Coatepeque's Lake Turns to Turquoise color.

Yesterday, I had nothing to do so I decided to make a post on one of my other social media profiles, asking to anybody who wanted, to go with me to Coatepeque's lake at Santa Ana, El Salvador.
The awesome thing about this lake during this time is that, it turns into a turquoise color... But why is that?

Reading a little bit I found the reason.

Lakes exist exist in many sizes and shapes but the most remarkable characteristic is the color of its water, there are lots of lakes with different colors and transparency, but even a single lake can change its color. Lake color can tell you many things about the water body (e.g., including nutrient load, algal growth, and water quality) and also about the surrounding landscape.

Blue water lakes contain low concentrations of algae and other substances, resulting in high clarity and a deep blue color.Water molecules absorb longer, visible wavelengths (e.g. red light, 600-700 nm) while shorter, blue wavelengths (< 500 nm) pass deeper into the water column.

Green water lakes commonly have high concentrations of chlorophyll-containing algae which can give water a green color. Green lakes are often eutrophic and typically contain more harmful algal blooms than other types of lakes. Activities such as farming or septic system failure can increase the green color of lakes through nutrient inputs which act as a fertilizer for algae. The high productivity of green lakes usually enables them to support more fish, but the poor water quality conditions can depress dissolved oxygen levels in hot summer months; these conditions can cause fish kills where oxygen drops too low for fish to survive.

Brown water lakes contain high amounts of tea-like substances, known as dissolved organic matter. Typically, brown lakes are surrounded by forests or wetlands. Dense forests provide dark organic material that dissolves in lake water like a teabag. This dissolved organic material stains the water brown and shades the underwater world.

Overall, brown water lakes tend to be light-limited. The algae in these lakes survive through certain adaptations that allow them to adjust to low light levels. These lakes can also sometimes be acidic and contain few fish or other organisms.

Both natural and human activities can cause changes in lake color and clarity. The development of communities or the use of agricultural fertilizers around lakes often reduces water clarity and adds nutrients, shifting lakes from blue water to green water. Lakes can also naturally become more eutrophic and green over time. As lakes age over centuries, nutrients, sediment and plant material slowly build up. This natural process is much slower than changes caused by human impacts.

While human impacts often change lakes from blue to green, conservation and protection can improve the clarity and color of lakes. In areas where water quality has been degraded by pollution, eutrophication, or changes in land use, community action to improve water quality through enhanced laws and zoning can improve water quality and shift lakes from green water to blue water. This process is often difficult, however, as lakes tend to remain in the color state in which they currently exist.

Seasonally, lakes can change in color. In many lakes, rapid algal growth in the spring months produces a green color. However, this period is usually followed by a clear water phase (i.e., blue water lake) as zooplankton emerge and consume algae. The length of clear water phases can vary and is determined by the ecological interactions among aquatic organisms. In addition, sunlight can bleach organic matter in the same way that materials left outside for too long become bleached and faded. The bleaching typically follows day length and lakes can be most transparent (e.g. most blue in color) when the most bleaching occurs around the summer solstice.

SOURCE:
http://www.lakescientist.com/lake-color/
Kalff, J., 2002. Limnology, New York.
Stolzenbach, K.D. Atmospheric Deposition: Figure 3: An eutrophic lake choked by an algae bloom. Retrieved online May 2010 at: http://www.ioe.ucla.edu/reportcard/article.asp?parentid=1497
NH Division of Forest and Lands. Acidic brownwater lake/pond. Retrieved online May 2010 at: http://www.nhdfl.org/about-forests-and-lands/bureaus/natural-heritage-bureau/photo-index/acidic-brownwater-lake-pond.aspx
Greeson 1969. Lake eutrophication – A natural process. JAWRA.
Jeppesen, Jensen, Søndergaard and Lauridsen. 1999. Trophic dynamics in turbid and clearwater lakes with special emphasis on the role of zooplankton for water clarity. Hydrobiologia 408/409:217–231
Tõnno, Kunnap and Noges. 2003. The role of zooplankton grazing in the formation of ‘clear water phase’ in a shallow charophyte-dominated lake. Hydrobiologia 506:353–358
Morris and Hargreaves. 1997. The Role of Photochemical Degradation of Dissolved Organic Carbon in Regulating the UV Transparency of Three Lakes on the Pocono Plateau. Limnology and Oceanography 42: 239-249.