Algal blooms hurt the system in two ways First, they cloud the water and block sunlight, causing underwater grasses to die. Because these grasses provide food and shelter for aquatic creatures, spawning and nursery habitat is destroved and waterfow have less to eat when grasses die offAlgal blooms hurt the system in two ways. First, they cloud the water and block sunlight, causing underwater grasses to die. Because these grasses provide food and shelter for aquatic creatures, spawning and nursery habitat is destroyed and waterfowl have less to eat when grasses die off.