In order to properly identify and catalog the biodiversity of a site, researchers often must physically collect specimens by hand for more thorough study in a laboratory. Examples of species are collected by SCUBA divers using nets and collection bottles, and by using devices called suction samplers that act like vacuum cleaners to collect small organisms. More quantitative methods include more systematic approaches such as quadrat sampling along the intertidal zone.
Much like observation by passive quadrat sampling, active collection using quadrat sampling involves using a series of squares (quadrats) of a set size placed across a habitat of interest. Species found within quadrats are collected for later identification. As with passive quadrat sampling, abundances of organisms found at the study site can be calculated using the number found per quadrat and the size of the quadrat area. Example specimens are often kept in long-term research collections for historical records. This is a time-tested sampling technique that is, as with all hand collecting, best suited for coastal areas where access to a habitat is relatively easy.
Scientists and assistants quadrat sampling along a transect line on the coast of Hokkaido, Japan. (Natural Geography in Shore Areas - NaGISA)
A picture of a quadrat full of organisms. (Natural Geography in Shore Areas - NaGISA)
The same quadrat after all the specimens have been thoroughly removed for later identification. (Natural Geography in Shore Areas - NaGISA)
Scientists sort specimens taken in quadrat sampling along the coast of Kodiak Island, Alaska. (Natural Geography in Shore Areas - NaGISA. Gayle Neufeld)