Towed-Diver Observations in the Main Hawaiian Islands to Assess the Mass Coral Bleaching Event in November 2015

A team from the Pacific Islands Fisheries Science Center (PIFSC), Coral Reef Ecosystem Program (CREP) deployed on a two-week research cruise in November 2015 to evaluate the impacts of the 2015 mass coral bleaching event in the Main Hawaiian Islands via towed-diver surveys. Areas surveyed included south Oahu, west Maui, Lana’i, and west Hawaii island. Over the course of 10 survey days, the team surveyed approximately 90 km of 15-m wide transects at depths ranging from 2 to 10 m.

Data provided in this dataset include visual estimates recorded by towed divers of percentage of live coral that was pale and bleached, as well as presence/absence data of condition by generic composition. Analysis of observer data reveals estimates of live coral affected by the event (pale or bleached) show a regional mean of 38.8% (+/- 1.96% CI95), with large variation in impact apparent between transects on the same island separated by as little as 13 km.

Additionally, instruments mounted on the towboards collected other in-situ data that are documented separately. A downward-facing DSLR camera with strobes collected photographic quadrat data by capturing an image of the benthos at 15-second intervals during the surveys. Oceanographic data was collected continuously throughout each survey with a suite of mounted sensors recording conductivity, temperature, depth, flourometry (chlorophyll-a), turbidity and dissolved oxygen.

The towed-diver visual estimate data can be accessed online via the NOAA National Centers for Environmental Information (NCEI) Ocean Archive.

The 2014–2015 global coral bleaching event brought widespread and severe impacts to the entire Hawaiian archipelago. In 2015, the corals of the Main Hawaiian Islands were subjected to unprecedented levels of thermal stress that resulted in the most severe coral bleaching ever recorded in the islands. To report on the event, local researchers and reef managers conducted free-swimming diver surveys in areas generally accessible via same-day field excursions. In an effort to survey larger high coral cover areas that are difficult for local researchers and managers to access via day-long field trips, a team from CREP deployed on a two-week research cruise in November 2015 aboard the NOAA ship Hi‘ialaka‘i to evaluate the impacts of the 2015 coral bleaching event in the Main Hawaiian Islands via towed-diver surveys.

While every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages caused by errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.

Main Hawaiian Islands

Not applicable

Not applicable

NOAA Coral Reef Ecosystem Program (CREP) Data Sharing Recommendations, version 9.0 updated August 12, 2015:

CREP welcomes the opportunity to collaborate on research issues contributing to the scientific basis for better management of marine ecosystems. CREP has a very diverse set of field activities that generates large volumes of data using an array of data collection protocols.

The following recommendations are for your consideration as you use this data:

1) Data analyses should take all field exigencies into account. The most effective way to do this would be active collaboration with CREP principal investigators.

2) In all presentations, product releases, or publications using data generated by CREP, proper acknowledgement of both CREP and the individuals responsible for data collection is expected. Citing the DOI (if available) is preferred, a non-DOI example is listed below.

3) If you collect or generate data for the same study areas, CREP requests that you share relevant information on complimentary data collections.

4) Those receiving data are strongly urged to inform the CREP Data Management Team of any errors and discrepancies that are discovered during the course of using these data. They are further urged to bring to the attention of the Team all problems and difficulties encountered in using these data. This information is necessary in order to improve the collections and to facilitate more efficient and economical data processing and retrieval. The users are asked to supply copies of any missing data that may be located, and to provide information as to significant subsets and special aggregations of data that are developed in using the material provided.

Example citation:

"This publication makes use of data products provided by the Coral Reef Ecosystem Program (CREP), Pacific Islands Fisheries Science Center (PIFSC), National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), with funding support from the NOAA Coral Reef Conservation Program (CRCP). The analysis and interpretations presented here are solely that of the current authors.”

Data can be accessed online via the NOAA National Centers for Environmental Information (NCEI) Ocean Archive.

None

Please cite NOAA Coral Reef Ecosystem Program (CREP) when using the data.

Suggested citation:

Coral Reef Ecosystem Program; Pacific Islands Fisheries Science Center (2016). Towed-Diver Observations in the Main Hawaiian Islands to Assess the Mass Coral Bleaching Event in November 2015. NOAA National Centers for Environmental Information. https://www.fisheries.noaa.gov/inport/item/32588

None

None

PIFSC Oracle database view: VS_BENT_TDS_BLEACHING_OBS

The latitude and longitude coordinates of the survey track are recorded using a Global Positioning System (GPS) receiver on-board the tow boat. The survey track is georeferenced and a layback model is applied (python script in ESRI ArcGIS for Desktop) that more accurately maps the positions of the recorded observations.

This survey effort specifically targeted areas of known high coral coverage to evaluate bleaching impact. Although efforts are made to include broad spatial coverage of high coral cover areas at each island, poor weather and sea conditions prevented the team from surveying various reef areas.

Towed-diver visual observations were made by divers who have been trained in the identification of coral genera and the estimation of area of coverage. Prior to the research cruise, divers calibrated their estimates of area of coverage and judgement of paling or bleaching via free-swimming diver surveys of 10 m x 10 m transect boxes. The positions of observations are determined by (GPS) data collected on the small boat towing the divers that is adjusted with a layback script to account for the actual distance behind the boat the divers are being towed.

There are a few scenarios that will affect the completeness of the data:

-If the GPS points are not collected, associated diver's positions and survey tracks are not generated

-If the estimation of the divers' positions are erroneous and it is impossible to make corrections, the tow tracks/points are flagged and removed from further analyses

-If SEABIRD sensor (SB 39) is not operational during surveys, temperature and depth data are not available

Visual estimates of coral bleaching are useful as a broad indication of the bleaching impact on the scale of several kilometers. Towed-diver surveys require a trade-off in which the observation detail one might obtain in a free-swimming diver survey is traded for the ability to survey a 2 km x 15 m stretch of reef in about an hour.

Observations, including species identification and coverage area estimates were periodically checked during the expedition for consistency between divers. Data entry was usually conducted on the same day as the surveys using MS Access. Data was quality controlled by the divers using a two-person system. The data was then run through rigorous quality control checks by the data management team before the data was migrated to the Oracle database. Given the size of the data set, there remains some possibility of typographical or other errors.

NOAA IRC and NOAA Fisheries ITS resources and assets.