Land management implications for ecosystem services in a South African rangeland

In South Africa, restoration and sustainable management of historically overgrazed and degraded rangelands are promoted to increase biodiversity and ecosystem service provision. This study evaluates different land management scenarios in terms of ecosystem services in a South African rangeland, the Baviaanskloof catchment. As measured data were limited, we used simple models to quantify and map the effect of the different combination of agricultural, nature conservation and restoration practices on multiple ecosystem services. The land management scenarios were evaluated against management targets set for individual ecosystem services. Results highlight how the provision of ecosystem services is related to land management as unmanaged, pristine ecosystems provide a different mix of ecosystem services than ecosystems recently restored or managed as grazing lands. Results also indicate that historically overgrazed lands provide no forage, may retain 40% less sediment and have 38% lower biodiversity, while providing 60% more fuel wood and supplying two and half times more water (i.e. retaining less water), than pristine or restored lands. We conclude that a combination of light grazing, low input agriculture, nature conservation and restoration is the best for the sufficient provision of multiple ecosystem services. Applying such mixed management would improve biodiversity, ecotourism and maintain forage production and regulating services on farmers’ land. This management option also fits into and further optimizes local decision-makers’ vision regarding the future management of the area.     

Shifts in coralline algae,macroalgae, and coral juveniles in the Great Barrier Reef associated with present‐day ocean acidification

Seawater acidification from increasing CO₂ is often enhanced in coastal waters due to elevated nutrients and sedimentation. Our understanding of the effects of ocean and coastal acidification on present‐day ecosystems is limited. Here we use data from three independent large‐scale reef monitoring programs to assess coral reef responses associated with changes in mean aragonite saturation state (Ω_ar) in the Great Barrier Reef World Heritage Area (GBR). Spatial declines in mean Ω_ar are associated with monotonic declines in crustose coralline algae (up to 3.1‐fold) and coral juvenile densities (1.3‐fold), while non‐calcifying macroalgae greatly increase (up to 3.2‐fold), additionally to their natural changes across and along the GBR. These three key groups of organisms are important proxies for coral reef health. Our data suggest a tipping point at Ω_ar 3.5–3.6 for these coral reef health indicators. Suspended sediments acted as an additive stressor. The latter suggests that effective water quality management to reduce suspended sediments might locally and temporarily reduce the pressure from ocean acidification on these organisms.     

Influence of cattle grazing practices on forest understorey structure in north‐eastern New South Wales

Abstract In eastern Australia the practice of grazing cattle in eucalypt forests and woodlands, as a supplementary activity to farmland grazing, is widespread. It is typically accompanied by burning at frequent intervals by graziers to promote more nutritious and digestible growth of the ground cover for their livestock. Collectively, these forest grazing practices affect understorey structure, which in turn affects other biotic and abiotic components of these ecosystems. In order to test how significant the effects of forest grazing practices are relative to the effects of other management practices and environmental variables and the degree to which grazing practices determine understorey vegetation structure, we surveyed 58 sites on the northern tablelands of New South Wales, Australia. All sites were located in eucalypt forest and were stratified by grazing status (presence or absence): time since logging, time since wildfire, geology, aspect, slope and topographic position. At each site an index of vegetation complexity and the most abundant plant species were recorded. The data were analysed by a backwards stepwise multiple regression. Grazing practices had the greatest influence on understorey vegetation complexity of any of the measured attributes. The grazed sites were characterized by a significantly lower vegetation complexity score, different dominant understorey species, reduced or absent shrub layers, and an open, simplified and more grassy understorey structure compared with ungrazed sites. Time since logging and time since wildfire also significantly affected understorey structure. Our results indicate that cattle grazing practices (i.e. grazing and the associated frequent fire regimes) can have major effects on forest structure and composition at a regional level.     

Restoration of Degraded Grazing Lands through Grazing Management: Can It Work?

Grazing lands are the most degraded land use type in the world, particularly in arid and semiarid areas, as a result of improper human activities such as overgrazing coupled with drought. For restoration of degraded grazing lands, large-scale projects are implemented, which include extensive vegetation improvements (e.g., reseeding, weed control, shrub plantations, reforestations, etc.). Such interventions, apart from being very expensive, often create environmental problems. In situations where the abiotic function of the degraded grazing land has not been irreversibly damaged, application of appropriate grazing management is an ecologically viable solution to their restoration. This is especially necessary for grazed lands with a long history of grazing by large herbivores, including livestock. Excluding domestic animals from such ecosystems may lead to several ecological problems such as loss of biodiversity and devastating wildfires. Appropriate grazing management should include an adjusted stocking rate to the grazing capacity of the restored land, the right kind of animal species, and an appropriate grazing system. In addition, grazing management should be implemented on the basis of a plan that is part of the restoration project. It is concluded that grazing management should become a priority option in restoration of the biotic function of degraded grazing lands, especially in those that have had a long history with the presence of domestic animals.     

