RESUMEN
While the physical dimensions of climate change are now routinely assessed through multimodel intercomparisons, projected impacts on the global ocean ecosystem generally rely on individual models with a specific set of assumptions. To address these single-model limitations, we present standardized ensemble projections from six global marine ecosystem models forced with two Earth system models and four emission scenarios with and without fishing. We derive average biomass trends and associated uncertainties across the marine food web. Without fishing, mean global animal biomass decreased by 5% (±4% SD) under low emissions and 17% (±11% SD) under high emissions by 2100, with an average 5% decline for every 1 °C of warming. Projected biomass declines were primarily driven by increasing temperature and decreasing primary production, and were more pronounced at higher trophic levels, a process known as trophic amplification. Fishing did not substantially alter the effects of climate change. Considerable regional variation featured strong biomass increases at high latitudes and decreases at middle to low latitudes, with good model agreement on the direction of change but variable magnitude. Uncertainties due to variations in marine ecosystem and Earth system models were similar. Ensemble projections performed well compared with empirical data, emphasizing the benefits of multimodel inference to project future outcomes. Our results indicate that global ocean animal biomass consistently declines with climate change, and that these impacts are amplified at higher trophic levels. Next steps for model development include dynamic scenarios of fishing, cumulative human impacts, and the effects of management measures on future ocean biomass trends.
Asunto(s)
Biomasa , Cambio Climático , Océanos y Mares , Animales , Organismos Acuáticos/fisiología , Explotaciones Pesqueras/estadística & datos numéricos , Peces/fisiología , Cadena Alimentaria , Modelos TeóricosRESUMEN
Background and Aims: Enhancement of light harvesting in annual crops has successfully led to yield increases since the green revolution. Such an improvement has mainly been achieved by selecting plants with optimal canopy architecture for specific agronomic practices. For perennials such as oil palm, breeding programmes were focused more on fruit yield, but now aim at exploring more complex traits. The aim of the present study is to investigate potential improvements in light interception and carbon assimilation in the study case of oil palm, by manipulating leaf traits and proposing architectural ideotypes. Methods: Sensitivity analyses (Morris method and metamodel) were performed on a functional-structural plant model recently developed for oil palm which takes into account genetic variability, in order to virtually assess the impact of plant architecture on light interception efficiency and potential carbon acquisition. Key Results: The most sensitive parameters found over plant development were those related to leaf area (rachis length, number of leaflets, leaflet morphology), although fine attributes related to leaf geometry showed increasing influence when the canopy became closed. In adult stands, optimized carbon assimilation was estimated on plants with a leaf area index between 3.2 and 5.5 m2 m-2 (corresponding to usual agronomic conditions), with erect leaves, short rachis and petiole, and high number of leaflets on the rachis. Four architectural ideotypes for carbon assimilation are proposed based on specific combinations of organ dimensions and arrangement that limit mutual shading and optimize light distribution within the plant crown. Conclusions: A rapid set-up of leaf area is critical at young age to optimize light interception and subsequently carbon acquisition. At the adult stage, optimization of carbon assimilation could be achieved through specific combinations of architectural traits. The proposition of multiple morphotypes with comparable level of carbon assimilation opens the way to further investigate ideotypes carrying an optimal trade-off between carbon assimilation, plant transpiration and biomass partitioning.
