Fernandez-Carvalho, J. 2008. Application of underwater video techniques for the characterization of underwater benthic communities.

A simple and practical towed video camera sled was developed, and used for the first time in the southern Portuguese coast (Algarve), in order to characterize the marine communities occurring there. A total of 19612m2 were filmed, between June and November 2005, at depths from the shoreline to 30m. From the video records, the taxa both in qualitative and quantitative terms, as well as habitat features were registered. A total of 19401 specimens were observed from 64 different taxa (23 fish taxa and 41 invertebrate taxa). The abundance was significantly different between the three depth classes studied ([0-10], [10-20] and [20-30]) with the [20-30] m depth class yielding the greater abundance. Regarding bottom type, the abundance was significantly different between coarse and fine sand substrates, with fine sand showing the highest abundance. Both depth and substrate were analysed and compared with multivariate analysis that was then used to identify and classify the biotopes within the study area. From this analysis, six different biotopes were defined: 1) Callionymus in infralitoral coarse sand, 2) Serpulidae and Sphaerechinus granularis in coarse sand, 3) infauna dominated fine sand, 4) Ophiocomina nigra beds in mud and fine sand, 5) Phallusia mammillata and Serranus hepatus in circalitoral gravel sand and 6) Turritella beds in circalitoral sand. In order to evaluate its applicability as a surveying technique, the video results were compared with two more traditional surveying techniques, namely scientific trawl and dive census. Qualitatively, the video results were more similar to dive results, while quantitatively video data were more similar to trawl data. This work discusses the applicability of this technique as a surveying technique, and demonstrates that the underwater sledge video is a very efficient technique both for classifying and mapping marine benthic habitats and communities.