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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 360 (1992), S. 579-580 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The prediction that failure of larvae to return to shore is a common cause of variable recruitment in coastal species follows from numerous observations (such as location of fish spawning grounds10, correlations between recruitment and shifts in wind direction9'10'12'14'15, behaviour of ...
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  • 2
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    Unknown
    University of Chicago Press
    In:  The American Naturalist, 117 (5). pp. 754-773.
    Publication Date: 2017-04-20
    Description: The reproductive ecology of three sympatric hermit crab species from the Bay of Panama is examined. All three species reveal patterns of size and reproduction mediated by their supply of shells. Shells are demonstrated to be in limited supply. Crabs with shells large enough to allow growth, put effort into growth at the expense of reducing reproductive expenditures, while crabs in shells too small to permit growth allocate more time and effort into immediate reproductive gains. This resource regulated trade-off between growth and reproduction gives these tropical crabs plasticity in important life-history traits. Crabs with a relatively poor supply of shells reproduce at smaller sizes, reproduce more frequently, have larger clutches, and are unable to reach the larger sizes of crabs with a less limiting supply of shells. This flexibility in life-history traits allows these crabs to tailor their reproductive schedules to resource supplies controlled by gastropod mortality, as well as the presence of competitors and predators.
    Type: Article , PeerReviewed
    Format: text
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  • 3
    ISSN: 1432-1939
    Keywords: Key words Nitrogen ; Salt marsh ; Positive interaction ; Insect herbivory ; Trophic interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nutrients can structure communities by influencing both plant interactions and plant herbivore interactions, though rarely do studies integrate these processes. In this study we examined how nitrogen fertilization influenced (1) the positive interaction between the marsh elder, Iva frutescens, and the black rush, Juncusgerardi, and (2) the quality of Iva as a host plant for the aphid, Uroleuconambrosiae. Previous studies have shown that by mitigating soil salt accumulation and hypoxia, Juncus is essential to the survival of Iva and its aphid herbivore at mid-marsh elevations. To address the effects of nitrogen on this interaction, we compared fertilized and unfertilized Iva plants subject to Juncus removal and control treatments in the field. Additionally, we measured the monthly population growth rates of aphids transplanted onto these Iva plants. Iva leaf biomass and flower number results indicated that fertilizing Iva eliminated its dependence upon Juncus, such that fertilized plants grown without Juncus were not different from unmanipulated plants. Aphid monthly population growth rates through mid-summer revealed that fertilization also eliminated the indirect dependency of aphids on Juncus, so that aphid growth rates on fertilized Iva without Juncus neighbors were similar to rates on unmanipulated Iva. Results also indicated that fertilizing Iva grown with Juncus increased Iva size, potentially enabling these plants to support larger aphid populations. Our results suggest that only under conditions of nitrogen limitation are the positive effects of Juncus essential to the mid-marsh persistence of Iva and its aphid herbivore. Furthermore, we found that nitrogen effects on aphid populations may arise not only from a direct effect of nutrients on Iva size but also through the indirect effects of nitrogen on the interaction between Juncus and Iva. We argue that studies integrating processes occurring both within and between trophic levels, are important to fully understanding the community-wide effects of nutrients.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1939
    Keywords: Key words Density-dependent foraging ; Flow-mediated recruitment ; New England rocky intertidal zone ; Positive interactions ; Species borders
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the relative contribution of recruitment, intraspecific species interactions, and predation in controlling the upper intertidal border of the northern acorn barnacle, Semibalanusbalanoides, in a tidal estuary in Maine. We hypothesized that the contracted border at sites that experienced low tidal currents was due to flow-mediated recruitment that resulted in reduced survival due to the absence of neighbor buffering of thermal stress (i.e., positive intraspecific interactions). We tested this hypothesis by manipulating the density of recently settled barnacles and their thermal environment in a field experiment. Counter to our original hypothesis, barnacles with neighbors suffered severe mortality at low-flow sites. When density-dependent predation by the green crab (Carcinusmaenus) was experimentally eliminated, however, we did detect evidence for positive interactions at the low-flow sites but not at the high-flow sites. In spite of the close proximity of the sites, maximum daily rock temperatures at the low-flow sites were slightly, but consistently, greater than those at high-flow sites. Our findings suggest that the upper intertidal border of S. balanoides in the Damariscotta River is limited at low-flow sites by a combination of reduced recruitment, elevated mortality from thermal stress and enhanced predation by green crabs. More generally, our findings highlight how physical stress and predation interact to alter the nature of density-dependent species interactions in natural assemblages.