Towards protecting the Great Barrier Reef from land‐based pollution

The Great Barrier Reef (GBR) is an iconic coral reef system extending over 2000 km along the north‐east coast of Australia. Global recognition of its Outstanding Universal Value resulted in the listing of the 348 000 km² GBR World Heritage Area (WHA) by UNESCO in 1981. Despite various levels of national and international protection, the condition of GBR ecosystems has deteriorated over the past decades, with land‐based pollution from the adjacent catchments being a major and ongoing cause for this decline. To reduce land‐based pollution, the Australian and Queensland Governments have implemented a range of policy initiatives since 2003. Here, we evaluate the effectiveness of existing initiatives to reduce discharge of land‐based pollutants into the waters of the GBR. We conclude that recent efforts in the GBR catchments to reduce land‐based pollution are unlikely to be sufficient to protect the GBR ecosystems from declining water quality within the aspired time frames. To support management decisions for desired ecological outcomes for the GBR WHA, we identify potential improvements to current policies and incentives, as well as potential changes to current agricultural land use, based on overseas experiences and Australia's unique potential. The experience in the GBR may provide useful guidance for the management of other marine ecosystems, as reducing land‐based pollution by better managing agricultural sources is a challenge for coastal communities around the world.     

Untangling the roles of fire,grazing and rainfall on small mammal communities in grassland ecosystems

In grassland systems across the globe, ecologists have been attempting to understand the complex role of fire, grazing and rainfall in creating habitat heterogeneity and the consequences of anthropogenic control of these factors on ecosystem integrity and functioning. Using a South African grassland ecosystem as a model, we investigated the impact of fire and grazing pressure on small mammal communities during three differing periods of a rainfall cycle. Over 2 years, 15,203 trap nights revealed 1598 captures of 11 species (nine rodents, one macroscelid and one insectivore). Results highlighted the importance of the interplay between factors and showed that the role of fire, grazing and rainfall in determining small mammal abundance was species-dependant. While no two species were affected by the same environmental variables, grass cover or height was important to 56% of species. Considered independently, high rainfall had a positive influence on small mammal abundance and diversity, although the lag period in population response was species-specific. High grazing negatively affected overall abundance, but specifically in Mastomys coucha; fire alone had little immediate impact on small mammal diversity. Six months after the fire, vegetation cover had recovered to similar levels as unburned areas, although small mammal diversity and richness were higher in burned areas than unburned areas. Grazing levels influenced the rate of vegetation recovery. In conclusion, low-level grazing and burning can help to maintain small mammal biodiversity, if conducted under appropriate rainfall levels. A too high grazing pressure, combined with fire, and/or fire conducted under drought conditions can have a negative impact on small mammal biodiversity. To maintain small mammal diversity in grassland ecosystems, the combined effects of the previous year’s rainfall and existing population level as well as the inhibition of vegetation recovery via grazing pressure need to be taken into consideration before fire management is applied. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effect of substrate type on bacterial community composition in biofilms from the Great Barrier Reef

Natural and anthropogenic impacts such as terrestrial runoff, influence the water quality along the coast of the Great Barrier Reef (GBR) and may in turn affect coral reef communities. Associated bacterial biofilms respond rapidly to environmental conditions and are potential bioindicators for changes in water quality. As a prerequisite to study the effects of water quality on biofilm communities, appropriate biofilm substrates for deployment in the field must be developed and evaluated. This study investigates the effect of different settlement substrates (i.e. glass slides, ceramic tiles, coral skeletons and reef sediments) on bacterial biofilm communities grown in situ for 48 days at two locations in the Whitsunday Island Group (Central GBR) during two sampling times. Bacterial communities associated with the biofilms were analysed using terminal restriction fragment length polymorphism (T-RFLP) and clone library analyses of 16S rRNA genes. Findings revealed that substrate type had little influence on bacterial community composition. Of particular relevance, glass slides and coral skeletons exhibited very similar communities during both sampling times, suggesting the suitability of standardized glass slides for long-term biofilm indicator studies in tropical coral reef ecosystems.     

