Final answer:
Marine ecologists study interactions within marine ecosystems, focusing on diverse marine species, monitoring alien and invasive species, and utilizing non-invasive methods to research organisms such as deep sea corals.
Step-by-step explanation:
A marine ecologist focuses on the study of interactions within marine ecosystems. This includes conducting research on marine alien species, making accurate lists of fish, macroalgae, and mollusks, and efforts to detain invasive species like Caulerpa webbiana.
As part of their work, marine ecologists may examine vectors for marine species introductions such as ballast water analysis and boat hull incrustation identification, perform biogeographic studies, and engage in large-scale monitoring efforts, though such programs often require additional funding.
Moreover, a marine ecologist would study diverse aspects of marine life, including the class Hydrozoa, which comprises nearly 3,500 species, most of which are marine and have both polyp and medusa forms throughout their life cycle.
An aspect of their research could involve categorizing cnidarians based on characteristics such as the location of their gonads or their lifestyle (sessile or mobile).
To study organisms like deep sea corals without disrupting their habitat, marine ecologists can use methods such as multibeam echo sounders rather than invasive techniques like deep sea diving.