In order to assess the impact of recreational diving on the benthic community of Zenobia shipwreck, I used a now very common methodology well knows as photoquadrats techinique.
This technique has almost completely replaced visual methods since it improved a lot the amount of data collected and the efficienty of data collection in subtidal communities with a limited margin of informations loss, provided to be conducted in the appropriate way. Indeed, digital photography offers an excellent compromise between data accuracy and safe diving.
– rapid data collection;
– permanent photographic record;
– massive amounts of data collected;
– less tedious data collection: accuracy increased.
– digital equipment susceptible to breakage/flooding;
– equipment failure can result in data loss;
– hiding and tiny organisms can be omitted;
– a minimum experience is required.
Generally, we use the transects for sampling photoquadrats and we can use three different sampling methods:
– continuous sampling;
– random sampling;
– systematic sampling.
In my MSc thesis I also tested the difference of statistic significance among the three methods applied.
IMAGE ANALYSIS WITH CPCe If digital techniques have replaced visual methods for data collection, softwares have replaced visual methods for data process.
Coral Point Count with excel extensions, from Nova Southeastern University, is an excellent software specificly designed for that: a matrix of point is randomly distributed over a digital image and the species or substrate-type under each point is visually identified.