1,721,035 research outputs found
Ecological experiments: Between a rock and a hard place (Editorial)
No full textWhen I ask my first-year marine science students what they think science is, apart from some blank looks, I get a range of answers. One of the most common themes that emerges is that science is not a thing, but a way of doing things and that way of doing centres on experiments. Brought up in a western culture, for them science has become synonymous with a ‘Popparian philosophy’ (Popper, 1962), focused on the experimental falsification of hypotheses. This is difficult to do in the marine environment. In the dynamic offshore environment, the concept of replication becomes challenging, conditions are never matched exactly in space or time; while constraining organisms such as plankton or fish that live in intimate contact with the medium and travel large distances likely brings with it the potential for experimental artefacts. It is, perhaps, therefore surprising that marine rocky shores have been a major site for ecological experiments that have been fundamental to our understanding of the ecological workings of the world and underpin a significant amount of ecological theory. Hawkins et al. (2020) describes the evolution of our knowledge of rocky shore ecology and in particular how experimental studies on rocky shores have been used to develop theoretical frameworks and to test ecological hypothesesNo Full Tex
Biodiversity, trait composition and ecological functioning: Impacts of coastal urbanisation on subtropical mudflats
No full textThe world’s coastlines have become heavily modified over the last century, with the adjacent natural habitats declining in biodiversity and health under increasing pressure from urbanisation. In this study we assessed the structure and biological traits of macrofaunal assemblages from 24 south-east Queensland mudflats in order to determine whether ecological functioning (e.g. primary production, nutrient cycling) and the delivery of ecosystem services was affected by urbanisation. This work represents the most comprehensive assessment of mudflat assemblages in the region to date. The mudflats contained 50 macrofaunal taxa and so were comparable to other local intertidal systems. Summer assemblages contained more species, more individuals and had differing taxonomic composition. When indexed as a proportion of subcatchment area, urbanisation did not correspond to a clear impact on macrofaunal composition; rather, the nature of the industry or activity was critical. Mudflats from subcatchments with industries producing organic wastes significantly differed from subcatchments with <1.3% cover of these industries. Functioning was conserved in mudflats experiencing current levels of enrichment, but this may decline with growing pressure from human populations. The results of this study illustrate that large-scale spatial data, such as from satellites, can be used to detect the cumulative effects of urbanisation when the pressures are highly resolved.No Full Tex
Managing the health of the seafloor
No full textWith the oceans covering almost two-thirds of our planet, it is important that we be able to measure whether the seafloor ecosystem is healthy. One way to do this is to create a framework that could reduce the problems of applying "objective based" management to seafloor systems. This paper examines the ability of the available indicators to serve as management targets. Most of the currently available metrics of ecosystem health are only weakly tied to manageable activities. The approach advocated here involves the measurement of some general measures of "health" and the use of targeted assessment of measures of specific human impacts. The former need to be monitored at relatively frequent intervals over the entire area of concern. For seafloor communities, we have some metrics that can perform this role, although there are fewer that directly track manageable activities. Development of these performance metrics is an important challenge for ecologists
Flow regimes among rivers influences benthic biota biodiversity, but not abundance or biomass, in intertidal mudflats and sandflats in wet-dry tropical estuaries
No full textFlow is a fundamental driver of ecological processes in river networks and estuaries. In estuaries, river flow interacts with tidal and wave energy to structure the physiochemical environment and the relative strength of these interactions changes in space and time. Thus, ecological processes in estuaries are best understood within the context of these physical processes. In this study, we explore how changes in river flow regime influence the structure of benthic communities in three estuaries in northern Australia's Gulf of Carpentaria. This region resides in the wet-dry tropics and the rivers have among the most variable flow regimes in the world. During two sequential dry seasons, we compared measures of benthic macroinvertebrate biodiversity, abundance, and biomass in intertidal mudflats and sandflats among three estuaries with differing river flow regimes. We found that the number of consecutive days of zero river flow during the preceding dry season best explained inter- and intra-annual patterns in benthic community composition. Specifically, we suggest that the dry season river flow regime dictated the salinity regime of each estuary, which in-turn influenced benthic community composition. However, neither the differences in the salinity regime or community composition influenced total abundance or biomass of the benthic community, indicating that the regional taxa pool currently contains enough functional redundancy to maintain abundances and biomasses under various physicochemical conditions. This in turn provides consistent resources for higher trophic levels such as birds and fish.No Full Tex
Conclusions
No full textMarine ecosystems provide a range of essential benefits to society, including food and other products, waste assimilation, coastal protection and climate regulation as well as less tangible, but no less important cultural and aesthetic benefits (Chapter 2). To a considerable degree, those benefits are underpinned by ecosystem services dependent on the efficient functioning of the ecosystems, although detailed understanding of relationships between particular services and particular functional processes is currently being developed (Chapter 2). In turn, the efficient functioning of ecosystems has been linked to the number and identity of species present, as well as the prevailing environmental conditions (Chapter 5).
