SEVENSEAS Marine Conservation & Travel Issue 11, April 2016 - Page 41

I’m lying in bed, taking a few deep breaths, and giving myself a pep talk. I finally convince myself to get out of bed and look out of my porthole. Six meter waves are crashing against the window–I feel excitement pushing through my seasickness induced nausea–I’m headed to Antarctica! The choppy Drake Passage crossing makes it impossible to not ponder what sea life could possibly live amongst this harsh environment.

As we cross the Antarctic Convergence, birds are feasting on the nutrient–rich plankton that were recently brought to the surface by strong upwellings. Looking out towards the cold, dark, rough water, it is easy for one to assume that life beneath the waves is impossible. I’m here to tell you that that’s not true. Many people ONLY associate productivity with bright coral reefs surrounded by schools of fish. However, the biological productivity in Antarctic waters is the highest in the world! Why? Phytoplankton (aka: photosynthesizing microscopic organisms)! Let’s delve a little deeper into what is happening in the Antarctic waters, shall we?

It is estimated that the Antarctic phytoplankton population consists of about 99% diatoms (unicellular golden brown algae). Diatoms are autotrophic organisms that, similarly to terrestrial plants, possess chlorophyll. This enables them to use sunlight to convert inorganic material to organic material through the process of photosynthesis. They make their own food! Cool, so there are a lot of diatoms in Antarctic waters–but WHY?

There are three main reasons for the abundance of diatom life in Antarctic waters:

1) The water is cold. Cold water holds dissolved gases (example: oxygen and carbon dioxide) better than warm water. These gasses are necessary to sustain life.

2) Long daylight hours. In the austral summer, long exposure to sunlight promotes ample photosynthesis. Boom, algae bloom!

3) The sea is turbulent, producing strong upwellings. Turbulent waters suspend vital nutrients, such as carbonates, nitrates, and phosphates in the water column where they can be utilized by the phytoplankton.

Ok, so we now know why phytoplankton are so abundant in Antarctic waters, but where are we going with all of this information? Well, this phytoplankton abundance is why life is sustainable both on the Antarctic continent and below the dark waves! Phytoplankton make up the base of the Antarctic food web. With relatively few species and trophic levels compared to other marine ecosystems, the Antarctic food web is simple. As primary producers (remember, phytoplankton make their own food via photosynthesis) the phytoplankton feed the primary consumers, such as fish, krill, and squid. These primary consumers are then eaten by the larger animals we most commonly associate with Antarctica: penguins, sea birds, seals, and whales. Krill are incredibly abundant in the Southern Ocean and are a staple food source for the Antarctic animals. Baleen whales travel thousands of miles each austral summer specifically to feed in these phytoplankton/krill rich waters. When talking about survival in Antarctic waters, krill is always mentioned. But, let’s not forget, the krill cannot survive without the phytoplankton.

So, long story short:

Abundant sunshine hitting the cold, turbulent Antarctic waters makes an ideal environment for phytoplankton to thrive. This phytoplankton abundance creates the base for an incredibly productive marine environment. Phytoplankton feed the massive amount of krill (and other small animals) that then provide food for the larger animals like seals, penguins, and whales.

Just a friendly reminder why it is important to save our plankton!

Antarctica, Phytoplankton Paradise