11.   Possible causes were a virus, a bacteria or a toxic algal bloom.

12.   Also, agricultural chemicals applied on plantations find their way into the lake, polluting it and providing nutrients for algal blooms and the hyacinths.

13.   One such algal bloom is red tide, a microscopic organism that colors the sea and can be toxic to humans and marine life.

14.   Tests for algal bloom toxins are continuing.

15.   The clearance of natural vegetation along the shores, and the prolific growth of unwanted, unsightly algal blooms.

16.   The local trigger-level of water nitrogen content for algal bloom is estimated at one milligram per litre.

17.   Viruses move from tropical to sub-temperate climates while algal blooms flourish forming potentially hazardous red tides.