Myrichthys magnificus, the Magnificent Snake Eel (Photo: Steve Smith)
Lisianski Island, September 28, 2008 - The day began with a bang. Our team of scuba divers surveying reef fishes was chased off the water by loud crashes of thunder and flashes of lightning all around us. By midday, however, the weather cleared and we were able to get back under the water and complete our surveys as planned.
We are 12 days into the expedition, my first to the Papahanaumokuakea Monument, and I have seen some spectacular sights underwater valleys and pinnacles covered with beautiful corals of all shapes and sizes, colorful reef fishes, schools of ulua (jacks) and sharks, a snake eel that would rival any of the top scuba diving locations around the globe. These types of spots attract underwater photographers and coral reef scientists alike. Photographers like these sites because they can take pretty pictures of reef flora and fauna that will eventually grace the pages of nature magazines and environmental websites. Scientists are attracted to these areas because they typically harbor a wide variety of coral and fish species.
Deep habitat (95 feet) at Maro Reef (Photo: Steve Smith)
The focus of this expedition to the Monument is a bit different in one key respect: we are charged with surveying corals, algae, and fishes over the complete range of reef habitats shallower than 100 feet, the normal depth range for scuba diving. To do this, maps of the seafloor are classified by reef zone (fringing reefs, lagoons, etc.) and depth. Specific dive sites within each reef zone-depth combination are then chosen at random. Many of the random sites end up being beautiful, photogenic reefs full of all sorts of corals and fishes. At times, however, the reef habitat may be something altogether different. Such was the case several days ago at Maro Reef. Our first two dives were at sites between 95 and 100 feet deep, right at the edge of our depth limit. The 'reef' consisted of a very flat, sandy bottom strewn with small rocks covered with algae and on occasion a small coral only a few inches in diameter. At first glance, there appeared to be no fish. After we started surveying, however, we saw all sorts of reef fishes, parrotfishes, goatfishes, emperors, surgeonfishes but they were all tiny, only about 1-2 inches in length. It turns out they were early stage juveniles, only a few months old, of the same species we'd been seeing at the "glamorous' sites. Yet, we rarely observe these early life stages in the same habitats where the larger, older fishes live. Our next two dives were at the other extreme of depth, in water only 3 feet deep. We left the scuba tanks on the boat and just donned mask, fins, and snorkel to do our surveys. While not as barren-looking as the deep sites, these shallow habitats were comprised of mostly small corals and algae-covered rocks. Again, many of the fishes were small juveniles of the common reef species.
Juvenile fishes at 95 feet (Photo: Steve Smith)
As coral reef scientists begin to take a more holistic view of coral reef ecosystems, they are discovering that one species of fish may switch between a variety of different habitats throughout its lifetime. Some habitats, like the ones we happened upon, provide food and shelter for animals during their first few months of life, while others serve as spawning grounds for the adults, and there may be even more types of reef habitats that are most suitable during the intervening years between infancy and adulthood. Aesthetically-pleasing reefs may be the most conspicuous component of a coral reef ecosystem, but many of the heretofore overlooked, mundane reef habitats also play vital roles in the healthy functioning of the whole system. The information we are gathering on this expedition will help us put together a more complete picture of the different habitats comprising the coral reef ecosystem of the Monument, and how species of fishes utilize this mix of habitats at different phases of their life. It is indeed a new era of coral reef science, and an exciting time to be a scientist working in this field.