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9/21/05 - Mapping
by David Nichols, State of Hawaii, DLNR, HIHWNMS

Graphical representation of a multi-beam system at work mapping the ocean floor.

There was a full day of activity at Maro Reef today. The Rapid Ecological Assessment (REA) teams continued their monitoring of the species composition, abundance, percent cover, size distribution, and general health of the fish, corals, other invertebrates, and algae of the coral reef. The collection teams continued to collect specimens of reef fishes and invertebrates for characterization of genetic diversity and connectivity to better understand biological linkages supporting and maintaining these island/atoll ecosystems. The apex predator team recovered, downloaded, and redeployed receivers set in May-June 2005 to recover data on detections of fishes tagged with transmitters.

In addition to assessment and monitoring of the biological component of the coral reef ecosystem, the NOAA Ship Hi`ialakai is also equipped to perform multibeam mapping. While the research scientists are busy analyzing the data and sorting specimens following their day in the water, the survey technician is just starting his day. HI’IALAKAI Crewmember Jeremy Taylor is currently responsible for making sure the insanely complicated multibeam mapping system onboard does its thing - map the ocean floor.

First it is necessary to launch a CTD instrument into the water that will continuously provide information on the conductivity (salinity) and temperature at various depths. This is necessary in order for the sonar mapping system to calibrate correctly. Sound travels differently at differing salinities, temperatures, and densities. All this information gets computed as the ship’s sonar passes over the sea floor. The result is a very picturesque three-dimensional output of the ocean bottom illustrating features such as canyons and pinnacles.

At any given moment there is much activity aboard the ship. Activity focused at maximizing the scientific information gathered from this spectacular underwater landscape.

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