964 resultados para Anthropogenic disturbances


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When a habitat undergoes change, the first response of an individual is often behavioural adjustment. This immediate response can determine whether the population will survive or not, as behavioural flexibility gives time for genetic changes to arise later on. Habitat changes that alter reproductive behaviours can have long-lasting effects on populations. If the selective regime has changed under the new conditions, mate choice cues may no longer reliably reflect an individual s quality. Thus, animals have to be able to adjust their reproductive behaviours to the local conditions. The aim of my thesis was to discuss if and how animals are able to respond to rapid anthropogenic environmental change, and to study the mechanisms of the responses and the evolutionary consequences. The main focus was on the effects of human-induced eutrophication on the reproductive behaviour of fishes. Eutrophication is the result of increased nutrient input and can cause dense underwater vegetation and algal blooms. I used fishes from two very different ecosystems as model species, the Baltic Sea threespine stickleback (Gasterosteus aculeatus) and the desert goby (Chlamydogobius eremius), an endemic species of the Lake Eyre region in Central Australia. I investigated the effects of increased habitat complexity on courtship behaviour and the possibility of local differentiation in courtship and nest building behaviour depending on the level eutrophication in the habitat of origin. Furthermore, I observed the effect of turbidity on stickleback nest building behaviour. The results show that threespine stickleback males, which were born in areas that have been eutrophied for decades, court females at a higher intensity than males from clear water areas. Similarly, male desert gobies increased their courtship effort in dense vegetation. Intense courtship could be an adjustment to reduced visibility and lowered predation risk in the densely vegetated sites. However, there were no clear differences in nest building between males from clear and eutrophied areas under standardized conditions. This was expected as Baltic Sea sticklebacks prefer to nest under vegetation cover and are fairly rigid in adjusting their nest characteristics. Nest building was affected by increased turbidity: males built smaller nests with a larger nest entrance in turbid water. The large variation in the magnitude of phytoplankton blooms may require a rapid adjustment of the optimal nest structure to the current conditions. This thesis highlights the complex interactions that are set- off by human-induced changes in habitats and are followed by the immediate behavioural responses. It also encourages more research to tease apart the phenotypic and genetic components of the observed behavioural differences.

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O rio Corumbataí é um dos principais tributários da margem direita do rio Piracicaba que é um tributário do rio Tietê. O rio Corumbataí integra a bacia do rio Paraná e é regionalmente importante não só por possuir águas de boa qualidade, mas também por possuir elementos raros na paisagem local. Este estudo visou caracterizar as assembléias de peixes do rio Corumbataí e fornecer dados que contribuam para uma avaliação da sua qualidade ambiental. Na bacia do rio Corumbataí, foram amostrados 4 rios principais, cada um com 3 pontos de coleta. Vinte e quatro amostras foram coletadas durante os meses de março a julho e de setembro a dezembro de 2001. Dados bióticos foram avaliados por medidas de diversidade. Um modelo linear ANCOVA foi utilizado para testar a hipótese de variação espaço-temporal nas assembléias de peixes, com a riqueza de espécies como variável resposta, ordem do rio como fator e temperatura e logaritmo natural do número de indivíduos como covariáveis. Esta análise mostrou uma variação espaço-temporal que é corroborada por conceitos exaustivamente discutidos na literatura, tais como relação espécie-área e o conceito de rio contínuo. Dados provenientes do rio Ribeirão Claro mostraram um padrão diferente quando comparados com os outros rios. Esta diferença foi provavelmente devido à interferência humana e atesta o processo de fragmentação de hábitats aquáticos que podem ter levado a um isolamento das populações locais de peixes.

