Suchergebnisse

Este artículo contiene 13 páginas, 6 figuras, 2 tablas. ; Predators exert a strong influence on ecological communities by reducing the abundance of prey (consumptive effects) and shaping their foraging behavior (non-consumptive effects). Although the prevalence of trophic cascades triggered by non-consumptive effects is increasingly recognized in a wide range of ecosystems, how its relative strength changes as prey individuals grow in size along various life stages remains poorly resolved. We investigated how the effects of predators vary with the ontogeny of a key herbivorous sea urchin, which is responsible for transforming diverse macroalgal forests to a barren state dominated by bare rock and encrusting coralline algae. We conducted a series of field and laboratory experiments to determine how susceptibility to predation, prey behavioral responses, and grazing impact on algal cover vary with sea urchin size. The consumptive effects of predators were greater on smaller sea urchin size classes, which were more susceptible to predation. Unexpectedly however, predator non-consumptive effects acted only on larger sea urchins, significantly reducing their grazing activity in the presence of predator cues. Crucially, only these larger sea urchins were capable of overgrazing macroalgae in the field, with non-consumptive effects reducing sea urchin foraging activity and macroalgal grazing impact by 60%. The decoupling between risk and fear as prey grow indicates that the strength of consumptive and non-consumptive trophic cascades may act differently at different ontogenetic stages of prey. While the consumptive effects of predators directly influence population numbers, the consequences of non-consumptive effects may far outlive consumptive effects as prey grow, finding refuge in size, but not from fear. ; The Spanish Ministry of Science and Innovation funded this research (UMBRAL; Respuestas de la vegetaci on marina bent onica al estr es: transiciones cr ıticas, resiliencia y oportunidades de gesti on', CTM2017-86695-C3-3-R) and supported J. Boada's scholarship (no. BES-2011-043630). The Spanish National Research Council supported R. Arthur's visitorship with the Memorandum of Understanding between CEAB-IMEDEA-NCF. J. Boada acknowledges the funding received by the Australian Government (ERF_PDR_5888_2017). J. F. Pag es acknowledges financial support from the Welsh Government and Higher Education Funding Council for Wales through the S^er Cymru National Research Network for Low Carbon, Energy and Environment. ; Peer reviewed

Este artículo contiene 12 páginas, 7 figuras, 2 tablas. ; The relative benefts of group foraging change as animals grow. Metabolic requirements, competitive abilities and predation risk are often allometric and infuenced by group size. How individuals optimise costs and benefts as they grow can strongly infuence consumption patterns. The shoaling fsh Sarpa salpa is the principal herbivore of temperate Posidonia oceanica seagrass meadows. We used in-situ observations to describe how ontogeny infuenced S. salpa individual feeding behaviour, shoaling behaviour and group foraging strategies, and its potential consequences to seagrass meadows. Shoaling was strongly infuenced by body length: shoals were highly length-assorted and there was a clear positive relationship between body length and shoal size. Foraging strategies changed dramatically with shoal size. Small shoals foraged simultaneously and scattered over large areas. In contrast, larger shoals (made of larger individuals) employed a potentially cooperative strategy where individuals fed rotationally and focused in smaller areas for longer times (spot feeding). Thus, as individuals grew, they increased their potential impact as well, not merely because they consumed more, but because they formed larger shoals capable of considerably concentrating their grazing within the landscape. Our results indicate that ontogenetic shifts in group foraging strategies can have large ecosystem-wide consequences when the species is an important ecosystem modifer. ; Te Spanish Ministry of Science funded this research through RECCAM project (CMT2013-48027-C03-R). Te Spanish National Research Council supported Rohan Arthur's visitorship with the Memorandum of Understanding between CEAB-IMEDEA-NCF. Jordi F. Pages acknowledges fnancial support from the Welsh Government and Higher Education Funding Council for Wales through the Sȇr Cymru National Research Network for Low Carbon, Energy and Environment and from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant Agreement No 795315. Te work was supported by UMBRAL National Project CTM2017-86695-C3-3-R. ; Peer reviewed

