1,721,157 research outputs found
Ecological observations associated with an anomalous warming event at the Houtman Abrolhos Islands, Western Australia
No full textExtreme climatic event drives range contraction of a habitat-forming species
No full textSpecies distributions have shifted in response to global warming in all major ecosystems on the Earth. Despite cogent evidence for these changes, the underlying mechanisms are poorly understood and currently imply gradual shifts. Yet there is an increasing appreciation of the role of discrete events in driving ecological change. We show how a marine heat wave (HW) eliminated a prominent habitat-forming seaweed, Scytothalia dorycarpa, at its warm distribution limit, causing a range contraction of approximately 100 km (approx. 5% of its global distribution). Seawater temperatures during the HW exceeded the seaweed's physiological threshold and caused extirpation of marginal populations, which are unlikely to recover owing to life-history traits and oceanographic processes. Scytothalia dorycarpa is an important canopy-forming seaweed in temperate Australia, and loss of the species at its range edge has caused structural changes at the community level and is likely to have ecosystem-level implications. We show that extreme warming events, which are increasing in magnitude and frequency, can force step-wise changes in species distributions in marine ecosystems. As such, return times of these events have major implications for projections of species distributions and ecosystem structure, which have typically been based on gradual warming trends
Population structure of the purple sea urchin Heliocidaris erythrogramma along a latitudinal gradient in south-west Australia
No full textSea urchins are key herbivores in many coastal ecosystems. The purple sea urchin, Heliocidaris erythrogramma, is widely distributed across temperate Australia where it exhibits considerable plasticity in feeding behaviour and ecophysiology. In this study we examined H. erythrogramma populations on subtidal reefs along ~4° of latitude in south-west Australia. We used a multi-factorial survey design to assess variability in H. erythrogramma abundances between locations (>200 km part), sites (≥1 km apart) and habitat types (reef flats and slopes). We also examined spatial variability in urchin size, condition (measured by gonad index), and the relative abundances of two co-occurring subspecies. Urchin densities were generally low and did not vary between locations, but did vary between habitat types and amongst sites. Site-level variability in urchin size and condition was also pronounced. The southernmost population comprised smaller individuals and greater relative abundance of the H. e. erythrogramma subspecies, which is abundant on the east coast of Australia. We observed no indication of population-level responses to a recent extreme warming event that impacted the wider ecology of the region, but further investigation into the effects of both gradual warming and short-term climatic events on the ecology of H. erythrogramma and other key herbivores is required
Satellite-derived SST data as a proxy for water temperature in nearshore benthic ecology
Get PDFSatellite-derived sea surface temperatures (SSTs) are increasingly being used as a proxy for water temperature in nearshore marine ecology, but there have been very few evaluations of how accurately SSTs reflect actual temperatures experienced by subtidal organisms. Here, we describe the benthic temperature climatology of 4 coastal locations along a ~1000 km latitudinal gradient in ocean temperature in Western Australia (WA), and compare temperature records from in situ loggers at 10 to 12 m depth with records from 2 independent satellite-derived SST datasets over 2 years. Satellite-derived SSTs were significantly correlated with in situ logger data at all locations, which demonstrate their overall ability to detect general patterns of ecological importance. However, SSTs were also significantly different from benthic water temperatures (usually 1 to 2°C higher), and they did not adequately detect ecologically important small-scale variability or provide reliable information on temperature extremes. Furthermore, rank orders of the study locations differed between the methodologies, especially in winter. We emphasize the need to carefully consider whether the accuracy and resolution of satellite-derived SSTs are appropriate for the specific ecological hypothesis being tested in nearshore subtidal habitats, and advocate the use of in situ loggers otherwise. We also highlight the suitability of the WA coastline for experimental work on the effects of temperature (and synergistic factors) on marine organisms
Community development on subtidal temperate reefs: the influences of wave energy and the stochastic recruitment of a dominant kelp
No full textPatterns of community development on subtidal rocky reefs in Marmion Lagoon, southwest Australia, were investigated with a settlement panel experiment. We tested the hypothesis that community development would differ between outer and inner reefs lines, because exposure to swell and wave energy was significantly greater on outer reefs. Following a 14-month deployment, we recorded pronounced variability between panels and sites, but did not detect any effect of wave exposure on the structure of panel assemblages. Subsequent data exploration suggested the importance of the presence of kelp recruits (Ecklonia radiata) in structuring the overall assemblage. Panel assemblages with kelp recruits were significantly different in structure to those without, principally because of greater space coverage of encrusting coralline algae and less coverage of red turfing algae, spirorbids, and bryozoans. Mature E. radiata act as ecosystem engineers in subtidal rocky reefs in southwest Australia. Our results suggested the importance of young, recruiting kelps in determining patterns of early community development on newly available hard substrata