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In coastal waters and estuaries, seagrass meadows are often subject to light deprivation over short time scales (days to weeks) in response to increased turbidity from anthropogenic disturbances. Seagrasses may exhibit negative physiological responses to light deprivation and suffer stress, or tolerate such stresses through photo-adaptation of physiological processes allowing more efficient use of low light. Pulse Amplitude Modulated (PAM) fluorometery has been used to rapidly assess changes in photosynthetic responses along in situ gradients in light. In this study, however, light is experimentally manipulated in the field to examine the photosynthesis of Halophila ovalis and Zostera capricorni. We aimed to evaluate the tolerance of these seagrasses to short-term light reductions. The seagrasses were subject to four light treatments, 0, 5, 60, and 90% shading, for a period of 14 days. In both species, as shading increased the photosynthetic variables significantly (P < 0.05) decreased by up to 40% for maximum electron transport rates (ETRmax) and 70% for saturating irradiances (Ek). Photosynthetic efficiencies (a) and effective quantum yields (ΔF/Fm′ ) increased significantly (P < 0.05), in both species, for 90% shaded plants compared with 0% shaded plants. H. ovalis was more sensitive to 90% shading than Z. capricorni, showing greater reductions in ETR max, indicative of a reduced photosynthetic capacity. An increase in Ek, Fm′ and ΔF/Fm′ for H. ovalis and Z. capricorni under 90% shading suggested an increase in photochemical efficiency and a more efficient use of low-photon flux, consistent with photo-acclimation to shading. Similar responses were found along a depth gradient from 0 to10 m, where depth related changes in ETRmax and Ek in H. ovalis implied a strong difference of irradiance history between depths of 0 and 5-10 m. The results suggest that H. ovalis is more vulnerable to light deprivation than Z. capricorni and that H. ovalis, at depths of 5-10 m, would be more vulnerable to light deprivation than intertidal populations. Both species showed a strong degree of photo-adaptation to light manipulation that may enable them to tolerate and adapt to short-term reductions in light. These consistent responses to changes in light suggest that photosynthetic variables can be used to rapidly assess the status of seagrasses when subjected to sudden and prolonged periods of reduced light

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Dynamic Bayesian Networks (DBNs) provide a versatile platform for predicting and analysing the behaviour of complex systems. As such, they are well suited to the prediction of complex ecosystem population trajectories under anthropogenic disturbances such as the dredging of marine seagrass ecosystems. However, DBNs assume a homogeneous Markov chain whereas a key characteristics of complex ecosystems is the presence of feedback loops, path dependencies and regime changes whereby the behaviour of the system can vary based on past states. This paper develops a method based on the small world structure of complex systems networks to modularise a non-homogeneous DBN and enable the computation of posterior marginal probabilities given evidence in forwards inference. It also provides an approach for an approximate solution for backwards inference as convergence is not guaranteed for a path dependent system. When applied to the seagrass dredging problem, the incorporation of path dependency can implement conditional absorption and allows release from the zero state in line with environmental and ecological observations. As dredging has a marked global impact on seagrass and other marine ecosystems of high environmental and economic value, using such a complex systems model to develop practical ways to meet the needs of conservation and industry through enhancing resistance and/or recovery is of paramount importance.

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Predicting temporal responses of ecosystems to disturbances associated with industrial activities is critical for their management and conservation. However, prediction of ecosystem responses is challenging due to the complexity and potential non-linearities stemming from interactions between system components and multiple environmental drivers. Prediction is particularly difficult for marine ecosystems due to their often highly variable and complex natures and large uncertainties surrounding their dynamic responses. Consequently, current management of such systems often rely on expert judgement and/or complex quantitative models that consider only a subset of the relevant ecological processes. Hence there exists an urgent need for the development of whole-of-systems predictive models to support decision and policy makers in managing complex marine systems in the context of industry based disturbances. This paper presents Dynamic Bayesian Networks (DBNs) for predicting the temporal response of a marine ecosystem to anthropogenic disturbances. The DBN provides a visual representation of the problem domain in terms of factors (parts of the ecosystem) and their relationships. These relationships are quantified via Conditional Probability Tables (CPTs), which estimate the variability and uncertainty in the distribution of each factor. The combination of qualitative visual and quantitative elements in a DBN facilitates the integration of a wide array of data, published and expert knowledge and other models. Such multiple sources are often essential as one single source of information is rarely sufficient to cover the diverse range of factors relevant to a management task. Here, a DBN model is developed for tropical, annual Halophila and temperate, persistent Amphibolis seagrass meadows to inform dredging management and help meet environmental guidelines. Specifically, the impacts of capital (e.g. new port development) and maintenance (e.g. maintaining channel depths in established ports) dredging is evaluated with respect to the risk of permanent loss, defined as no recovery within 5 years (Environmental Protection Agency guidelines). The model is developed using expert knowledge, existing literature, statistical models of environmental light, and experimental data. The model is then demonstrated in a case study through the analysis of a variety of dredging, environmental and seagrass ecosystem recovery scenarios. In spatial zones significantly affected by dredging, such as the zone of moderate impact, shoot density has a very high probability of being driven to zero by capital dredging due to the duration of such dredging. Here, fast growing Halophila species can recover, however, the probability of recovery depends on the presence of seed banks. On the other hand, slow growing Amphibolis meadows have a high probability of suffering permanent loss. However, in the maintenance dredging scenario, due to the shorter duration of dredging, Amphibolis is better able to resist the impacts of dredging. For both types of seagrass meadows, the probability of loss was strongly dependent on the biological and ecological status of the meadow, as well as environmental conditions post-dredging. The ability to predict the ecosystem response under cumulative, non-linear interactions across a complex ecosystem highlights the utility of DBNs for decision support and environmental management.

