Scant summer rain may be behind absent algae bloom in Lake Shinji

MATSUE -- Blooms of algae typically seen in Lake Shinji here were absent this summer, probably due to the rising salt concentration of the brackish lake triggered by low rainfall, local researchers said.

The algae bloom high season has passed. If no blooms are confirmed later this year, 2017 will be the third consecutive year without the photosynthetic organisms making an appearance, according to the Shimane Prefectural Institute of Public Health and Environmental Science.

Algae blooms at Lake Shinji are triggered by the mass propagation of phytoplankton, and are linked to the lake's low salt concentration, moderate water temperatures and lots of sunlight. Many details of the algae, however, remain mysterious.

The number of days when the bloom could be seen in Lake Shinji has been shifting in recent years, from 123 in 2010 to 61 in 2011, 155 in 2012, nine in 2013 and three in 2014. Local residents complained of a gas-like odor from the lake between 2010 and 2012, according to the Matsue Municipal Government.

The Shimane Prefectural Government allocated some 18 million yen for removing algae blooms from the lake in its June 2013 supplementary budget. This fiscal year, the prefecture once again earmarked roughly 8 million yen to that end. The prefectural Institute of Public Health and Environmental Science also formed a team of six researchers dedicated to studying the algae.

While it is necessary to collect data on water quality and temperature to detect the signs of an algae bloom outbreak, the recent absence of the blooms has troubled researchers.

"It's good that we have no blooms, but it also hinders our research as we need to gather data to unravel how they are produced. We will continue our studies based on past data and other resources," said an institute representative.