Posted by: Alison Cawood | August 3, 2009

SEAPLEX Day 2

Today’s post is from Meg Rippy.

Meg writes:

Hello. I’m Meg Rippy, a 4th year graduate student at Scripps Institution of Oceanography. Tonight I was helping Darcy Taniguchi collect phytoplankton samples for her thesis work. I also collected a few bacterial samples for my own work on this cruise, which focuses on the differences between bacterial communities in natural seawater and those associated with plastic debris.

The first night time CTD went down today. The water is thick with phytoplankton and so it is filtering very slowly. It looks like there may be a diatom bloom. Diatoms are phytoplankton with shells (tests) made out of silica. They often grow rapidly and achieve high densities (bloom) in areas where nutrient-rich water is upwelling from depth. This happens during most summers in the California Current. It will be really great to look at some phytoplankton samples under a microscope and try to identify the dominant bloom organism.

We also sent out the bongo net tonight. I have never deployed a net before and it was really a lot of fun. The bongo consists of two nets pulled side by side. From the front it looks like a set of large eyes. The nets came up absolutely full of zooplankton, especially copepods and euphasiids (a.k.a. krill). Organism abundances in the California Current are much higher than I expected. It will be really neat to compare what we’ve seen here with the gyre stations later on in the cruise.

August3

Here is Meg in New Horizon‘s science lab in front of a seawater filtration
system.  She is filtering water in order to examine particulate organic carbon.

Bongo-recovery-8-3

SEAPLEX expedition researchers recover bongo nets as they reach
the surface of the ocean alongside the research vessel New Horizon.
The nets are primarily used to capture plankton samples.

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Responses

  1. Give Mario Aguilera a shout out from his brother at SeaWorld. Wish him luck with his images.

  2. It would be great to also get coordinates where these blooms or other interesting things are seen.

    Are any tests being done of nutrient balance?

    What is the best place to find a summery of raw test results and observations? Will that be released during the cruise or after review?

    • There isn’t a good way for them to relay coordinates back to shore. They are off line most of the time, and their cruise track will change pretty often depending on that they see, weather, etc. The original plan was to head into the gyre at about 32 degrees latitude.

      I’m not entirely sure what you mean by nutrient balance. They will look at dissolved and particulate carbon and nitrogen and biologically available silica from different depths.

      While at sea, you don’t do much data processing. For the most part, they spend all of their time collecting, processing, and preserving the samples. So, they won’t have actual quantitative data until months (or longer) after the cruise returns. After that point, the data will be published as part of scientific, peer reviewed articles.

      • Thanks Alison. By “nutrient balance.” I mean the balance of iron, nitrogen and other essential nutrients needed for growth.

        I assume most of the ocean is biologically limited by a shortage of one or more nutrients in each area and that blooms are caused by current or upwelling mixing in whatever is missing.

        I’m interested in understanding what the primary limiting factor is, in the gyre, and if nutrients that are in short supply in surface water might be available in deeper water.

      • In oceanography, we call that balance the Redfield Ratio. The Redfield Ratio says that in seawater (and in most phytoplankton) the ratio of carbon to nitrogen to phosphorus is 106:16:1. Almost all marine systems are nitrogen limited, in contrast to freshwater systems which are almost all phosphorus limited. This is definitely the case in the North Pacific Gyre. As to your mention of iron, it is believed that there are regions of the ocean that are iron limited (there is sufficient nitrogen to support phytoplankton growth, but the growth remains low). However, studying iron from metal ships is an incredibly difficult task. Ships and most oceanographic equipment contain iron, so this contaminates the samples. It is possible to collect trace metal (like iron and copper) clean samples (in fact there is a group here at Scripps that does just that), but it requires specialized equipment. So iron measurements are not being made while on this cruise.

        The upper open ocean is generally nitrogen limited. So, in coastal oceans, there is plenty of nitrogen from terrestrial sources and from upwelling (some places even have too much, a condition known as eutrophication). However, most of this nitrogen is used very quickly, so there isn’t very much that makes it offshore. In the open ocean, the small amount of new nitrogen that enters the system comes from diffusion from the air, from specialized nitrogen fixing bacteria, and from the small amount of deep water that is upwelled into the upper ocean. In the deep water, there is plenty of nitrogen because as organisms die and sink, they are broken down and nitrogen is released into the water. However, it requires a lot of energy to mix water vertically, so most of this nitrogen is trapped in the deep ocean until it is upwelled into coastal systems. The other way to get nitrogen in the open ocean is by recycling what is already there. Organisms release nitrogen via urea, ammonium, etc, but these forms can’t be used by most organisms. However, there are some types of phytoplankton that can convert these forms of nitrogen back into nitrate, which is the type of nitrogen that most organisms need. In nitrogen limited systems, there is a tight recycling of the nitrogen that is available.

        This reply got rather long and quite sciency! You are asking some great biogeochemical cycling questions! Hope that my answers make sense and don’t scare you away!

  3. Good luck to all of you! This plastic pollutant in the ocean has been a nagging worry for me from the time I read it in National Geographic. I hope and pray that you folks will find the extent of impact it is having so that concerns over this problem in particular and of plastics in general can be raised enough to warrant global attention and restraint in the use of plastics. Good luck again. I will be following this website daily to hear more about what you find.

  4. Thank you for the answers!

    I have a house about 15 minutes from Newport if you guys need any help (volunteer of course) upon your return.

  5. [...] Our first post today is from Meg Rippy.  This is Meg’s second blog entry. [...]


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