| Date | May 2010 | Marks available | 1 | Reference code | 10M.3.SL.TZ2.7 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | State | Question number | 7 | Adapted from | N/A |
Question
Primary production is directly related to the amount of photosynthesis that occurs in a cubic metre of water. In the waters around Bermuda (32°N) in the Atlantic Ocean, microscopic phytoplankton are the producers. They use trace nutrients from seawater in their metabolism. These nutrients are a limiting factor in total population size. A dense phytoplankton population makes the water cloudy. The data shows primary production per day for each month for the year 2000 at different water depths.
State the month when total photosynthesis was greatest.
Identify, with a reason, the water depth that receives no light.
In the upper 40m there is a drop in photosynthesis from March to June. This is probably due to lack of nutrients, reducing the population density.
Suggest, with a reason other than nutrient levels, what might have increased photosynthesis at 100m from April to August.
Compare production in March with production in September.
Markscheme
March
(at) 140 m (of water depth) because there is no photosynthesis (except slight in June and October)
increased light penetration due to decrease in phytoplankton numbers/cloudiness;
(as the summer season approached) the Sun would be directly overhead making deeper light penetration probable;
there is greater total production in March than in September;
the water at 100m is relatively more productive in September than in March / the water at 100 m is unproductive in March, but is productive in September;
total production in March is approximately 28 to 29mg m-3 day-1 whereas in September it is approximately 8mg m-3 day-1 ;
the upper 40m have their highest productivity in March and their lowest productivity in September;
Examiners report
In C1 the graph and questions were quite straight forward.
In C1 the graph and questions were quite straight forward.
In C1 the graph and questions were quite straight forward and only (c) caused problems.
In C1 the graph and questions were quite straight forward.
