Rocky Shore Sampling Protocol

Sampling Design

The following is a summary of the Coastal Biodiversity Survey (CBS) sampling protocols. For the complete protocols and all other data sheets in PDF format please go to Protocols and Data Sheets.

Site Selection

Andrew Molera Typical site set up with one continuous survey section.

 The ideal location to conduct a Coastal Biodiversity Survey (CBS) is a rocky intertidal bench that is at least 30 meters wide (along the shore) and gently sloping from the high zone to low. It is important to select an area where the composition of the community is representative of the site. The site should be representative of the surrounding area. The survey site may also be split into two sections with sets of transects totaling 30 meters in different locations on the rocky bench.

Site Setup

Site setup at NW Talcott

To set up a survey area a 30 meter along shore baseline is established above the organisms in the high zone. Permanent bolts are installed at the 0m and 30m points along the baseline. Two transect lines are then laid out roughly perpendicular to the baseline in the cross-shore direction towards the ocean at 0m and 30m, and a second 30m baseline is stretched out between these lines in the mid zone, creating a parallelogram. (See diagram A below.)

Diagram A click for detail

This way both the 0m and 30m lines can shift as a unit. This enables us to adjust the grid to cover the most appropriate sampling area, avoiding any major pools or bench drop-offs. Bolts are then drilled the same distance down the 0m and 30m lines to secure the second baseline. Bolt to bolt measurements and photographs are taken to facilitate locating bolts and re-establishing the grid for future surveys.

Transect lines are then laid out in the cross-shore direction from the baseline to the ocean, parallel to the 0m and 30m transect lines, every three meters along the upper baseline resulting in 11 transect lines. The lower baseline is used to ensure a consistent 3 meter spacing and parallel orientation between transect lines. In general the transect lines are allowed to follow the contours of the bench.

Point Contact

Each of the eleven transect lines of the site grid is surveyed using the point intercept method. At least 100 uniformly spaced points per transect are sampled. At each point three organisms are identified (detailed below). This results in approximately 3300 data points per site. Sampling intervals along each transect are adjusted with respect to topographic features and size of the bench. For example, if a transect is 20m long the interval between points is 20cm.

 The organism that falls directly under each point is recorded first. Then the next two closest, but different organisms are recorded. If no second and/or third organisms are found, "none" is recorded. When an organism is located in a pool, on a cobble or boulder it is also recorded. Organisms living on another species are recorded as 'epibionts' and the organism they occur on is recorded as 'host.' Some examples of host organisms are mussels, coralline algae, barnacles, and colonial worms. The letters 'A', 'B', and 'C' are assigned to identify them as layers of organisms. A 'layer' is defined as a portion of an organism that is draped across another organism, and is not attached to the substrate directly below the point being sampled. For example, an algal frond draped across a barnacle would be recorded as "algae-A, barnacle-B." If an organism cannot be identified in the field, we assign it an "unknown" number and collect a sample to identify it in the lab. The spatial location of each organism relative to the alongshore transect position and cross-shore location along the transect is recorded, along with information on habitat and layering as described above.

Mobile Invertebrates



The point contact method is efficient for measuring the abundance of spatially common and sessile organisms, but it does not adequately represent rare or spatially uncommon organisms such as mobile invertebrates. The abundance of mobile invertebrates is measured using 50 x 50 cm quadrats. Each transect is divided into three regions, representing the high, mid and low zone biology. Ten quadrats are randomly placed within each of the three zones on each transect line resulting in 33 plots.  (See diagram B above).

All mobile invertebrates in the quadrat, such as snails, limpets and crabs, are identified, counted and recorded on a data sheet using non-destructive counting methods. Organisms living within the interstices (the spaces between the substrate and the sessile organisms such as mussels) are not recorded because in order to obtain an accurate count the organisms creating the interstices would have to be removed.


Pisaster - Seastar

The seastar, Pisaster ochraceus, is the target of our 'band transect' searches because it is an important predator in the intertidal, and typically occurs in cracks, crevices and in dense aggregations not well sampled by the methods described above. Other species of seastars and abalone are also recorded because they are underrepresented by our other sampling methods.

The distribution and abundance of these organisms are recorded from a two meter wide band centered over each transect line from high to low zone. This band is searched for all seastars and abalone. Their position (to the nearest half meter along the transect), number and species names are recorded on data sheets.


Topographic data Chilean Memorial

A topographic map of each survey grid is created using standard survey equipment (a rotating laser leveler). Elevations of fixed locations within the grid are measured relative to mean lower, low water (the US tidal datum reference standard) and elevation measurements are recorded throughout the grid along each transect line whenever there is a change in elevation. Topographic maps like the one below are generated using 3D computer software.

View topographic data sheet.

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