Asunto(s)
Arecaceae/anatomía & histología , Carbono/metabolismo , Hojas de la Planta/anatomía & histología , Arecaceae/crecimiento & desarrollo , Arecaceae/fisiología , Arecaceae/efectos de la radiación , Secuestro de Carbono , Luz , Modelos Biológicos , Fenotipo , Hojas de la Planta/efectos de los fármacos , Hojas de la Planta/crecimiento & desarrollo , Hojas de la Planta/fisiologíaRESUMEN
During routine monitoring of commercial purse seine catches in 2011, 87 fingerling specimens of scombrids were collected in the southern Adriatic Sea. Sequencing of the mitochondrial DNA control region locus inferred that specimens belonged to the Atlantic bluefin tuna, Thunnus thynnus (Linnaeus, 1758) (N = 29), bullet tuna, Auxis rochei (Risso, 1810) (N = 30) and little tunny, Euthynnus alletteratus, Rafinesque, 1810 (N = 28). According to previously published growth parameters, the age of the collected specimens was estimated at approximately 30-40 days, suggesting they might have been spawned in the Adriatic Sea, contrary to the current knowledge. A coupled modelling system with hydrodynamic (ROMS) and individual based model (IBM-Ichthyop) was set up to determine the location of the spawning event. Numerical simulations with the IBM model, both backward and forward in time, indicate commercial tuna cages in the middle Adriatic coastal area as possible spawning location. The two other non-commercial species likely opportunistically use the positive environmental (abiotic and biotic) conditions to spawn in the same area.
Asunto(s)
Atún , Animales , Océano Atlántico , Hidrodinámica , Mar Mediterráneo , Meteorología , Modelos Teóricos , Reproducción , Atún/crecimiento & desarrollo , Atún/fisiologíaRESUMEN
Marine reserves are viewed as flagship tools to protect exploited species and to contribute to the effective management of coastal fisheries. Yet, the extent to which marine reserves are globally interconnected and able to effectively seed areas, where fisheries are most critical for food and livelihood security is largely unknown. Using a hydrodynamic model of larval dispersal, we predict that most marine reserves are not interconnected by currents and that their potential benefits to fishing areas are presently limited, since countries with high dependency on coastal fisheries receive very little larval supply from marine reserves. This global mismatch could be reversed, however, by placing new marine reserves in areas sufficiently remote to minimize social and economic costs but sufficiently connected through sea currents to seed the most exploited fisheries and endangered ecosystems.
Asunto(s)
Distribución Animal , Conservación de los Recursos Naturales , Explotaciones Pesqueras , Peces , Modelos Teóricos , Animales , Hidrodinámica , Larva , Movimientos del AguaRESUMEN
In marine benthic ecosystems, larval connectivity is a major process influencing the maintenance and distribution of invertebrate populations. Larval connectivity is a complex process to study as it is determined by several interacting factors. Here we use an individual-based, biophysical model, to disentangle the effects of such factors, namely larval vertical migration, larval growth, larval mortality, adults fecundity, and habitat availability, for the marine gastropod Concholepas concholepas (loco) in Chile. Lower transport success and higher dispersal distances are observed including larval vertical migration in the model. We find an overall decrease in larval transport success to settlement areas from northern to southern Chile. This spatial gradient results from the combination of current direction and intensity, seawater temperature, and available habitat. From our simulated connectivity patterns we then identify subpopulations of loco along the Chilean coast, which could serve as a basis for spatial management of this resource in the future.
Asunto(s)
Factores Biológicos , Ecosistema , Gastrópodos/fisiología , Distribución Animal , Animales , Atmósfera , Fenómenos Biofísicos , Chile , Conservación de los Recursos Naturales , Geografía , Hidrodinámica , Larva/fisiología , Agua de Mar , TemperaturaRESUMEN
We investigated the extent that the 2010 Deepwater Horizon oil spill potentially affected oceanic-stage sea turtles from populations across the Atlantic. Within an ocean-circulation model, particles were backtracked from the Gulf of Mexico spill site to determine the probability of young turtles arriving in this area from major nesting beaches. The abundance of turtles in the vicinity of the oil spill was derived by forward-tracking particles from focal beaches and integrating population size, oceanic-stage duration and stage-specific survival rates. Simulations indicated that 321 401 (66 199-397 864) green (Chelonia mydas), loggerhead (Caretta caretta) and Kemp's ridley (Lepidochelys kempii) turtles were likely within the spill site. These predictions compared favourably with estimates from in-water observations recently made available to the public (though our initial predictions for Kemp's ridley were substantially lower than in-water estimates, better agreement was obtained with modifications to mimic behaviour of young Kemp's ridley turtles in the northern Gulf). Simulations predicted 75.2% (71.9-76.3%) of turtles came from Mexico, 14.8% (11-18%) from Costa Rica, 5.9% (4.8-7.9%) from countries in northern South America, 3.4% (2.4-3.5%) from the United States and 1.6% (0.6-2.0%) from West African countries. Thus, the spill's impacts may extend far beyond the current focus on the northern Gulf of Mexico.
