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Rapid Ecological Assessment
Posted by Mark Heckman, Educator, Waikiki Aquarium/ University of Hawai’i – Manoa

Rapid Ecological Assessments are "snapshots" of the state of the reef. At each stop in the Northwestern Hawaiian Islands, "REA" teams continue the work of finding new sites and documenting the fish, algae, invertebrates and corals at that site. Teams take a GPS (global positioning satellite) reading in decimal degrees on each site so they can return in later years. Here is how it works.

REA diver.Fish Teams
Have you ever tried to count, identify and size every fish at your favorite snorkel site? It is not easy - fish move. Try the method outlined below and see if it works for you. It sounds easier than it is. Fish counters need to be fast, accurate and not count the same fish twice.

Like all members of the REA teams, the members of the fish teams have trained for years to do these counts. They study the fish id's, confer with each other when they are in doubt, check their size estimates against reality, and have all had extensive experience before starting on this cruise.

Into the water first, the fish team lay three 25 meter transect lines on the bottom. As they set the line they count all fish greater than or equal to 20 centimeters (~ 8 inches) within 2 meters on each side of the line. This first count includes the larger mobile fish that may swim off as divers approach. This can include the 60 - 100 pound jacks and the 4 - 8 foot sharks. On the return, the crew does a detailed count and size estimation of the smaller fish (less than 20 centimeters). They record their data on special underwater slates.

A third diver does not swim (which causes some disturbance) but does four stationary point counts of a imaginary cylinder 10 meters in radius for five minutes. This count includes larger more mobile fish (> or = to 25 centimeters, or ~ 10 inches). After each transect (three per site, three dives a day), the fish team does a search of the nearby reef for any rare or unusual species not observed on transects or stationary point counts.

Photo quad.  Photo by Jim Watt.Team Algae
It sounds easy; after all, algae do not swim off while being counted. However, one characteristic of tropical reefs is that there are many grazers (herbivores) eating the seaweeds (or "limu" in Hawaiian) year round. Many tropical algal species are small, hidden, and hard to identify.

The algae team works its way along the transect line with a special camera, taking 6 photos along each of the 25 meter lines for later characterization of the reef. One of the divers records what is being photographed by writing the names and abundance of the species on a slate. In high surge conditions, both divers are needed to steady the camera.

At each stop, they pick reference samples of the seaweed to identify. Many of these identifications will require looking at microscopic features, and talking to other experts. There are over 400 species of algae in Hawai'i; most no bigger than the length of your hand, some thin as bits of hair or as small as a tiny scrap of paper.

The Invertebrate Team
This team seems to be up the latest each night, often still working at midnight or beyond, while the other teams are finally shutting down before the dives the next day. Our dive safety officer has to keep a close eye on everyone's schedule to keep them rested enough to be safe.

Mystery Nudibranch.The "invertebrates" actually include most of the animal life on earth. The vertebrates (fish, seals, turtles, birds, us) capture our eye and are really rather easy to identify in comparison. Marine invertebrates include the sponges (Porifera), corals, sea anemones, jellies, hydroids, siphoniphores, etc. (Cnidaria), worms and worm-like animals (Annelida, Platyhelminthes, Nemertea, Echiurida, Sipuncula, Hemichordata), the chitons, snails, sea slugs, clams, octopus, squid, etc. (Molluscs), the barnacles, shrimps, crabs, lobsters, insects, etc. (Arthropoda), the brittlestars, seastars, sea urchins, sea cucumbers, etc. (Echinodermata), and more. A scientist may spend an entire lifetime studying just one part of one of these groups.

Once in the water, one of the "Invert" team starts down the transect line with a video camera. This will give a general record of non- or slow-moving surface invertebrates like the corals and urchins. Next the team physically counts all of the macro invertebrates one meter to each side of the transect. A video camera is still no match for an actual diver.

Following the invertebrate diver is a coral specialist. This person will record types and numbers of coral colonies (again, not easy in the field), and will note any health issues, such as coral bleaching (a sign of stress), or coral diseases (still poorly documented and studied). After examining at least two transects, the invert team will spend additional time surveying the area for unique or unusual species. They will also collect some rubble to break apart for hidden animals.

Things to try:

Try a simple REA of an area near your house or school, perhaps your own lawn. Pick an "easy" site and a difficult site. There are several ways to do this. We suggest putting your quadrats on a transect line. Remember to have someone count the birds above early on (most similar to the fish counts of the REAs).

On land, you may need to extend your range somewhat (no fish, so try and find an area with a lot of birds). You may need to turn over rocks and stumps to find your invertebrates as well as sweeping the bushes with insect nets. You may want to identify plants to species. For instance, what type of grass do you have? A sample of your grass can be taken to a local nursery for identification. List and count everything - numbers and sizes are needed if you are going to compare the sites. You can make a transect line and survey everything to several meters to each side, or do smaller samples and extrapolate.

If you can identify the animal in the field without capturing it, that is much preferred. If it is windy or rainy, no problem (recommended for older students only) - science divers work in strong waves, murky and shark filled waters, cold or warm - welcome to the world of field science. Discuss working in "poor" conditions versus "good" conditions. Some habitats may be windy or rainy by nature - it is part of what they are.

Try an REA of your or your student's desks. Limit the time available for this (just as our divers are limited in the amount of bottom time and air that they have). How many keys and of what type are on your keyboard? Inventory every book, pencil (to kind and size). This can be very tedious for those of us that are organizationally challenged. Now consider that nature is even more complex. Discuss why it is important for REA teams to practice before going into the field.

References: Expedition scientists Dr. Alan Friedlander, Dr. Karla McDermid, Dr. Duane Minton, Anuschka Faucci, Kanekoa Shultz, Kimberly Peyton, and Brooke Stuercke.


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