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Rapid Ecological Assessment (REA)


Geography and history

In order to maximize the intercomparability and coverage of field in situ surveys, Rapid Ecological Assessment (REA) operations are organized into specialist teams which provide baseline data for improved decision making and planning for the ecological management of the Northwestern Hawaiian Islands (NWHI) coral reef ecosystem. REAs are like “snapshot “ assessments of the reef ecology. The teams are the (1) Towed Diver (Towboard) Team, (2) Fish Team, (3) Benthic Team, (4) Sediments Team, (5) Remote Sensing Team, and the (6) Land Team. The Teams take a global positioning position (GPS)) reading on each site so they can return in later years to determine the status and health of the reefs.

Towboard team

The Towboard team protocol used in the Northwestern Hawaiian Islands Coral Reef Assessment and Monitoring Program (NOWRAMP) involves two divers, each holding onto a separate towboard being towed behind the same small boat at a constant speed (1.5 knots). A towboard is a board with a bridle for attaching the towline and handles for the diver to hold on to. Each towboard has a temperature and depth sensor that records continuously during each towboard survey. Paired lasers project a scale onto the video. The towboard also has attachments for affixing watches and dive computers, and a signaling system to the boat operator.

Marine biologists conducting a survey of the benthic community
Marine biologists conducting a survey of the benthic community (Photo: Bishop Museum/NOWRAMP Expedition)

A global positioning system (GPS) on the boat records latitude and longitude. A digital video camcorder is mounted to each board, with one camcorder pointing down (900) and the other pointing at a forward angle (200) to capture a broader swath of habitat and ocean bottom information. The "forward-looking" board records information about habitat complexity and relative abundance of fish that are larger than 1.6 feet (50 cm) in length along a 33 feet (10 m) swath. The "downward-looking" board captures information about the composition of the substrate. The divers maintain the cameras one to two meters from the bottom. Tows are conducted in multiple habitats around the reef system. Most surveys focus on depths between 33 and 49 feet (10 and 15 m), except where the water is shallower.

Marine biologist recording data on a coral reef in the NWHI
Marine biologist recording data on a coral reef in the NWHI (Photo: Bishop Museum/NOWRAMP Expedition)

The divers also utilize charts on which they record visual observations. One diver records all species of fishes over 1.6 feet (50 cm). The other diver records types of benthic habitat every 5 minutes and identifies and counts large invertebrates, such as sea stars, lobsters, octopi, sea cucumbers, and bivalves, etc. These records are important because the cameras may not record fishes and invertebrates out of camera range.

Towed diver surveys provide an effective method for rapid broad overview monitoring of reef health.

Towboard Diver collecting data (QuickTime Movie, 1.5 mb) These videos were taken in the NWHI by researchers aboard the National Marine Fisheries Service Research Vessel, the Townsend Cromwell in 2001.

Fish team

The Fish team consists of three divers who are fish specialists. Two of the divers swim three 82 feet (25 m) transects per dive. During the "swim out" leg of the transect, both divers record size class-specific counts of all fishes greater than 20 cm in length, within two meters on each side of the transect line. Small and cryptic fishes are enumerated by size class during the "swim back" leg. The third diver of the fish team completes stationary point counts, each within a cylinder having a radius of 32.9 feet (10 m), to estimate the size and abundance of fishes larger than 9.8 inches (25 cm), and the more mobile fishes. This diver also uses a video camcorder to gather information on fish assemblages and size information using attached lasers. Upon completion of transect surveys, fish teams swim freely and randomly over the reef to record rare species.

Benthic team

Benthic teams survey Fish team transects for corals, algae, and other invertebrates. Initial NOWRAMP projects used two broad-scale approaches to study benthic organisms: towed divers who videotaped and estimated characteristics of long transects, and teams of taxonomic specialists who worked at the same finite sites to conduct extensive REAs. They focused on recording the presence, abundance, and population/community characteristics of all observable species in four main groups: corals, fishes, algae, and other invertebrates (Maragos et al, 2004).Some scientists employ a photoquadrat method during REAs to quantitatively survey benthic organisms. This technique utilizes a digital camera and computer software for photographic analysis.

Sediment team

The Sediment team focuses on the collection of sediments for later analysis of microorganisms and chemical contaminants, e.g. polychlorinated biphenyls (PCBs).

Scientists conducting
                          a photoquadrat survey of benthic organisms
Scientists conducting a photoquadrat survey of benthic organisms (Photo: James Watt)

Remote sensing team

The Remote sensing team collects data remotely sensed by instrumentation on satellites and aircraft. Aerial and satellite images of coral reefs can assist mapping and ecological characterization of coral reefs. Different components of a reef, such as carbonate, basalt, organisms, sand, and soft mud bottoms, reflect radiance differently. Specialized instrumentation captures these differences and groups them by type, from which a first estimation map can be derived. A critical step in this process is to capture in situ groundtruthing data in order to determine if the reflected radiance images accurately portrays the composition of the reef.

Land team

REA Land Team biologist conducting a survey for insects and other arthropods on Necker Island
REA Land Team biologist conducting a survey for insects and other arthropods on Necker Island (Photo: NOWRAMP)

The Land team lands on island surfaces while submerged REAs are conducted and makes surveys of algae, plants, insects, and other arthropods, such as spiders and mites, and birds, seals, and turtles.

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