Teachers Get Involved

Denise Lit asks:

How do they plan to use this Seasor data and is it shared with many different research groups at SIO or only the group who has sponsored it?  I also notice most of your sampling is done at night… is there a reason for this? The Mocness and Oozeki sampling for the zooplankton and mesoplankton is done once during the day and once during the night. Zooplanton are vertical migrators, and many feed on phytoplankton which live in the euphotic zone ( they need light because they are plants) but light also means that predators can see you…and eat you.  So, the zooplankton go down below the photic zone to hide during the day and come up (vertically migrate during the night).  The two daily samples allow the scientists to see the daytime biomass and compare it to the night time biomass. They are also looking at diurnal patterns, (when are they migrating) to asses daily rhythymns of grazing.  Also, one of the big parts of this research is looking at the different nutrients in the system out here and where and when they are being used. So, the groups looking at silicate, nitrate and C14 uptake need to do their sampling at night and set up their experiments and get them back in the water before dawn. They want to measure the usage of nutrients in the natural system and any light, will affect the rates.  So, much of the sampling and collection is done using opaque or dark bottles, the silica experiments are set up and put back out during the night and with all the lights turned off so that when it"s dawn and the sun comes up only the natural light is affecting the rate at which silica is converted to silicate.   Dr. Krause is looking at silica uptake and the measurements he is taking are so precise that any change (such as light in the lab on the organisms) that could affect uptake and conversion rates would skew his data. So, even in the isotope van when they are treating the samples with a tracer they have red lights that are not usable by the plankton, so as not to affect the rates. The same is true for the nitrate and C14 sampling which are affected by light.  Even when  processing some of the samples as in Dr. Landry’s experiments on grazing rates, he needs to use dark bottles and he covers some of his bottles while filtering so that unnatural light does not affect the experiments.

Denise Lit

What exactly is happening in the “storm” fronts? Is it animal activity, increase in numbers of animals, or actual water moving around instead of air? Great question, and the answer is: all of the above ( don’t your kids just hate it when you say stuff like that? ) But, you have the idea.  The “front” is an area where different water masses with different densities (based on temp and salinity) meet and mix, there is a gradient across this area.   We are making measurements to determine whether dissolved nutrients (needed by phytoplankton) are elevated at the front because of increased mixing from below the euphotic zone.  We are also assessing whether ocean currents at the front cause plankton to aggregate (or disperse), whether zooplankton grazing on phytoplankton is enhanced there, and whether mid-water fish and seabirds are affected. When they analyze the krill is it with the naked eye or under a microscope? What are they looking for?  On the ship we are just labeling and preserving them as we take samples.  The samples will the analysed ( identified and counted) back at Scripps using the microscope. We are doing some experiments with a couple of species of copepods that I mentioned in an earlier blog.  Dr. Ohman offered to give a tour of the Scripps Pelagic Invertebrates collection to any of the teachers who would be interested after we return. Just for curiosity sake, Are there any indications that pollution is causing mutations in the live samples you have been collecting?  They have not been looking for any mutations and are not seeing any signs of pollution out here.

Ariel Valentino asks:

What is the typical temperature difference between the upper and lower gradient of a “front”?  The temperature gradient across the front is small, 1 degree C or so, but the real difference across the front is a combination of temperature and salinity that when combined makes different densities of water parcels.  
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