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  • 5
    ISSN: 1432-1939
    Keywords: Key words Rocky intertidal ; Experimental ecology ; Facilitation ; Thermal stress ; Climate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To explore how climate may affect the structure of natural communities, we quantified the role of thermal stress in setting the high intertidal borders of the acorn barnacle, Semibalanus balanoides. At sites north and south of Cape Cod, a major faunal and thermal boundary on the east coast of North America, we examined the interacting effects of thermal stress and recruit density on individual survivorship. At hotter southern sites, particularly in bays, high intertidal barnacle survivorship was enhanced by experimental shading or by neighbors which ameliorate heat and desiccation stresses. In contrast, at cooler northern bay and coastal sites, neither shading nor group benefits increased barnacle survival, and mortality patterns were driven primarily by predators with largely boreal distributions. Our field results, like recent laboratory microcosm studies, suggest that predicting even simple community responses to climate change may be more complex than is currently appreciated.
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  • 6
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Although mussel beds are common in many intertidal habitats, the ecological significance of the aggregated distribution of mussels has not been examined. The ribbed mussel, Geukensia demissa, is found in dense aggregations on the seaward margin of many salt marshes in New England. Here, we examine the population structure of G. demissa in a New England salt marsh and investigate experimentally the costs and benefits of aggregation. Size, growth rate, and settlement rates of mussels decrease with increasing tidal height, whereas survivorship and longevity increase with increasing tidal height. Winter ice dislodges mussels from the substratum, resulting in mortality over all size classes, whereas crab predation results in the mortality of smaller mussels. The intensity of each of these mortality agents decreases with increasing tidal height. Effects of intraspecific competition on individual growth and mortality also decrease with increasing tidal height. At high densities, individual growth rates were reduced, with depression of growth rates most pronounced on smaller individuals. Mortality from sources other than intraspecific crowding, however, was reduced at high mussel densities, including mortality due to winter ice and crab predators. As a result, our data suggest that the mussel population at our study site would be reduced by 90% in only five years and no juveniles would survive through their second year without an aggregated distribution. Juveniles settle gregariously with or without adults present. The aggregated distribution of settlers and the postsettlement movement of smaller mussels to favorable microhabitats result in size and age class segregation within the population. This probably reduces intraspecific competition for food, while maintaining the survivorship advantages of an aggregated distribution.
