Photogrammetric classification of sponge morphometric diversity

Sponge communities form an important component of marine ecosystems. However, very little is known on the distribution of sponge species, and variations in sponge communities within south eastern Australia. This problem is compounded by inherent difficulties in sponge taxonomy. Previous studies have shown that sponge morphological diversity is a good proxy for sponge species diversity. This study investigated the capacity of close range photogrammetry to provide measurements of sponge morphology for classification of sponge functional groupings. A stereo camera system was designed and constructed. Calibration and accuracy assessment on the system showed it to provide measures within the predicted accuracy range. The system was subsequently deployed at two sites, one a soft sediment sponge community, and the other a rocky reef sponge community. 100 sponges were measured at each site, with 21 morphometric measurements made for each sponge. Of nine pre existing functional groupings (Bell and Barnes 2001), seven were observed across the two study sites. Discriminant analysis showed varying degrees of separation between these functional groupings based on the morphometric measurements. Between the two sites there was a difference in the makeup of the sponge community based on these functional groups. No differences were observed in the gross morphometric measurements for the common functional groups between the two sites.