The hydrochemical regime of the habitat of the red algaAhnfeltia tobuchiensis population in the Bay of Izmena (Kunashir Island)

In 1989–1990 and 1997, in the Bay of Izmena (Kunashir Island), the spatial distribution ofAhnfeltia tobuchiensis (Kanno et Matsubara) Mak, an unattached agar-containing red alga, was studied, and the availability of biogenic elements for the process ofA. tobuchiensis primary production was assessed. The concentrations of dissolved O₂, ammonium NH ₄ ⁺ ], and orthophosphate PO ₄ ³⁻ ], were highest in the central and northeastern areas of the bay, where the bulk of the population is situated. During the day, the mean oxygen concentration above the alga bed increased from 8.2±0.09 to 8.7±0.08 mg/l, showing a high rate of photosynthesis in the population. As a result of diurnal ammonium and orthophosphate assimilation by the alga, their concentration in bottom waters dropped from 5.1 to 3.5 and from 0.45 to 0.35 μM/l, respectively. Proceeding from the mean values of the nitrogen to phosphorus atomic ratio in the bay waters (11.5±3.3 in the morning and 10.6±3.3 in the evening) and in algal thalluses (33 in the case ofA. tobuchiensis), we conclude that the concentration of major biogenic elements is sufficient for the processes of primary production in the Bay of Izmena.