Harmful plumes of algae in waterways have been much in the news lately, in California and nationally. We talked to James Cloern, a senior scientist at the US Geological Survey and a member of the PPIC Water Policy Center’s research network, about this pressing water quality issue.
PPIC: What are algal blooms, and how big a problem are they for California?
James Cloern: Our waterways are home to many thousands of species of microscopic algae, but only a few dozen can develop into harmful blooms. They become harmful when they either produce toxic chemicals, which can make people and animals sick, or disrupt biological processes like animal feeding or bird flight—some species excrete goo that can gum up birds’ wings.
There’s growing evidence that harmful blooms are increasing because we are over-fertilizing our lakes, rivers, and estuaries such as the Bay-Delta. This over-fertilization comes largely from the discharge of treated sewage or runoff of nutrient-rich water from farms, cities, gardens, and animal lots. Two nutrients are causing these problems: nitrogen and phosphorus.
Algal blooms can grow very rapidly when they have the right conditions: warm water, high sunlight, and high concentrations of nutrients. California’s latest drought coincided with record-high temperatures, which warmed waterways and was a contributing factor to a number of algal blooms around the state.
One really nasty algae—Microcystis—seems to be increasing globally. It has an advantage as the climate and waters warm. Microcystis has become a challenge in California. In recent years we’ve seen it bloom in the Sacramento-San Joaquin Delta, Pinto Lake, Pyramid Lake, Shasta Lake, and reservoirs of the Bay Area’s East Bay Regional Parks.
PPIC: Could climate change worsen this problem?
JC: There is still much to learn about the ecology of these blooms, but we know these events are strongly tied to climate and especially to extremes such as heat waves and drought as well as El Niño/La Niña cycles. One grand challenge is to understand the interactions between climate variability, including climate change, and over-fertilization. Developing that knowledge is critical for establishing the quantities of nutrients that cause more frequent or intense harmful blooms.
PPIC: How well prepared are we to manage these water quality challenges?
JC: Water managers today are asking three essential questions of the scientific community. First, at what point do we have to take action? Second, which nutrient do we tackle first? And third, what level of action is required?
These are challenging questions, and they have global implications. They’re important in densely populated urban areas, where we dispose of treated sewage in water bodies, and in areas where water bodies drain large agricultural areas.
California’s Regional Water Quality Control Boards are tackling these issues. They have two new programs on nutrient management—one for San Francisco Bay, one for the Delta. The technical solutions are very different for dealing with land runoff and sewage. The sewage issue can be solved technically, but the fix is expensive. The San Francisco water board is now trying to determine what level of impairment should trigger mandated water treatment to reduce nutrients coming into the Bay. Since the problem could cost on the order of $5–$10 billion to solve, board members don’t want to mandate unnecessarily strict changes.
The land-runoff challenge is much harder to address, because the source of pollution is the application of fertilizers on land, feedlots, and septic systems. Solving the problem will require substantial behavioral changes such as new farming practices. But it has been done elsewhere—for example, Denmark mandated national-scale action to reduce both nitrogen and phosphorus.
We have a clear understanding of how nutrient pollution can make our waters unswimmable, unfishable and undrinkable. Solutions to the nutrient pollution problem exist, but they have costs. Californians must decide if the benefits justify the expense.