Asunto(s)
Contaminación por Petróleo , Tortugas/fisiología , Animales , Océano Atlántico , Golfo de México , Modelos Teóricos , Densidad de Población , Análisis Espacio-TemporalRESUMEN
During long-distance migrations, animals navigate using a variety of sensory cues, mechanisms and strategies. Although guidance mechanisms are usually studied under controlled laboratory conditions, such methods seldom allow for navigation behavior to be examined in an environmental context. Similarly, although realistic environmental models are often used to investigate the ecological implications of animal movement, explicit consideration of navigation mechanisms in such models is rare. Here, we used an interdisciplinary approach in which we first conducted lab-based experiments to determine how hatchling loggerhead sea turtles (Caretta caretta) respond to magnetic fields that exist at five widely separated locations along their migratory route, and then studied the consequences of the observed behavior by simulating it within an ocean circulation model. Magnetic fields associated with two geographic regions that pose risks to young turtles (due to cold wintertime temperatures or potential displacement from the migratory route) elicited oriented swimming, whereas fields from three locations where surface currents and temperature pose no such risk did not. Additionally, at locations with fields that elicited oriented swimming, simulations indicate that the observed behavior greatly increases the likelihood of turtles advancing along the migratory pathway. Our findings suggest that the magnetic navigation behavior of sea turtles is intimately tied to their oceanic ecology and is shaped by a complex interplay between ocean circulation and geomagnetic dynamics.
Asunto(s)
Migración Animal/fisiología , Campos Magnéticos , Tortugas/fisiología , Animales , Océano Atlántico , Simulación por Computador , Señales (Psicología) , Ecosistema , Orientación , Natación/fisiologíaRESUMEN
The inaccessibility of open ocean habitat and the cryptic nature of small animals are fundamental problems when assessing the distribution of oceanic-stage sea turtles and other marine animals sharing similar life-history traits. Most methods that estimate patterns of abundance cannot be applied in situations that are extremely data limited. Here, we use a movement ecology framework to generate the first predicted distributions for the oceanic stage of the Kemp's ridley sea turtle (Lepidochelys kempii). Our simulations of particle dispersal within ocean circulation models reveal substantial annual variation in distribution and survival among simulated cohorts. Such techniques can help prioritize areas for conservation, and supply inputs for more realistic demographic models attempting to characterize population trends.
Asunto(s)
Tortugas , Animales , Demografía , Océanos y MaresRESUMEN
Young loggerhead sea turtles (Caretta caretta) from eastern Florida, USA, undertake a transoceanic migration in which they gradually circle the Sargasso Sea before returning to the North American coast. Loggerheads possess a 'magnetic map' in which regional magnetic fields elicit changes in swimming direction along the migratory pathway. In some geographic areas, however, ocean currents move more rapidly than young turtles can swim. Thus, the degree to which turtles can control their migratory movements has remained unclear. In this study, the movements of young turtles were simulated within a high-resolution ocean circulation model using several different behavioral scenarios, including one in which turtles drifted passively and others in which turtles swam briefly in accordance with experimentally derived data on magnetic navigation. Results revealed that small amounts of oriented swimming in response to regional magnetic fields profoundly affected migratory routes and endpoints. Turtles that engaged in directed swimming for as little as 1-3 h per day were 43-187% more likely than passive drifters to reach the Azores, a productive foraging area frequented by Florida loggerheads. They were also more likely to remain within warm-water currents favorable for growth and survival, avoid areas on the perimeter of the migratory route where predation risk and thermal conditions pose threats, and successfully return to the open-sea migratory route if carried into coastal areas. These findings imply that even weakly swimming marine animals may be able to exert strong effects on their migratory trajectories and open-sea distributions through simple navigation responses and minimal swimming.