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  • 7
    ISSN: 1432-1939
    Keywords: Salt marsh ecology ; Halophytic plants ; Flooding ; Wetland plant communities ; Iva frutescens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Tidal flooding is widely believed to be an important determinant of marsh plant distributions but has rarely been tested in the field. In New England the marsh elder Iva frutescens often dominates the terrestrial border of salt marshes and we examined its flood tolerance and distribution patterns. Marsh elders only occur at elevations where their roots are not subject to prolonged water table flooding. Consequently they are found on the terrestrial border of marshes and at lower elevations associated with drainage ditches and locally elevated surfaces. Marsh elders transplanted to elevations lower than they normally occur died within a year with or without neighbors and greenhouse tests revealed that I. frutescens is much less tolerant of flooded soil conditions than plants found at lower marsh elevations. We also manipulated the water table level of field plots and found that increasing or decreasing water table drainage led to enhanced and diminished I. frutescens performance, respectively. Our results demonstrate the importance of water table dynamics in generating spatial patterns in marsh plant communities and provide further evidence that supports the hypothesis that the seaward distributional limits of marsh plant populations are generally dictated by physical processes.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1939
    Keywords: Halophytes ; Salt marsh ecology ; Secondary succession ; Seed bank ; Seedling recruitment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Seedling recruitment in salt marsh plant communities is generally precluded in dense vegetation by competition from adults, but is also relatively rare in disturbance-generated bare space. We examined the constraints on seedling recruitment in New England salt marsh bare patches. Under typical bare patch conditions seed germination is severely limited by high substrate salinities. We examined the germination requirements of common high marsh plants and found that except for one notably patch-dependent fugitive species, the germination of high marsh plants is strongly inhibited by the high soil salinities routinely encountered in natural bare patches. Watering high marsh soil in the greenhouse to alleviate salt stress resulted in the emergence of up to 600 seedlings/225 cm2. The vast majority of this seed bank consisted of Juncus gerardi, the only common high marsh plant with high seed set. We tested the hypothesis that salt stress limits seedling contributions to marsh patch secondary succession in the field. Watering bare patches with fresh water partially alleviated patch soil salinities and dramatically increased both the emergence and survival of seedlings. Our results show that seedling recruitment by high marsh perennial turfs is limited by high soil salinities and that consequently their population dynamics are determined primarily by clonal growth processes. In contrast, populations of patch-dependent fugitive marsh plants which cannot colonize vegetatively are likely governed by spatially and temporally unpredictable windows of low salinities in bare patches.
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  • 9
    Publication Date: 2016-09-23
    Description: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS One 9 (2014): e93296, doi:10.1371/journal.pone.0093296.
    Description: Direct and indirect human impacts on coastal ecosystems have increased over the last several centuries, leading to unprecedented degradation of coastal habitats and loss of ecological services. Here we document a two-century temporal disparity between salt marsh accretion and subsequent loss to indirect human impacts. Field surveys, manipulative experiments and GIS analyses reveal that crab burrowing weakens the marsh peat base and facilitates further burrowing, leading to bank calving, disruption of marsh accretion, and a loss of over two centuries of sequestered carbon from the marsh edge in only three decades. Analogous temporal disparities exist in other systems and are a largely unrecognized obstacle in attaining sustainable ecosystem services in an increasingly human impacted world. In light of the growing threat of indirect impacts worldwide and despite uncertainties in the fate of lost carbon, we suggest that estimates of carbon emissions based only on direct human impacts may significantly underestimate total anthropogenic carbon emissions.
    Description: This research was made possible by a grant from the National Science Foundation Biological Oceanography Program and the Brown University Undergraduate Teaching and Research Award Program.
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
    Format: application/postscript
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  • 10
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    Ecological Society of America
    In:  Ecology, 65 (2). pp. 370-381.
    Publication Date: 2019-09-17
    Description: Experimental removal of the introduced herbivorous snail Littorina littorea from a protected New England rocky beach resulted in rapid habitat and community changes. At normal snail densities, L. littorea grazing bulldozes sediments from hard substrate and precludes the presence of an algal canopy. Snail removal resulted in rapid sediment accumulation and the development of an algal canopy, which accelerated sedimentation and bound sediment to hard substrate. These changes led to the increased success of organisms characteristic of soft—sediment habitats, such as polychaetes, tubiculous amphipods, mud crabs, and mud snails, and decreased success of organisms characteristic of hard—substrate habitats, such as barnacles and encrusting algae. Snail removal also significantly influenced the success of the marsh grass Spartina alterniflora. L. littorea consumes the shoots and rhizomes of marsh grass, as well as mediating sediment accumulation, which is necessary for vegetative expansion of root mat. Removal of L. littorea resulted in expansion of the littoral area dominated by S. alterniflora, as well as increased productivity of the marsh grass. These results suggest that the North American invasion of the European periwinkle has altered habitats and communities in protected littoral waters. Prior to the introduction of L. littorea, soft—bottomed littoral habitats and fringing salt marsh environments may have been more common that they are presently. Herbivorous snails in general may have an important habitat—modifying effect in protected marine communities that has not been appreciated previously.
    Type: Article , PeerReviewed
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