Impacts of recent climate change on terrestrial flora and fauna: Some emerging Australian examples

The effects of anthropogenic climate change on biodiversity are well known for some high‐profile Australian marine systems, including coral bleaching and kelp forest devastation. Less well‐published are the impacts of climate change being observed in terrestrial ecosystems, although ecological models have predicted substantial changes are likely. Detecting and attributing terrestrial changes to anthropogenic factors is difficult due to the ecological importance of extreme conditions, the noisy nature of short‐term data collected with limited resources, and complexities introduced by biotic interactions. Here, we provide a suite of case studies that have considered possible impacts of anthropogenic climate change on Australian terrestrial systems. Our intention is to provide a diverse collection of stories illustrating how Australian flora and fauna are likely responding to direct and indirect effects of anthropogenic climate change. We aim to raise awareness rather than be comprehensive. We include case studies covering canopy dieback in forests, compositional shifts in vegetation, positive feedbacks between climate, vegetation and disturbance regimes, local extinctions in plants, size changes in birds, phenological shifts in reproduction and shifting biotic interactions that threaten communities and endangered species. Some of these changes are direct and clear cut, others are indirect and less clearly connected to climate change; however, all are important in providing insights into the future state of terrestrial ecosystems. We also highlight some of the management issues relevant to conserving terrestrial communities and ecosystems in the face of anthropogenic climate change.     

Effects of livestock grazing on rangeland biodiversity: A meta‐analysis of grouse populations

Livestock grazing affects over 60% of the world's agricultural lands and can influence rangeland ecosystem services and the quantity and quality of wildlife habitat, resulting in changes in biodiversity. Concomitantly, livestock grazing has the potential to be detrimental to some wildlife species while benefiting other rangeland organisms. Many imperiled grouse species require rangeland landscapes that exhibit diverse vegetation structure and composition to complete their life cycle. However, because of declining populations and reduced distributions, grouse are increasingly becoming a worldwide conservation concern. Grouse, as a suite of upland gamebirds, are often considered an umbrella species for other wildlife and thus used as indicators of rangeland health. With a projected increase in demand for livestock products, better information will be required to mitigate the anthropogenic effects of livestock grazing on rangeland biodiversity. To address this need, we completed a data‐driven and systematic review of the peer‐reviewed literature to determine the current knowledge of the effects of livestock grazing on grouse populations (i.e., chick production and population indices) worldwide. Our meta‐analysis revealed an overall negative effect of livestock grazing on grouse populations. Perhaps more importantly, we identified an information void regarding the effects of livestock grazing on the majority of grouse species. Additionally, the reported indirect effects of livestock grazing on grouse species were inconclusive and more reflective of differences in the experimental design of the available studies. Future studies designed to evaluate the direct and indirect effects of livestock grazing on wildlife should document (i) livestock type, (ii) timing and frequency of grazing, (iii) duration, and (iv) stocking rate. Much of this information was lacking in the available published studies we reviewed, but is essential when making comparisons between different livestock grazing management practices and their potential impacts on rangeland biodiversity.     

The role of the reef flat in coral reef trophodynamics: Past,present, and future

The reef flat is one of the largest and most distinctive habitats on coral reefs, yet its role in reef trophodynamics is poorly understood. Evolutionary evidence suggests that reef flat colonization by grazing fishes was a major innovation that permitted the exploitation of new space and trophic resources. However, the reef flat is hydrodynamically challenging, subject to high predation risks and covered with sediments that inhibit feeding by grazers. To explore these opposing influences, we examine the Great Barrier Reef (GBR) as a model system. We focus on grazing herbivores that directly access algal primary productivity in the epilithic algal matrix (EAM). By assessing abundance, biomass, and potential fish productivity, we explore the potential of the reef flat to support key ecosystem processes and its ability to maintain fisheries yields. On the GBR, the reef flat is, by far, the most important habitat for turf‐grazing fishes, supporting an estimated 79% of individuals and 58% of the total biomass of grazing surgeonfishes, parrotfishes, and rabbitfishes. Approximately 59% of all (reef‐wide) turf algal productivity is removed by reef flat grazers. The flat also supports approximately 75% of all grazer biomass growth. Our results highlight the evolutionary and ecological benefits of occupying shallow‐water habitats (permitting a ninefold population increase). The acquisition of key locomotor and feeding traits has enabled fishes to access the trophic benefits of the reef flat, outweighing the costs imposed by water movement, predation, and sediments. Benthic assemblages on reefs in the future may increasingly resemble those seen on reef flats today, with low coral cover, limited topographic complexity, and extensive EAM. Reef flat grazing fishes may therefore play an increasingly important role in key ecosystem processes and in sustaining future fisheries yields.     

