MARINe/PISCO: Intertidal: MARINe Long-Term Monitoring Surveys: Photo Plots and Transects Summarized

Study Extent

Sampling

Method steps

1. Photo plots are scored in the field by using a 50 cm X 75 cm frame with a 10 X 10 grid of evenly-spaced string lines. A species, higher taxon, or substrate located below each of the 100 intersection points is identified and recorded. Layering is not generally scored separately, so the total cover is 100 percent. However, there is an optional method for sampling photo plots that includes layering and spatial position. With this optional method, the top and bottom layers are recorded for each location on the grid. This provides extra data that can be used to gather information on species associations and small scale spatial changes over time.
2. Photo plots are scored in the lab either from film or digital photographs. For film photographs, each slide is projected onto a white board that is marked with a grid of one hundred evenly-spaced points (10 x 10). A species, higher taxon, or substrate located below each of the 100 intersection points is identified and recorded. When scoring digital images, a grid of one hundred evenly-spaced points (10 x 10) is created on the computer monitor (using Adobe Photoshop), and placed on a separate layer. This allows the scorer to easily remove the dot to see what lies beneath. The image can then be saved with the grid layer, clearly documenting the exact points scored. With either film or digital image scoring, grid size is manipulated to provide complete coverage of the plot within the quadrapod frame. Layering is not scored separately, so the total cover is 100 percent.
3. Transect sampling is conducted by field-scoring what occurs under 100 points spaced at 10 cm intervals along a 10 meter tape stretched across permanent markers at each site. In general, 3 replicate transects are monitored per target species. Surfgrass, algae and invertebrate species are recorded. Any site specific exceptions to the length, number of points, and number of replicates can be found on the transect info table. Please note that these data do not reflect all species present in a given area. In addition, the information in this Data Set is limited by the methods described in our survey protocols. For more information, see pacificrockyintertidal.org
4. Each surfgrass transect is divided into ten 1 m long segments. If the entire segment is covered by surfgrass, surfgrass layer thickness is measured in the segment middle. If surfgrass covers only a portion of the segment, thickness is measured in the middle of the covered portion. To measure surfgrass thickness, the lowermost through uppermost layers are compressed together (not bunched), then measured with calipers to the nearest 0.5 millimeter.