Loss of oxygen in the global ocean is accelerating due to climate change and eutrophication, but how acute deoxygenation events affect tropical marine ecosystems remains poorly understood. Here we ...integrate analyses of coral reef benthic communities with microbial community sequencing to show how a deoxygenation event rapidly altered benthic community composition and microbial assemblages in a shallow tropical reef ecosystem. Conditions associated with the event precipitated coral bleaching and mass mortality, causing a 50% loss of live coral and a shift in the benthic community that persisted a year later. Conversely, the unique taxonomic and functional profile of hypoxia-associated microbes rapidly reverted to a normoxic assemblage one month after the event. The decoupling of ecological trajectories among these major functional groups following an acute event emphasizes the need to incorporate deoxygenation as an emerging stressor into coral reef research and management plans to combat escalating threats to reef persistence.
Although knowledge of sandy beaches has increased recently, the benthic diversity of macrotidal sandy beaches in the northeastern Atlantic Ocean (more specifically, the western Channel and the ...northern Bay of Biscay) is poorly known. Here, we present a regional-scale account of the species diversity, both observed and estimated, of the macrobenthic fauna of Brittany based on an analysis of a species-level data set from 18 sandy beaches in Brittany that were sampled annually for 13 yr on the lower shore. In total, 526 species were identified, including 210 Annelida, 167 Arthropoda, 103 Mollusca, 19 Echinodermata and 27 species of other phyla. Four distinct habitats were distinguished based on their benthic communities and characterised using environmental variables. Sediment heterogeneity appeared to enhance diversity, as heterogeneous muddy sand harboured significantly more species than (muddy) fine sand. The role of environmental variables as structuring factors of benthic communities was investigated using redundancy analysis and variance partitioning. Beach morphodynamics and sediment structure explained most diversity variations (25.40 and 24.91%, respectively) followed by wave characteristics (13.46%). Finally, we offer some habitat-specific reference values regarding species richness and the Shannon index for M-AMBI computation during Water Framework Directive and Marine Strategy Directive evaluations for a more reliable characterisation of the ecological status of sandy beaches.
Photographic quadrat sampling is commonly used for the study of sessile benthic communities. However, photoquadrat data handling is fragmented into several processing methods, and there is a scarcity ...of dedicated software tools that integrate all major analysis options. photoQuad is a new software system for advanced image processing of photographic samples, dedicated to ecological applications. The software integrates a series of methods for the extraction of species area, percentage coverage, or presence/absence information, including random point counts (RP), grid cell counts (CL), freehand regions (FH), and image segmentation-based regions (SG). These are simultaneously functional in a layer-based environment, further supported by a variety of tools for image enhancement, image calibration, automatic quadrat boundary detection, and management of user-specific species libraries. The paper documents the main features of photoQuad, and demonstrates its performance through the simultaneous application of the RP, CL, FH, and SG methods on identical datasets, and the comparison of errors in species area and coverage measurements. The simulated data used for reference are disk-shaped patches, whose area and density statistics are equivalent to three benthic species characteristic of Mediterranean coralligenous communities. The analysis indicated that measurement methods differed in area and coverage bias, as well as in their sensitivity to species size. Large patches were accurately measured by all methods in terms of mean scaled error, but CL and RP provided high error variance, and their performance deteriorated with decreasing patch size; the region-based SG and FH methods provided the lowest errors and were both robust to patch size. The image and quadrat calibration process showed no statistically significant effect on the outputs, although further analysis is needed to validate this result. Overall, photoQuad constitutes a powerful software for elaborate analysis of photoquadrat images, facilitating fast and comparable evaluation of the ecological information contained therein. The photoQuad software is freely available to download and use from: http://www.mar.aegean.gr/sonarlab/photoquad.
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► photoQuad is a dedicated software for the study of sessile benthic communities. ► photoQuad offers multiple quadrat analysis options in a layer-based environment. ► An error analysis of four quadrat processing methods is performed on simulated data. ► Region and segment-based methods show lower errors and sensitivity to patch size.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•ROV footage unveiled thriving CWC reefs on the Cabliers Coral Mounds (W Mediterranean).•Four benthic assemblages were identified, mainly driven by substratum type and depth.•North ...and south Cabliers show different CWC reef stages from flourishing to decline ones.•H. dactylopterus recruits and juveniles use CWC reefs as nursery grounds.
