BLAGRRA Line Transects For rapidly assessing ecosystem-level changes in total live coral cover during, and following, mass bleaching events, outbreaks of disease, or other acute ecological perturbations. Permission is granted to use the photographs in this presentation with the BLAGRRA Program and, with attribution, for other valid educational projects. All other uses are strictly prohibited.
Relevance to Managers Sites can be rapidly and repeatedly surveyed over a large spatial scale by easily trained volunteers or staff to capture the immediate + any delayed effects of a given mortality event. Results can be compared to mortality levels occurring during “routine” environmental conditions. For example: during a severe bleaching event, mortality from bleaching is scored as new mortality. Several months later, when this initial mortality has shifted into the transitional mortality category, any ongoing, post-bleaching mortality is scored as new mortality.
Personnel 1-2 experienced divers (can be volunteers). Field Equipment Clipboard or slate with BLAGRRA Line UW-V2.0 datasheet printed on UW paper & pencils. 10-m long, lead-core rope, with marks at 0-m and at 10-m, and tie-off loops at each end. 50-cm PVC measuring pole marked in 10-cm increments + a 15-cm or 30-cm metric ruler. 25 cm x 25 cm PVC quadrat around which to wrap the line. Dive thermometer or other temperature recording device. \ See BLAGRRA Surveys & Gear-V2.0.pdf for Equipment details at:
Surveys Stratify reefs by zone and habitat. Randomly sample sites (at least 5/habitat, total number to vary with spatial extent of the habitat) for a representative assessment of reef condition in the area affected by the perturbation, and/or Strategically choose any sites of special interest for survey (e.g., within and outside an MPA). Survey before (if possible), during, and at intervals after, the mortality event until conditions return to “normal.” See BLAGRRA Surveys & Gear-V2.0.pdf for Survey details at:
Method Try to record bottom temperature at site. Haphazardly set line; note start and end depths. Swim line; measure intercept lengths of all live coral tissues as normal, pale, or bleached between the 0-m and 10-m marks. (Sum = live coral cover.) Re-swim line and measure intercept lengths for any new mortality and any trans (= transitional) mortality. (Sum = effects of “recent” perturbations.) Record any interesting observations in Comments. Repeat for a total of 10 transects/site. See BLAGRRA Line UW Datasheet-V2.0 for UW Datasheet & Method details at:
Note: individual corals are not noted nor identified to species. Part of a BLAGRRA Line UW-V2.0 Datasheet
Sum all cover category numbers for each transect. Every day, enter all data for each dive in a separate copy of the BLAGRRA Lines Data Entry-V2.0 spreadsheet. Check for accuracy. Store UW datasheets and data entry files in secure locations. Send data entry files to for processing, archiving, and possible posting online at Part of a BLAGRRA Line Data Entry-V2.0 Spreadsheet
BLAGRRA Line Transects During an ecological emergency, go directly to: Optional: to rapidly assess stony coral mortality at the population-level during ecological emergencies, see BLAGRRA Belt Transects at: For more about the AGRRA Project, see: Prepared for the AGRRA Project by: Judith C. Lang, September 2010