April 19, 2006

Sea of Lights

It has been said that the earth was given to man. With most of the earth covered in water it is a shame that we were not given gills as well. Our perspective on our planet is very terrestrial in nature. Take for example our knowledge of bioluminescence. Aside from the parade of glow sticks on the night of Halloween, we general view this form of light as a rarity. I can remember warm summer nights around the 4th of July chasing fireflies with my cousins and putting them in jars. They proved as entertaining as the fireworks. Even the adults in our family gathered round to be amazed at how an animal could generate light as it flickered on and off. Each firefly species has its own mating signal. For some it is three long flashes, and for others five short bursts. We were in awe of the greenish glow. How na•ve we really were. The oceans are teaming with bioluminescent organisms, from fish to dinoflagellates. The oceans' zooplankton are communities with their own Las Vegas light shows. They emit a menagerie of colors and patterns. Many of the messages being signaled are still left to be discovered. Much of the diversity on the planet resides in the ancient seas, and the norm out here is bioluminescence. Most organisms in the oceans can generate their own light, therefore biological light production is a common feature of life forms, not a rarity. As land-bound humans we do not get to see the underwater fireworks show very often. You may be wondering why ocean animals use bioluminescence so commonly. The better question I think is, why did the land dwellers give it up when we left the ancestral seas.

In our attempts to better understand these creatures we are collecting samples from the depths the Atlantic. One of the novel aspects of the CMarZ mission is the deep-water plankton tows. The nets are being lowered to 5000m. At this depth underwater hazards are a concern. Currently sonar is being used to get a high-resolution image of the seafloor. This sonar turns out to be the source of the repetitive chirp that I cannot seem to ignore. The region of the ocean we are sampling was partly chosen for its homogenous topography. The water depth has been varying from 5000 to 5700 meters and it is very flat. This is ideal because you would not want to fly the plankton net into a hydrothermal vent or a seamount. That would be equivalent to crashing a plane into a cirque cliff.

With mild winds and featureless bottom we are about to lower the MOC 10 into the water. Eight hours later we will pull it from the depths. Many of the experts are excited to compare these waters to our last station. The waters have calmed and the ship is barely moving now that we are at station 3. The divers are currently returning from their blue water night dive. Earlier we collected MOC 1 samples from 4000 meters, but the group was disappointed to find that the nets did not open properly. The wires on the release mechanism had been set wrong and the nets were unable to open properly. We did manage to collect some plankton and a whale fish, which excited our resident ichthyologist. I will help launch the large net tonight, and then it's off to the land of dreams. The rocking motion of the ship has created some vivid and imaginative ones. I think they are caused by partially waking up when your body is rocked against the wall of the ship. I look forward to the upcoming illusions my mind will create tonight.

Daily question: How is biological light created? What other land animals besides fireflies use bioluminescence?


Picture 1: Blue water diving for surface zooplankton.

Picture 2: Getting MOC 10 ready to dive.

Picture 3: Russ Hopcroft and Dhugal Lindsay discussing sample collecting.

Picture 4: Cumulus clouds on the horizon.

Picture 5: Joe Catron, ARMADA Teacher at Sea.

Picture 6: Barbara Costas sending messenger to trip Niskin bottle.

Picture 7: Sunset April 19, 2006, on the Ron H. Brown.