Changes in the Structure of the Subtidal Phytocoenosis along the Gradient of the Concentrations of Biogenic Elements in the Sukhoputnaya Bay (Ussuriisky Bay, Sea of Japan)

Resumo

The modification of the structure of the subtidal phytocoenosis was investigated along the gradient of the concentration of nutrients brought with sewage effluents into the Sukhoputnaya Bay (Ussuriisky Bay, the Sea of Japan). It was shown that an increase in the concentration of dissolved inorganic nitrogen (DIN) from 4.2 to 16.6 μM was followed by a decrease of 1.7 times in species richness, while the relative biomass of opportunistic species increased simultaneously by more than 1.5 times and by more than 5 times for Ulva lactuca. A decrease in the number of dominant species and in the number of layers in the structure simplified the algal phytocoenoses. The complex polydominant multi-layered phytocoenosis of Stephanocystis crassipes–Laurencia nipponica + Ulva lactuca–Ahnfeltiopsis flabelliformis was first substituted for a bidominant two-layered phytocoenosis of Stephanocystis crassipes–Tichocarpus crinitus, and further by a one-layer monodominant phytocoenosis of Ulva lactuca. A comparison of our own and published data allows us to conclude that complex phytocoenoses of perennial macrophytes can develop in water areas with DIN concentrations that do not exceed 15 μM.