From: Haley Smith Kingsland, Stanford University
Although ICESCAPE is a NASA-supported project, in the interest of fostering international collaboration with programs conducting related research, we invited three budding young scientists from Canada’s MALINA program — Eva Ortega-Retuerta, Cedric Fichot, and Atsushi Matsuoka — to participate in ICESCAPE.
Cedric is a graduate student at the University of South Carolina. Here, he’s with a set-up that allows him to measure how much dissolved organic matter enters the ocean from land. (Photo by Haley Smith Kingsland)
My ICESCAPE work focuses on dissolved organic matter (DOM), a major food source for microbes in the ocean. Microbes transform DOM into carbon dioxide during a process known as respiration— basically the opposite of photosynthesis carried out by phytoplankton. During ICESCAPE, I collect samples for the chemical and optical characterization of DOM and conduct experiments to determine how reactive it is.
DOM comes to the ocean from land by rivers, or from living organisms present in seawater itself (including phytoplankton, zooplankton, and even the microbes themselves). DOM’s origin determines its “lability”— basically a measure of how likable it is as a food source for microbes. Just like humans, microbes prefer certain foods, and lability can help us predict how fast microbes will consume their food. Part of my work on ICESCAPE is trying to figure out how much food is available and how labile it is.
DOM is also important because it absorbs ultraviolet radiation (UV) and can protect living organisms from this harmful radiation. In that sense, DOM acts as a “sunscreen” in seawater! Using a spectrophotometer in the lab, we can easily measure how well DOM absorbs UV. Upon absorption of UV radiation, DOM tends to undergo photochemical reactions, so I’m also conducting lab experiments in order to study them.
Eva is a post-doctoral researcher in Microbial Ecology at Laboratoire d’Oceanographie in France. Here, she’s preparing tubes in the radioisotope experiment isolation van to measure bacteria production. (Photo by Haley Smith Kingsland)
I’m the “microbial ecologist” of the ICESCAPE team, so I focus my work on studying heterotrophic bacteria— or bacteria that don’t produce their own food, unlike algae that sustain themselves through photosynthesis.
Why study bacteria? These organisms, though tiny (no more than a few micrometers, sometimes less than a micron), are the most abundant living thing on Earth. You can find more than a million bacteria cells in a thumble full of seawater! Heterotrophic bacteria are the “recyclers” of the Artic ecosystem because they use dissolved organic matter for energy and to create new biomass.
During ICESCAPE, I’m describing the patterns of bacterial abundance, carbon uptake, and diversity in our study area, and trying to assess how environmental factors like temperature, ultraviolet radiation, and nutrients might be controlling these patterns. My ultimate goal is to improve our understanding of how changes going on in the Arctic Ocean today will affect bacteria metabolism and carbon cycling.
Atsushi is a scientist at Laboratoire d’Oceanographie in France. Here, he works with his UltraPath instrument to measure how colored dissolved organic matter absorbs light. (Photo by Haley Smith Kingsland)
Colored dissolved organic matter (CDOM), similar to the stuff that makes tea brown, leaks from vegetated land surfaces and pours into the Arctic Ocean from its many rivers and streams. I analyze light absorption by this CDOM in water samples collected from both the Healy and the smaller Arctic Survey Boat (ASB), which can be deployed whenever waters are calm enough. The Healy provides water from various ocean depths, while the ASB only collects surface water samples. Although we are still analyzing the data, we’ve already discovered a thin layer on the surface of the Arctic Ocean where light properties change remarkably. I’ve also seen that samples taken near the sea ice sometimes reveal the presence of algal degradation products, suggesting that a thriving community once lived there. Our results have important implications, especially for the next generation of satellite ocean color sensors. I’ll combine my data with other measurements from the optical research teams to develop more accurate satellite algorithms that can distinguish CDOM from phytoplankton.