Question

station 4: temperature & algae blooms
scenario: in a shallow pond, a long stretch of hot, sunny weather raises the water temperature to new highs. at the same time, fertilizer runoff from a nearby farm enters the pond, providing a massive supply of nutrients. this perfect combination of conditions causes an overgrowth of algae, which forms a thick, green layer on the surface of the water. this phenomenon is called an algae bloom. this dense layer prevents sunlight from reaching the plants below and eventually, as the algae die and decompose, they use up all the available dissolved oxygen, leading to the death of fish and other aquatic life.

graph: effect of temperature on algae growth, with x-axis temperature (°c) (15.0 to 35.0) and y-axis algae growth rate (0.0 to 1.0), curve labeled \optimal temperature for algae bloom\

your task:
answer the following question:

1. what two variables are compared in this graph? identify the independent variable and the dependent variable.
2. in your own words, describe the relationship between water temperature and the algae growth rate. as the temperature increases from 15°c, what happens to the algae’s growth?
3. according to the graph, at approximately what temperature does algae growth reach its maximum rate? this is known as the optimal temperature.
4. imagine you are a park ranger monitoring a local lake. weather forecasts predict a week-long heatwave that will raise the lake’s water temperature to 25-28°c (77-82°f). based on the graph, what concern might you have for the lake’s health, and why?
5. the scenario describes a \perfect combination of conditions\ that caused the algae bloom. what were the two key abiotic factors that worked together to trigger the massive overgrowth of algae?
6. explain the chain of events that occur after the thick layer of algae has already formed. how does the algae bloom lead to the death of fish and other aquatic life in the pond?

Explanation:

Question 1

The graph is titled "Effect of Temperature on Algae Growth". The x - axis represents temperature (in °C) and the y - axis represents algae growth rate. In an experiment, the independent variable is the one that is manipulated (temperature here, as we can change it to see its effect), and the dependent variable is the one that depends on the independent variable (algae growth rate, as it changes with temperature).

Looking at the graph, as the temperature increases from 15°C, the algae growth rate starts to increase. Initially, the growth rate increases at an increasing rate (the curve is concave up), and then as it approaches the optimal temperature, the rate of increase of the growth rate slows down until it reaches a maximum (the curve becomes more flat). So overall, as temperature increases from 15°C, the algae growth rate increases, and it will reach a maximum (optimal) rate at a certain temperature.

By looking at the graph, we can see that the curve of algae growth rate vs. temperature starts to level off (reach a maximum) around 30 - 35°C. From the shape of the curve, we can estimate that the optimal temperature (where growth rate is maximum) is approximately 30 - 35°C (more precisely, looking at the graph, around 30 - 35°C, the growth rate stops increasing and stays relatively constant, so the optimal temperature is in this range, say around 30 - 35°C, and from the graph's x - axis and the curve, we can see that around 30 - 35°C, the growth rate reaches its peak.

Answer:

The two variables compared are water temperature (in °C) and algae growth rate. The independent variable is water temperature, and the dependent variable is algae growth rate.

Question 2