Distribution, biomass and primary production of an Ahnfeltia tobuchiensis (Ahnfeltiales, Rhodophyta) population in the Bay of Izmena, Kunashir Island

Abstract

SUMMARYRegularities of distribution and primary production of an Ahnfeltia tobuchiensis (Kanno et Matsubara) Mak. population, an agar‐containing red alga, were studied in the Bay ot Izmena. Experiments were conducted in a flow‐through system under conditions similar to algal habitats. The population of A. tobuchiensis unattached to the ground may be from a few centimeters to as much as 1 m thick. It has been shown that only the upper part of a stratum 15–20 cm thick receives a sufficient amount ot light to realize its production potential. While 15–20% of photosynthetically active radiation (PAR) of that falling on the water surface reaches the stratum surface, only 0.1% of PAR from that falling on the water surface penetrates through stratum 15 cm thick. It has been shown for A. tobuchiensis that its photosynthetic rate curve during the daytime mainly follows the PAR intensity curve. The highest values of photosynthetic rate have been measured in the afternoon when PAR reaches its maximum. It is noted that a stratum 15–20 cm thick has peak values ot net primary production (NPP) which averages 3.2 g C m−2 day−1. The total area of A. tobuchiensis population was 23.4 km2, and its biomass was 125 000 tons in this area. On average, the NPP of the A. tobuchiensis population made up in summer and in autumn was 46.8 and 25.0% of its biomass, respectively.