Biogeographical and ecological context for managing threats to coral and rocky reef communities in the Lord Howe Island Marine Park, south‐western Pacific

Abstract

ABSTRACT1. Quantitative subtidal surveys of fishes, macro-invertebrates and sessile organisms at 33 sites within the Lord Howe Island Marine Park revealed a rich fauna and flora, including 164 fishes, 40 mobile invertebrate taxa, 53 coral and other sessile invertebrate taxa, 32 algal taxa, and two seagrasses. The biota in this newly-zoned marine park was overwhelmingly tropical when species lists were tabulated; however, species with distributions centred on temperate coasts of eastern Australia and New Zealand occurred in disproportionately high densities compared with the tropical species.2. Lord Howe Island reefs were generally in good condition. Virtually no bleached coral was observed (0.2% of the reef surface; 0.8% of total hard coral cover). Living scleractinian coral comprised the predominant group of organisms growing on reef surfaces, with 25.5% cover overall. Other major taxa observed were brown algae (18.8% cover) and red algae (16.9% cover).3. Three distinctive community types were identified within the marine park-coral reefs, macroalgal beds and an offshore/open coast community. The distribution of these community types was strongly related to wave exposure, as indicated by an extremely high correlation with the first principal coordinates axis for biotic data (R 2 5 0.80). 4. The close (o3 km) proximity of tropical coral and temperate macroalgal community types off Lord Howe Island is highly unusual, with localized patterns of nutrient enrichment suggested as the primary cause. The macroalgal community type is only known from a small area off the south-western coast that is not protected from fishing. This community is considered highly susceptible to threats because of potential impacts of global warming and the possibility of expansion of sea urchin barrens. Coral bleaching and ocean acidification associated with global climate change also threaten the coral reef community, which includes relatively high numbers of endemic and near endemic fish species.

Short-term performance of three underwater sampling techniques for assessing differences in the absolute abundances and in the inventories of the coastal fish communities of the Northeast Atlantic Ocean

“…The transect width varied depending on the visibility, estimated using the metremarked guide rope, and was obtained by multiplying the average visibility by 2, and was, on average, 2.8 AE 0.8 m (s.d.). A pair of scuba divers swam along the rope and carried out a UVC in each of the four transects, repeating it on the return journey (in a way similar to that in Edgar et al 2010). Fish were visually identified and the total abundance of each taxon was obtained.…”

Distinct cross-shelf gradient in mesophotic reef fish assemblages in subtropical eastern Australia

“…However, the influence of these processes on deeper reefs is poorly known, in part because of the cost and logistical difficulties associated with working in areas beyond the practical range of standard SCUBA equipment. In recent years, advances in lowcost and lightweight camera equipment, as well as in diving technology, have helped to fuel growing interest in the ecology of reefs in the mesophotic zone (30 to 150 m depth) (Hughes et al 2003, Riegl & Piller 2003, Lesser et al 2009, Puglise et al 2009, Edgar et al 2010. Tropical shallow water reefal species may be able to use reefs in the mesophotic zone and/or sub tropical reefs as refuges in the face of anthro-pogenic and climate related challenges (Hughes et al 2003, Riegl & Piller 2003, Bongaerts et al 2010, Kahng et al 2014.…”

“…A handful of studies have highlighted specific trends in the cross-shelf assemblages of fishes, molluscs, and corals within the eastern Australian subtropics (Edgar et al 2010, Malcolm et al 2010a,b, 2011a,b, Harrison & Smith 2012. Most notably, consistent trends exist across all tested taxa in the Solitary Islands Marine Park (SIMP), where the proportion of tropical species increases with distance from shore on shallow reefs (Malcolm et al 2007, 2010a, Harrison & Smith 2012) but decreases with depth (Malcolm et al 2011b).…”

High coral cover on a mesophotic, subtropical island platform at the limits of coral reef growth

“…The waters surrounding Lord Howe Island and Balls Pyramid contain a unique mix of tropical and temperate marine benthic and demersal species with high endemism and biodiversity (Veron and Done, 1979;de Forges et al, 2000;Edgar et al, 2010). These unique attributes are recognised through World Heritage (UNESCO, 2015) and Marine Protected Area status (NSW Marine Parks Authority, 2010; Department of Environment, 2016), with 47% of the shelf area surrounding Balls Pyramid incorporating no-take reserves.…”