Analysis On Ecological Characteristics of Mississippian Coral Reefs in Langping, Guangxi

Several Late Viséan-Serpukhovian coral reefs were identified in Langping, Tianlin. To further understand of environment that was suitable for the development of reef-building communities and the construction of coral reefs in Langping, in this paper, part of the reef-building environmental and the ecological characteristics of coral reefs then were recovered by analyzing the development settings, palaeogeography, sedimentation of reefs, the response to hydrodynamic conditions of reef-building corals, effects of disturbance and non-reef-building organism on reef communities, and the influence of coral morphology on reef development. The sedimentary environment of Langping in Late Viséan-Serpukhovian is considered to be suitable for the development of benthic communities. The current appearance of reefs is determined by both coral populations ecological characteristics and reef-building environment.

Underwater Light Characteristics of Turbid Coral Reefs of the Inner Central Great Barrier Reef

Hyper-spectral and multi-spectral light sensors were used to examine the effects of elevated suspended sediment concentration (SSC) on the quantity and quality (spectral changes) of underwater downwelling irradiance in the turbid-zone coral reef communities of the inner, central Great Barrier Reef (GBR). Under elevated SSCs the shorter blue wavelengths were preferentially attenuated which together with attenuation of longer red wavelengths by pure water shifted the peak in the underwater irradiance spectrum ~100 nm to the less photosynthetically useful green-yellow waveband (peaking at ~575 nm). The spectral changes were attributed to mineral and detrital content of the terrestrially-derived coastal sediments as opposed to chromophoric (coloured) dissolved organic matter (CDOM). A simple blue to green (B/G, λ455:555 nm) ratio was shown to be useful in detecting sediment (turbidity) related decreases in underwater light as opposed to those associated with clouds which acted as neutral density filters. From a series of vertical profiles through turbid water, a simple, multiple component empirical optical model was developed that could accurately predict the light reduction and associated spectral changes as a function of SSC and water depth for a turbid-zone coral reef community of the inner GBR. The relationship was used to assess the response of a light sensitive coral, Pocillopora verrucosa in a 28-d exposure laboratory-based exposure study to a daily light integral of 1 or 6 mol quanta m2. PAR with either a broad spectrum or a green-yellow shifted spectrum. Light reduction resulted in a loss of the algal symbionts (zooxanthellae) of the corals (bleaching) and significant reduction in growth and lipid content. The 6 mol quanta m2 d−1 PAR treatment with a green-yellow spectrum also resulted in a reduction in the algal density, Chl a content per cm2, lipids and growth compared to the same PAR daily light integral under a broad spectrum. Turbid zone coral reef communities are naturally light limited and given the frequency of sediment resuspension events that occur, spectral shifts are a common and previously unrecognised circumstance. Dedicated underwater light monitoring programs and further assessment of the spectral shifts by suspended sediments are essential for contextualising and further understanding the risk of enhanced sediment run-off to the inshore turbid water communities.

Assessing ecological patterns in Wellington south coast's nearshore rocky-reef communities for resource conservation and management

<p>Many coastal marine communities are increasingly affected by terrestrial and maritime human activities and growing coastal populations. Protection of coastal assets and the sustainable use of coastal resources requires knowledge of nearshore benthic community status; the environmental processes that structure and connect them; the quality, abundance, and distribution of physical habitat; essential habitat for species requiring protective measures, and the spatio-temporal scales at which these patterns and processes occur. To assess the status of Wellington South Coast’s (WSC) rocky-reef assemblages prior to the enactment of the Taputeranga Marine Reserve in 2009, two annual baseline surveys were conducted during the austral summers of 2007/08 and 2008/09. These surveys evaluated the biotic and abiotic components of the assemblages in terms of diversity, abundance distribution, and size-class frequency patterns of key macroalgal and mobile macro-invertebrate species. These results were analysed to develop recommendations for best post-reserve monitoring practices, including the identification of “indicator” species for rapid yet representative field surveys to assess structural and status changes. In combination with patterns described by a previous pre-reserve baseline survey series (2000) that focussed on a reduced list of macro-algal and mobile macro-invertebrate species, this final pre-reserve survey forms the basis of a historical dataset for WSC rocky reefs that can be used for long-term monitoring of ecosystem shifts due to the new reserve and to possible changes caused by anthropogenic activity or altered natural processes. These aims were addressed by collecting information directly at local/site scale and remotely, at the larger area scale. Dived baseline surveys quantified nearshore WSC rocky-reef epibenthic assemblages at 9 sites at depths ranging from 5-13.6m and at a mean distance from shore = 113m. A survey design that included three sites west of the pending marine reserve, three sites to the east, and three sites within the designated reserve was selected to permit later BACI analyses of post-reserve changes. Species surveyed were those commonly encountered during daylight on exposed surfaces and in accessible crevices and belonged to one of three epibenthic groups: macro-algae (48 species), mobile macro-invertebrates (36 species), and sessile macro-invertebrates (30 morphotypes). These surveys did not include epizoa or smaller, cryptic newly recruited macro-invertebrates. Sessile macro-invertebrate cover was only logged if >0.1%/m2. To gauge possible spatio-temporal patterns in primary productivity as a measure of ecosystem function, biomass and plant size were measured semiannually (winter, summer) for dominant kelp and fucoid species and for two key recreationally and commercially important mobile macro-invertebrate species (sea urchin and abalone). Predictive regression equations developed from wet weight and plant size can be used for future non-destructive estimates of local primary productivity and in trophic modelling. [...] This mapping data forms the basis of a legacy dataset that will assist with monitoring changes in the integrity of critical physical habitat and associated biotic cover. It has also demonstrated that representative descriptions of both biotic and abiotic benthic components can be achieved with a minimum of sampling points and by using the quicker semi-quantitative visual analysis of video. These data can also be used to ground-truth a recently-completed multi-beam acoustic survey of the area. This work has used the approach of landscape ecology, which explains patterns in community structure, function, status and biophysical causes from a spatial perspective, to study biophysical patterns in WSC epibenthic rocky-reef communities. The work identified a high degree of spatial and temporal variation within the abiotic and biotic community within and outside of the reserve area and the limited availability of preferred habitat. The work also identified the need to include indicator species in monitoring to improve the chance of detecting impacted assemblages. These results, and the development of non-destructive sampling tools for assessing ecosystem status, are relevant locally and nationally for resource managers.</p>

