1,721,071 research outputs found
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Shading from Topographical Complexity Mitigates Bleaching Severity of Pocillopora spp. During Thermal Stress
Full text linkBleaching susceptibility of coral varies among species, environmental conditions, and spatial patterns on a reef. As bleaching events become more frequent and severe, understanding the factors that increase resiliency against thermal stress is critical. Here, we used large scale imagery collected at the remote atoll of Palmyra in the central Pacific during the 2015 thermal stress event to investigate the role of topographically produced shade in mitigating bleaching severity. Change in planar area over two years, bleaching severity, and estimated amount of shade provided by neighboring reef structures was measured for the common coral genus Pocillopora. Colonies that bleached more severely had higher rates of mortality than colonies with less severe bleaching. Further, those colonies with less severe bleaching had a higher proportion of colonies experiencing growth. Bleaching severity was correlated with the estimated irradiance, as more daily sunlight resulted in more severe bleaching than corals experiencing less daily sunlight. Structural complexity and variability in reef topography provide regions of shade where the compound impact of temperature and irradiance is alleviated, resulting in less-severe bleaching outcomes for an abundant and cosmopolitan coral genus. While some studies have considered artificially shading reefs during warm water events, we highlight the importance of existing structural complexity in providing shade, ultimately leading to increased reef resilience in the face of a changing climate
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The Mediating Factors of land Sea Connectivity on Islands
Full text linkAre island ecosystems connected to their nearshore marine environment? Islands are global biodiversity hotspots and the management of their natural resources is vital to the maintenance of global biodiversity and the survival of Earth's life support systems. However, both research and management have been slow to incorporate the importance of land-sea connections into their practice. Terrestrial and marine habitats are inextricably connected; incorporating the connections between the two to any research or management of these systems will improve efficacy by improving the resolution of our understanding of ecosystem drivers. If we are to incorporate land-sea connectivity into research and management, we first need to clarify our understanding of the patterns and variability of connectivity across geographic and biological contexts. The focus of this paper is to identify the factors mediating the ecological connection between land and sea on islands, which can be interpreted to determine the local importance of land-sea connectivity and identify candidate mechanisms defining the connectivity. With more detailed understanding of land-sea linkages, there is opportunity to apply this knowledge toward applied issues of island resource management and restoration. Using a practical case study of island restoration, we operationalize our proposed factors mediating the strength of land-sea connectivity to compare a set of islands targeted for restoration efforts, creating a prioritization based upon the island-specific estimated potential for improved land-sea connectivity and associated marine co-benefit of terrestrial management
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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Species Coexistence in Spatial, Non-Equilibrium Environments
Full text linkA challenge in ecology is to understand how so many species are organized in their communities and which coexistence mechanisms act to maintain diversity. The methods of ecological theory can further challenge by incorporating implicit assumptions. The non-equilibrium approach is useful as it includes the fluctuating environments so prevalent in nature. A growing number of empirical works attempt to quantify coexistence mechanisms. Recent developments in Modern Coexistence Theory in combination with tools from Spatial Simulation can leverage long-term field observations as well as the experience of field ecologists to create spatial models for use as a hypotheses-testing platform. An individual-based model of community dynamics is presented using a framework of Pattern-Oriented Modeling to serve as validation
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Who's next door? Using GIS to understand neighbor patterns of coral and algae at Palmyra Atoll.
Full text linkThe spatial distributions of benthic organisms within a coral reef ecosystem are structured by biological and physical mechanisms such as coral competition, reproduction, and reef structure. By examining the neighborhood patterns between scleractinian coral, soft coral, and algae, we can understand who typically lives near who and vice versa in a coral reef ecosystem. This brings insight into how organisms’ interactions, life histories, and the reef’s physical processes all impact the spatial distributions of colonies within their environment. Past coral spatial pattern studies relied on spatial point pattern (SPP) techniques such as nearest neighbor analysis. SPPs utilize the centroid of a colony, which poorly represents benthic organisms due to their variability in shape and size. In this study, we used an in-situ imaging technique to produce 14 plots of the reef based around Palmyra Atoll, covering 1400 m2 of benthic habitat in total. All colonies within these plots were identified to the lowest taxonomic classification possible. The utilization of GIS programming allowed us to take the shape of organisms into account and calculate the percent occupancy in 10 cm buffer regions around each colony. A bootstrapping approach was used to determine if the observed average neighborhood of each taxon and morphological type was more or less frequent compared to that of a null of equal occupancy. Few significant co-occurrence patterns were found due to the high abundance of a few taxa and competition between colonies. Of those significant neighbor patterns found, most positive patterns were intraspecific and biologically driven (via competition, reproduction, and partial mortality), and negative patterns were interspecific and were habitat driven (via physical processes and structure of the physical environment)
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Quantifying Life History Demographics of the Scleractinian Coral Genus Pocillopora at Palmyra Atoll