Society derives many of its benefits from ecosystems via sectoral activities and industries, such as fishing, construction, energy, shipping, leisure and tourism. These activities can impose pressures on ecosystems, such as removal of biomass, inputs of nutrients and other contaminants and the introduction of artificial structures and non-indigenous species (Chapter 3). Such pressures act through a range of mechanisms affecting different levels of biological organisation to modify biodiversity and ecosystem functioning (Chapters 3 and 4). The chapters in this book have reviewed current knowledge of how the spectrum of human activities and pressures (collectively referred to as stressors) affect biodiversity, ecosystem functioning and the provision of services and benefits to society. A key objective was to provide a synthesis of evidence for policy makers and managers to facilitate trade-offs between sectors of activity based on the benefits they provide weighed against the degree to which they may compromise the delivery of ecosystem services now and into the future (see Chapter 11).
In this chapter, we first synthesise and summarise the inferences presented in the book about the range of impacts of different activities and pressures on biodiversity and ecosystem processes. We then ask how this kind of knowledge can help policy makers and managers, particularly in the achievement of the international targets laid down in the Millennium Development Goals (Chapter 1) and whether the ecosystem approach and the concept of ecosystem services can provide an effective framework for facilitating the achievement of those goals.No Full Tex
Occurrence of hydromedusae in the plankton off Northumberland (western central North Sea) and the role of planktonic predators
No full textThe pattern of occurrence of medusae off the north-east coast of England are described for the period 1990-1996. The predatory role of the medusae, Aglantha digitale, was examined by comparison of estimated predation rates with those of other planktonic predators. Aglanthe digitale was found to have the potential to considerably reduce copepod abundances, particularly in winter. Other important predators were the amphipod Themisto compressa and the chaetognath Sagitta elegans. There was a great deal of seasonal and interannual variability in predatory impact, with predators such as Pleurobrachia pileus and Meganyctiphanes norvegica occasionally exerting a high predatory impact. Previous studies have identified an important community structuring role for predation in winter in this area, this study shows that planktonic predators can influence copepod abundances throughout the year
Long-term trends in the central-west North Sea
No full textLong-term changes over the latter half of the 20th century have been evaluated for a number of planktonic and benthic time series for the central-west North Sea region, alongside long-term changes in large-scale climatic and regional meteorological variables. Parallel long-term increases were observed in most of the climatic and meteorological series, and in one of the benthic series. In addition to these long-term changes, quasi-coincident changes were also observed during the early 1980s and mid to late 1980s across the abiotic and biotic series. We discuss the similarities and dissimilarities observed across these long-term time series, and the importance of considering the influence of both direct and indirect effects on long-term changes in the central-west North Sea ecosystem
Ecological Quality Objectives for benthic communities: If we protect the habitat do we need to do more?
No full text- …
