Rocky Shore

Survey Methods

A total of 8 sites (2 sites x 4 sections) with at least 20 m of continuous or semi-continuous hard rocks were chosen. Two replicate surveys were conducted in each wet and dry season. During the wet season, subject to time and manpower availability, a third survey was also conducted at selected site(s) where another stretch of continuous rocky shore was available, in order to encompass within-site spatial variability.

At each study site, 20 m transects were positioned at four different, fixed (permanently marked) tidal heights (1.15, 1.45, 1.75 and 2.05 m above C.D.) from low to high shore. Twenty replicate quadrats (25 × 25 cm) were placed randomly at each height. All sessile and mobile organisms in the quadrats were identified on site wherever possible and the numbers of slow-moving mobile organisms were counted, including those found in crevices.

Photographs of each quadrat were also taken to investigate the abundance of sessile organisms, including algae, bivalves and barnacles. The percentage cover of individual sessile organism was assessed using Coral Point Count with Excel extensions (CPCe). Since encrusting algae ware sometimes difficult to identify visually, samples were collected and identified in the laboratory. As algal abundance can be a measure of primary production, small rock chips were randomly taken from each quadrat on site and chlorophyll a concentration were measured following established protocols in the laboratory. To record the presence of fast-moving mobile species such as crabs or species that could not be represented by the quadrats, rapid assessments were conducted along transects in order to record as many species as possible during wet season. Species that could not be identified on site were photographed, or collected for later identification in the laboratory.

Three destructive samples collected within 25 × 25 cm quadrats were taken from low and mid tidal heights during the second replicate survey at most sites in each season. If possible, destructive samples were collected from areas with dense oyster communities, as oysters shells could host species undetected from the surface. Only biotas on rock surfaces were collected to avoid damaging the rocks. Samples were then transported in the laboratory for further species identification. Destructive sample collections were permitted in the Country Park and Geopark areas as a field collection permit was granted from AFCD.