Final answer:
The correct answer is D: Wetlands and Estuaries. Wetlands are characterized by standing water, while estuaries are transitional zones where rivers meet the ocean and are vital for various marine species.
Step-by-step explanation:
The two types of specialized marine ecosystems are Wetlands and Estuaries, making D the correct answer. Wetlands, which encompass a variety of habitats such as marshes and bogs, are renowned for their standing water and serve as critical zones for biodiversity and water purification. Estuaries, on the other hand, are dynamic environments where freshwater from rivers mixes with saltwater from the ocean; they are essential nurseries for many marine species due to the rich nutrients found there.