Well first of all, happy belated Fourth of July! This past week I spent time further analyzing the data from the first run through of the experiment, while also doing all the preparation necessary to start it up again. Interestingly, a test used to more accurately measure chlorophyll (a different test from the initial results) showed less confidence in our data set. As a consequence we have decided to add another replicate to each treatment. For those keeping track at home, the math now changes to 4 x 4 x4 or 64 bottles floating around in our little mesocosms. I won’t bore you with the details, but this significantly adds to the work involved in running the experiment.
I promised last week to discuss the consequences of nutrient limitations in estuaries, so lets delve into that a bit. Nutrient limitations of phytoplankton are an interesting topic of discussion. You may have heard about two relatively popular topics in the media related to these ideas. These are iron fertilization and the dreaded “dead zones.” These topics show the potential benefits of understanding nutrient limitation, and also the potential for havoc. They are two sides of the same coin. Iron fertilization seeks to enhance phytoplankton blooms in an under productive area of the ocean in an attempt to remove carbon dioxide levels in the atmosphere. In these areas, iron is largely seen as the limiting nutrient. “Dead zones” in contrast to the less productive open ocean, usually occur in the productive areas and result in eutrophication. Eutrophication is the direct result of an abundance of the nutrients in a system. These nutrients may come from natural processes like upwelling events and nitrogen fixers, but also from human wastes. These nutrients, in contrast with the iron limited open ocean, are largely nitrogen and phosphorous. Eutrophication decreases the available dissolved oxygen in the water as an abundance of phytoplankton bloom and ultimately die like all life on earth. This decrease in available oxygen is the reason for the term “dead zone.” As you can imagine, a decrease in available oxygen is undesirable for marine ecosystems.
So what does all this mean for Oregon’s estuaries? Well, if out of our 64 bottles a treatment shows a significant response for say phosphorous or “P”, we know that region is phosphorous limited. For an agency like the EPA, this directly translates into tools for management and policy. My advisor is working on tools for scientists from states throughout the country to be able to identify conditions in which nutrient limitations may be a factor. Regulations may also be crafted to prevent phosphorous wastes in fertilizers and other sources from polluting aquatic systems and ultimately harming species by depleting the available oxygen. And so, while I spend my hours of the day pulling bottles out of a tank and doing science on them, I can take pride in knowing that yes, this matters. Alrighty, that’s all for this week. Stay tuned for next week in which I may have some more results from the experiment! Here’s hoping for clarity!