Algae are ever present in bodies of freshwater, absorbing sunlight and releasing gases into the air as they grow. Algae becomes more visually noticeable and often problematic when growing conditions are favorable. An abundance of sunlight and warmth of water coupled with lots of nutrients can cause algae to grow fast and out-compete other organisms, leading to a bloom or massive overpopuation of algae that discolors the water.
Algae are microscopic plant organisms that contain chlorophyll and other pigments that allow for photosynthesis, the conversion of sun energy in food. Although species-specific, algae require sunlight to survive. Some algae merely survive in lower light levels while other types grow only when sunlight is unimpeded and intense. Regardless, abundant light tends to promote and increase growth of algae, even in water that may be cool in temperature.
Warm Water Temperatures
Often accompanying abundant sunshine is the effect of an increase in water temperatures. A dark-colored liner can also have the effect of increasing warmth of water because of its tendency to absorb heat. As water temperatures increase, algae growth also increases. Generally speaking, when water temperatures exceed 60 degrees Fahrenheit, the rate of growth hastens.
Ample Supplies of Nutrients
Like other plants, algae needs basic nutrients to sustain its metabolism and grow. Nitrogen, phosphorus and potassium as well as other trace minerals are absorbed by these one-cell or multi-cellular organisms. Water teeming with mineral ions permits healthy, steady growth of algae. As long as minerals are not too abundant, the growth rate of algae is not excessive.
When nutrients are in high quantity in water, algae growth can explode, particularly if the nutrient phosphorus is plentiful. Excessive growth of algae is called a "bloom," a situation where so much algae grows that water quality and oxygen content are deleteriously affected. The inhospitable environment created by algal bloom causes a water ecosystem to self-destruct as the algae shades sunlight, robs water of oxygen and plant and animal death leads to an increased amount of nutrients.