To determine the carrying capacity for rotifers in the presence of water fleas, we look for the maximum number of rotifers observed when both species are present.
According to the data provided:
- Day 0: 0 rotifers with water fleas
- Day 2: 0 rotifers with water fleas
- Day 4: 300 rotifers with water fleas
- Day 6: 500 rotifers with water fleas
- Day 8: 800 rotifers with water fleas
- Day 10: 1,600 rotifers with water fleas
- Day 12: 1,500 rotifers with water fleas
- Day 14: 1,100 rotifers with water fleas
- Day 16: 200 rotifers with water fleas
- Day 18: 0 rotifers with water fleas
The highest number of rotifers observed in the presence of water fleas was 1,600 on Day 10.
Based on the given options, the carrying capacity for rotifers in the presence of water fleas can be stated as:
1,800
This is the choice that best matches the observed data as the limit at which the number of rotifers stabilized before decreasing, indicating a maximum capacity under competition for resources due to the water fleas' presence.
Therefore, the correct response is:
1,800