Inferring Landscape-Scale Land-Use Impacts on Rivers Using Data from Mesocosm Experiments and Artificial Neural Networks

Identifying land-use drivers of changes in river condition is complicated by spatial scale, geomorphological context, land management, and correlations among responding variables such as nutrients and sediments. Furthermore, variations in standard metrics, such as substratum composition, do not necessarily relate causally to ecological impacts. Consequently, the absence of a significant relationship between a hypothesised driver and a dependent variable does not necessarily indicate the absence of a causal relationship. We conducted a gradient survey to identify impacts of catchment-scale grazing by domestic livestock on river macroinvertebrate communities. A standard correlative approach showed that community structure was strongly related to the upstream catchment area under grazing. We then used data from a stream mesocosm experiment that independently quantified the impacts of nutrients and fine sediments on macroinvertebrate communities to train artificial neural networks (ANNs) to assess the relative influence of nutrients and fine sediments on the survey sites from their community composition. The ANNs developed to predict nutrient impacts did not find a relationship between nutrients and catchment area under grazing, suggesting that nutrients were not an important factor mediating grazing impacts on community composition, or that these ANNs had no generality or insufficient power at the landscape-scale. In contrast, ANNs trained to predict the impacts of fine sediments indicated a significant relationship between fine sediments and catchment area under grazing. Macroinvertebrate communities at sites with a high proportion of land under grazing were thus more similar to those resulting from high fine sediments in a mesocosm experiment than to those resulting from high nutrients. Our study confirms that 1) fine sediment is an important mediator of land-use impacts on river macroinvertebrate communities, 2) ANNs can successfully identify subtle effects and separate the effects of correlated variables, and 3) data from small-scale experiments can generate relationships that help explain landscape-scale patterns.     

Reconstructing Anthropogenic Disturbance Regimes in Forest Ecosystems: A Case Study from the Swiss Rhone Valley

Anthropogenic disturbances of forest ecosystems are increasingly recognized as fundamental ecological processes with important long-term implications for biogeochemical cycles and vegetation patterns. This article aims at reconstructing the extent and intensity of the two most common types of traditional forest uses—forest litter collecting and wood pasture—in the Swiss Rhone valley (Valais) by (i) identifying the spatiotemporal patterns, and (ii) modeling the biomass removal through these practices. Detailed information on agricultural practices and socio-economic context were essential to develop reliable estimates of anthropogenic disturbance regimes. In the Valais, predominately goats and sheep grazed in the forests. The intensity of grazing was a function of the number of grazing animals and the available grazing area. Forest litter was used as bedding for farm animals during the winter. Key factors determining the intensity of litter collecting were the number of animal units, the amount of available substitute products (straw), and the area where litter raking could be practiced. The results show that wood pasture and forest litter collecting were practiced on a significant proportion of the forested landscape in the Valais up to the second half of the 20th century. Until the implementation of forest management plans in the 1930s, almost half of the forests in the study area were affected by wood pasture and/or forest litter collecting. The regulations in the management plans led to an essential reduction of the area available for these traditional practices but likewise to an increased pressure on the remaining areas. The results suggest that the notion of a slow but steady disappearance of traditional non-timber forest uses and the associated effects on forest ecosystems is oversimplified. Quantitative reconstructions of biomass output resulting from these practices confirm the importance of traditional non-timber forest uses for ecosystem development in this region. Furthermore, it is very likely that similar effects have been widespread throughout regions with similar natural and socio-economic context, for example, throughout a significant proportion of the European Alps. This study underlines the importance of environmental history for ecological sciences as well as for forest management and conservation planning.     

