What is it? The dominant algae has officially been identified and verified by several scientists and water quality experts as Pyramichlamys sp. It is closely related to the species Carteris sp., but is separated by the presence of a notch adjacent to the flagella. Each individual "plant" is about 14 to 18 microns in size. It is a member of Chlorophyta or green algae. Green Algae is considered to be the most ancient green plants.

It is not a species of Blue-green algae.

Why is it here? Algae spores are common in most bodies of fresh and salt water. The species identified in Lake Mead (Pyramichlamys) has been quite prevalent throughout the entire United States over the last three years. It takes several factors for algae to bloom. Abnormal weather conditions, (cold, then warm, then mild alternating over a several day period). In order to bloom, Pyramichlamys requires a large concentration of nitrogen and a small concentration of phosphorous. This is not unusual. The phenomenon has occurred in 1996, 1997, 1998, and 2001 in the inner Las Vegas Bay. The 2001 growth was the largest of these and expanded into an extensive algae bloom.

Is the water OK for Body Contact activities? No toxins have been associated with a green algae bloom. In fact, in some cultures green algae is considered a perfect food source. In 2001, the National Park Service and the Southern Nevada Water Authority tested two sites in the areas with the algae bloom for fecal streptocaccus, E. coli and fecal coliform. The tests returned within the acceptable standards for full body contact. Although it reduces the clarity of the water, green algae is not considered a hazard to body contact recreation.

Is it a problem if I swallow some of the green water? Although the water does not look clear, according to the scientific literature, there is no threat to public health from the green algae bloom if a healthy person swallows a small amount . However, no matter how clear a body of water looks, no one should drink the water if it has not been treated to drinking water standards. Drinking any non-potable water presents some health risks.

Are the fish OK to eat? Green algae is a natural food source in the aquatic environment and will not influence the edibility of fish. The food chain of Lake Mead National Recreation Area will thrive on the nutrient packed algae. It is expected that fishing will become very good after green algae blooms due to the abundance of green algae available to the lower aquatic life forms in the foodchain.

Is the algae toxic? Unlike the Blue-green algae, no toxins have been identified in blooms of the green algae. As mentioned above, samples of the water were tested for levels of fecal streptococci, E. coli, and fecal coliform. The results showed findings that were well within standards for body contact.

What happens if my dog drinks some of the water/swims in the lake? As with people, dogs should be discouraged from drinking any water that is in a lake or stream. Treat your pet as if they are a member of your family. When you bring your pet to the lake carry a potable supply of water for them as you would do for yourself and your children. Swimming in any body of water has risks for pets.

What is being done about it?
After the extensive algae bloom in 2001, the Lake Mead Water Quality Forum, chaired by the Nevada Division of Environmental protection, established an algae sub-committee. The group investigated the 2001 bloom and feels that the factors that led to it included: above average spring rains, dropping lake elevations, exposure of the mile-long Las Vegas Wash delta, wash plume overflow, and phosphorus load. Based upon recommendations of the group, the wastewater plant operators voluntarily increased their phosphorus removal during the winter of 2001-2002. The Clean Water Coalition, Bureau of Reclamation, and National Park Service are initiating a planning process and Environmental Impact Statement which will seek alternative discharge options into the Colorado River system, with reducing/minimizing algae blooms in Lake Mead as one of the goals.

The National Park Service, Lake Mead National Recreation Area, is a member of the Lake Mead Water Quality Forum, a multi-agency group established to address water quality concerns in Lake Mead. The NPS has expressed a strong desire for the long-term preservation of the existing high water quality of Lake Mead, including water clarity.