Some don't have any able to see effects,but some cause diseases
I think the answer would be pesticides... i see you selected it though. was that a wring answer?
Answer:
D)
Explanation:
Turtles eat the grass, grass is needed for fish breeding. If there are more turtles, they will eat more grass and there will obvious be less of it. If there is not enough grass, other populations of fish will leave because they can't breed.