Mission Journal 4 — Chris Martens: Mission Day 2: Tuesday, August 10th, 2004
Got up early after a good night’s sleep- we always sleep well after a diving day. Had my Kix w/milk then it was off to do our first full experiment with living sponges. We want to understand what the role of abundant sponge species is on the nitrogen cycle of Conch Reef. Sponges process small particles of organic matter just like humans consume food. Sponges host large numbers of bacteria and we think that these bacteria help convert nitrogen in the organic matter into forms of nitrogen that may both harm and help the reef. If the bacteria make ammonium and nitrate these forms of nitrogen are like fertilizer and can help undesirable organisms grow on the reef. However if they make nitrogen gas, the same as in the air we breath, then the nitrogen can escape back to the atmosphere thus helping to maintain the low nutrient environment necessary for natural coral-algal reefs to thrive. One of our faculty colleagues at UNC-Chapel Hill, John Bruno, and his team have shown that high nutrient concentrations enhance the susceptibility of corals to diseases now commonly found in the Caribbean.
The water is not too clear today but we don’t care because the work will be done out on the deck at 50 feet depth. As we get ready to suit up, I casually check my always faithful meter for measuring oxygen levels in the experimental bottles…..Surprise! The oxygen meter is dead, absolutely stone dead. Nothing turns on, not even low voltage parts. It’s a great instrument made in Denmark for underwater use, however, today something is wrong. After an hour’s work I still can’t find the problem but suspect it’s either a charging problem or a dead battery. We decide to send the meter ashore with the NURC operations support crew from the shore base. The Navy doctor is out to check on our health and this provides the opportunity I need to send it up to get fully checked out by Dominic, our computer pro.
Sometimes, actually often, things don’t go as expected and it’s good to have a back-up plan. Plan B is to conduct a survey of the amount of sponge biomass on the reef seafloor. This data will allow us to apply the bottle experiment results to calculate the overall role of the sponges in the reef nitrogen budget. After shipping the meter off for tests ashore, Meredith and I suit up for the survey work and head out. Before the day is done, we’ve conducted four sponge surveys near the NE Way Station. We head in at 7:30 PM so as to be in before 8:00 PM. We need 12 hours downtime in the Habitat before we’ll be allowed to have another full dive day.
On the way back and at the Habitat we have some extra time for a little fun in the darkening water column. I flash around our new halogen high intensity beam lights. The fish go bonkers….At the Habitat we peer under the main lock at beautiful, bright orange corals which have begun their nighttime feeding. Their tentacles flow with the water movement as water swirls past- a continuous dance that brings them into contact with tiny food particles that they capture with a graceful withdrawal of each tentacle. Night diving is wonderful and I’m already looking forward to those planned for later in the mission.
Time to go in and get a shower and some chow!