Algal biomass in the Rottnest Island region were identified from quadrat surveys , as part of the SRFME research program. The aim of the SRFME Coastal project is to characterize the coastal benthic ecosystems of southwestern WA, with particular focus on benthic reef cosystems, their productivity and dynamics, and the physical, chemical and biological factors driving variability along dominant spatial and temporal scales. To achieve this, we undertook 3-monthly seasonal sampling from 2003 - 2005 at a series of coastal sites situated between Cape Naturaliste in the south and Jurien Bay in the north. Benthic Sampling was integrated with satellite observations of SST, ocean colour and subsurface measurements of other water column properties, as well as sediment biogeochemical sampling. Within this region benthic sampling was nested at Regional (100s km) Local (10s km) and Site (1 km) scales and within each of the regions additional sites were sampled to incorporate site scale variability along cross-shore gradients.