Mission Journal 2 — Jeremy Weisz: Mission Day 1: Monday, August 9th, 2004
Mission: August, 2004 Saturation
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We entered the water this morning, leaving the bright sunshine for the murky ocean. The reef was beautiful, but the water was very cloudy today. It reminded us all of diving at home in North Carolina. Niels and I are measuring the rate at which water flows out of a sponge, also known as the excurrent velocity. We want to be able to make estimates of the flux of nutrients leaving the sponge, and also I want to look at differences between the sponges that have bacteria living inside versus those that don’t. One way in which we are doing this is with an Acoustic Doppler Velocimeter (ADV) which is an instrument that uses pulses of sound to measure the speed of particles in the water. However, because sponges are filter feeders, there are not enough particles in the excurrent water, so we have to add some particles to the flow. After much experimentation, we have settled on using a mixture of baker’s yeast in seawater.
Unfortunately, we discovered this afternoon that this in also an appetizing treat for fish. We discovered an inquisitive grunt happily feeding away on the slow stream of yeast flowing out of our delivery device. He soon left, though, leaving only a small blip in our dataset for the day.
Our afternoon excursion ended with me interrupting some jacks roaming the reef. We have now finished our dinner, and will soon gather at the galley window to watch fish feed.