Final answer:
Crustaceans, such as crabs, have developed sensory organs like compound eyes to detect movement and light, aiding them in finding plankton near the ocean floor. Factors like nitrogen in the Atlantic and iron in the Pacific limit phytoplankton growth, which is a primary food source for many marine animals, including crabs.
Step-by-step explanation:
Crustaceans, which include crabs, possess complex sensory organs, including two compound eyes that allow them to see in various environments. While visibility near the ocean floor can be limited due to the lack of light, crabs have adapted to these conditions. Their eyes are sensitive to movement and light, which can help in locating plankton.
When considering the growth of phytoplankton, certain elements like nitrogen or iron could boost their population in the oceans. In the Atlantic Ocean, nitrogen is the limiting factor, while in the Pacific Ocean, iron availability tends to limit phytoplankton growth. An increase in these elements would likely lead to a larger supply of plankton, possibly making them more visible to crustaceans like crabs on the ocean floor.
Crustaceans are largely carnivorous, and the presence of sufficient plankton is crucial for their diet. Hence, the ability of crabs to detect plankton in their environment, despite challenging conditions, is fundamental to their survival and suggests that they do have the capability to locate and consume plankton in their habitat.