An early spring bloom of large diatoms in the ice-covered Saroma-ko Lagoon, Hokkaido, Japan

• Published in: Journal of the Marine Biological Association of the United Kingdom 2012-02, Vol.92 (1), p.29-37
• Main Authors: Shiomoto, Akihiro, Asakuma, Koji, Hoon, Han-Dong, Sakaguchi, Koichi, Maekawa, Kimihiko
• Format: Article
• Language: English
• Subjects: Algae; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Brackish water ecosystems; Carbon; Chaetoceros; Chlorophyll; Climate change; Climatology. Bioclimatology. Climate change; Earth, ocean, space; Exact sciences and technology; External geophysics; Fundamental and applied biological sciences. Psychology; Global warming; Ice; Lagoons; Lakes; Marine; Meteorology; Phytoplankton; Plankton; Plant cytology, morphology, systematics, chorology and evolution; Primary production; Spring; Surface water; Synecology; Thalassiosira; Thallophyta; Winter
• ISSN: 0025-3154; 1469-7769
• DOI: 10.1017/S0025315411000361

Saroma-ko Lagoon, the largest body of water that has complete ice coverage during winter in Japan, was not completely covered by ice in the winter of 2009. This condition is considered to be a result of the progression of global warming. A bloom of large diatoms was observed in the ice-free area between February and April. This early spring bloom seemed to have started in the latter part of January, and lasted for about three months. The maximum chlorophyll-a (Chl a) concentration of about 10 mg m−3 was observed in March, and was similar to the level of 5–20 mg m−3 previously reported for the ordinary spring bloom in Saroma-ko Lagoon. The maximum primary production of 786 mgC m−2 day−1 and the maximum Chl a-specific primary production, an index of the phytoplankton growth rate, were also found in March. Species changes from Thalassiosira spp. to Chaetoceros spp. were observed during the bloom. This early spring bloom could extend into the ordinary spring bloom period. Its duration was obviously longer than that of the spring bloom, which is typically about one month. These results show the phytoplankton condition that could be expected during winter and spring as global warming progresses.