I really want to do this course. I really do find it interesting. I really, really want a change of direction in my life, away from making pointless bloody websites and indulging the every whim of lunatics, and towards doing something exciting and worthwhile. This matters to me, and apart from anything else I’ve paid good money to do this course and spent a lot of time on it already.
So why the chuffing hell can’t I concentrate on college work? Here I am blogging about it, no problem at all typing out how pissed off I am about being unable to concentrate, and yet all I have to actually do today is type something about the effects of excess plant nutrients on a watercourse ecosystem.
Of course, it doesn’t help that the shit seems to hit the fan whenever I have an assignment due. Last time – moving house, succession of friends experiencing personal turmoil, bout of minor depression. This time, close relative breaking an ankle and a stinking cold. Next time, who knows – war with Iran, hepatitis and an alien invasion?
As if that’s not bad enough, a cat just ricoched off the desk. I think it was after attention, however it landed on an item of my course material which acted as a non-stick device, and the cat slid off backwards as quickly as it appeared.
So, a new idea. Reverse psychology. I’m going to blog about the effects of excess plant nutrients on a watercourse ecosystem. Ha! brain, not so sodding clever now, are we?
Briefly outline the processes by which excess plant nutrients applied to agricultural land can cause damage to the ecosystem of a watercourse. You should include specific reference in your answer to the role of oxygen.
(15 marks)
The primary risk to a watercourse ecosystem associated with the application of excess plant nutrients to agricultural land is eutrophication, resulting in disruption of photosynthesis in water-based plant systems, and anoxia.
Surface runoff of excessive amounts of phosphate and nitrate fertilisers, as well as normal leaching of nitrates, leads to an accumulation of high levels of nutrients in watercourses. This eutrophication encourages algal bloom and bacterial growth, with particular problems being caused by the growth of phytoplankton (blue-green algae).
As the density of algal bloom increases, it blocks sunlight from penetrating the surface of the water, so starving autotrophic organisms deeper underwater, blocking photosynthesis, and causing reduced production of oxygen and death of the autotrophic organism. Excessive plant and algal growth further contribute to the load of decaying organic matter in the watercourse, which overall increases biochemical oxygen demand, causing anoxia, or insufficient oxygen supply.
Anoxia poses a direct threat to fish and other aquatic organisms, as well as affecting food chains through damage to producers, and in turn to each trophic level of the food chain. This finally results in a widescale change to the watercourse ecosystem, as the favoured organisms become bacteria, and the ecosystem is no longer capable of supporting other aquatic organisms.
Additional ecosystem damage can also result from nitrate toxicity, and from consumption of toxic algal blooms by aquatic organisms.
Done.
Next question.
I knew some of this, but now I know a bit more. Thanks for sharing.