Quadrat sampling is a classic tool for the study of ecology, especially biodiversity. In general, a series of squares (quadrats) of a set size are placed in a habitat of interest and the species within those quadrats are identified and recorded. Passive quadrat sampling (done without removing the organisms found within the quadrat) can be either done by hand, with researchers carefully sorting through each individual quadrat or, more efficiently, can be done by taking a photograph of the quadrat for future analysis. Abundances of organisms found at the study site can be calculated using the number found per quadrat and the size of the quadrat area. Quadrat methods  are time-tested sampling techniques that are best suited for coastal areas where access to a habitat is relatively easy. Quadrat sampling has been the main technique used by the Natural Geography in Shore Areas (NaGISA) project. It allows NaGISA scientists to collect standardized data at locations separated by vast distances, and then to compare the sites and determine, for example, whether the abundance or diversity of organisms varies at locations along a north-south gradient.
Research assistants record the organisms found in quadrats along a transect line in Kasitsna Bay, Alaska. (Natural Geography in Shore Areas - NaGISA . Katrin Iken)
A research scientist uses a quadrat to study the biodiversity in Prince William Sound, Alaska. (Natural Geography in Shore Areas - NaGISA. Brenda Konar)
A photograph of a quadrat sample that can be used to document the organisms present without having to remove them. (Natural Geography in Shore Areas - NaGISA)