Pacific Rocky Intertidal Monitoring: Trends and Synthesis

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Survey Methods

Click here (PDF link) for Long-Term Monitoring Survey protocol

Click here (PDF link) for Biodiversity Survey protocol

For a species lookup table (including general taxonomic group name and common name, if available) of ALL species observed during the Biodiversity Surveys, please click here (PDF link).

Long-Term Monitoring and Biodiversity Surveys are done by MARINe (Multi-Agency Rocky Intertidal Network). These intertidal monitoring surveys occur throughout the year at sites ranging from Southeast Alaska to Mexico.

Long-Term Monitoring

Long-Term Monitoring Surveys use fixed plots to document changes in percent cover, or abundance of targeted species or species assemblages. This fixed-plot approach allows the dynamics of rocky intertidal species to be monitored with reasonable sampling effort and provides sufficient statistical power to detect changes over space or time. The MARINe survey methods can be divided into two tiers: “core” procedures that are done by all groups at all sites, and “optional” procedures that are done by groups with funding & staffing to support additional work.

Core procedures include the following: 1) "Photoplots" used to monitor percent cover in assemblages such as barnacles, mussels, and rockweed. Percent cover of all species occurring within these assemblages is estimated by using a point contact grid, either in the field or from photos in the lab.  2) Line transects used to estimate cover of surfgrass, kelps and other algae not well-sampled by photoplots. 3) Irregular plots used for counts and sizes of large, mobile species such as seastars and limpets.

Optional procedures include the following: 1) Counts of mobile species within photoplots, 2) Estimates of barnacle recruitment from rock clearings and plates, 3) Estimates of Mytilus californianus (CA mussel) size structure, 4) Deployment of temperature loggers.

Long-Term Monitoring Surveys currently target 25 key species or species assemblages. Not all target species are sampled at each site. For more information regarding the sampling methods, please consult the Long-Term Monitoring Protocol (PDF link).

Photo Plots

PermanentPhoto plot methods photo photoplots are used to monitor percent cover of organisms within target species assemblages. Plots are established for a given species assemblage if overall cover at a site is sufficient for monitoring. In general, 5 replicate plots (50 x 75 cm) are placed in a stratified random manner throughout the target species' zone of maximum abundance.

Plots are photographed in the field, and are scored for percent cover using a grid of 100 points either in the field or in the lab from photos. A species, higher taxon, or substrate located below each of the 100 points is identified and recorded. Layering is not scored separately, so the total cover is 100 percent.

Transects

PermanentTransects method photo point-intercept transects are used to monitor percent cover of surfgrass, kelps, and other algae. In general, 3 replicate transects are established for each target species.

Transects are generally 10 m long and percent cover is estimated by recording the taxa or substrate occurring under each 10 cm interval (for a total of 100 points).

Species Counts and Sizes

SpeciesSpecies Counts method photo Count sampling is conducted by recording the number of a specific organism found in a permanent plot at a given site.

For some species, at certain sites, size and color are also recorded. The type of plot and number of replicates monitored is dependent on the target species.

Biodiversity Surveys

The Biodiversity Surveys provide detailed information about biodiversity and community structure. These surveys were designed to measure diversity and abundance of algae and invertebrates found within rocky intertidal communities on the western coast of temperate North America.

Biodiversity Surveys are comprised of four components, all sampled along the same transects: 1) point contact estimates of intertidal cover and substrate characteristics; 2) quadrat sampling to estimate the density of mobile invertebrates; 3) swath transects to estimate the density of seastars, abalone, and other large mobile invertebrates; and 4) topography (elevation relative to mean low low water (mllw). For more information regarding the sampling methods, please consult the Biodiversity Survey Protocol (PDF link). Additional information about Biodiversity Surveys can also be found by viewing the Biodiversity Website; please note that this page is no longer being updated.

For a species lookup table (including general taxonomic group name and common name, if available) of ALL species observed during the Biodiversity Surveys, please click here (PDF link).

Point Contact Surveys

Point Point Contact methods photoContact sampling consists of recording the diversity and abundance of invertebrates and algae, by recording what is found directly underneath or in the near vicinity of 100 points on each transect.

Algae and invertebrate species, hosts and epiphytes, layering, and substrate characteristics are all taken into account.

Quadrat Surveys

Quadrat Quadrat methods photosampling consists of recording the number of mobile invertebrate species within thirty-three 0.5m x 0.5m quadrats placed along each transect.

These quadrats are randomly placed within each of the three biological intertidal zones (high, mid, and low) along each transect.

Swath Surveys

Swath Swath methods photoswampling consists of recording the number of seastars in a two meter wide band centered over each transects.

The location (to the nearest half meter along the transect), number and species names are recorded.

Topography Surveys

TopographyTopography methods photo sampling consists of recording the elevation (relative to mean low low water) along each transect.

Heights are measured whenever there is a change in elevation.

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