Mission Journal 9 — Greg Shellenbarger: Mission Day 6: Monday, July 18th, 2005
A peek out the port this morning revealed the best visibility in the water that we have had so far during the mission – over 50’! It is wonderful to see that far – the reef jumps out though the habitat ports, and from the water, the habitat can be seen in its entirety. The watery blue is so rich and complete – what an amazing sight. Aquarius was made for mornings like this!
We had an incredibly productive science day today. Jim and I repositioned some of the flow probes over different barrel sponges to measure the rate that they can pump water. Tomorrow, Jim will collect water samples from the same sponges to be analyzed for different components to see how much material they are removing from the water with their efficient filtering mechanisms and how much they are releasing in terms of certain nutrients.
n addition, the four of us spent most of today working on our control volume sampling apparatus. We successfully collected six sets of samples – totaling about 60 samples in all – to be analyzed for chlorophyll and nutrient concentrations. As mentioned earlier, this will allow us to see how much ‘stuff’ the reef is removing from the water column. This is a relatively labor intensive process and requires significant help from and coordination with our amazing surface support team (without whom, this project would be impossible!). Our two aquanaut dive teams spent over well over twelve hours total in the water today – mostly around 70’ deep. This would be impossible to do if diving from the surface (without significant decompression each day). Everyday, we realize more and more how valuable the Aquarius platform is for accomplishing science out on the reef. Studies like ours simply could not be done here otherwise.
Long amounts of time out in the water give us the chance to observe and reflect on phenomena around us. One observation that we have all made is the amount of scour and sediment movement that occurred from the waves generated about a week ago by hurricane Dennis. In the shallow waters (around 50’ deep), most of the former sand patches have been eroded to a hard, old coral reef pavement. Some of this pavement probably has not been exposed in many years. As you get deeper in amongst the spur and groove of the lower reef, we still see significant scour (at around 65’) in the deeper sand channels. However, starting around 70’ deep, sand waves appear in the sand channels that, though relatively small, are still about 10-15 cm high. In these areas, there are alternating bands of exposed old reef and buried new reef. Some corals and soft corals that were healthy only a week ago are now buried under the sand, and new, barren substrate is exposed opening space for the colonization of other organisms. This is a very natural process that transports sediment from the shallow to the deep reef, but large storms tend to accelerate what is generally observed to be a reasonably slow process. It is fascinating to observe these dramatic effects, and our curious minds have already been mulling potential projects to explore the details of such events.
At the end of the day, we are exhausted, yet happy knowing that we accomplished so much. We are beginning to realize that our time under the sea is drawing to a close (only one full working day left!!!), but, for now, we must focus on the science that we need to accomplish and enjoying the watery world around us.