1. a. In my experiment there would be three experimental groups: the first would have both nitrogen (N) and phosphorus (P), the second would only have N, and the third would only have P; all three groups can be tested in order between April and mid-June where the graph shows the lake had some of the highest biomass of Diatoms, Dinoflagellates, and Green algae. The independent variables would be the N and P in each experimental group and the amount added in each setting; other factors like light, temperature, predation, and competition will vary from month to month. The dependent variable would the phytoplankton biomass in each experimental group. The first experimental group would help give a ratio between the two nutrients …show more content…
Cyanobacteria’s population growth rates seem to increase as nitrogen concentration decreases in June and continues to do so until its population growth rates start to decrease around August as nitrogen concentration begins to increase again. Because some cyanobacteria are capable of fixing nitrogen, they are able to still grow despite there being such a low concentration that the population growth rates of the Diatoms, Green Algae, and Dinoflagellates has decreased dramatically or is at 0 since there are none present during that time. As the Diatoms’ population growth rate starts to increase due to the increase in nitrogen concentration, the Cyanobacteria is outcompeted and starts to decrease and drop to 0 for the rest of the year.
c. Some of the trade-offs related to nitrogen fixation would be the dependency the organism would have on it consequently dying without it and the productivity it will allow the organism to have.
d. Since it seems that cyanobacteria are mostly based off of nitrogen fixation, without it the cyanobacteria died out; also, because the nitrogen concentration was beginning to increase again along with the phosphorus concentration, it allowed the Diatoms to grow and eventually outcompete the other