Effects of different fencing regimes on community structure of degraded desert grasslands on Mu Us desert,China

Grazing is one of the major anthropogenic driving factors influencing community structure and ecological function of grasslands. Fencing has been proved to be one of the main measures for rehabilitating degraded grasslands in northwestern China. However, data from combined empirical studies on the effects of different management regimes in desert grasslands are lacking. So we selected long‐term fencing (fenced since 1991), mid‐term fencing and seasonal fencing (fenced since 2002), and adjacent free‐grazing grasslands to investigate vegetation and soil properties on southwest Mu Us desert. Our results showed that fencing increased plant cover, height, aboveground biomass (AGB) of different plant life‐form groups, Shannon–Wiener diversity index, Evenness index, Simpson index, total soil nitrogen, total soil phosphorus, and soil organic matter, but decreased plant density, species richness, Richness index, soil bulk density, water content, and pH. However, 22–24 years of long‐term complete fencing might cause redegradation of vegetation and soil nutrients, characterized by the reduction of some vegetation properties, biodiversity, total AGB, and some soil properties. Seasonal fencing with 11–13 year was more beneficial to vegetation restoration than that with completely fencing measures. Our study suggests that appropriate artificial disturbances, such as seasonal fencing (winter grazing and summer fencing), should be used after long‐term fencing in order to maintain grassland productivity and biodiversity. These findings will help to provide theoretical support for vegetation restoration and sustainable management in grassland under grazing prohibition at Mu Us desert.     

Oak tree and grazing impacts on soil properties and nutrients in a California oak woodland

There is great interest in understandinghow rangeland management practices affectthe long-term sustainability of California oakwoodland ecosystems through their influence onnutrient cycling. This study examines the effects ofoak trees and low to moderate intensity grazing onsoil properties and nutrient pools in a blue oak (Quercus douglasii H.&A.) woodland in the SierraNevada foothills of northern California. Fourcombinations of vegetation and management wereinvestigated: oak with grazing, oak without grazing,open grasslands with grazing, and open grasslandswithout grazing. Results indicate that oak treescreate islands of enhanced fertility through organicmatter incorporation and nutrient cycling. Comparedto adjacent grasslands, soils beneath the oak canopyhave a lower bulk density, higher pH, and greaterconcentrations of organic carbon, nitrogen, total andavailable P, and exchangeable Ca, Mg, and K,especially in the upper soil horizons (0–35 cm). Incontrast, the light grazing utilized at this site hadminimal effects on soil properties which included anincrease in the bulk density of the surface horizonand an increase in available P throughout the entiresoil profile. While low to moderate intensity grazinghas little effect at this study site, there could bemuch larger impacts under the more intensive grazingpractices utilized on many rangelands. The lack ofoak regeneration and oak tree removal to enhanceforage production may eventually lead to large lossesof nutrients and soil fertility from these ecosystems.Results of this study have important implications forpredicting how management practices may potentiallyaffect oak regeneration, water quality, and ecosystemsustainability.     

Water Quality Trends in a Coastal Lagoon Impacted by Non-point Source Pollution after Implementation of Protective Measures

Water quality data from two different monitoring periods are used to evaluate the trophic state and effectiveness of various protective measures on the restoration of a eutrophic, coastal Mediterranean lagoon. Main protective measures included elimination of municipal/industrial raw wastewater discharges in the rivers outflowing to the lagoon, sediment/erosion control practices in the lagoon’s drainage basin (i.e., construction of sediment/debris dams and grade control structures, reforestation and ban on livestock grazing), and reduction of fertilizer application quantities as a result of changes in crops. Water quality data include, among others, chlorophyll a, dissolved oxygen and nutrient concentrations, various physicochemical parameters, and transparency, measured during two monitoring periods, i.e., before (1983–84) and after (1998–99) implementation of protective measures. Rainfall depth for the two time periods was also available. Empirical equations were developed, from statistical analyses of the data, relating the water quality parameters during the two monitoring periods. These models help identify water quality trends. Based on the analyses, it seems that measures were effective in reducing sediments transported into the lagoon. However, the lagoon remains eutrophic to hypereutrophic, mostly due to phosphorus released in the water column from bottom sediments. Therefore, future restoration efforts should be directed towards the management of bottom sediments.     

