Answer:
b. water depth
Step-by-step explanation:
The abiotic factors are the factors that are not part of the biosphere, thus they are not living organisms. In this case, the water depth is that type of factor that would influence the marine ecosystems. The depth of the water is crucial for the type of organisms that can exist in it, their density, and diversity. This is because the water has certain characteristics that provide certain conditions, like if the water is shallow, it will be warmer, but if its deep, then it will be colder. The amount of nutrients in it also depends on the depth. The sunlight can penetrate into the water only in the shallow parts, but not in the deep ones, so the basis of the ecosystems, the producers can exist only where they can have sunlight to perform the process of photosynthesis.