英文生物题谢谢

河口区潮汐涨落明显，盐度、温度变动较大；表层盐度小，底层盐度大。河口区潮汐通常为半日潮汐，一日两次涨潮。在涨潮时，海水会沿河道自河口向上游上溯，致使海水倒灌入河。涨潮时盐度增高，落潮时盐度变低。盐度有季节性变化，春季冬季盐度变小；夏季盐度近海水较远海水高。

生物角度？貌似是个地理题，或者力学题。

潮汐时，海水涌入，河口盐度逐渐升高
潮汐后期逐渐减小至正常水平

这哪里是高中水平
Tides are the periodic rise and fall of ocean level. Tides cause tidal currents where, in coastal areas, especially estuaries, these currents "cleanse" the seawater if it has been impacted by the input of wastes (e.g., sewage) from human activities. Sewage treatment plants are frequently placed at or near the shores of estuaries. The sewage treatment designer is taking advantage of tidal currents that move sewage from an estuary to the ocean. The tidal process (currents and mixing) dilute sewage wastes and over several tidal cycles the sewage/seawater mixture is transported in a seaward direction--to the ocean where even a greater dilution occurs. The net seawater direction of the back and forth movement of estuarine water diluted with river water (