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Day 4, August 4, 2005 TER daily cruise report
Awoke to the sound of distant thunder and to find a line of towering thunder heads to our east back light by the rising sun. Seas were calm and the storms drifted away towards the mainland.
tanks on board ship
Today we are again scheduled to visit five of our permanent monitoring sites. These survey sites average over 80 feet in depth and require long surface interval between dives to allow nitrogen gas to diffuse from the diver's blood. This prevents formation of bubbles in the blood which can cause decompression sickness or the dreaded 'bends'. As a result, we are constrained in the number of dives we can complete in a day. To maximize the time we can spend at depth we have been using oxygen enriched gas in our SCUBA tanks (32% versus normal, atmospheric 21%). The higher concentration of oxygen in the gas (NITROX 32) that we breathe while diving acts to reduce nitrogen uptake into our bloodstream and tissues.
The afternoon is fair with a light breeze that makes the strong tropical sun bearable for short periods. Dives have gone well with all fish census divers reporting counts of mutton snapper, a variety of groupers, and some monster hogfish. Currently we are retrieving sonar receivers but have two more scuba surveys scheduled . I've got to gear up to visit the deep.
Night ops: Working in the North East quadrat of the reserve we completed video observations and beam trawl samples at four of our shelf monitoring stations. We are consistently finding higher densities of very large pink shrimp within the Reserve than outside it. Such large shrimp are in their second year of life and serve as brood stock for the next generation. We expect that providing these large pink shrimp a sanctuary from fishing mortality will insure the productivity of the shrimping grounds in the future.