Temporal and spatial distribution characteristics of nutrients in Clarion-Clipperton Fracture Zone in the Pacific in 2017

This research investigated eight stations in Clarion-Clipperton Fracture Zone (CCFZ) in the eastern tropical Pacific in 2017 to study the spatial distribution characteristics of nutrients and chlorophyll a (Chl a ) concentration, and compared nutrient concentrations and molar ratios with those of other investigations 20 years ago in the same area. The study found that dissolved inorganic nutrient (N, P and Si) concentrations were lowest in the upper layer, and increased from surface to some depths, then they decreased a little to the bottom. N was the limited nutrient factor for the growth of phytoplankton community. Although nutrient concentrations and molar ratios have no obvious changes in 2017 comparing those in 1998–2003, supplemented from the equatorial Pacific, nutrient concentrations in the study area were higher than those in seamounts in the North Pacific and Station ALOHA. Furthermore, this study used Generalized Additive Models (GAMs) to infer the underlying bottom-up factors controlling phytoplankton abundance (Chl a concentration), showing that depth, salinity and PO 4 3− -P concentration were major factors controlling the growth of phytoplankton community. Furthermore, this study can provide basic data and theoretical support for the development of polymetallic nodule area and its long-term impact assessment on the environment.