Scleractinian cold-water coral (CWC) reefs are key habitats for benthic fauna as they enhance spatial heterogeneity and biodiversity. Understanding their environmental and ecological dynamics has therefore important implications for biodiversity conservation. This is especially true for the Mediterranean Sea, where living cold-water coral reefs are rare. In this study, we present a quantitative analysis of the CWC assemblages from Cabliers Coral Mound Province, located in the Alboran Sea (westernmost Mediterranean). The province extends for 25 km, with some mounds rising up to 140 m from the surrounding seafloor and being partly topped by living CWC reefs. The observed megabenthic species were quantified through video analysis of three Remotely Operated Vehicle (ROV) dives (280–485 m water depth) and their distribution was related to mound geomorphic characteristics and seafloor terrain parameters, extracted from a high-resolution Autonomous Underwater Vehicle (AUV) multi-beam bathymetry. The pronounced abundance and size of scleractinian CWCs among the observed assemblages, makes Cabliers the only known coral mound province in the Mediterranean Sea with currently growing reefs. Within these reefs, several recruits and juveniles of the sebastid Helicolenus dactylopterus were observed, confirming the use of such habitats as nursery grounds by some commercially valuable fish species. The qualitative comparison between the fauna of Cabliers and Atlantic coral mounds suggest that the number of species associated with CWC mounds worldwide is even higher than previously thought. This finding has important implications for the conservation and management of CWC habitats in different geographic regions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Global climate change and other anthropogenic stressors have heightened the need to rapidly characterize ecological changes in marine benthic communities across large scales. Digital photography ...enables rapid collection of survey images to meet this need, but the subsequent image annotation is typically a time consuming, manual task. We investigated the feasibility of using automated point-annotation to expedite cover estimation of the 17 dominant benthic categories from survey-images captured at four Pacific coral reefs. Inter- and intra- annotator variability among six human experts was quantified and compared to semi- and fully- automated annotation methods, which are made available at coralnet.ucsd.edu. Our results indicate high expert agreement for identification of coral genera, but lower agreement for algal functional groups, in particular between turf algae and crustose coralline algae. This indicates the need for unequivocal definitions of algal groups, careful training of multiple annotators, and enhanced imaging technology. Semi-automated annotation, where 50% of the annotation decisions were performed automatically, yielded cover estimate errors comparable to those of the human experts. Furthermore, fully-automated annotation yielded rapid, unbiased cover estimates but with increased variance. These results show that automated annotation can increase spatial coverage and decrease time and financial outlay for image-based reef surveys.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The invertebrate by-catch of the Argentinean squid Illex argentinus collected by bottom trawls off San Jorge Gulf during an expedition performed in December 2020 was employed to characterize the ...bottom assemblages of the area, with special emphasis on sponges. According to the results, sponges were conspicuous and abundant components in these benthic communities, representing up to 40% of the total invertebrate by-catch (average: ~130 kg·nm2 per site). Tedania (T.) mucosa was the dominant species. Other recorded species were T. (T.) charcoti, T. (T.) murdochi, Isodictya verrucosa, Iophon proximum, Clathria (C.) microxa, C. (C.) discreta, Haliclona bilamellata, Siphonochalina fortis, and Myxilla (M.) mollis. The results of this study contribute to filling in the gaps in the distribution records of sponges in the continental shelf of Argentina in a previously poorly studied area.
Global warming and ocean acidification are forecast to exert significant impacts on marine ecosystems worldwide. However, most of these projections are based on ecological proxies or experiments on ...single species or simplified food webs. How energy fluxes are likely to change in marine food webs in response to future climates remains unclear, hampering forecasts of ecosystem functioning. Using a sophisticated mesocosm experiment, we model energy flows through a species-rich multilevel food web, with live habitats, natural abiotic variability, and the potential for intra- and intergenerational adaptation. We show experimentally that the combined stress of acidification and warming reduced energy flows from the first trophic level (primary producers and detritus) to the second (herbivores), and from the second to the third trophic level (carnivores). Warming in isolation also reduced the energy flow from herbivores to carnivores, the efficiency of energy transfer from primary producers and detritus to herbivores and detritivores, and the living biomass of detritivores, herbivores, and carnivores. Whilst warming and acidification jointly boosted primary producer biomass through an expansion of cyanobacteria, this biomass was converted to detritus rather than to biomass at higher trophic levels-i.e., production was constrained to the base of the food web. In contrast, ocean acidification affected the food web positively by enhancing trophic flow from detritus and primary producers to herbivores, and by increasing the biomass of carnivores. Our results show how future climate change can potentially weaken marine food webs through reduced energy flow to higher trophic levels and a shift towards a more detritus-based system, leading to food web simplification and altered producer-consumer dynamics, both of which have important implications for the structuring of benthic communities.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Manual analysis of large amounts of benthic images is time consuming and costly. This challenge has led to the development of automated image analysis techniques such as CoralNet. The technique ...combines an online repository and machine learning to completely or partially automate classification of benthic images. Here, the integration of Coral Point Count with Excel Extensions (CPCe) and CoralNet is showcased. CPCe was applied to manually annotate images captured by an autonomous underwater vehicle (AUV) deployed at Pemba Island, Tanzania and then to train and build confidence in CoralNet to automatically annotate more images. Further, possible outputs that can be derived from assessing the relationships between the cover of benthic variables and depth are demonstrated.
Temperate Mesophotic Ecosystems (TMEs) are stable habitats, usually dominated by slow-growing, long-lived sessile invertebrates and sciaphilous algae. Organisms inhabiting TMEs can form complex ...three-dimensional structures and support many commercially important species. However, TMEs have been poorly studied, with little known about their vulnerability to environmental impacts. Lough Hyne Marine Nature Reserve (Ireland) supports TMEs in shallower waters (12–40 m) compared with other locations (30–150+ m) as a result of the unusual hydrodynamic conditions. Here, we report changes that have occurred on the sponge-dominated cliffs at Lough Hyne between 1990 and 2019, providing insights into TME long-term stability and vulnerability to environmental impacts. Our main finding was a marked decline in most three-dimensional sponges at the internal sites of the lough. This was likely the result of one or more mass mortality events that occurred between 2010 and 2015. We also found an increase in ascidians, which might have been more tolerant and benefited from the space freed by the sponge mortality. Finally, in the most recent surveys, we found a high abundance of sponge recruits, indicating that a natural recovery may be underway. The possible factors involved in these community changes include eutrophication, increased temperature, and a toxic event due to an anomaly in the oxycline breakdown. However, the absence of comprehensive monitoring of biotic and abiotic variables makes it impossible to identify the cause with certainty. Our Lough Hyne example shows the potential vulnerability of TMEs to short-term disturbance events, highlighting the importance of monitoring these habitats globally to ensure they are appropriately conserved.
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•Temperate mesophotic ecosystems are vulnerable and poorly studied ecosystems.•Changes in subtidal benthic communities in a marine protected area.•Changes from sponge-dominated to ascidian-dominated communities.•Monitoring is essential for conservation of temperate mesophotic ecosystems.•Sponge mass mortality in a temperate marine reserve.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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