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This document presents the results of the first three monitoring events to track the recovery of a repaired coral reef injured by the M/V Elpis vessel grounding incident of November 11, 1989. This grounding occurred within the boundaries of what at the time was designated the Key Largo National Marine Sanctuary (NMS), now designated the Key Largo NMS Existing Management Area within the Florida Keys National Marine Sanctuary (FKNMS). Pursuant to the National Marine Sanctuaries Act (NMSA) 16 U.S.C. 1431 et seq., and the Florida Keys National Marine Sanctuary and Protection Act (FKNMSPA) of 1990, NOAA is the federal trustee for the natural and cultural resources of the FKNMS. Under Section 312 of the NMSA, NOAA has the authority to recover monetary damages for injury, destruction, or loss of Sanctuary resources, and to use the recovered monies to restore injured or lost sanctuary resources within the FKNMS. The restoration monitoring program tracks patterns of biological recovery, determines the success of restoration measures, and assesses the resiliency to environmental and anthropogenic disturbances of the site over time. To evaluate restoration success, reference habitats adjacent to the restoration site are concurrently monitored to compare the condition of restored reef areas with natural coral reef areas unimpacted by the vessel grounding. Restoration of the site was completed September 1995, and thus far three monitoring events have occurred; one in the summer of 2004, one in the summer of 2005, and the latest in the summer of 2007. The monitoring in 2004 was in the nature of a “pilot project,” or proof of concept. Only the quantitative results of the 2005 and 2007 monitoring are presented and discussed. Monitoring has consisted of assessment of the structural stability of limestone boulders used in the restoration and comparison of the coral communities on the boulders and reference areas. Corals are divided into Gorgonians, Milleporans, and Scleractinians. Coral densities at the Restored and Reference areas for the 2005 and 2007 events are compared, and it is shown that the densities of all taxa in the Restored area are greater by 2007, though not significantly so. For the Scleractinians, number and percentage of colonies by species, as well as several common biodiversity indices are provided. The greater biodiversity of the Restored area is evidenced. Also, size-class frequency distributions for Agaricia spp. (Scleractinia) are presented. These demonstrate the approaching convergence of the Restored and Reference areas in this regard. An inter-annual comparison of densities, within both areas, for all three Orders, is presented. The most noteworthy finding was the relative consistency across time for all taxa in each area. Finally, certain anomalies regarding species settlement patterns are presented. (PDF contains 48 pages.)