Assessing ecological patterns in Wellington south coast's nearshore rocky-reef communities for resource conservation and management

<p>Many coastal marine communities are increasingly affected by terrestrial and maritime human activities and growing coastal populations. Protection of coastal assets and the sustainable use of coastal resources requires knowledge of nearshore benthic community status; the environmental processes that structure and connect them; the quality, abundance, and distribution of physical habitat; essential habitat for species requiring protective measures, and the spatio-temporal scales at which these patterns and processes occur. To assess the status of Wellington South Coast’s (WSC) rocky-reef assemblages prior to the enactment of the Taputeranga Marine Reserve in 2009, two annual baseline surveys were conducted during the austral summers of 2007/08 and 2008/09. These surveys evaluated the biotic and abiotic components of the assemblages in terms of diversity, abundance distribution, and size-class frequency patterns of key macroalgal and mobile macro-invertebrate species. These results were analysed to develop recommendations for best post-reserve monitoring practices, including the identification of “indicator” species for rapid yet representative field surveys to assess structural and status changes. In combination with patterns described by a previous pre-reserve baseline survey series (2000) that focussed on a reduced list of macro-algal and mobile macro-invertebrate species, this final pre-reserve survey forms the basis of a historical dataset for WSC rocky reefs that can be used for long-term monitoring of ecosystem shifts due to the new reserve and to possible changes caused by anthropogenic activity or altered natural processes. These aims were addressed by collecting information directly at local/site scale and remotely, at the larger area scale. Dived baseline surveys quantified nearshore WSC rocky-reef epibenthic assemblages at 9 sites at depths ranging from 5-13.6m and at a mean distance from shore = 113m. A survey design that included three sites west of the pending marine reserve, three sites to the east, and three sites within the designated reserve was selected to permit later BACI analyses of post-reserve changes. Species surveyed were those commonly encountered during daylight on exposed surfaces and in accessible crevices and belonged to one of three epibenthic groups: macro-algae (48 species), mobile macro-invertebrates (36 species), and sessile macro-invertebrates (30 morphotypes). These surveys did not include epizoa or smaller, cryptic newly recruited macro-invertebrates. Sessile macro-invertebrate cover was only logged if >0.1%/m2. To gauge possible spatio-temporal patterns in primary productivity as a measure of ecosystem function, biomass and plant size were measured semiannually (winter, summer) for dominant kelp and fucoid species and for two key recreationally and commercially important mobile macro-invertebrate species (sea urchin and abalone). Predictive regression equations developed from wet weight and plant size can be used for future non-destructive estimates of local primary productivity and in trophic modelling. [...] This mapping data forms the basis of a legacy dataset that will assist with monitoring changes in the integrity of critical physical habitat and associated biotic cover. It has also demonstrated that representative descriptions of both biotic and abiotic benthic components can be achieved with a minimum of sampling points and by using the quicker semi-quantitative visual analysis of video. These data can also be used to ground-truth a recently-completed multi-beam acoustic survey of the area. This work has used the approach of landscape ecology, which explains patterns in community structure, function, status and biophysical causes from a spatial perspective, to study biophysical patterns in WSC epibenthic rocky-reef communities. The work identified a high degree of spatial and temporal variation within the abiotic and biotic community within and outside of the reserve area and the limited availability of preferred habitat. The work also identified the need to include indicator species in monitoring to improve the chance of detecting impacted assemblages. These results, and the development of non-destructive sampling tools for assessing ecosystem status, are relevant locally and nationally for resource managers.</p>

Classifying 3-D Models of Coral Reefs Using Structure-From-Motion and Multi-View Semantic Segmentation

