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Emily Davenport's picture

Depth: **175 meters **Temperature: 30 degrees F

I first want to mention that during our science personnel exchange, a journalist/scientist joined our crew.  Her name is Gaelin Rosenwaks, and she is on board to help out and learn about what every group is doing on board Healy.  She is keeping an online blog, and will highlight each research group on board.  Since I am busy sampling and helping our group out, I cannot highlight ever other group on board.  So, if you are interested in reading about all the other science that goes on, visit Gaelin's page at <a href="http://arctic.globaloceanexploration.com/">http://arctic.globaloceanexploration.com</a> 

This week has become a whirlwind of sampling for most of the scientists on board Healy.  Many are interested in studying the onset of the spring phytoplankton bloom, which fuels the entire Bering Sea ecosystem, and helps make the Bering Sea one of the most productive fishing grounds in the world.  The way the Bering Sea food chain works is that zooplankton eat the phytoplankton, and zooplankton get eaten by fish and larger animals (krill is a tasty treat for many whales out there).  Any uneaten phytoplankton falls to the sediment below and is eaten by benthic animals, which are in turn eaten by larger organisms like walrus, sea birds and some whales.  

The spring ice melt really helps drive the spring bloom- as the fresh water from the ice melts, it forms a less salty water &quot;lens&quot; over the top of the Bering Sea (because the fresh water is less dense than the salt water).  This layer is not easily mixed in with the salt water layer, and so phytoplankton in this layer are &quot;trapped&quot; in this very stable layer that doesn't mix with the layer below it.  They get held up in this layer, where they can get more light which helps them make their food.  

<img class="standalone-image" src="/files/members/emily-davenport/images/icealgae.jpg" alt="Phytoplankton from the Bering Sea (photo by Evelyn Sherr)" title="These are an example of some of the phytoplankton species that some of the scientists on board are finding.  The phytoplankton were viewed and photographed using an epifluorescence microscope.  " />

It is hypothesized that the timing of the spring bloom dramatically affects the amount of phytoplankton available to different organisms in the Bering Sea. If the ice retreats early in the year, due to warm temperatures, the fresh water lens occurs at a time of year when there isn't enough light for the phytoplankton to bloom, and winds mix the fresh and salt water layers together before the phytoplankton can bloom. The phytoplankton bloom has to then occur later in the year, when the water column stabilizes again due to warmer air temperatures (instead of ice melt). Around this time, the zooplankton are out in full force because the water is warmer, and they are hungry!! They eat a lot of this phytoplankton, and leave very little for the benthic organisms. The zooplankton are then eaten by lots of fish and some whales.

<img class="standalone-image" src="/files/members/emily-davenport/images/crablarvae.jpg" alt="Crab larvae" title="It is hard to imagine that this little guy will become a big crab crawling on the sea floor one day, but right now he swims in the water column and grazes on the phytoplankton.  Cute!!" />

<img class="standalone-image" src="/files/members/emily-davenport/images/krill.jpg" alt="Krill" title="A krill- important food for baleen whales, who use their baleen to strain the krill out of the water column.  These are also zooplankton and graze on phytoplankton and other smaller zooplankton in the water column." />

If it is a cold year in the Bering Sea, then the ice melts later in the spring, when there is enough light for the phytoplankton to bloom. It is usually too cold for the zooplankton to be out in such large numbers, so a lot of the phytoplankton bloom dies and falls to the bottom, where it is eaten by benthic organisms. These benthic organisms then become food for larger animals, like grey whales and walrus. It is hypothesized (and this trend has already been noticed) that with global climate change, the phytoplankton in the Bering Sea will go to feed more fish than benthic organisms, and animals like walrus and grey whales will have to travel farther distances to find food.

<img class="standalone-image" src="/files/members/emily-davenport/images/benthicorganisms.jpg" alt="Benthic Organisms" title="A sample of some of the different kinds of benthic organisms we have found in the Bering Sea sediment." />

This is essentially why we are studying the entire Bering Sea ecosystem, and for many years in a row- to get a better idea of the long term trend. There will always be variation from year to year- some years will be colder than others, and some will be warmer- but we can look at all the data we've gathered in a few years and see what the trend is- is it getting warmer over time or colder? How is global climate change affecting the Bering Sea food web?

Over the course of the cruise, we have instruments on board that tell us things about the water we are cruising in.  One of these things is fluorescence- a way of measuring how much phytoplankton is in the water.  A lot of scientists have been keeping their eye on this reading, looking for a sign of a spring phytoplankton bloom.  We have had a little extra time to &quot;play&quot;, so the ship has been zig zagging across the shelf, looking for a &quot;hot spot&quot; and then stopping to sample the water at those spots.  

During all this sampling over the past week, we sampled another really deep station- over 3000 meters!!  This part of the Bering Sea is called &quot;Zhemchug  Canyon&quot; and it is the largest submarine canyon in the entire world- it is deeper than the Grand  Canyon!  This canyon is an important habitat for many marine organisms- short tailed albatross (which are endangered) feed over the surface waters of the canyon.  Northern fur seals feed in the canyon along with many different whale species.  And of course, lots of different invertebrates live in the sediment, even at 3000 meters deep!