We Blogged It!
Lat/Long: 06.54N 047.32W
Air Temp: 27.5C 81.5F
Surface Temp: 28.96C 84F
Beginning Week Two!
We’re farther out at sea and out of the plume for now. It’s a balmy and slightly overcast. The ocean still looks very blue, with very calm seas. And work continues!
Last night the plankton net brought up some very interesting specimens. (see photos in gallery).
I had a chance the other day to talk with Dr. Edward Carpenter from the Romberg Tiburon Center of San Francisco State University. Dr. Carpenter is looking at the species and abundances of cyanobacteria and phytoplankton, as well as the chlorophyll in the water column. He is interested in what the plume water is doing to the populations.
The Amazon mixing with the oceans is creating abundances of diatoms. They begin to run out of Nitrogen because as zooplankton feed on them Nitrogen and other essential elements are lost as fecal matter into the deep ocean. However, there is still enough silica and phosphorous for diatoms to grow. Symbionts living inside of the diatoms fix nitrogen (referred to as diazotrophs) and supply them with the nitrogen they need. So how abundant are these organisms in the plume? Dr. Carpenter says that from Day 1 they have already seen that these diatom-diazatrophs (DDA’s) are very abundant in and under the plume. So how does Dr. Carpenter count and identify these organisms? Working in a dark room, he uses a microscope that causes the symbionts to fluoresce making it easier to identify them.
Dr. Carpenter’s team on the ship includes Dr. Ina Benner from the Romberg Tiburon Center and Dr. Rachel Foster from UC Santa Cruz. Dr. Benner is incubating phytoplankton under three different levels of CO2: 180ppm (glacial), 380ppm (present day), and 1000ppm (thought to be the concentration at the end of this century). The Amazon measures 150ppm and when it comes out to the ocean it goes up to 300s ppm. As the phytoplankton grow, they pull out the CO2 (through photosynthesis) from the seawater. These phytoplankton eventually sink out through being grazed by zooplankton. CO2 from the atmosphere then diffuses into seawater to replace that lost when the carbon is transferred from surface to deep water by the phytoplankton.
Dr. Rachel A. Foster (UC Santa Cruz) is studying the symbiosis between diatoms and unicellular and heterocystous cyanobacteria, Richelia intracellularis and Calothrix rhizosoleniae. On this cruise she is running a series of incubation experiments to better understand and quantify the exchange of nutrients (nitrogen and carbon) between the two partners. She collects whole seawater from the CTD and adds stable isotope labeled carbon (C) and di-nitrogen (N2) gas. After incubation she collects the cells by gentle filtration and preserves them. In the lab she uses a high-resolution nanometer scale secondary ion mass spectrometer(nanoSIMS) to visualize the location of the C and nitrogen (N) in both the symbiont and host cells. Using the nanoSIMS allows her to visualize the transfer between partners. She can also estimate growth rates and rates of N2 and C fixation for the various symbioses.
Her favorite part is working on the microscope, observing all the different types of photoplankton. Rachel says this is the true inspiration for her research! Her greatest challenge is developing innovative methods to link her qualitative observations of individual cells to their contribution on a larger, ocean-basin scale. Rachel is posting images of the phytoplankton in the image gallery called Phytoplankton of the Day. Click on the green tab (More Photos) on the home page to see it!!!
Question of the Day
- Do the bacteria in the water make us sick?
Only a few of them. Bacteria are in every habitat on Earth, growing in soil, hot springs, radioactive waste, water, as well as in organic matter and the live bodies of plants and animals. Bacteria recycle nutrients, with many steps in nutrient cycles depending on these organisms, such as nitrogen fixation.