Splashing around

Apologies for the gap in posting, but it has been one of those crazy weeks.   It has been suggested that maybe, when I don’t have the time to research and write an evolution post (They usually take 4-6 hours), that I should write general science and  nature posts.

I have not been sure about this, because I try not to write about my opinions, but I have figured that I can write about things I am passionate about, whilst not having to research for quite so long for each post, and also save some of my fellow bloggers from the email spam I send them with links and stuff.

So, I hope you like this new section of posts, and that I can still manage to show you things you did not know.

Today I would like to introduce you to the Southern Ocean.

This is where the Southern Ocean is located:

Southern Ocean (marked in blue). Image from wikipedia

The Southern Ocean is (in)famous as being a wild place, full of mountainous waves, and generally a very scary place.

The waves are so big, and the weather is so fierce there because basically, there is no land mass for the winds to run into, and lose their strength, and there is no shallower water as we find on the continental shelves, or islands, or land masses to break up storms and waves.

The gap between Antarctica and South America is known as the Drake Passage, and it is notorious for having the worst storms in the Southern Ocean, which is saying something!  The storms which occur here are stronger than the others in the Southern Ocean because the current which circles Antarctica (the Antarctic Circumpolar Current) is one of the largest currents on the planet, moving 125*106 cubic meters of water per second.  This cold water current basically just zips around and around Antarctica, like a car stuck on a roundabout, and keeps the warmer waters from the other oceans away from Antarctica.  This current is squeezed through a gap of 800 km between the tip of South America and Antarctica, and, as a result, the current speeds up, and creates rougher seas (Like when a river is narrower in some parts than others, the speed increases through the narrow parts).  Add this to the winds which circle Antarctica butting up against the warmer air from South America, and you have a recipe for some very very big storms!

The waters are much deeper than average ocean waters, with the depths of 4000-5000m, and the depth of the continental shelf being 400m or so, compared to the “normal” continental shelf depth of approx 130m.

Despite all this (or perhaps because of this), the Southern Ocean is one of the most productive oceans on Earth.  Everyone has seen the penguins in the Antarctic on TV, but they are merely near the top of a huge food web, as this picture shows:

Antarctic Food Web, image from Discovering Antarctica

The reason the Southern Ocean is so productive can seem a bit complicated, but it is really quite straightforward, and I will try to explain it as easily as I can:

One of the cool things about water is that frozen water is less dense than liquid water (hence ice floats), and there is a lot of ice around near the Antarctic.  This frozen water does not contain salt, so the salt is deposited into the surrounding water as it freezes, making that water more salty, and denser.

This increase in saltiness (salinity) makes the surface water denser than the water below it, and because salty water has a higher freezing point than fresh water, it can become colder than the water just below it.

As we know, warm air rises, and cold air sinks, and the same applies to water, so this surface water sinks, and is replaced by warmer water from below, which then cools, and sinks, and so the cycle repeats.

This is crucial, because the water from the bottom of the ocean has a whole load of nutrients in it.  The reasons for this are also fairly straightforward:

In the other oceans, the Atlantic, Pacific, Indian etc, dust blows off of the continents which contains nutrients from the soil.  This falls into the oceans, and drifts down to the bottom (along with any “marine dust” from animals between the surface and the bottom), and is then carried along in ocean currents until it reaches Antarctica, where it rises to the surface. (Sciency link showing the Antarctic thermocline is in “Further Reading”)

These nutrients are used by organisms such as phytoplankton (we met them in this blog post HERE ), which are at the very base of the food web.  Because of this abundance of nutrients, the ocean is able to support a very large number of these photosynthesizing organisms (also known as primary producers).

As an indicator of how many of these organisms there are, in the food web just above them is an animal which looks like a shrimp, called Krill.  This animal is extremely small, 1-2cm long on average, and yet, the 2011 harvest from Antarctica was 180,000 tons, so thats a LOT of Krill!  The estimates of the overall population are hard to come by, due to the difficulties in accessing the region, and the different methods used for calculating the population, however, current estimates are around 350 million tons.