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This document presents the results of the first two monitoring events to track the recovery of a repaired coral reef injured by the M/V Wellwood vessel grounding incident of August 4, 1984. This grounding occurred within the boundaries of what at the time was designated the Key Largo National Marine Sanctuary (NMS), now designated the Key Largo NMS Existing Management Area within the Florida Keys National Marine Sanctuary (FKNMS). Pursuant to the National Marine Sanctuaries Act (NMSA) 16 U.S.C. 1431 et seq., and the Florida Keys National Marine Sanctuary and Protection Act (FKNMSPA) of 1990, NOAA is the federal trustee for the natural and cultural resources of the FKNMS. Under Section 312 of the NMSA, NOAA has the authority to recover monetary damages for injury, destruction, or loss of Sanctuary resources, and to use the recovered monies to restore injured or lost sanctuary resources within the FKNMS. The restoration monitoring program tracks patterns of biological recovery, determines the success of restoration measures, and assesses the resiliency to environmental and anthropogenic disturbances of the site over time. To evaluate restoration success, reference habitats adjacent to the restoration site are concurrently monitored to compare the condition of restored reef areas with “natural” coral reef areas unimpacted by the vessel grounding or other injury. Restoration of the site was completed on July 22, 2002, and thus far two monitoring events have occurred; one in the Fall of 2004, and one in the Summer/Fall of 2006. The monitoring has consisted of: assessment of the structural stability of restoration modules and comparison of the coral recruitment conditions of the modules and reference sites. Corals are divided into Gorgonians, Milleporans, and Scleractinians and (except where noted) recruits are defined as follows: Gorgonians—maximum size (height) 150 mm at first monitoring event, 270 mm at second; Milleporans—maximum size (height) 65 mm at first event, 125 mm at second; Scleractinians—maximum size (greatest diameter) 50 mm at second event (only one species was size-classed at first event, at smaller size). Recruit densities at the restored and reference areas for each event are compared, as are size-class frequency distributions. For the Scleractinians, number and percentage of recruits by species, as well as several common biodiversity indices are provided. Finally, a qualitative comparison of recruit substrate settlement preference is indicated. Generally, results indicate that restored areas are converging on reference areas, based on almost all parameters examined, with one noted exception. Further monitoring is planned and the trends are anticipated to continue; close attention will be paid to the indicated anomaly. (PDF contains 63 pages.)

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This document presents the results of the monitoring of a repaired coral reef injured by the M/V Connected vessel grounding incident of March 27, 2001. This grounding occurred in Florida state waters within the boundaries of the Florida Keys National Marine Sanctuary (FKNMS). The National Oceanic and Atmospheric Administration (NOAA) and the Board of Trustees of the Internal Improvement Trust Fund of the State of Florida, (“State of Florida” or “state”) are the co-trustees for the natural resources within the FKNMS and, thus, are responsible for mediating the restoration of the damaged marine resources and monitoring the outcome of the restoration actions. The restoration monitoring program tracks patterns of biological recovery, determines the success of restoration measures, and assesses the resiliency to environmental and anthropogenic disturbances of the site over time. The monitoring program at the Connected site was to have included an assessment of the structural stability of installed restoration modules and biological condition of reattached corals performed on the following schedule: immediately (i.e., baseline), 1, 3, and 6 years after restoration and following a catastrophic event. Restoration of this site was completed on July 20, 2001. Due to unavoidable delays in the settlement of the case, the “baseline” monitoring event for this site occurred in July 2004. The catastrophic monitoring event occurred on August 31, 2004, some 2 ½ weeks after the passage of Hurricane Charley which passed nearby, almost directly over the Dry Tortugas. In September 2005, the year one monitoring event occurred shortly after the passage of Hurricane Katrina, some 70 km to the NW. This report presents the results of all three monitoring events. (PDF contains 37 pages.)

