Through photosynthesis, algea produce oxygen. The animation below shows the evolution of phytoplankton concentration throughout the year. Phytoplankton require Chlorophyll to produce oxygen through photosynthesis, which is why the animation uses chlorophyll concentrations as an indicator for phytoplankton prevalence. 

• Question 1: based on the animation, which conclusions can be draw with regards to the changes in chlorophyll concentrations throughout the year?
  The animation shows a continuous change in chlorophyll concentrations throughout the year. This is particularly the case around the earth's poles, where sunshine is lacking for around 4 months a year - this significantly impacts photosynthesis.
• Question 2: what can be said about the schale at which the issue of algal bloom prevails?
  Algea bloom is a global problem.

The causes of algal bloom in water can actually be found on land. Fertilizers travel through our soil and rivers and end up in our coastal waters, increasing the growth of algea. This process is called 'eutrophication' - it will be discussed extensively in this task. 

This task invites you to answer the following question: 

What is the environmental importance of models for soil-water systems and how can issues surrounding nitrogen deposition be incorporated?

In order to answer this question, you will first of all dive deeper into the issue of nitrogen deposition. The next part of this task will guide you through this process.