[求助]GRE难句－32

birdie

32. In the periods　of peak zooplankton abundance，that is，in the late spring and in the summer，　　Haney recorded maximum daily community grazing rates，for nutrient-poor　lakes and bog lakes，respectively，of 6.6 percent and 114 percent of daily phytoplankton production.

请教NN，上面那句里的 that is 起什么作用啊？that is 后面所跟的句子是 Haney recorded ……吗？

wxt

我觉得是：“即” ，做进一步解释。

wxt

In the periods　of peak zooplankton abundance，that is，in the late spring and in the summer，　都是介词状语，that is 对前面状语做进一步解释。

Haney recorded maximum daily community grazing rates..............是主句，

birdie

哦，明白了，谢谢WXT mm鼎力襄助