Specimen Collection or In-situ Measurement
Divers are often used over surface-based collection methods (e.g. trawls) to minimise the environment impact of collection, to allow for the most humane collection methods such as using anaesthetics underwater to allow specimens to be captured and measured etc, and, at times, to measure in-situ to avoid destroying the specimen through retrieval to the surface.
Underwater video is used to construct longer-term analyses of events. The equipment can either store the images self-contained or transmits the images to the surface through umbilical’s. The use of time-lapse can prolong the operation; infrared cameras can record both at night and day. Correct positioning of the cameras by divers is often an essential component of the study. Divers can also maintain the equipment underwater meaning that the apparatus does not have to come to the surface each time.
Diver-based underwater surveys are often used to quantify biological communities or single species over defined areas.
Benthic cores contain a lot of information about the receiving environment and the impacts on it. Sometimes the cores are taken for pollutant analysis, sometimes to assess the biological community within the benthos, and at other times in order to make physio-chemical measurements on the cores post-collection. The advantages of using divers to core by hand is that they can be precise on where the cores are taken from and the level of disturbance is less than if some form of surface deployed corer was used.
Equipment Deployment and Maintenance
Often divers are employed in support of science simply to deploy, maintain and/or retrieve monitoring equipment underwater. By attaching the equipment to permanent or long-term moorings using divers means that the whole mooring does not have to be lifted each time. If a large surface vessel is required for this lifting process then it can be expensive. Continual deployment and recovery of moorings can impact the sea floor in vulnerable areas.