Ecosystem Response of the Avachinsky Gulf (Eastern Kamchatka) to the Runoff of the Nalycheva River in the Summer Season

A new complex of biohydrochemical characteristics has been obtained from the middle basin of the Nalycheva River to the deep-water part of the Avachinsky Gulf and adjacent water area of the Pacific Ocean. It has been established that phytoplankton bloom with a chlorophyll a concentration of up to 44 μg/L in the zone of the Nalycheva River plume is caused by an intensive flux of nutrients with river runoff during spring–summer flood and by the formation of maximum water stratification. The variability of DIN/DIP ratios in the Avachinsky Gulf due to fluxes of nutrients from volcanic catchments is considered the main cause of the occurrence of “red tides” in the summer–autumn period.