Yellow-Brown Algal Bloom Makes White River Water Brown and Foamy and May Be Responsible for Fish Kill
July 2009

Many people have noticed a dark brown color on the White River in Hamilton and Marion Counties in the past week (July 18 -28, 2009).  There are also patches of foam and areas where a brownish scum is collecting.  The algal bloom is known to extend from north of 116th street in Hamilton County down to at least 16th street in Indianapolis.  

These conditions are being caused by a bloom of single-celled algae in the group of algae known commonly as yellow-brown algae or diatoms.   

Scientists from the Center for Earth and Environmental Science (CEES) at IUPUI, observed the bloom on the White River on Friday, July 24, 2009 in an area just south of Conner Prairie, extending downstream for a significant distance. Conditions on the river varied from areas of very dark brown water color, to areas with patchy foam and bubbles, to areas with a brownish scum that in places looked like a film, froth, or scum surface.  

Nicolas Clercin, a research scientist at CEES who is an expert on algae analyzed the sample and determined that it was dominated (>99%) by a diatom called Cyclotella meneghiniana.  Diatoms are microscopic single-celled algae that photosynthesize like all plants.  They are tiny (20-25 microns in size) – so that more than 80-100 diatoms would fit on a pinhead. These algae have a yellow-brown cell structure that enables them to photosynthesize giving them the yellow-brown color.

Cyclotella meneghiniana from 2009-07-24 White River Sample (250x magnification)

Cyclotella meneghiniana from 2009-07-24 White River Sample (400x magnification)

An algal bloom simply means that the population concentration is very high.  Bloom can occur naturally but are intensified by a series of factors including high nutrients (especially nitrogen and phosphorous) and likely the relatively low flow conditions in the river right now.  Algae blooms are a symptom of nutrient enriched conditions. Excess nutrients are in the river from a host of sources – most of which are man-made and include discharges from wastewater treatment plants, failing septic systems, stormwater runoff, and both agricultural and household fertilizer runoff.  

During bloom conditions, there are very high oxygen demands in the river. Fish kills can be associated with blooms of algae because these organisms photosynthesize during the day utilizing carbon dioxide and producing oxygen – but at night they respire or breath – consuming oxygen.  When they are in very high concentrations – like they are right now in the White River – they have the ability to utilize the available oxygen and lower the oxygen levels to critical levels for fish and other aquatic organisms that need oxygen for survival.  An additional drain on oxygen comes from the very high organic load caused by the high numbers of diatoms in the water.  As these algae die, other microorganisms break them down – and those breakdown processes also consume oxygen.   

Right now we are seeing algal blooms in many of our freshwater systems including the reservoirs, river and even many of the stormwater basins in neighborhood subdivisions.  There are many different groups of algae in freshwater systems.  Another common problem is blooms of blue-green algae that are potentially toxic.  This is typical in middle to late summer and indicative of nutrient – or fertilizer – enriched waters.  Algal blooms are becoming a persistent problem in Indiana rivers, lakes, and reservoirs and are telling us that water quality has degraded to levels where we are seeing environmental impact.  These nuisance algal blooms are causing impairments to recreational use and drinking water production. At the root of the problem are excessive nutrients.  It is becoming more and more critical that we all (residents, businesses, municipalities, and communities groups) start working together to address better management of our water resources to limit nutrient inputs.