How Do You Get Diatoms Out of Seawater?
At this point, you are probably wondering what happens to all of this water that is collected from the Southern Ocean. A few hundred bottles have already been used to store and transfer ocean water from the two sampling rosettes to various lab areas of the ship. Some of the water will be shipped to the various university labs at the end of the cruise for future research experiments. Much of the water, however, is processed during the research cruise in order to collect different information on the water, the diatoms in the water or other biological components of the water. In order to separate each of these items, the science team uses a number of different filters. These filters are similar to air filters in your furnace or oil filters in a vehicle. Both allow certain items (air and oil, respectively) to pass through while other particle are trapped by the filter. The idea is the same with the filters used by the science team. Let's take a look at some of the filters used by the science team to separate the ocean water from the diatoms.
Cold Room AKA Big Antarctica
If you read yesterday's journal you know that seawater samples are removed from the incubation van on set days throughout the experiment. Some of this water is transferred to the cold room known as Big Antarctica. This room is a large walk in cooler. Currently, the temperature in Big Antarctica is kept at a temperature of around 4C/39F. The filter system in this cold room consists of a peristaltic pump, tubing and two filters. Two different filters are stacked to trap different sizes organisms. In this case, diatoms and other small plankton stick to the 3 micron filter and bacteria to the .2 micron filter. The filters are removed from the apparatus, each placed in solution, flash frozen and shipped back to the labs for analysis. These samples will go to labs at the University of Rhode Island (URI) and Old Dominion University (ODU) for DNA and RNA analysis.
This peristaltic pump, located in the walk-in cooler known as Big Antarctica, is used to filter water from the incubation samples. The colored tape on each graduated cylinder corresponds to the colors of each incubation group (A-F). As water flows through the pump (right) it travels through tubes to a filter. Diatoms are collected on the filter and the water collects in the graduated cylinders.
The filter unit has two small filters and is positioned at the end of the tubes from the peristaltic pump. One filter has holes that are 3 microns in size to filter for diatoms (clear filter on the left). The second filter is .2 microns in size to filter bacteria (white filter on the right). The pump in the previous pictures creates added force to push the water through the small pores.
Bio Lab
In another lab on the main deck, a different filtering system is used to collect the biomass (biological material from the water samples) from the water samples. The biomass and filter combination is collected from the pump, placed in 95% ethanol and stored for 12-24 hours. After storage, the liquid is placed in a fluorometer to measure the chlorophyll levels. As you may remember from the diatom journal, chlorophyll is used to in the process of photosynthesis. If chlorophyll is detected, it may indicate the presence of photosynthetic activity in the sample.
Water samples are filtered at this station in order to test for chlorophyll levels. Each clear funnel has a filter at the base to remove biomass (living samples). This biomass sample is then stored in 95% ethanol for 12-24 hours. After the time period, the chlorophyll level is read using a fluorometer.
Trace Metal Bubble
Filtering is also done inside the trace metal bubble. In this case, the filtering is done for two reasons. First, to remove large particles (biological or non-biological) components from the water so that the water can be used for trace metal analyses. Second, the different sized filters in the pump will separate the cellular parts from the non-biological pumps. The cellular parts will be shipped to the University of South Florida (USF) to analyze the location of iron within the cells.
Incubation samples are brought to the trace metal bubble to be distributed to various labs.The trace metal chemists then use part of this sample in these filtration towers.
Each filtration tower contains two Teflon filters of different sizes. The filters will help to separate out biological and non-biological components from the seawater. The biological components (diatoms) can be used for analysis. The filtered water is also analyzed by the chemist to look for trace metals.
Love From Little Landlubbers
I am now two weeks into my expedition. I am loving my time on the research cruise and feel right at home of the ship. That being said, I do sometimes miss my friends and family. Before I left for the research cruise, a number of the littles (children) in my life made me pictures to help decorate my cabin. In order to thank them and let them know I am thinking of them, I will feature some of the photos each week. There is no specific order because I love them all the same! Thank you Ellie and Mayah (and Christopher) for my drawings.
Penguins and turtles all the way from Pennsylvania! Thank you Ellie and Mayah!
As you might guess from the picture - I love penguins. Speaking of penguins...tomorrow's journal is all about wildlife and scenery!!
Journal Comments
I want to take a moment to thank everyone for their journal comments and questions. The science team and ship's crew are enjoying your questions. I am learning so much more because of your insightful questions! One thing to keep in mind - there will be delay in the submitting process. There is no need to continue submitting the same question - just give the page time (maybe a few hours) to update. Once I receive the comment, I will answer as quickly as I can. THANK YOU!
Comments