名词后的 abundance 作什么用

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.

开头这个abundance，它为何放在zooplankton之后，而且前面已经有peak作为修饰词了。

peak zooplankton abundance 这个名词词组中，abundance是中心词，zooplankton修饰abundance，而peak修饰zooplankton abundance.