Tom R. Davis

Distribution and spatial modelling of a soft coral habitat in the Port Stephens-Great Lakes Marine Park: implications for management

Habitat mapping is a useful method for understanding the complex spatial relationships that exist in the marine environment, and is used to evaluate the effectiveness of management strategies, particularly in regards to marine protected areas. This study explored the observed and predicted distribution of an uncommon soft coral species, Dendronephthya australis within the Port Stephens–Great Lakes Marine Park. Dendronephthya australis was mapped by video operated by a SCUBA diver towing a time synchronised GPS. A species distribution model was created to explore the possible occurrence of D. australis outside of the mapped area, using four environmental parameters: bathymetry, slope of seabed, velocity of tidal currents, and distance from estuary mouth. Dendronephthya australis colonies occurred along the southern shoreline in the Port Stephens estuary between Fly Point and Corlette Point, but no colonies were found within sanctuary (no-take) zones within the marine park. The model illustrated limited habitat suitability for D. australis within a larger section of the estuary, suggesting this species has specific environmental requirements survival. Owing to its current threats (anchor damage and fishing line entanglement), implications from these findings will assist future management and protection decisions, particularly in regard to its protection within a marine park.

Southern range extensions for twelve heterobranch sea slugs (Gastropoda: Heterobranchia) on the eastern coast of Australia

Port Stephens, on the central New South Wales coast, provides ideal oceanographic and benthic conditions for the settlement and growth of larvae of tropical species delivered from the north by the East Australian Current. The popularity of the bay for recreational and scientific diving has facilitated extensive documentation of the biota over several decades, confirming its high biodiversity. Of the 313 species of heterobranch sea slugs recorded from Port Stephens to date, 30 are not known to occur further south. Our observations increase the number of taxa with a southern distribution limit at Port Stephens by 12 species and add to a growing list of marine taxa that are progressively extending their southern range, potentially as a result of climate change.

Assessing national biodiversity trends for rocky and coral reefs through the integration of citizen science and scientific monitoring programs.

Abstract Reporting progress against targets for international biodiversity agreements is hindered by a shortage of suitable biodiversity data. We describe a cost-effective system involving Reef Life Survey citizen scientists in the systematic collection of quantitative data covering multiple phyla that can underpin numerous marine biodiversity indicators at high spatial and temporal resolution. We then summarize the findings of a continental- and decadal-scale State of the Environment assessment for rocky and coral reefs based on indicators of ecosystem state relating to fishing, ocean warming, and invasive species and describing the distribution of threatened species. Fishing impacts are widespread, whereas substantial warming-related change affected some regions between 2005 and 2015. Invasive species are concentrated near harbors in southeastern Australia, and the threatened-species index is highest for the Great Australian Bight and Tasman Sea. Our approach can be applied globally to improve reporting against biodiversity targets and enhance public and policymakers’ understanding of marine biodiversity trends.

Developing a habitat classification typology for subtidal habitats in a temperate estuary in New South Wales, Australia

Effective estuarine management depends on adequate data about the ecology, extent and biodiversity of component habitats. However, these data are often scant, as exemplified by the Port Stephens estuary, part of the Port Stephens–Great Lakes Marine Park (NSW, Australia), for which even basic descriptions of habitat types and extent are lacking. Herein we present the results of the first quantitative assessment of subtidal benthic communities within the estuary, involving 130km of towed video transects over an area exceeding 50km2. We identified previously undocumented macroalgae-dominated habitat types and found strong correlations between habitat types and depth. The soft coral Dendronephthya australis habitat is of particular interest because this was found to occur exclusively outside current sanctuary (no take) zones. The habitat map of Port Stephens generated during the study provides the basis for more objective representative planning in future iterations of zoning in the estuarine section of the marine park. The study also suggests that depth may be a useful proxy for estuarine habitat types where specific data are lacking. The classification methodology developed during the study was cost-effective, generated robust data and consequently has potential for wider application in other large estuarine bays.

Compensating for length biases in underwater visual census of fishes using stereo video measurements

Underwater visual census (UVC) is a widely used technique for estimating species richness, abundance, and lengths of reef fishes. The technique has the advantage of being non-destructive, and can therefore be used for monitoring in marine protected areas. However, acquisition of robust data using UVC is reliant on the ability of individual divers to accurately identify fish, and estimate their lengths. Both of these variables can be affected by observer bias, which may also differ among observers. This study examines a technique with the potential to quantify and correct for observer bias in individual divers. We used simultaneous diver-operated stereo video and underwater visual census surveys, and compared the results to generate diver-specific correction factors. These correction factors were subsequently applied in additional estimates of fish length, with measurable improvement in the accuracy of the data.

First records of three fishes, and southern records of a further four fishes, from New South Wales, Australia

A study of fishes from Port Stephens in New South Wales, Australia has identified first records for three species in New South Wales — Genicanthus watanabei (Yasuda & Tominaga, 1970), Parupeneus indicus (Shaw, 1803), and Plectorhinchus chaetodonoides (Lacepede, 1801) — and southernmost records for a further four species: Cantherhines fronticinctus (Gunther, 1866), Coris bulbifrons (Randall & Kuiter, 1982), Mulloidichthys vanicolensis (Valenciennes, 1831), and Paracirrhites forsteri (Schneider, 1801). New sightings were up to 980 km south of previous records, indicating prolonged survival of tropical fish larvae in the East Australian Current.

Responses of Dendronephthya australis to predation by Dermatobranchus sp. nudibranchs

The soft coral Dendronephthya australis occurs only in large abundance within the tidal-dominated Port Stephens estuary in eastern Australia. In recent years, substantial declines in the spatial extent of D. australis within Port Stephens has led to calls for the species to be listed as ‘threatened’. The causes for these declines are likely to include a range of anthropogenic impacts, as well as natural effects such as predation by the nudibranch Dermatobranchus sp., which can be abundant in winter and spring. The responses of D. australis to the presence of Dermatobranchus sp. were studied at two sites in Port Stephens, using time-lapse and still photography combined with visual surveys. Dermatobranchus sp. was observed consuming D. australis polyps, and colony inflation and polyp expansion were both reduced when Dermatobranchus sp. was present. Although predation by Dermatobranchus sp. is a natural impact, our observations suggest that interactions with additional anthropogenic stressors may exacerbate its overall impact on the spatial extent and survival of the geographically restricted soft coral D. australis.

Assessing National Biodiversity Trends for Rocky and Coral Reefs through the Integration of Citizen Science and Scientific Monitoring Programs (vol 67, pg 134, 2017)

[This corrects the article DOI: 10.1093/biosci/biw180.].