Final answer:
The increase in algae in the neighborhood lake could be related to nutrients from Sarah's farm fertilizers leading to algal blooms, similar to how a single species of fish in a microcosm experiment allowed more sunlight and smaller DOC particles, promoting algae growth.
Step-by-step explanation:
The increase in algae in the neighborhood lake could indeed be related to Sarah's farm, particularly if the farm uses fertilizers. When high levels of nutrients, which come from substances like fertilizers, enter a water body, they can lead to algal blooms. This overgrowth of algae is harmful because, as the algae die and decompose, they use up the oxygen in the water, creating anoxic conditions where fish and other aquatic organisms cannot survive. This process is known as eutrophication.
In relation to the microcosm experiment mentioned, having only one species of fish led to smaller dissolved organic carbon (DOC) particles and more sunlight penetration, which in turn fueled algal blooms. Conversely, two fish species increased the size of the DOC particles, reducing sunlight penetration and preventing algal blooms. If Sarah's farm activities are increasing the nutrient levels in the lake, it could cause similar conditions to those tanks with single-species fish, thereby contributing to the increase in algae.