Blue Water to Red?

Don't know if this is related or not, but FWIW... - HerbVic

The lake Nyos disaster, which claimed 1800 victims in August 1986, was not unprecedented, but never before one had heard of Mother Nature asphyxiating human beings and all terrestrial animals on such a scale in a single and brief event.

Two years previously however, a lethal gas burst originated from the neighbouring lake Monoun, in the same remote area of Cameroon, and killed 37 people, an odd and tragic episode that went almost unnoticed.

Both lakes occupy the crater of a supposedly extinct volcano, in a region known by geologists for its numerous gaseous water springs, a common feature of old volcanic areas. The region belongs to the so-called volcanic chain of Cameroon, which ends and culminates 300 km farther south-west at the still active Mt. Cameroon (4,000 m ).

In both cases, without prior notice, a cloud of dense gas erupted from the lake, covering the surrounding area under a deadly blanket several tens of meters thick, for an unknown amount of time. The source of the gas became clear in the aftermath of the disasters, since the normally clear waters of the lakes turned reddish and the lake shores were severely disturbed by waves and strong winds. No one in the path of the cloud managed to escape its lethal effects. Skin discoloration found on some victims were tentatively interpreted as burns, but this diagnosis is still controversial. Witnesses on topographic hights report a loud noise originating from the lake and, in the case of lake Nyos, flashes of light visible over the lake ; both disasters occurred at night, darkness adding to the mystery of these dreadful natural catastrophes.

Ten years later, thanks to the dedication of scientists - such as H. Sigurdsson, K. Tietze, G. Kling, W. Evans, M. Kusakabe and G. Tanyileke, to name but a few - who put both lakes under almost continuous scrutiny, the causes and mechanism of these tragedies are much better understood, albeit not yet completely elucidated.

http://perso.wanadoo.fr/mhalb/nyos/disaster/indexd isaster.htm

Could be alguaes also. This is not always very positive since it could be indication of acidity change in the water, due to new or different/increased quantity of volcanic gases releases in the lake. Non volcanic lakes are not red. There are some volcanic lakes which are permanently red on some volcanic island somewhere in Pacific. I do not remember where. In that place, there are/was 3 lakes in 3 volcanoes located close to each other, one is green (chlorine acid), one is red and the third one has some other color.

The gas venting from the volcano is co2 and or methane. co2 is asitic and could make a alge blum.The co2 vents into the bottom of the lake and gose into saturation, traped under pressure. They ran a pipe to the bottom, injected an air bubble and the rising air sucked the water up and started the co2 rising to come out of solution. Thay ended with a giser 165 ft. in the air. Discovery chanel. Don't remember title or date.

Without a check on the water chemistry all you can do is toss out W.A.G.s. Algae? Disturbed sediment? Iron Stain? Red metalic sulphates? Red colloidal alotropic sulphur? Even a litmus test and visual & olifactory exams of a sample would eliminate a lot of possibilities. Someone must have had the sense to do this. Provide all the info if you want a meaningful guess otherwise you invite a lot of wheel spinning.