52.保护动物免遭风暴和洪水

protect animals and plants

51.对环境污染很敏感

be sensitive to environmental pollution

50.吸收营养物质和污染物

absorb nutrients and pollutants

49.海洋哺乳动物　 marine mammals

48.生物的密集度

　the density of living creatures

47.三用面支很多危险

without having to face many of the dangers

46.河口是自然界中幼小生命的繁衍地

estuaries are great places for nature’s young ones

45.陆地与海洋的衔接地带

a zone between the land and the sea

44.制造出一种独特的环境

create a unique environment

43.在河口相混合mix together in an estuary