Este artículo contiene 8 páginas, 6 figuras, 1 tabla. ; Interactions among species are essential in shaping ecological communities, although it is not always clear under what conditions they can persist when the number of species involved is higher than two. Here we describe a three-species assemblage involving the seagrass Cymodocea nodosa, the pen shell Pinna nobilis and the herbivore sea urchin Paracentrotus lividus, and we explore the mechanisms allowing its persistence through field obser vations and manipulative experiments. The abundance of pen shells was higher in seagrass beds than in bare sand, suggesting a recruitment facilitation. The presence of sea urchins, almost exclusively attached or around pen shells, indicated habitat facilitation for sea urchins, which overgrazed the meadow around the pen shells forming seagrass-free halos. Our results suggest that this system persists thanks to: (i) the behavioral reluctance of sea urchins to move far from pen shells, making their impact on seagrass strictly local, (ii) the sparse distri bution of pen shells and (iii) the plant's resistance mechanisms to herbivory. Unpacking these mechanisms allows a better understanding of how ecological communities are assembled. ; This study received financial support from the Spanish Government (project UM BRAL CTM2017-86695-C3-1R; CTM2017-86695-C3-3R). The Spanish National Research Council supported R. Arthur's visitorship with the Memorandum of Understanding between CEAB-NCF. ; Peer reviewed

6 páginas, 2 figuras ; Efforts to conserve globally declining herbivorous green sea turtles have resulted in promising growth of some populations. These trends could significantly impact critical ecosystem services provided by seagrass meadows on which turtles feed. Expanding turtle populations could improve seagrass ecosystem health by removing seagrass biomass and preventing of the formation of sediment anoxia. However, overfishing of large sharks, the primary green turtle predators, could facilitate turtle populations growing beyond historical sizes and trigger detrimental ecosystem impacts mirroring those on land when top predators were extirpated. Experimental data from multiple ocean basins suggest that increasing turtle populations can negatively impact seagrasses, including triggering virtual ecosystem collapse. Impacts of large turtle populations on seagrasses are reduced in the presence of intact shark populations. Healthy populations of sharks and turtles, therefore, are likely vital to restoring or maintaining seagrass ecosystem structure, function, and their value in supporting fisheries and as a carbon sink. ; Studies in Shark Bay were funded byNSF grantsOCE0526065 and OCE0745606 and Florida International University.Work in India was supported by the Norwegian Institute of Nature Research, the Rufford Small Grants Programme and Spanish Ministry of Economia y Competitividad [projects: CTM2010-22273-C02-02 and PIE-201330E062 (CSIC)]. Work in Bermuda was funded by the Department of Conservation Services, Government of Bermuda and B. Dilke, a private benefactor. This is contribution # 681 of the Southeast Environmental Research Center, Florida International University, contribution # BBP218 of the BBP series at the Bermuda Department of Conservation Services library, and contribution 76 of the Shark Bay Ecosystem Research Project. ; Peer reviewed

Vegetated coastal ecosystems provide goods and services to billions of people. In the aftermath of a series of recent natural disasters, including the Indian Ocean Tsunami, Hurricane Katrina and Cyclone Nargis, coastal vegetation has been widely promoted for the purpose of reducing the impact of large storm surges and tsunami. In this paper, we review the use of coastal vegetation as a "bioshield" against these extreme events. Our objective is to alter bioshield policy and reduce the long-term negative consequences for biodiversity and human capital. We begin with an overview of the scientific literature, in particular focusing on studies published since the Indian Ocean Tsunami in 2004 and discuss the science of wave attenuation by vegetation. We then explore case studies from the Indian subcontinent and evaluate the detrimental impacts bioshield plantations can have upon native ecosystems, drawing a distinction between coastal restoration and the introduction of exotic species in inappropriate locations. Finally, we place bioshield policies into a political context, and outline a new direction for coastal vegetation policy and research. ©2009 Wiley Periodicals, Inc. ; SCOPUS: re.j ; info:eu-repo/semantics/published

Vegetated coastal ecosystems provide goods and services to billions of people. In the aftermath of a series of recent natural disasters, including the Indian Ocean Tsunami, Hurricane Katrina and Cyclone Nargis, coastal vegetation has been widely promoted for the purpose of reducing the impact of large storm surges and tsunami. In this paper, we review the use of coastal vegetation as a "bioshield" against these extreme events. Our objective is to alter bioshield policy and reduce the long-term negative consequences for biodiversity and human capital. We begin with an overview of the scientific literature, in particular focusing on studies published since the Indian Ocean Tsunami in 2004 and discuss the science of wave attenuation by vegetation. We then explore case studies from the Indian subcontinent and evaluate the detrimental impacts bioshield plantations can have upon native ecosystems, drawing a distinction between coastal restoration and the introduction of exotic species in inappropriate locations. Finally, we place bioshield policies into a political context, and outline a new direction for coastal vegetation policy and research.