Biodiversity Methods | MARINe

Last updated Sept 19, 2023

Saunders Reef Biodiversity site


Biodiversity Surveys were established in 2001 to complement our ongoing Long-Term Monitoring program (established in the early 1990's) that looks at patterns of intertidal species' abundance and distribution over a large geographical and temporal scale. Dramatic community structure changes have occured at Long-Term Monitoring sites. For example, many plots established to monitor barnacle communities have become overgrown by turf algae which usually live below barnacles along the shore. This shift changed the overall community of those plots and sites in general. Many other species have also shown distributional shifts. These dramatic changes, coupled with an enhanced appreciation of the need to make detailed evaluations of patterns of species composition, led us to design the Biodiversity Surveys. These surveys have unofficially been called the 'SWAT' surveys, a nickname that came along with the idea that a group of researchers was needed to travel along the coast quickly, surveying as many sites within a minus tide series as possible. Some have postulated that 'SWAT' stands for Stinking, Wet, And Tired or SeaWeed Action Team...(Old SWAT website). Information gathered by these surveys is unprecedented in scale and depth. It sets a baseline of knowledge about what is living on our fragile coast. From this we can better understand changes in our environment and the ways in which we can aggravate or alleviate these changes.

Biodiversity Surveys are comprised of four components, all sampled along the same transects:

  1. Point contact estimates of intertidal species cover and substrate characteristics.
  2. Quadrat sampling to estimate the density of small mobile invertebrates.
  3. Swath transects to estimate the density of seastars and other large mobile invertebrates.
  4. Topography (elevation relative to mean low low water (mllw)).

Modified protocols are occasionally used for specific studies, such as assessing Areas of Special Biological Significance where mussels are of particular interest. For more information regarding the sampling methods, please consult the Biodiversity Survey Protocol (PDF link). A list of ALL species observed during the Biodiversity Surveys is available in our species lookup table (PDF link including general taxonomic group name and common name, if available).

To quantify species' distribution and abundance, topographical and species data are recorded across an entire rocky bench. This enables us to create a three-dimensional fine-scale map of the intertidal bench. Each species can then be mapped over the topography, yielding a layered Geographical Information System (GIS) rendition of the species' distribution.

Past efforts directed at sampling biodiversity patterns have been compromised because of variation in sampling design, sampling effort, and sampler expertise. Hence, we have used identical sampling in terms of design, effort, and expertise at all of our sites. Through this consistency, we are able to track changes at an ecosystem level. In particular, we are able to address fundamental questions related to biogeography, effects of human use, management of coastal resources, and conservation at a relevant spatial scale (the temperate West Coast of North America).

Site Selection

Site location is selected based on many factors. Initially, the surveys were conducted on rocky intertidal reefs where Long-Term Monitoring intertidal studies were already taking place. Additional sites were selected for their proximity to known regional biological boundaries caused by geo-oceanographic features. Sites have since been added to fill in gaps and create a more even spacing along the coast. Some long stretches of beach, mud flat, cobbles/boulders, and/or sheer cliff have left natural gaps between sites, most noticeably in the northern regions.

The ideal location to conduct a Biodiversity Survey is:

  • A rocky intertidal bench that is at least 20 to 30 meters wide (along the shore) and sloping from the high to low zone (major pools and bench drop-offs are avoided).
  • An area where the composition of the community is representative of the site and the site is representative of the surrounding area (the photo below is a typical site set up with one continuous baseline or survey section).
  • The survey site may also be split into two sections with sets of transects totaling 20 to 30 meters in different locations on the rocky bench.

Biodiversity Survey set up at Kibesillah Hill, CA

To set up a survey area:

  • A 30 (or 20) meter baseline parallel to the ocean is established above the organisms in the high zone.
  • Permanent bolts are installed at the 0m and 30m (or 20m) locations along the baseline.
  • Two transect lines are then laid out from the baseline towards the ocean at 0m and 30m (or 20m), and a second 30m (or 20m) baseline is stretched out between these lines in the mid zone, creating a parallelogram (see diagram below).
  • Bolts are then drilled the same distance down the 0m and 30m (or 20m) lines to secure the second baseline.
  • Bolt to bolt measurements and photographs are taken to facilitate finding bolts in the future.
  • Transect lines are then laid out from the baseline to the ocean every three meters (or 2 meters if the baseline is 20m long) along the upper baseline resulting in 11 transect lines (the lower baseline is used to insure a parallel orientation between transect lines).
  • In general, the transect lines are allowed to follow the contours of the bench.

Simplified cartoon depiction of biodiversity survey site setup/gridchimneyrock01crop.jpg

Point Contact Surveys

Point Point Contact methods photoContact sampling consists of noting 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.

Each transect is surveyed using the point intercept method. Ideally, 100 points per transect are sampled. At each point three organisms are identified. This results in approximately 3,300 data points per site. Sampling intervals are determined based on the length of the bench.

  • The organism that falls directly under each point is recorded first.
  • Then the next two closest, but always different, organisms are 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.
  • If an organism under a point cannot be identified in the field, we assign it an "unknown" number and collect a sample to identify later in the lab.

In 2017, we upgraded from using Palm Pilots to iPad mini's in order to expedite data recording and entry. MARINe contracted DiveNav to create an app specifically designed for the biodiversity protocol which includes regional species templates and error-checking features. Waterproof cases allow the iPads to function safely in the intertidal zone and in any type of weather. Data collected in the field are stored as CSV files and uploaded to the Coastal Biodiversity Surveys database.

Biodiversity appiPads in field

Quadrat Surveys

The point contact method is efficient for measuring the abundance of spatially common organisms, but it does not adequately represent rare or spatially uncommon organisms such as mobile invertebrates. Quadrat Quadrat methods photosampling consists of recording the number of mobile invertebrate species within thirty-three 0.5m x 0.5m quadrats, three placed along each of the eleven transects. These quadrats are randomly placed within each of the three biological intertidal zones (high, mid, and low zones, as show in the diagram below).

Simplified cartoon depiction of biodiversity survey grid with mobile quadratsQuadrat sampling

Mobile invertebrates in the quadrat, such as snails, limpets, and crabs are identified, counted, and recorded on a data sheet. Organisms living within the interstices (the spaces between the substrate and the sessile organisms such as mussels) may be underrepresented because in order to obtain an accurate count, the organisms creating the interstices would have to be removed, and we avoid destructive sampling.

Swath Surveys

Swath Swath methods photoswampling consists of recording the number of sea stars and other large invertebrates in a two meter wide band centered over each transect. The location (to the nearest half meter along the transect), number, health, and species names are recorded. Size is also recorded for some species, such as abalone and ochre stars.

Topography Surveys

TopographyTopography methods photo sampling consists of recording the elevation (relative to mean low low water) along each transect using a rotating laser leveller. Heights are measured whenever there is a significant change in elevation.

Topographic maps like the one below are then generated using 3D computer software.

Topography map of Kayak Island

Biodiversity Linked Vertical Photoplots (BLVP)

Biodiversity BLVP methods photo Linked Vertical Photoplots are sampled along the same transects used for Biodiversity Surveys. There are ten 50 x 75 cm photoplots per transect, spaced equidistant with the interval based on the length of the transect. The photos are then scored for percent cover using a grid of 100 points in the lab. 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. BLVP have been used primarily as part of Natural Resource Damage Assessment.