Benthic quadrat surveys using 2-D images are one of the most common methods of quantifying the composition of coral reef communities, but they and other methods fail to assess changes in species composition as a 3-dimensional system, arguably one of the most important attributes in foundational systems. Structure-from-motion (SfM) algorithms that utilize images collected from various viewpoints to form an accurate 3-D model have become more common among ecologists in recent years. However, there exist few efficient methods that can classify portions of the 3-D model to specific ecological functional groups. This lack of granularity makes it more difficult to identify the class category responsible for changes in the structure of coral reef communities. We present a novel method that can efficiently provide semantic labels of functional groups to 3-D reconstructed models created from commonly used SfM software (i.e., Agisoft Metashape) using fully convolutional networks (FCNs). Unlike other methods, ours involves creating dense labels for each of the images used in the 3-D reconstruction and then reusing the projection matrices created during the SfM process to project semantic labels onto either the point cloud or mesh to create fully classified versions. When quantitatively validating the classification results we found that this method is capable of accurately projecting semantic labels from image-space to model-space with scores as high as 91% pixel accuracy. Furthermore, because each image only needs to be provided with a single set of dense labels this method scales linearly making it useful for large areas or high resolution-models. Although SfM has become widely adopted by ecologists, deep learning presents a steep learning curve for many. To ensure repeatability and ease-of-use, we provide a comprehensive workflow with detailed instructions and open-sourced the programming code to assist others in replicating our methodology. Our method will allow researchers to assess precise changes in 3-D community composition of reef habitats in an entirely novel way, providing more insight into changes in ecological paradigms, such as those that occur during coral-algae shifts.

Heterogeneity around CO2 vents obscures the effects of ocean acidification on shallow reef communities

Studies that use CO2 vents as natural laboratories to investigate the impacts of ocean acidification (OA) typically employ control-impact designs or local-scale gradients in pH or pCO2, where impacted sites are compared to reference sites. While these strategies can accurately represent well-defined and stable vent systems in relatively homogenous environments, it may not adequately encompass the natural variability of heterogeneous coastal environments where many CO2 vents exist. Here, we assess the influence of spatial heterogeneity on the perceived impacts of OA at a vent system well established in the OA literature. Specifically, we use a multi-scale approach to investigate and map the spatial variability in seawater pH and benthic communities surrounding vents at Whakaari-White Island, New Zealand to better understand the scale and complexity of ecological impacts of an acidified environment. We found a network of vents embedded in complex topography throughout the study area, and spatially variable pH and pCO2 levels. The distribution of habitats (i.e. macroalgal forests and turfing algae) was most strongly related to substratum type and sea urchin densities, rather than pH. Epifaunal communities within turfing algae differed with sampling distance from vents, but this pattern was driven by higher abundances of a number of taxa immediately adjacent to vents, where pH and temperature gradients are steep and white bacterial mats are prevalent. Our results contrast with previous studies at White Island that have used a control-impact design and suggested significant impacts of elevated CO2 on benthic communities. Instead, we demonstrate a highly heterogeneous reef where it is difficult to separate effects of reduced pH from spatial variation in reef communities. We urge that future research carefully considers and quantifies the biological and physical complexity of venting environments, and suggest that in dynamic systems, such as White Island, the use of control-impact designs can oversimplify and potentially overestimate the future impacts of OA.

Biodiversity of coral reef cryptobiota shuffles but does not decline under the combined stressors of ocean warming and acidification

Ocean-warming and acidification are predicted to reduce coral reef biodiversity, but the combined effects of these stressors on overall biodiversity are largely unmeasured. Here, we examined the individual and combined effects of elevated temperature (+2 °C) and reduced pH (−0.2 units) on the biodiversity of coral reef communities that developed on standardized sampling units over a 2-y mesocosm experiment. Biodiversity and species composition were measured using amplicon sequencing libraries targeting the cytochrome oxidase I (COI) barcoding gene. Ocean-warming significantly increased species richness relative to present-day control conditions, whereas acidification significantly reduced richness. Contrary to expectations, species richness in the combined future ocean treatment with both warming and acidification was not significantly different from the present-day control treatment. Rather than the predicted collapse of biodiversity under the dual stressors, we find significant changes in the relative abundance but not in the occurrence of species, resulting in a shuffling of coral reef community structure among the highly species-rich cryptobenthic community. The ultimate outcome of altered community structure for coral reef ecosystems will depend on species-specific ecological functions and community interactions. Given that most species on coral reefs are members of the understudied cryptobenthos, holistic research on reef communities is needed to accurately predict diversity–function relationships and ecosystem responses to future climate conditions.

Experimental reef communities persist under future ocean acidification and warming

Coral reefs are among the most sensitive ecosystems affected by ocean acidification and warming, and are predicted to shift from net accreting calcifier-dominated systems to net eroding algal-dominated systems over the coming decades. Here we present a long-term experimental study examining the responses of entire mesocosm coral reef communities to acidification (-0.2 pH units), warming (+ 2°C), and combined future ocean (-0.2 pH, + 2°C) treatments. We show that under future ocean conditions, net calcification rates declined yet remained positive, corals showed reduced abundance yet were not extirpated, and community composition shifted while species richness was maintained. Our results suggest that under Paris Climate Agreement targets, coral reefs could persist in an altered functional state rather than collapse.