The area of potential shallow-water tropical and subtropical coral ecosystems in the United States

Geographic information system-based analysis was used to derive comprehensive, consistent estimates of the potential area of broadly defined, shallow-water, tropical and subtropical coral ecosystems within the territorial sea and exclusive economic zone of the United States. A coral ecosystem is composed of habitats including unconsolidated sediment, mangrove, hermatypic coral, colonized hardbottom, and submerged vegetation, and major structural zones like reef crest, lagoon, and fore reef. This broad definition reflects the importance of both reef and non-reef habitats and structural zones in the function of these ecosystems. Nautical charts, published by the National Oceanic and Atmospheric Administration’s Office of the Coast Survey, provide a consistent source of 10-fathom (∼18 m) and 100-fathom (∼183 m) depth curve information. The 10-fathom or 100-fathom depth curves are used as surrogates for the potential distribution and extent of shallow-water coral ecosystems in tropical and subtropical U.S. waters. An estimated 36,813 sq·km area has been identified where coral ecosystems can potentially be found in waters less than 10 fathoms (18 m) deep. In addition, an estimated 143,059 sq·km area has been identified where coral ecosystems potentially can be found in U.S. waters at depths down to 100 fathoms (183 m). Results also indicate that previous studies underestimated the extent of potential coral ecosystems for some locations in U.S. tropical and subtropical waters by as much as 100% and that the regional distribution of coral ecosystems has been incorrectly reported.     

Anthropogenic impact on water quality of Chilika lagoon RAMSAR site: a statistical approach

This paper investigated the spatio-temporal variability of water quality parameters (transparency, salinity, dissolved oxygen, nutrients viz. NH₃-N, NO₂-N, NO₃⁻-N, PO₄³-P, total nitrogen, total phosphorous and chlorophyll-a) in Chilika lagoon during 2001–2003 in order to better understand its ecological characteristics. Marked spatial and seasonal variations were detected with respect to almost all parameters studied. Northern sector of the lagoon is more affected by the anthropogenic stress from the catchments than the southern sector. Addition of nitrogen and phosphorous compounds to the lagoon mainly occurred through the drainage from agricultural lands and river run off during the early months of paddy cultivating seasons. Phytoplankton productivity of the lagoon was nitrogen limited, as suggested by nitrogen to phosphorous ratio. Processes affecting the water quality of the lagoon system included agricultural drainage, sewage intrusion, macrophyte litter fall and exchange of water between lagoon and the sea (Bay of Bengal). Further in depth study pertaining to quantification of exogenous material input and their disposal is recommended to ensure proper management of the lagoon and its resources.     

Maximizing biodiversity, information and sustainability

Numerous global changes—notably anthropogenic extinction—force reconsideration of our management practices and the ways we regulate human influence in today’s world. Here, I define management to maximize biodiversity and illustrate the science that provides information to set goals for such management. Maximizing biodiversity simultaneously achieves sustainability and systemic health by avoiding the abnormal or pathological. The normal or sustainable are determined through the use of empirical integrative patterns to objectively account for the complexity of systems within which we find ourselves as a species. The science that reveals these integrative patterns provides measures of problems that can be solved by maximizing biodiversity—problems heretofore recognized only qualitatively. I use the Shannon-Weiner information index to test, and, with no surprise, reject the null hypothesis that there is no direct anthropogenic effect on biodiversity. The results of this science serve as examples of the kind of information most useful for guiding management and illustrate maximized biodiversity as a standard for management. Reference points based on maximized biodiversity are preferable to statistical parameters in meeting the objective of avoiding the abnormal or pathological in our interactions with other species, ecosystems and the biosphere. Management to maximize biodiversity is implemented by modifying human interactions with other biotic systems to achieve consistency in such interactions by mimicking natural role models of sustainability. Human influence is a significant factor in today’s world and the magnitude of such influence is illustrated by comparing humans with other species.     

Meiofauna sediment relations in leeward slope turf algae of Heron Island reef

As part of studies investigating the influence of grazers on reef meiofauna, we assessed the density, composition and richness of meiofauna (retained on a 100-μm sieve) on the leeward reef slope of Heron Reef, GBR, Australia using an airlift vacuum sampling device. Estimates of meiofauna densities ranged between 40 individuals 10 cm⁻² and 290 individuals 10 cm⁻², which is considerably lower than many estimates from carbonate sediments and hard substrates from other reefs and marine habitats. The 17 taxa of meiofauna were dominated by harpacticoid copepods (40%) and nematodes (32%). Varying sediment load within algal turfs explained 37% of variation of meiofauna density. A model is proposed in which increased shelter afforded by high living coral cover reduces meiofaunal losses from grazing and increases sediment loads, balanced by areas of low coral cover in which sedimentation rates are lower and grazing rates higher. At none of the four sites did major differences in abundance occur between November and March sampling events. Together these observations suggest that epilithic meiofaunal communities are generally spatially and temporally predictable at small scales in this reef system, indicating that their ecological services are similarly conservative. Handling editor: I. Nagelkerken