relatively low human impacts. We found support for the use of seasonal areas depending on the seabird assemblage used, because there was a loss in conservation value for the seasonal compared to the non-seasonal approach when using ‘cost’ layers. Our approach, accounting for seasonal changes in seabird assemblages and their risk of extinction, identified additional candidate areas for incorporation in the network of pelagic MPAs.
Coleman MA, Cetina-Heredia P, Roughan M, et al., 2017, Anticipating changes to future connectivity within a network of marine protected areas, Global Change Biology, Vol: 23, Pages: 3533-3542, ISSN: 1365-2486
Continental boundary currents are projected to be altered under future scenarios of climate change. As these currents often influence dispersal and connectivity among populations of many marine organisms, changes to boundary currents may have dramatic implications for population persistence. Networks of marine protected areas (MPAs) often aim to maintain connectivity, but anticipation of the scale and extent of climatic impacts on connectivity are required to achieve this critical conservation goal in a future of climate change. For two key marine species (kelp and sea urchins), we use oceanographic modelling to predict how continental boundary currents are likely to change connectivity among a network of MPAs spanning over 1000 km of coastline off the coast of eastern Australia. Overall change in predicted connectivity among pairs of MPAs within the network did not change significantly over and above temporal variation within climatic scenarios, highlighting the need for future studies to incorporate temporal variation in dispersal to robustly anticipate likely change. However, the intricacies of connectivity between different pairs of MPAs were noteworthy. For kelp, poleward connectivity among pairs of MPAs tended to increase in the future, whereas equatorward connectivity tended to decrease. In contrast, for sea urchins, connectivity among pairs of MPAs generally decreased in both directions. Self-seeding within higher-latitude MPAs tended to increase, and the role of low-latitude MPAs as a sink for urchins changed significantly in contrasting ways. These projected changes have the potential to alter important genetic parameters with implications for adaptation and ecosystem vulnerability to climate change. Considering such changes, in the context of managing and designing MPA networks, may ensure that conservation goals are achieved into the future.
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