2. Why can't sea stars live in terrestrial environments?

The sea stars are echinoderms and are fully dependent on a having a saline aquatic or marine environment, from shallow intertidal to the deepest trenches or sea bottom. No member of Phylum Echinodermata (sea stars, brittle stars, sea lilies, basket stars, sand dollars, sea urchins, sea cucumbers) have been known to survive in a non-marine or non-seawater environment. They might tolerate moderate changes in salinity such as in brackishwater (lower salinity) or even air exposure but they may not survive for long because they lack a capability for osmoregulation of salinity as well as full resistance to dessication. Nor will they be able to reproduce properly because their gametes and larvae will most likely die quickly when exposed for extended periods to freshwater or air. None of the echinoderms will survive for longer than 24 hours when exposed to the air environment despite their somewhat thicker epidermis and/or exoskeleton.

Wetlands form where water and land meet. a lake with a wetland fringe can fill in with decayed plant and animal material to become a wet meadow. a pond can fill in to become a bog or fen. sediment can fill in a river marsh to become a swamp.flooding of coastal lowlands from rising sea levels has created broad coastal marshes that are protected from wave action by barrier islands or reefs. coastal wetlands also form when rivers deposit sediment as they reach the ocean. plants then take root and hold the soil firm against the forces of tides and waves.