阅读下列短文，根据短文内容填空。在未给提示词的空白处仅填写1个恰当的单词，在给出提示词的空白处用括号内所给词的正确形式填空。

Pillar coral (柱状珊瑚), 【小题1】 (find) throughout the Caribbean, is critically endangered now. Its population

【小题2】 (decline) by more than 80 percent since 1990. 【小题3】(rise) ocean temperatures and pollution make corals more easily get certain deadly diseases. And the pillar coral is really just the tip of the iceberg 【小题4】 it comes to the difficulty of corals.