Full text linkMechanisms of change in coral colonies are necessary components to accurately predict trajectories of coral reef health. Yet, little in-field data has been quantified regarding the demographic rates of change in colonies and the factors that influence them. In this study, we use a large-area imaging approach to estimate baseline demographic rates of the coral genus Pocillopora and test for the influence of colony-specific predictors on growth, shrinkage (i.e. colony survivorship with loss of live tissue), and mortality (i.e. whole colony loss). We found that a colony’s fate was linked to its initial size, with larger colonies experiencing far lower mortality rates but higher shrinkage rates than smaller colonies. In addition, historical effects also significantly affected colony fate, as colonies with recent history of shrinkage experienced further shrinkage and mortality the following year. Finally, we found that significant variability in growth and mortality rates were linked to in inter-island site differences, which we suspect is driven by differences in heterotrophic feeding rates
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U.S. Exempted Fishing Permits: Role, Value, and Lessons Learned for Adaptive Fisheries Management
Full text linkExperimental fishing is a tool within adaptive management, but greater capacity exists to use experimentation to test alternative ideas to meet the national standards of the Magnuson-Stevens Act and promote sustainable fisheries. Few programs exist to allow for experimentation in federal waters, 3-200nm offshore, which is a crucial component of adaptive fisheries management. The exempted fishing permit (EFP) program, administered by the National Oceanic and Atmospheric Administration (NOAA), promotes collaboration between scientists, managers, and industry to develop creative solutions to evolving fisheries challenges by leveraging resources across fisheries sectors. To date, no synthesis of EFP implementation and efficacy has been conducted, leaving those who manage these fisheries in the dark as to their success more generally. Although regional managers discuss EFP projects on an individual basis, an analysis of the entire program provides useful guidance to management more broadly and describes trends in success to effectively translate experimentation to management. Here we developed the first standardized database of EFPs in the U.S. to summarize regional trends in applicant types, fisheries, gear types, goals, and exempted regulations. EFP documentation from 2008-2018 was compiled across seven broadly defined fisheries in four coastal regions in the U.S. We also evaluated factors that were associated with the degree to which EFPs were informative for fisheries management; ‘informative’ being defined as either informing regulatory change within a fishery or providing supporting data to fisheries reports (e.g. stock assessments, fishery management plans). We found strong differences between regions of the U.S. with the groundfish fishery strongly represented in the western regions and a mixed assortment of fisheries for the eastern regions. Western region projects had a greater focus on new gear and methods testing to reduce bycatch, whereas eastern regions had a mixture of goals, including projects that supplemented biological or ecological knowledge or contributed to stock assessments. We found strong coastal differences in the types of primary applicants that proposed projects, with eastern projects deriving from “top-down” approaches and western from “bottom-up”. Finally, we found that management region, applicant type, fishery, and size of project were positively associated with success in EFP projects, with Alaska and West Coast regions accounting for the highest proportion of successful projects
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A Length-Based Approach to Estimating Age Among Tropical Reef Fish Populations
Full text linkTime and energy are finite resources in any environment, and how and when organisms use their available resources to survive and reproduce is the crux of life history theory (Gadgil and Bossert 1970; Balon 1975; Stearns 1976). The different survival strategies used by animals are often shaped by their environment in addition to their biology (Winemiller and Rose 1992), which allows for exploration into biological variability when environmental factors are known. For this reason, the Line Islands in the Central Pacific provide an ideal location to perform observational studies due to their unique productivity gradient and fish assemblage structures across the island chain (Sandin et al. 2008; DeMartini et al. 2008; Fox et al. 2018; Zgliczynski et al. 2019). Many of the world’s coral reefs are in remote regions that lack monitoring programs or even local populations, so conducting ecological surveys on fish communities in these regions can require extensive amounts of time, energy, resources and people. The inherent variability an environment exerts on the many factors that contribute to growth over a lifetime make it difficult to generate a directly proportional formula that calculates age. A novel age estimation method was developed that utilizes in-situ visual census data to estimate the age of fishes, and as a case study, several fish were chosen as representative species to explore its capabilities. Through this process, new ecological information and insight can be gained about the age structures of fish populations both between and throughout the Line Islands
How Large Area Imagery Can Be Used to Quantify Growth of a Complex Branching Coral Species
Full text linkSpecies of branching Acropora, once dominant, complex coral species, have experienced major decline over the last several decades due to physical and anthropogenic disturbances. Following this decline, species of Acropora have been a direct focus of coral monitoring and restoration efforts across the Caribbean, in hopes of recovering populations of these threatened species. Measuring growth in the field presents countless challenges, including inaccuracy and imprecision of measurements due to intricate branching morphologies, the amount of time a diver can spend underwater measuring aspects of coral health, and unpredictable diving conditions. Here we used large-scale 3D imagery derived using Structure from Motion photogrammetric techniques to quantify branching Acropora species across multiple reef terrace sites on Palmyra Atoll. We estimated branch density (number of branches per thicket) and various metrics of linear and areal size of colonies within imagery which facilitates a direct comparison of commonly used metrics to track growth. We were able to monitor growth based on initial size through larger thicket form for six Acropora thickets through multiple time points from 2012-2019. The use of large area imaging technology provides a permanent record and a powerful tool to quantify growth using a variety of metrics, not constrained by in situ logistics. Gaining access to and perfecting methods that account for accurate size and growth measurements for reef accretion can hold the key to long-term successful ecological monitoring and restoration efforts
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