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This document presents the results of the monitoring of a repaired coral reef injured by the M/V Jacquelyn L vessel grounding incident of July 7, 1991. This grounding occurred in Florida state waters within the boundaries of the Florida Keys National Marine Sanctuary (FKNMS). The National Oceanic and Atmospheric Administration (NOAA) and the Board of Trustees of the Internal Improvement Trust Fund of the State of Florida, (“State of Florida” or “state”) are the co-trustees for the natural resources within the FKNMS and, thus, are responsible for mediating the restoration of the damaged marine resources and monitoring the outcome of the restoration actions. The restoration monitoring program tracks patterns of biological recovery, determines the success of restoration measures, and assesses the resiliency to environmental and anthropogenic disturbances of the site over time. The monitoring program at the Jacquelyn L site was to have included an assessment of the structural stability of installed restoration modules and biological condition of reattached corals performed on the following schedule: immediately (i.e., baseline), 1, 3, and 6 years after restoration and following a catastrophic event. Restoration of this site was completed on July 20, 2000. Due to unavoidable delays in the settlement of the case, the “baseline” monitoring event for this site occurred in July 2004. The catastrophic monitoring event occurred on August 31, 2004, some 2 ½ weeks after the passage of Hurricane Charley which passed nearby, almost directly over the Dry Tortugas. In September 2005, the year one monitoring event occurred shortly after the passage of Hurricane Katrina, some 70 km to the NW. This report presents the results of all three monitoring events. (PDF contains 31 pages.)

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Long-term research in the western English Channel, undertaken by the marine laboratories in Plymouth, is described and details of survey methods, sites, and time series given in this chapter. Major findings are summarized and their limitations outlined. Current research, with recent reestablishment and expansion of many sampling programmes, is presented, and possible future approaches are indicated. These unique long-term data sets provide an environmental baseline for predicting complex ecological responses to local, regional, and global environmental change. Between 1888 and the present, investigations have been carried out into the physical, chemical, and biological components (ranging from plankton and fish to benthic and intertidal assemblages) of the western English Channel ecosystem. The Marine Biological Association of the United Kingdom has performed the main body of these observations. More recent contributions come from the Continuous Plankton Recorder Survey, now the Sir Alister Hardy Foundation for Ocean Science, dating from 1957; the Institute for Marine Environmental Research, from 1974 to 1987; and the Plymouth Marine Laboratory, which was formed by amalgamation of the Institute for Marine Environmental Research and part of the Marine Biological Association, from 1988. Together, these contributions constitute a unique data series; one of the longest and most comprehensive samplings of environmental and marine biological variables in the world. Since the termination of many of these time series in 1987-1988 during a reorganisation of UK marine research, there has been a resurgence of interest in long-term environmental change. Many programmes have been restarted and expanded with support from several agencies. The observations span significant periods of warming (1921-1961; 1985-present) and cooling (1962-1980). During these periods of change, the abundance of key species underwent dramatic shifts. The first period of warming saw changes in zooplankton, pelagic fish, and larval fish, including the collapse of an important herring fishery. During later periods of change, shifts in species abundances have been reflected in other assemblages, such as the intertidal zone and the benthic fauna. Many of these changes appear to be related to climate, manifested as temperature changes, acting directly or indirectly. The hypothesis that climate is a forcing factor is widely supported today and has been reinforced by recent studies that show responses of marine organisms to climatic attributes such as the strength of the North Atlantic Oscillation. The long-term data also yield important insights into the effects of anthropogenic disturbances such as fisheries exploitation and pollution. Comparison of demersal fish hauls over time highlights fisheries effects not only on commercially important species but also on the entire demersal community. The effects of acute ("Torrey Canyon" oil spill) and chronic (tributyltin [TBT] antifoulants) pollution are clearly seen in the intertidal records. Significant advances in diverse scientific disciplines have been generated from research undertaken alongside the long-term data series.

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Fine-resolution palaeoecological and dendrochronological methods were used to investigate the impacts of climate change, and natural and anthropogenic disturbances on vegetation in the North Patagonian rainforest of southern Chile at decadal to century timescales during the late Holocene. A lake sediment mud–water interface core was collected from the northern Chonos Archipelago and analysed for pollen and charcoal. Dendrochronological analysis of tree cores collected from stands of Pilgerodendron uviferum close to the lake site was incorporated into the study. The combined analysis showed that the present mosaic of vegetation types in this region is a function of environmental changes across a range of timescales: millennial climate change, more recent natural and anthropogenic disturbances, and possibly short-term climatic variations. Of particular interest is the spatiotemporal distribution of Pilgerodendron uviferum dieback/burning in the Chonos Archipelago region.

