Phytoplankton
They are the only one that are both animals and protists as they can be either
The carbon cycle maintains the balance between the organic remains and carbon dioxide. In this cycle the the incorporation of carbon dioxide inside the plants by photosynthesis occurs and it is returned to the atmosphere by the process of respiration as well as the decaying dead organisms.
Answer - Fewer Species or Little of life
Reasoning - Usually in an island surrounded by water has little of life because the limited resources but also if there were to be species living within the island it will be very little because of the resources they compete. Especially moving away from mainland since (No Humans) lol.