Having an accurate picture of species diversity in a given habitat is critical for understanding and ultimately protecting our environment. However, the sheer volume of species means that simply counting them is not practical. Researchers instead rely on counting a subset of the population, which can predict species diversity and community composition. One commonly used method for terrestrial surveys is the use of a quadrat. This method requires researchers to define a much smaller area (quadrat) and identify the species found in that area. This is repeated either randomly or along a predefined line (transect). Collation of the quadrat data combined with statistical analysis provides an accurate picture of the community composition and species diversity without sampling the entire community. The application of this method to terrestrial habitats has now become straightforward. You take your quadrat, pencil, and clipboard, possibly a transect line, and survey the area accordingly.
But what about the less accessible ocean habitats? How are they classified? Until recently, surveying habitats deeper than 30 m was based either on extractive methods such as dredging (which are destructive) or predictions based on environmental variables and known species distributions. However, advances in technology now allow us to survey ocean habitats much more efficiently. One such technology called a jump camera places an underwater camera a set distance from the seafloor and takes photos of the habitat. These photos are called photoquadrats, and just like terrestrial quadrats, species and other habitat information captured in these photoquadrats can then be extracted and used to classify the habitat without any destruction. While photoquadrats go a long way to solving the ocean sampling problem, identifying species from photos is still tricky. Often, identifying smaller animals to species level requires access to the actual specimen.
Researchers at the KwaZulu-Natal Museum using the research platform RV Phakisa (South African Institute for Aquatic Biodiversity) are now comparing information obtained from photoquadrats to information gathered by dredging methods. This will allow us to determine what information can be reliably obtained from non-destructive photoquadrat methods. In doing so, we hope that we will be able to predict more accurately the types of species found in soft sediment habitats without the risk of damaging them further.
Figure 1. A dredge (left) and the dredgings (right) used to collect specimens from the ocean floor.
Figure 2. A jump camera system (left) and a photoquadrat (right) taken from soft sediment habitats in the Durban Bay area.