Abrupt change in primary productivity in a littoral zone of Lake Biwa with the development of a filamentous green‐algal community

Abstract

1. Some characteristics of the photosynthesis and primary production of benthic and planktonic algal communities were investigated in a littoral zone covered with gravel in the north basin of Lake Biwa, paying special attention to the recent development of filamentous green algae (FGA) in the benthic algal community. 2. Pmax (maximum gross photosynthesis rate) values of the benthic algal community (0.1–1.2 mg C mg chl. a−1 h−1) obtained from photosynthesis–irradiance (P–I) curves were lower than those of the planktonic algal community (2.4–11.5 mg C mg chl. a−1 h−1). This is apparently a result of the high degree of self shading in the benthic algal community and its low turnover as compared with that of the planktonic algal community. 3. Relatively high Ik values (150–200 μmol photon m−2 s−1) were observed in the benthic algal community only in June–July when a FGA, Spirogyra sp., was abundant. This reflected a photosynthetic characteristic of the Spirogyra itself, in which photosynthesis was saturated at high light intensity. 4. The FGA community established in the layer between planktonic and sessile (benthic algae except for FGA) algal communities. It brought about extraordinarily high organic matter production in the littoral zone at the expense of production in the sessile algal community.

Development of filamentous green algae in the benthic algal community in a littoral sand-beach zone of Lake Biwa

“…Therefore, the maximum benthic algal biomass in the stony zone of Lake Biwa was attributed to the appearance of Spirogyra sp. in recent years (Nozaki 1999(Nozaki , 2001Nozaki and Mitsuhashi 2000;Nozaki and Mitamura 2002). In the present study, the chlorophylla amounts in benthic algal communities increased from May to June, simultaneously with the propagation of the filamentous green algae Oedogonium sp.…”

“…Saijo et al (1966) investigated benthic algal communities dominated mainly by diatoms throughout the year in 1963-1964 in a littoral stony zone in the north basin of Lake Biwa and found a maximum biomass in February and a minimum in July to August. On the other hand, Nozaki (2001) investigated the chlorophyll-a of benthic algal communities formed on stones in a stony zone in the north basin of Lake Biwa from 1995-1996. The maximum values were obtained in June and July when a filamentous green alga, Spirogyra sp., appeared in abundance.…”

“…However, most studies of the benthic algal community in the littoral zone of Lake Biwa have been conducted in the stony zone (Saijo et al 1966;Negoro et al 1966;Nozaki et al 1998;Nozaki 1999Nozaki , 2001Nozaki and Mitsuhashi 2000;Nozaki and Mitamura 2002) and the macrophytic (reed) zone (Negoro et al 1966;Higashi et al 1981;Tanimizu et al 1981;Kusakabe 1988;Mitamura and Tachibana 1999). There is only one report of the flora of diatoms in the sand-beach zone of Lake Biwa (Tuji 1995).…”

Seasonal variation in biomass and photosynthetic activity of epilithic algae on a rock at the upper littoral area in the north basin of Lake Biwa, Japan

“…Goldsborough and Robinson (1996) summarized the few available data of saturating irradiance (Ik) values (about 300-400 µmol photon m −2 s −1 ) in freshwater marsh assemblages. For Spirogyra, Nozaki (2001), on the other hand, observed the Ik values (150-200 µmol photon m −2 s −1 ) of a Spirogyra sp.-dominated community collected from a gravel zone in Lake Biwa. In addition, Nozaki and Mitamura (2002) showed that the photosynthesis-irradiance (P-I) curves of cultured Spirogyra were saturated at approximately 500 µmol photon m −2 s −1 under all water temperature conditions (25°-40°C).…”

“…Nozaki (2001) investigated benthic algal productivity in a gravel-covered littoral zone in that basin with special emphasis on the filamentous green algal community. Nozaki et al (2003) also reported on the development of benthic algae in a predominantly sand-beach area in Biwa's littoral zone.…”