Cold-water coral (CWC) mounds are biogenic, long-lived morphostructures composed primarily by scleractinian CWC’s and hemipelagic sediments that form complex deep-sea microhabitats found globally but specifically along the European-Atlantic margin. In this work, high-resolution mapping was applied to identify individual organismal distribution and zonation across a CWC Piddington Mound within the Porcupine Seabight, Ireland Margin. Marine Object-Based Image Analysis (MOBIA) and different machine learning classification methods (decision tree, logistic regression, and deep neural network) were applied to a high-resolution (2 mm) reef-scale video mosaic and ROV-mounted multibeam data in order to provide new insights into the spatial organization of coral frameworks and environmental factors on CWC mounds. The results showed an accurate quantification of the amount of Coral Framework (14.5%; ~2% live and ~12.5% dead) and sponges (~3.5%) with heterogeneous distribution, restricted to a certain portion of the mound. This is the first object level quantification of live and dead coral framework facies and individual sponges across an entire CWC mound. This approach has application for habitat and conservation studies, provides a quantification tool for carbon budget assessments and can provide a baseline to assess CWC mound change. The approach can also be modified for application in other habitats.

Strong currents are a key component of benthic habitats by supplying food and nutrients to filter-feeding organisms such as cold-water corals. Although field measurements show that cold-water coral habitats exist in areas of elevated bottom currents, flume studies show that cold-water corals feed more effectively at lower flow speeds. This research aims to explore this disconnect in situ by utilising high spatial resolution ROV photogrammetric data coupled with high temporal resolution in situ acoustic doppler current profile measurements at seven study sites within the upper Porcupine Bank Canyon (uPBC), NE Atlantic. Object-based image analysis of photogrammetric data show that coral habitats vary considerably within the upper canyon. Although there is a regional hydrodynamic trend across the uPBC, this variation is likely driven locally by topographic steering. Although live coral tends not to face directly into the prevailing current direction, preferring lower local flows speeds, they can tolerate exposure to high-flow speeds of up to 114 cm s−1, the highest recorded in a Desmophyllum pertusum habitat. Not only do these high flow speeds supply food and nutrients, they may also help contribute to coral rubble production through physical erosion. These results can be incorporated into simulations of future deep-water habitat response to changing environmental conditions while extending the upper current speed threshold for cold-water corals.

Resumo Esta pesquisa teve como objetivo a análise geomorfológica da região de Plataforma Continental do Estado de São Paulo, mais especificamente a área que compreende a porção centro-norte do Embaimento de Santos (de Cananéia a Ilha Grande). Foram elaborados modelos digitais de terreno (MDTs) da plataforma continental a partir da digitalização de 65260 pontos cotados obtidos através de folhas de bordo da Diretoria de Hidrografia e Navegação (DHN) a partir dos quais foi elaborado uma grade batimétrica com precisão de 200 metros. O Modelo Digital de Terreno foi, então, submetido a uma série de modelagens objetivando a identificação e caracterização de feições morfo-sedimentares associadas ao regime de variação do nível do mar e processos atuais, como análises de superfície de tendência, declividades e orientação do relevo e extração de paleo-drenagens. Foram realizadas, também, correlações, em ambientes de Sistema de Informações Geográficas (SIGs), das informações morfológicas com a distribuição de sedimentos superficiais. Foi possível identificar e analisar uma série de feições morfo-sedimentares como faixas de declives associadas a antigos níveis de estabilização do nível do mar, sistemas de paleo-vales bem conectados com desembocaduras atuais dos principais rios da costa do estado de São Paulo, zonas de anomalias sedimentares e topográficas associadas a áreas de maior erosão ou deposição e zonas de altos teores de carbonatos, que associadas a mudanças na rede de paleo-vales, indicam o posicionamento da faixa do Último Máximo Regressivo (UMR) assim como sua posterior evolução.

Cold-water coral (CWC) habitats are considered important centers of biodiversity in the deep sea, acting as spawning grounds and feeding area for many fish and invertebrates. Given their occurrence in remote parts of the planet, research on CWC habitats has largely been derived from remotely-sensed marine spatial data. However, with ever-developing marine data acquisition and processing methods and non-ubiquitous nature of infrastructure, many studies are completed in isolation resulting in large inconsistencies. Here, we present a concise review of marine remotely-sensed spatial raster data acquisition and processing methods in CWC habitats to highlight trends and knowledge gaps. Sixty-three studies that acquire and process marine spatial raster data since the year 2000 were reviewed, noting regional geographic location, data types (‘acquired data’) and how the data were analyzed (‘processing methods’). Results show that global efforts are not uniform with most studies concentrating in the NE Atlantic. Although side scan sonar was a popular mapping method between 2002 and 2012, since then, research has focused on the use of multibeam echosounder and photogrammetric methods. Despite advances in terrestrial mapping with machine learning, it is clear that manual processing methods are largely favored in marine mapping. On a broader scale, with large-scale mapping programs (INFOMAR, Mareano, Seabed2030), results from this review can help identify where more urgent research efforts can be concentrated for CWC habitats and other vulnerable marine ecosystems.