New research has found a type of coral reef called Octocorals, previously thought to have diminished off the east coast of the US in the Gulf of Maine, has been recently discovered surviving in dense coral garden communities in more than one location.
The paper 'Octocoral gardens in the Gulf of Maine (NW Atlantic), by Peter Auster et al, published in Biodiversity, studied Octocorals, a type of fragile deep-sea coral reef that grow and reproduce at very slow rates.
Octocorals used to be a common part of seafloor fauna in the Gulf of Maine. However, based on past accounts of where corals had been found, it had appeared that a century of fishing with bottom contact gear had reduced their distribution to just a small habitable area.
A recent expedition in July this year to the western Jordan Basin and Schoodic Ridge regions of the Gulf of Maine revealed an initial report of impressive octoral gardens. The coral gardens were defined as areas where octocorals were among the dominant fauna and occurred at densities higher than surrounding patches.
The researchers revealed: "We found areas with steep and vertical rock faces had the highest densities of octocorals. Primarily Paramuricea placomus with lower abundances of Primnoa resedaeformis and Acanthogorgia cf. armata compared to nearby areas with less vertical relief."
Using a camera platform with real-time colour video and digital still photographic imaging the researchers were able to assess the presence and arrangement of coral communities in a difficult to see area at a depth of 200-250 meters.
The researchers' findings confirm that: "Using 20 cm spaced parallel laser dots to adjust the area of digital still images, coral colonies on sloping rock faces had the highest density values, well above the threshold of 0.1 colony m−2 used in ICES to define coral garden habitat."
Some Paramuricea placomus colonies were over one metre in height from the base, showing both yellow and purple colour morphs. Other areas were found to have supported single and small collections of coral on exposed gravel patches.
In addition, Pandalid shrimp were frequently found on coral colonies. Fish including; Atlantic cod, cusk, pollock and silver hake were observed searching and catching prey amidst corals, whilst Acadian redfish used the coral for cover.
The researchers recommend greater conservation attention to these spatially rare octocoral garden communities in the Gulf.
- Peter J. Auster, Morgan Kilgour, David Packer, Rhian Waller, Steven Auscavitch, Les Watling. Octocoral gardens in the Gulf of Maine (NW Atlantic). Biodiversity, 2013; 1 DOI: 10.1080/14888386.2013.850446
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