Vertical Variability of Primary Production and Features of Subsurface Chlorophyll Maximum in the Laptev Sea in August–September of 2015, 2017 and 2018
Vertical distribution of phytoplankton primary production (PP) and chlorophyll a (Chl) was studied based on the data of three cruises carried out in August–September of 2015, 2017 and 2018. PP maximum was located at the surface or within 0–5 m of subsurface layer. Subsurface chlorophyll maximum (SCM) was registered at 39% sites on the outer shelf and in vicinity of the continental slope. Along the northward transect (130° E) from the Lena`s river delta SCM was not detected. As in the other areas of the World Ocean SCM was located below upper mixed layer (UML), in nitracline, near an euphotic depth (1% photosynthetically available radiation). Generally, SCM was not accompanied by additional maximum of PP. Chl concentration at SCM not exceeded 1 mg m<sup>–3</sup>. PP produced within UML and SCM contributed 72% and 23% to water column primary production (IPP), respectively. Our results suggest that impact of SCM on IPP was insufficient due to low Chl concentration and PP co-limitation by light and temperature.