Halley's comet is 35AU at its farthest approach.
Answer:
it can protect from invaders
it can give water to build water canals.
The effects of rising ocean levels on marine ecosystems would represent the widest study ie world wide because when the ocean rises it rises all over the world so therefore it will have an worldwide impact for example it may create shallow water marine environments where the coastal floodplains are inundated more by the oceans.
The different plants that replace earlier varieties in the wake of a brush fire is an example of plant succession.
~Hope this helps!
The image above shows an ocean, a narrow body of water that connects two larger bodies of water