Question

Most aquatic organisms are adapted to a narrow range of salinity. Why must aquatic organisms living in coastal areas be adapted to survive in both low and high salinity? During high tide, freshwater mixes easily with ocean water, lowering salinity. During low tide, the ocean water becomes concentrated, increasing salinity. Ocean currents bring in deep-ocean water with high salinity concentrations. Temperature fluctuations can cause changes in the salinity levels of the water.

Answer 1

The correct answer of the given question above would be the second option. Most aquatic  organisms are adapted to a narrow range of salinity but these aquatic organisms living in coastal areas must be adapted to survive in both low and high salinity because during low tide, the ocean water becomes concentrated, increasing salinity. Hope this helps.

Answer 2

Answer:

Option B, During low tide, the ocean water becomes concentrated, increasing salinity.

Explanation:

The varying moisture content and evaporation rate during tides causes variations in salinity of sea/ocean water. The surface pore water salinity reduces during high tides because of inundation and increases during low tides.  While in aquatic ecosystem, there is no as such variation of salinity and that so frequently.  

Hence, a marine species must be capable of surviving in condition of varying salinity while an aquatic species live in narrow salinity range.  

Thus, option B is correct.