Antarctic Krill. Image from Wikipedia

This seems like a large amount, but it is not just us using the Krill (We do not really eat krill, we use it for farmed fish, something my fellow blogger Argylesock has been writing about a bit lately).  The krill are what is known as a keystone species, that is, they underpin the ecosystem.   They keep the phytoplankton numbers down, and are food for pretty much every other species which feeds in the ocean, including the enormous Blue Whale, which eats nothing but krill, with each adult eating around 6 million krill per day!

Blue whale filtering sea water out of its mouth after dining on some krill. Image from Blue Whale info

So, why am I telling you things you already know instead of writing about more weird evolution stuff?

Well, this morning there was an article in the papers, about a presentation made at the Science Museum in London by the crew of an Antarctic research ship which has been sailing round the Antarctic for a couple of years, gathering lots of really cool data for scientists to spend the next 5 years or so going over (in 6 months, they have analysed 1% of data), and during this trip they made a not so cool discovery:

In the 1980s, a paper was published stating that plastics which were dumped were ending up as small pellets in the open ocean, many hundreds of kilometers from land.  This has led to a lot of scary stories, especially over the last 5 years or so about the “Atlantic Garbage Patch” or the “Pacific Garbage Patch”, with claims that there was more plastic in the sea than plankton (There is not), or that there is a garbage island the size of America (there also is not). What there is however, is many small pellets of plastic floating on, or near the surface of the ocean, which get ingested by marine animals.  There is also a lot of plastic debris washing up on beaches around the world, as we have all noticed.

The Southern Ocean, being so remote, and with its own currents and wind systems, was assumed to be a fairly pristine ocean.  That is until these researchers came back from their trip down there.

Southern Ocean, looking calm for once! Image from NOAA

They found 50,000 pieces of plastic per square kilometre, mostly consisting of microscopic pellets, and weirdly, fibres thought to be clothes residues from washing machines.

For me, as an environmental biologist, and generally someone crazy about nature, this is not good news, but as always, I try to focus on the “What can we do?” rather than yell about how bad we all are.

We cannot at present, remove this plastic from the oceans easily, so we are stuck with what is already there, so we should look at what we can do to not add any more to it.

Firstly, if you use plastic bags from the supermarket, re-use them, or, get a re-useable cloth bag.

Secondly, find out if there is any recycling in your area.  Here in Denmark, we can drop our bottles back to the shop for recycling (and a little extra cash, which is always good!).

There is increasing pressure on corporations, and governments to work to find biodegradable materials for plastics.  I got hold of some rulers which were made of corn starch of all things! (This means it is edible apparently, but it doesn’t look too tasty!)

Finally, try to not buy products which have a ton of plastic wrapping on them.   I saw a single pepper in the supermarket a few days ago which was shrink-wrapped…..what the hell is that about?

The oceans are not just there to look awesome and scary for us, the organisms in them play a vital role in the global food supply, and with the problems that are surrounding global fish stocks, I am not sure we want to mess up the oceans anymore than we already have.   We may not have known before, but we do now, so we should start acting on what we know.

Further Reading:

Guardian Article about the plastic: http://www.guardian.co.uk/environment/2012/sep/27/plastic-debris-southern-ocean-pristine?newsfeed=true

UN FAO: Krill fact-sheet: http://www.fao.org/fishery/species/3393/en

Sarmiento et al: High latitude controls of thermocline nutrients and low latitude biological activity (Figure 4): http://www.nature.com/nature/journal/v427/n6969/fig_tab/nature02127_F4.html

Moore, Lattin & Zellers: Density of Plastic Particles found in zooplankton trawls from Coastal Waters of California to the North Pacific Central Gyre:http://alguita.com/pdf/Density-of-Particles.pdf

Morris: Plastic debris in the surface waters of the South Atlantic (Marine Pollution Bulletin 1980): http://5gyres.org/media/Plastic_Debris_the_South_Atlantic_Gyre.pdf

Tara Ocean Interview with Chris Bowler: http://oceans.taraexpeditions.org/en/interview-with-chris-bowler-scientific-coordinator-of-tara-oceans-expedition.php?id_page=1150

Nature.com News “Ecologists Fear Antarctic Krill Crisis”: http://www.nature.com/news/2010/100901/full/467015a.html


One thought on “Splashing around

  1. Pingback: Corals and Starfish | Skeptical Squirrel

Leave a Reply


WordPress.com Logo


Google+ photo


Twitter picture


Facebook photo



Connecting to %s