The Microbes in the Field: Halloween

by Forest Rohwer, head researcher on the Microbe Team

The Microbes, The Benthics, and The Fish. Source.*

Pre-coffee and half-asleep this morning, I opened my cabin door and was assaulted by a giant (3 ft) black spider. Apparently The Fish didn’t have enough to do last night so they decided to try to kill off Alan or I with an early morning heart attack. The ship is now decorated with a Jack-O-Lantern, a sparkling pink skeleton (picked out before departure by my 5 year-old daughter Willow), and the spider.

Up to this point in the cruise, The Microbes (Katie Barott, Tracy McDole, Mark Vermeij, and I) have been supporting deployment of the CBAT tents. This included their initial set-up, as well as putting in the plumbing to gather water samples. These waters samples are taken back to the ship and processed so that we will know the concentration of dissolved organic carbon (DOC) and nutrients in the tents, and can correlate this with other measurements such as algal growth rates. In theory, the DOC levels should go up during the day when photosynthesis is happening and DOC is released into the water, and then should drop back down at night as the microbes eat the DOC. We aren’t actually taking dark samples on Kingman because of the distinct possibility of getting eaten by the abundant sharks that swarm in the evening. We did try to get one of The Fish to go retrieve some samples during the hours of darkness, but they were strangely circumspect in this regard. We’ll get night samples at one of the less pristine reefs.

Now that the tents are up and running, the Microbes are concentrating instead on gathering their own data. For Tracey and Mark, this means collecting and filtering lots of water. For each of his samples, Mark collects the microbes from 80 liters of seawater. When we get home, DNA will be extracted from those microbial samples and sequenced (i.e., giving us microbial metagenomes). Tracey is setting up more growth rate experiments from different sites around the reef.

Katie and I are investigating what is going on at the coral-algal interfaces on the reef. Since grazing of the algae by fish and invertebrates (sea urchins, for example) plays an important role in limiting algal growth on the reef and possibly promoting coral success, we’ve strategically scattered underwater cameras all over the reef to monitor grazing levels. We are particularly interested in monitoring how fish, sea urchins, and any other herbivores are eating algae along the borders where corals and algae meet. We’ve also taken over much of the ship with our microscopes. If you look close at those interfaces, you can see the effects of the battles raging between the corals and the algae as they fight for space on the bottom. Sometimes the algae are overgrowing the coral tissue, which shows signs of stress (bleaching, discoloration, etc.). In other cases the coral is attacking the algae causing similar signs of bleaching in the algae, or directly growing over it.

Now its time to go plot the demise of the Fish this Hallows’ Eve…

*Image source.