Teacher Logbook:
Saturday, July 8, 2000 1700 hrs.

Overcast skies. A thin sheath of clouds causes a dull, even-tempered quality to the lighting outside. No shadows, no bright harsh light. The key word here is light. We live in a world that ultimately depends on light for survival. Follow any terrestrial or marine food chain and you will ultimately come to the sun. Primary producers, the green plants, form the base of food chain. During the process of photosynthesis they convert water and carbon dioxide, in the presence of light energy, into oxygen and simple sugars. Consumers, including humans, depend on these sugars for food. It's simple. No sunlight, no life.

ROPOS is currently diving at a vent called Snail. At this diffuse vent there are millions of the tiny creatures it was named for. Our brief visit for sampling is the only opportunity they have to experience light, for their world is forever dark. How then does Snail support primary production? The answer is chemosynthesis. All vent community animals ultimately depend on chemical energy from vent fluids instead of light, as the building block for simple sugar production. Who do the snails have to thank for this? Bacteria and archaea. These prokaryotic organisms take advantage of chemical energy released from hydrogen sulfide in the vent fluids to synthesize oxygen and carbon dioxide into simple sugars. There is life without light.

Microbes flourish growing in thick off-white mats that cover all the surfaces around the vents. Sometimes these mats get broken up (termed floc) and float around on bottom currents giving the water a milky appearance. Whole communities develop as a result of microbial growth including worms, clams, snails, limpets, crabs, fish among others. The biodiversity and biomass surrounding hydrothermal vents is astounding. More than 370 new species have been discovered in vent regions and 90 percent of these creatures are found no where else. Population densities exceed those of sunny nutrient-rich coastal waters. This is a deep-sea paradise that owes its existence to chemosynthesis. Cindy Van Dover, a prominent vent biologist, stated that "one of the most significant events in the earth and life sciences in this century was the realization that hydrothermal activity can support life in the absence of sunlight."

Jeff

Jeff filing his daily reports from the scientist's office aboard the Brown.

Castle Vent, one of the only high-temperature vents so far discovered on the east side of the caldera (274degC). Pictured in background is an MTR, tubeworms in the middle and the anhydrite chimney if the foreground.