Barrier role of Cystoseira phytocenosis in the phosphorus detrophication in waters of the specially protected natural area “Cape Martyan” (Crimea, Black Sea)

Abstract

Abstract The goal of this study was to assess the role of Cystoseira phytocenosis as a biochemical barrier to the phosphorus detrophication through the phytoplankton primary production in waters of the specially protected natural area (SPNA) “Cape Martyan” on the southern coast of Crimea. We present data on the mineral phosphorus concentration in seawater and in the brown algae Cystoseira (Cystoseira s.l.) phytocenosis in 2021 and the phytoplankton primary production in 2017 – 2019. In the SPNA sublittoral zone, wet weight of the Cystoseira phytocenosis was estimated at 1425.6 tons, the production 3136.3 tons year–1, and the phosphorus accumulation factor 20,900 – 54,500. The phosphorus pool in the Cystoseira biotope ranged from 69.6 to 78.99% of that in the sublittoral zone and decreased with the phosphate concentration increase. The primary production in the SPNA sublittoral zone was mainly phosphate-limited. With the phosphate concentration increase, the primary production can reach hypereutrophication levels (100 mg Corg m–3 day–1). The phosphorus accumulation in the Cystoseira biotope reduced the phosphorus availability for the primary production to 10.4 – 30.4%. By the example of the SPNA “Cape Martyan”, we show that Cystoseira phytocenosis is a highly efficient barrier to the phosphorus detrophication in coastal waters.