phosphorous

Wetlands: Earth’s Kidneys

By Marguerite Huber

Stream restoration research

Stream restoration research

Our organs are vital to our health, with each one playing a significant part. Kidneys, for instance, filter our blood to remove waste and fluid. Wetlands are often referred to as “Earth’s kidneys” because they provide the same functions, absorbing wastes such as nitrogen and phosphorous. When excess amounts of these substances—nutrient loading—flow into waterways it can mean harmful algal blooms, hypoxia, and summer fish kills.

Recognizing the importance of wetlands, many communities are taking steps to protect, restore, and even create wetlands.

For example, many stream restoration projects include constructing wetlands to absorb stormwater runoff and absorb excess nutrients and other pollutants that flow in from a host of sources across the watershed (known collectively as nonpoint source pollutants).

These constructed wetlands can provide key elements to urban stormwater management because they help reduce the impacts of runoff after a rainstorm or big snowmelt event. Such runoff typically transports high concentrations of nitrogen and phosphorous and suspended solids from road surfaces into waterways.

One such type of wetland that may provide these kinds of benefits is the oxbow lake, so named because of their curved shape. These form naturally when a wide bend in a stream gets cut off from the main channel, but EPA researchers are taking advantage of a couple of oxbow wetlands created during stream restoration activities at Minebank Run, an urban stream in Baltimore County, MD.

The researchers are studying the oxbow wetlands to quantify how effective such artificially created wetlands are at absorbing nitrogen and phosphorous in an urban setting. If these types of wetlands are effective, then deliberately constructing oxbow wetlands could be an important nutrient management strategy in such landscapes.

From May 2008 through June 2009, the researchers analyzed water, nitrate (a form of nitrogen pollution), and phosphate flow during four storms to better understand the impacts of hydrology on the potential for the two oxbow wetlands and the adjacent restored streambed to absorb or release nutrients.

The results suggest that oxbow wetlands in urban watersheds have the potential to be “sinks” that absorb and store nitrogen. They also reinforced information pointing to the dynamic hydrologic connection linking water and nutrient flow between streams and nearby oxbow wetlands, findings that if confirmed through further investigation can be used to improve restoration efforts that improve water quality across entire watersheds.

When it comes to phosphorus, the researchers found that oxbows don’t function as “sinks,” but “sources,” that contribute a net increase of the nutrient. They hypothesize that this is because the nutrient is released from wetland sediments during storms or other similar events. Future studies are needed to investigate the magnitude of phosphorous release, and how important that contribution is across the watershed.

Just like how our kidneys are an essential aspect of the human body, wetlands are an important aspect of nature. Retaining additional nutrients and treating non-point source pollutants help give natural and constructed wetlands the affectionate nickname of “Earth’s Kidneys.”

About the Author: Marguerite Huber is a Student Contractor with EPA’s Science Communications Team.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action.

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SPARROWs, Lakes, and Nutrients?

By Jeff Hollister

Dock extending into a lake with forested background.Based on the title above, you probably think I don’t know what I am talking about. I mean really, what do sparrows, lakes, and nutrients have in common? In this case, a lot. So much so, an inter-agency team of EPA researchers in Narragansett RI, and a colleague from the U.S. Geological Survey (USGS) in New Hampshire have been working together to better understand how these three seemingly disparate concepts can be linked together. Some of the results of this work are outlined in a recent publication in the Open Access journal, PLos One

The sparrow I am referring to isn’t small and feathered, it is a model developed and refined by the USGS. Since the late 1990’s, USGS has been developing SPARROW models which have been widely used to understand and predict the total amount of nutrients (among other materials) that streams are exposed to over the long-term. This is known as “nutrient load.” The models are important because they provide a picture over a very large extent of where nutrients might be relatively high.

However, when it comes to lakes, SPARROW doesn’t directly provide the information we need. For our research on lakes, we need reasonable estimates of the quantity of nutrients in a given volume of water (i.e., nitrogen and phosphorus concentration), not long term nutrient load for the year. This is important, because the higher the nutrient concentrations at any given time, the greater the chance of triggering algal blooms—and more blooms mean a greater probability of toxins released by algae reaching unhealthy levels.

In order to better estimate the nutrient concentrations, we needed to use the SPARROW model for total load, but also account for the differences between load and concentration. Our solution: combining field data, data on lake volume and the SPARROW Model.

In our paper “Estimating Summer Nutrient Concentrations in Northeastern Lakes from SPARROW Load Predictions and Modeled Lake Depth and Volume,” recently published in PLoS One, we describe how we combined modeling information from SPARROW, summertime nutrient concentrations collected during EPA’s 2007 National Lakes Assessment, and estimated lake volume (see this and this for more).

The end result of this effort is better predictions, by an average of 18.7% and 19.0% for nitrogen and phosphorus, respectively.

What is the meaning of this in terms of our environment, and importantly, the potential human health impacts? If we are able to better predict concentrations of nutrients it will hopefully also improve our ability to know where and when we might expect to see harmful algal blooms, specifically harmful cyanobacterial algal blooms. Cyanobacteria have been associated with many human health issues, from gastro-intestinal problems, to skin rash, and even a hypothesized association with Lou Gehrig’s Disease (for example, see this). So, in short, better predictions of nutrients, will, in the long run, improve our understanding of cyanobacteria and hopefully reduce the public’s exposure to a potential threat to health.

About the author: Jeff Hollister, a co-author on the study outlined in this blog post, is a research ecologist with an interest in landscape ecology, Geographic Information Systems (GIS), the statistical language R, and open science. The focus of Jeff’s work is to develop computational and statistics tools to help with the cyanobacteria groups research efforts. Jeff is also an outspoken advocate for open science and open access among his colleagues.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action.

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Challenging Nutrients: EPA and Partners Launch New Ideation Prize

Effects from excess nutrients in American waterways cost the country more than $2 billion each year.

Activities of daily modern life add small amounts of the nutrients nitrogen and phosphorus to our lakes, rivers and estuaries, either directly or indirectly.

We all contribute to the widespread problem. Runoff from our suburban lawns, city streets and rural fields is just one of many ways we introduce more nutrients into the environment.

The partnership for this challenge currently includes: - White House Office of Science and Technology Policy - U.S. Environmental Protection Agency - U.S. Department of Agriculture - National Oceanic and Atmospheric Administration  - U.S. Geological Survey - Tulane University - Everglades Foundation

The partnership for this challenge currently includes:
– White House Office of Science and Technology Policy
– U.S. Environmental Protection Agency
– U.S. Department of Agriculture
– National Oceanic and Atmospheric Administration
– U.S. Geological Survey
– Tulane University
– Everglades Foundation

These excess nutrients end up in our waterways and fuel algae growth that exceeds healthy ecosystem limits. In turn, algal blooms can contaminate drinking water, kill aquatic species and negatively affect water-based recreation and tourism.

A partnership of federal agencies and stakeholders has announced a new prize competition to collect innovative ideas for addressing nutrient overloads.

The challenge aims to identify next-generation solutions from across the world that can help with excess nutrient reduction, mediation and elimination. The total payout will be $15,000, with no award smaller than $5,000. Proposals can range from completely developed ideas to exploratory research projects.

Ideas will be judged on a range of criteria, including technical feasibility and strategic plans for user adoption. Additionally, the challenge entries will inform the partnership members’ broader commitment and vision to find new ways to approach this decades-long problem.

Submit your idea today!

About the Author: Dustin Renwick works as part of the innovation team in the EPA Office of Research and Development.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action.

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