Last night the wind picked up. We’ve had gusty, sporadic wind before, but it always died down sometime during the night which left everyone not smart enough to bring a hammock very sweaty and sticky. But this wind has been consistently and strongly blowing for almost 24 hours now. We all appreciate the cooling effects of the breeze, but the increased wind has created a lot of high surf and waves outside the atoll. Since our island sits right on the edge, we can compare the calm, inner waters with the raging outer waters. And the captain and our various divemasters made the decision not to attempt our first dive outside the atoll. We went to a spot inside where there’s a steep drop off. However, unlike the walls we’ve dove on before, we could see the sandy bottom that was about 120 feet deep.
The time we have at 90 feet is only about 20 minutes – much too short to do some of the science surveys. Instead, I instructed the ‘nauts to observe the reef closely. When we got back to the lab, we discussed what differences they observed between deeper reefs and shallow reefs. They told me that there were fewer large fish at 90 feet, but if you looked up at the top of the wall, you could see large schools of fish. There were fewer corals total, but a lot more algae and sponges. The number of different types of species of coral was much lower, and the corals themselves were smaller and flatter. Coral depends on light, and at deeper depths, it tends to grow in a flattened, plate-like morphology to catch as much of light that penetrates to that depth as it can.
Before our second dive, a few of the ‘nauts and parents got the chance to visit a research site near the station. Several of the research scientists who are living at the station are studying sting rays.There is a small patch reef located near the dock that serves as a cleaning station for sting rays, and the researchers often snorkel out and observe the rays, counting, measuring, and identifying them. The rays swim onto the reef and arch their backs. This is a signal for the small fish that live there to swarm all over the ray, picking off dead skin and parasites. This is a mutually beneficial symbiosis – the rays get cleaned of potentially harmful parasites and the fishes get a good meal. Stations like this exist on coral reefs too. It’s not unusual to see large fish sitting perfectly still with their mouths open and fins splayed wide, with small fish pecking at their gills. The small fish have to trust that the big fish won’t eat them!
~Julie Galkiewicz, Education Officer, SNI Tarpon Springs Chapter