It is a curious situation that the sea, from which life first arose, should now be threatened by the activities of one form of that life. But the sea, though changed in a sinister way, will continue to exist: the threat is rather to life itself...
- Rachel Carson
Monday, 31 October 2011
The Deep Sea
For our 'Marine Ecosystems' lecture today we were given an overview of the Deep Sea environment, the main threats and what has been done to protect it. I'm actually quite shocked at the amount of management surrounding the deep sea, i.e. very little has been done or is due to be done thus is remains relatively unprotected. I guess this is due to the amount of information that we know about this habitat, we just don't know enough to protect it efficiently. I mean, think of it like this, 87% of the sea is dominated by this 'deep sea'. It is the most widespread habitat yet we only know about 0.0005% of it. I'd say it was shocking but some of these areas are ridiculously deep. Light becomes limited in the mesopelagic zone (also known as the Twilight Zone) which is between 200 and 1000m deep. Then you read the bathypelagic zone (the midnight zone) which is totally pitch black (1000-2000m deep). In both of these zones you do get some bioluminescent organisms though. Then you reach the Abyssopelagic and Hadopelagic zone and suddenly everything is very... sparse. The hadal zone includes those deep ocean trenches that you find and can reach depths up to (and maybe exceeding) 11000m.
Anyway, I've done very little research surrounding the deep sea. I think we may have touched on it a little in the first year of my undergraduate degree but I don't think much time was spent on it. I remember various facts, like the important of food falls or 'ocean snow' in order to provide those living in the deep with food since primary productivity is limited to bacteria whom synthesise organic compounds using chemical energy (chemosynthesis), and that whale carcasses often provide a 'stepping stone' for organisms recolonising to different hydrothermal vents... I recall this much but I never really acknowledged the main threats associated with the anthropogenic exploitation of the deep sea and it was quite shocking!
We were shown comparable sites of... Lophela pertusa for example (photo below) and it was just disgusting how much damage a single trawl can do to hundreds of years of coral reef.
Lophelia pertusa, a stony coral (scleractinian) which produces reefs. Most well known example of a cold water coral, and currently under threat from deep sea trawling (deep sea fisheries). Below is a before and after photo of damage in Norway.
To think that as a result of anthropogenic greed for money and food, hundreds of organisms have lost their habitat.
I found this species very interesting too, I'd never actually seen one before. It is a scaly-foot gastropod Crysomallon squamiferum and has a foot reinforced with scales made of iron and organic materials.
Giant isopod, a perfect example of gigantism.
Greenland shark (Somniosus microcephalus) has been observed at depths of 2200m.