Project Day 4: 2 March 2011
Today was our first day without a planned coordinated dive between the Pisces V submersible. The purpose was to to investigate a site that had been seen by submersible science adviser Heather Spalding on Day 2, which had very rich growths of coral and many fish. Dave Pence and I both had a lot of work to do, and because we did not have any specific tasks to perform on today;s dive, we both decided to sit this one out. This was a decision we would both come to regret! Ken Longenecker and CJ Bradley headed out to the coordinates that Heather had reported. Ken's plan was to collect a few fish specimens for two different research activities that are part of our Deep-CRES project here in Hawaii. One is to examine ratios of stable nitrogen and carbon isotopes in the tissues of the same species of fishes from shallow reefs and from deep reefs, which is being carried out by CJ and her PhD Advisor, Brian Popp (who was the science observer on Day 1). Similar to the experiment with the Corals that look at isotope ratios, examining the ratio of these isotopes in fishes can reveal both the approximate position of the fish in the food chain (e.g., algae-eating herbivores, vs. plankton-eating planktivors, vs. fish-eating piscivores), as well as insights into where the energy source for the entire community is derrived from (e.g., photosynthesis from benthic algae, vs. phytoplankton, vs. zooxanthellae int he corals, etc.) Understanding these "trophic" patterns (i.e., food-web) and sources of energy provides important information on managing these mesophotic reef communities. The second reason for capturing fish specimens is to examine their DNA, and compare it to the same species from shallow water. CRES-project partner Brian Bowen of the Hawai'i Institute of Marine Biology (HIMB) is an expert in studying the population genetics of fishes, and his research can tell us whether the fishes on the deep reefs are from the same genetic stock as the same species on the shallow reefs. This is important to help us understand the genetic "connectivity" between the two populations. If the seep and shallow comminities are from the same genetic population, then it's possible that these deep reefs can serve as "refuigia" for certain species that may be over-fished or otherwise impacted on the shallow reefs. If the deep- and shallow-reef fish stocks show different genetic pattrns, then the connectivity may be low, and the deep-reef stocks may not be as effective for re-populating over-fished shallow stocks. Both of these research activities are key to undestanding the overal dynamics of these mesophotic communities.
The Pisces V submersible was operating in a different area, so the divers (Ken and CJ) were on their own. While Ken went after the fish specimens, CJ took my video camera to document the reef. If you look at the video highlights fromt he dive, you'll see that the reef was absolutely spectacular! Not only was there an incredible amount of coral cover (dominated by the plate coral, Leptoseris yabei), but there was also an incredible abundance of fish! As soon as Dave and I saw this video, we knew we had mage a big mistake in sitting this dive out! Ken and CJ report that both the reef and the huge populations of reef fishes went on as far as the eye could see. We defintiely plan to come back to this site again later in the trip, to run some more controlled surveys. No doubt it will be an exciting dive! Stay tuned....
Click this link for the day's Video Highlights. Video by C.J. Bradley.