A rare ‘deep-water’ coral assemblage in a shallow lagoon in Micronesia

• Published in: Marine biodiversity 2016-09, Vol.46 (3), p.543-544
• Main Authors: Muir, Paul R., Wallace, Carden C.
• Format: Article
• Language: English
• Subjects: Animal Systematics/Taxonomy/Biogeography; Biodiversity; Biomedical and Life Sciences; Colour; Coral reefs; Corals; Deep water; Freshwater & Marine Ecology; Hydrodynamics; Interspecific relationships; Lagoons; Life Sciences; Light; Light levels; Oceanarium; Plant Systematics/Taxonomy/Biogeography; Predation; Reefs; Seawater; Shallow water; Surface layers
• ISSN: 1867-1616; 1867-1624
• DOI: 10.1007/s12526-015-0419-4

During a reef coral survey in 2009, we found a shallow (10–20 m) southwest lagoon site (6.93° N, 158.11° E) with a scleractinian reef coral assemblage typical of the mesophotic zone (Kahng et al. 2010; Muir et al. 2015), dominated by deep-water Acropora species [mainly A. pichoni Wallace, 1999 and A. tenella (Brook, 1892)] and large coral plates of the genera Mycedium, Oxypora, Pachyseris and Montipora (Fig. 1). A. pichoni has laterally flattened branches typical of deep-water forms and was recorded in depths as shallow as 10 m Levels of light were noticeably low at the site, which we attributed to high levels of dissolved tannins giving the seawater a brown coloration, particularly in the surface layers. The unusual shallow occurrence of this deep fauna is likely related to the site’s unusual light conditions and hydrodynamics, allowing fragile deep-water species to exist with reduced competition from shallow-water species that require relatively high levels of light. The future of this habitat is of concern: the site is approximately 2 km2 in surface area, only small populations were detected, and high levels of Acanthaster planci predation were found on other parts of the island’s reefs.