Assemblage turnover and taxonomic sufficiency of subtidal macroalgae at multiple spatial scales
Get PDFSpatial variability in the structure of subtidal macroalgal assemblages in southwest Australia was examined at multiple spatial scales using a three-factor hierarchal design. Spatial extents ranged from metres (between quadrats) to many hundreds of kilometres (between regions), and the study encompassed > 2000 km of temperate coastline. In addition, the influence of taxonomic resolution, from species level data to class level, on spatial patterns was investigated to assess the potential evolutionary timescales of the pattern and for developing cost effective regionally applicable surrogates for biodiversity monitoring. Almost 300 species were identified from 14 sites, representing considerable biodiversity and a significant subset of the total benthic macroalgal diversity in the region (? 1000 species). Multivariate variability was significant at all spatial scales examined, but most prominent at smallest spatial scales, regardless of taxonomic resolution. Assemblage and species turnover was pronounced at scales of metres to hundreds of metres. Generally, small scale patchiness was a ubiquitous pattern for all individual taxa examined, regardless of taxonomic resolution, while variability at the scale of 10s of km was less important. Even so, differences in spatial variability between taxa were observed, and ecological and historical reasons for such differences are proposed. Taxonomic aggregation to family level had minimal effect on spatial patterns, but aggregation to order level led to changes in some aspects of patterns of assemblage structure. The unique and speciose macroalgal assemblages on subtidal reefs in southwest Australia are shaped by a complex array of historical and contemporary processes that act at multiple spatial (and temporal) scales. Understanding the relative importance of these processes requires that further manipulative and correlative work is conducted across a range of ecologically-important spatial scales
A decade of climate change experiments on marine organisms: procedures, patterns and problems
No full textThe first decade of the new millennium saw a flurry of experiments to establish a mechanistic understanding of how climate change might transform the global biota, including marine organisms. However, the biophysical properties of the marine environment impose challenges to experiments, which can weaken their inference space. To facilitate strengthening the experimental evidence for possible ecological consequences of climate change, we reviewed the physical, biological and procedural scope of 110 marine climate change experiments published between 2000 and 2009. We found that 65% of these experiments only tested a single climate change factor (warming or acidification), 54% targeted temperate organisms, 58% were restricted to a single species and 73% to benthic invertebrates. In addition, 49% of the reviewed experiments had issues with the experimental design, principally related to replication of the main test-factors (temperature or pH), and only 11% included field assessments of processes or associated patterns. Guiding future research by this inventory of current strengths and weaknesses will expand the overall inference space of marine climate change experiments. Specifically, increased effort is required in five areas: (i) the combined effects of concurrent climate and non-climate stressors; (ii) responses of a broader range of species, particularly from tropical and polar regions as well as primary producers, pelagic invertebrates, and fish; (iii) species interactions and responses of species assemblages, (iv) reducing pseudo-replication in controlled experiments; and (v) increasing realism in experiments through broad-scale observations and field experiments. Attention in these areas will improve the generality and accuracy of our understanding of climate change as a driver of biological change in marine ecosystems
Subtidal macroalgal richness, diversity and turnover, at multiple spatial scales, along the southwestern Australian coastline
Get PDFPatterns of species richness are governed by processes that act at vastly different spatial scales. In the marine system of southwest Australia, macroalgal assemblage structure and richness is thought to be strongly influenced by both the Leeuwin Current, which acts at large regional spatial scales, and small-scale processes such as competition, wave disturbance and habitat heterogeneity. We examined macroalgal species richness and diversity at multiple spatial scales using a three-factor hierarchal design. Spatial extents ranged from metres (between quadrats) to many hundreds of kilometres (between regions), and the study encompassed almost 2000 km of temperate coastline. Macroalgal assemblages were highly speciose and the number, identity, and diversity of species varied considerably at all spatial scales. Small scale variability, at the scale of site or quadrat, contributed most to total variation in species richness and diversity, suggesting that small-scale processes are important drivers of ecological pattern in this system. Species richness, diversity and taxonomic distinctness increased sequentially along the coastline, from warmer to cooler waters. Small scale variability was most likely maintained by wave disturbance and habitat heterogeneity at these scales, while regional scale diversity and richness clines were attributed to the fact that most species had cool-water affinities and the southern coast of Australia is a hotspot of floral speciation and diversity. Macroalgal assemblages in southwest Australia are speciose and largely endemic, and biodiversity patterns are structured by multiple processes operating at multiple spatial scales
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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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