Seafloor Mapping Mission: Maui

By Kell Bliss

On 1 May 2015, four members of the EcoSpatial Information Team (ESI) in the Coral Reef Ecosystem Division, of NOAA’s Pacific Islands Fisheries Science Center, traveled to Maui to begin the first part of a two-part field mission. The mission involves mapping seafloor composition and coral cover, first on the west side of Maui between Ka‘anapali and Honolua Bay, and second, on the west side of Hawai‘i Island south of Kawaihae Harbor, depending on weather conditions. Both sites are priority areas designated by the State of Hawai‘i Division of Aquatic Resources and the NOAA Coral Reef Conservation Program and within the waters of the Hawaiian Islands Humpback Whale National Marine Sanctuary. The West Hawai‘i site is also a NOAA Habitat Blueprint focus area.

The Hawaiian Islands Humpback Whale National Marine Sanctuary’s M/V Koholā.

The Hawaiian Islands Humpback Whale National Marine Sanctuary’s M/V Koholā.

Dr. John Rooney, Rhonda Suka, and NOAA Corps LTJGs Kell Bliss and Kristin Golmon met up with ENS Carmen DeFazio to load gear onto the Hawaiian Islands Humpback Whale National Marine Sanctuary’s M/V Koholā. ENS DeFazio is the current operator in charge of the vessel for the Sanctuary and she familiarized the team with the vessel and in the first few days trained and qualified members of the ESI team to run the vessel.

The Koholā is an 11.6 meter AMBAR with twin 200 horsepower outboard engines capable of being operated from either the flying bridge or inside the sheltered cabin. A pot-hauler is attached to a davit to facilitate deploying the Towed Optical Assessment Device (“TOAD”) over the side.

Towed Optical Assessment Device (TOAD) sled and her cable. Photo credit: LTJG Golmon

Towed Optical Assessment Device (TOAD) sled and her cable. Photo credit: LTJG Golmon

The TOAD is an underwater camera sled designed to take photographs and video imagery of the seafloor. Ideally, the vessel drifts at a speed of about one knot to acquire high quality photos. The photos are used for mapping the distribution of key benthic organisms, such as hard corals, as well as providing ground-truthing data to integrate with acoustic multi-beam, bathymetric LiDAR (a remote sensing method), and other data for habitat mapping. Numerous partner agencies have provided additional ground-truthing data for this project, including the Division of Aquatic Resources, the U.S. Geological Survey, The Nature Conservancy, the U.S. Army Corps of Engineers, the Hawai‘i Institute for Marine Biology, the NOAA Biogeography Program, and other teams within the Coral Reef Ecosystem Division.

On arrival day, after offloading some gear from the boat, ENS DeFazio, Dr. Rooney, and LTJG Bliss moved the Koholā from her home port in Ma‘alaea to a pier in Lahaina for the duration of the first part of the mission. Lahaina Harbor is closest to the working grounds on the west side of the Maui. Day two was spent testing the TOAD, setting up the scientific gear, and conducting one tow survey.

LTJG Bliss and LTJG Golmon hand-hauling the TOAD and her cable back aboard when the pot hauler died. Photo credit: LTJG Golmon

LTJG Bliss and LTJG Golmon hand-hauling the TOAD and her cable back aboard when the pot hauler died. Photo credit: LTJG Golmon

The remainder of the Maui portion of the project involved selecting locations to launch the TOAD each day depending on water depth and weather conditions. As with any field project, there were numerous operational challenges to overcome. The team dealt with a pot-hauler that stopped working and had to pull the TOAD up by hand, not an easy task, but successfully retrieved the sled and then installed the spare pot-hauler for the next day’s surveys.

Can you spot the flying gurnard in this seafloor image taken by the TOAD?

Can you spot the flying gurnard in this seafloor image taken by the TOAD?

The data collected on the survey, as well as data previously collected by the ESI team and partners, will be used to create seafloor maps that will depict areas covered by sediment and rock as well as the major structural features such as pavement, aggregate reef, patch reef, and reef rubble. Major types of biological cover will be identified as well, such as coral, macroalgae, and coralline algae. The maps will be available online and will provide important information for watershed and marine resource managers to enable them to plan effective actions to improve the health and resilience of Maui’s coral reef ecosystems. Plans are being developed to improve the health of coral reef ecosystems off West Maui by reducing the flow of terrestrial sediments into the coastal ocean. Locating existing or potential coral reef areas will help managers plan effective mitigation efforts, or any other management activity that includes a spatial component, for example, delineating marine protected areas and anchorages.

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