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Recent research has generally shown that a small change in the number of species in a food web can have consequences both for community structure and ecosystem processes. However 'change' is not limited to just the number of species in a community, but might include an alteration to such properties as precipitation, nutrient cycling and temperature, all of which are correlated with productivity. Here we argue that predicted scenarios of global change will result in increased plant productivity. We model three scenarios of change using simple Lotka-Volterra dynamics, which explore how a global change in productivity might affect the strength of local species interactions and detail the consequences for community and ecosystem level stability. Our results indicate that (i) at local scales the average population size of consumers may decline because of poor quality food resources, (ii) that the strength of species interactions at equilibrium may become weaker because of reduced population size, and (iii) that species populations may become more variable and may take longer to recover from environmental or anthropogenic disturbances. At local scales interaction strengths encompass such properties as feeding rates and assimilation efficiencies, and encapsulate functionatty important information with regard to ecosystem processes. Interaction strengths represent the pathways and transfer of energy through an ecosystem. We examine how such local patterns might be affected given various scenarios of 'global change' and discuss the consequences for community stability and ecosystem functioning. (C) 2004 Elsevier GmbH. All rights reserved.

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Coral reefs are of utmost ecological and economical importance but are currently in global decline due to climate change and anthropogenic disturbances. Corals, as well as other cnidarian species, live in symbiosis with photosynthetic dinoflagellates of the genus Symbiodinium. This relationship provides the cnidarian host with alternative metabolic pathways, as the symbionts translocate photosynthetic carbon to the animal. Besides this autotrophic nutrition mode, symbiotic cnidarians also take up organic matter from the environment (heterotrophy). The nutritional balance between auto- and heterotrophy is critical for the functioning, fitness and resilience of the cnidariandinoflagellate symbiosis. New methodological approaches were developed to better understand the role of auto- and heterotrophy in the ecophysiology of cnidarians associated with Symbiodinium, and the ecological implications of this trophic plasticity. Specifically, the new approaches were developed to assess photophysiology, biomass production of the model organism Aiptasia sp. and molecular tools to investigate heterotrophy in the cnidarian-dinoflagellate symbiosis. Using these approaches, we were able to non-invasively assess the photophysiological spatial heterogeneity of symbiotic cnidarians and identify spatial patterns between chlorophyll fluorescence and relative content of chlorophyll a and green-fluorescent proteins. Optimal culture conditions to maximize the biomass production of Aiptasia pallida were identified, as well as their implications on the fatty acid composition of the anemones. Molecular trophic markers were used to determine prey digestion times in symbiotic cnidarians, which vary between 1-3 days depending on prey species, predator species and the feeding history of the predator. This method was also used to demonstrate that microalgae is a potential food source for symbiotic corals. By using a stable isotope approach to assess the trophic ecology of the facultative symbiotic Oculina arbuscula in situ, it was possible to demonstrate the importance of pico- and nanoplanktonic organisms, particularly autotrophic, in the nutrition of symbiotic corals. Finally, we showed the effects of functional diversity of Symbiodinium on the nutritional plasticity of the cnidarian-dinoflagellate symbiosis. Symbiont identity defines this plasticity through its individual metabolic requirements, capacity to fix carbon, quantity of translocated carbon and the host’s capacity to feed and digest prey.

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The genetic diversity of populations, which contributes greatly to their adaptive potential, is negatively affected by anthropogenic habitat fragmentation and destruction. However, continental-scale losses of genetic diversity also resulted from the population expansions that followed the end of the last glaciation, an element that is rarely considered in a conservation context. We addressed this issue in a meta-analysis in which we compared the spatial patterns of vulnerability of 18 widespread European amphibians in light of phylogeographic histories (glacial refugia and postglacial routes) and anthropogenic disturbances. Conservation statuses significantly worsened with distances from refugia, particularly in the context of industrial agriculture; human population density also had a negative effect. These findings suggest that features associated with the loss of genetic diversity in post-glacial amphibian populations (such as enhanced fixation load or depressed adaptive potential) may increase their susceptibility to current threats (e.g., habitat fragmentation and pesticide use). We propose that the phylogeographic status of populations (i.e., refugial vs. post-glacial) should be considered in conservation assessments for regional and national red lists.