Influence of benthic currents on cold-water coral habitats: a combined benthic monitoring and 3D photogrammetric investigation

Abstract

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.

Cold-water Coral Microbiome and Environmental Microbial Communities in a Remote NE Atlantic Submarine Canyon Setting: Microbial Diversity, Coral Health and Prospects

“…Seabed morphology is known to in uence the dynamics of the physical and chemical properties (e.g. dissolved and particulate organic matter, oxygen saturation and current regimes) of the deep-sea 40 including the upper PBC 41 . These properties can potentially in uence the composition of microbial communities on CWCs, sediment and the ambient water 26,6 .…”

Fine-Scale Heterogeneity of a Cold-Water Coral Reef and Its Influence on the Distribution of Associated Taxa

“…Images were enhanced in Photoshop CS6, by de-interlacing and raising the shadow values to increase exposure in the shaded areas on the periphery of the lighting and camera field of view, improving the 2D mosaic visuals. Agisoft Metashape (version 1.5.2; previously known as Photoscan) was chosen to create 3D models of the reef as it has been used in several marine habitat studies (Burns et al, 2015;Leon et al, 2015;Bennecke et al, 2016;Robert et al, 2017;Young et al, 2017;Bayley et al, 2019;Price et al, 2019;Lim et al, 2020), proving to be reliable and accurate software (Burns and Delparte, 2017). High image alignment accuracy was chosen to utilise the full resolution image.…”

“…Recently, point pattern analyses (PPAs) have gained traction in the study of intertidal and subtidal marine habitats, in tandem with advancing technologies and survey capabilities. For example, the use of image mosaicing and 3D photogrammetry [Structure from Motion (SfM)] in subtidal and intertidal waters has become more widespread, based on a range of camera platforms deployed by SCUBA diving (Burns et al, 2015), snorkelling (Leon et al, 2015;Pizarro et al, 2017), remotely operated vehicles (ROVs) (Robert et al, 2017;Price et al, 2019;Lim et al, 2020), autonomous underwater vehicles (AUVs) (Friedman et al, 2012;Ling et al, 2016), unmanned aerial vehicles (UAVs) (Casella et al, 2017;Murfitt et al, 2017), and unmanned surface vehicles (USVs) (Raber and Schill, 2019). The use of image mosaicing and SfM has improved our ability to accurately register each organism's relative position.…”

“…Nevertheless, photomosaics and 3D reconstructions have been used to visualise and characterise scleractinian cold-water coral habitats (Wheeler et al, 2005b,c;Lessard-Pilon et al, 2010;Vertino et al, 2010), derive their geomorphic properties (Robert et al, 2017(Robert et al, , 2019Price et al, 2019), detect colony size (Fabri et al, 2019) and create substrate/coral cover maps (Lim et al, 2017(Lim et al, , 2020Conti et al, 2019). However, so far these datasets have not been analysed with PPA, and thus relatively little is known about fine scale spatial organisation of reef building coral and reef inhabitants.…”

The “Little MonSta” Deep-Sea Benthic, Precision Deployable, Multi-Sensor and Sampling Lander Array

“…Surge is used to program the sampling rate, cell size, and sampling period, as well as to calibrate the instrument for local magnetic variability. Although sampling rate, period, and duration considerably control battery life, previous usage of the system shows that it can operate from three to nine months [16,17]. The data recorded by the ADCP is stored internally on a local mini-SD card which is only accessible on recovery of the Little MonSta.…”