Health of U.S. Streams Reduced by Streamflow Modifications and Contaminants plus 1 more

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Title: USGS Newsroom

Health of U.S. Streams Reduced by Streamflow Modifications and Contaminants plus 1 more

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Health of U.S. Streams Reduced by Streamflow Modifications and Contaminants

Posted: 11 Jul 2013 06:42 AM PDT

 

A new USGS report describes how the health of our Nation’s streams is being degraded by streamflow modifications and elevated levels of nutrients and pesticides.

The national assessment of stream health was unprecedented in the breadth of the measurements—including assessments of multiple biological communities as well as streamflow modifications and measurements of over 100 chemical constituents in water and streambed sediments.

"Healthy streams are an essential part of our natural heritage. They are important to everyone — not only for recreation and for public water supply and public health, but also for economic growth," said USGS acting Director Suzette Kimball. "A broad understanding of the complex factors that affect stream health across the Nation will aid us in making efficient, long term decisions that support healthy streams."

 

The ability of a stream to support algal, macroinvertebrate, and fish communities is a direct measure of stream health. USGS image. (High resolution image)

To assess ecological health, USGS scientists examined the relationship of the condition of three biological communities (algae, macroinvertebrates, and fish) to man-made changes in streamflow characteristics and water quality. The ability of a stream to support these biological communities is a direct measure of stream health.

Stream health was reduced at the vast majority of streams assessed in agricultural and urban areas. In these areas, at least one of the three aquatic communities was altered at 83 percent of the streams assessed.

In contrast, nearly one in five streams in agricultural and urban areas was in relatively good health, signaling that it is possible to maintain stream health in watersheds with substantial land and water-use development.

"Understanding the interacting factors that impact multiple aquatic communities is essential to developing effective stream restoration strategies," said Daren Carlisle, USGS ecologist and lead scientist of this study.

Streamflow modification is a critical factor in stream health because the life cycles of many native fish species are synchronized with—and therefore dependent upon—the timing and variation in natural streamflow patterns.

Annual low and high streamflows were modified in 86 percent of the streams assessed. Over 70,000 dams and diversions contribute to modified streamflows across the Nation. Flood control structures in the East and groundwater withdrawals for irrigation and drinking water in the arid West also contribute to streamflow modification.

Biological alteration associated with elevated nutrient concentrations was most pronounced for algal communities. The occurrence of altered algal communities increased by as much as 40 percent above baseline in streams with elevated nitrogen and phosphorus concentrations.

Macroinvertebrate communities were altered by as much as 40 percent above baseline conditions in streams with elevated pesticide toxicity. Although concentrations of insecticide mixtures, such as chlorpyrifos, carbaryl, and diazinon, in streams are highly variable seasonally and from year to year, they can reach levels that are harmful to aquatic life, particularly in agricultural and urban streams.

Ecological Health in the Nation's Streams, 1993-2005 (USGS Circular 1391, 132 pp.) is available online.

Learn more about the ecological health of the Nation’s streams from related USGS reports, a fact sheet, and a video on our website. The site also features educational illustrations of natural, agricultural, and urban stream ecosystems (PDF format, suitable for posters).

This study was done by the USGS National Water-Quality Assessment Program, which conducts regional and national assessments of the nation’s water quality to provide an understanding of water-quality conditions, whether conditions are getting better or worse over time, and how natural processes and human activities affect those conditions.

The USGS also continuously monitors water levels and streamflows at thousands of the nation's streams on a real-time basis. These data are available at USGS Current Streamflow Conditions. Water-quality data from more than 1,300 locations, much of it in real-time, are available through USGS Water Quality Watch.

New Approach to Measuring Coral Growth Offers Valuable Tool for Reef Managers

Posted: 10 Jul 2013 10:13 AM PDT

Finds surprising growth patterns in the Florida Keys

Report is available on-line via open access at the publisher. View the abstract on the SpringerLink website.

Photo of SCUBA diver working on a clacification station at Fowey Rocks, Biscayne National Park, Florida: Photo credit: Carlie Williams (USGS). (High resolution image)

ST. PETERSBURG, Fla. — A new more sensitive weight-based approach for monitoring coral growth in the wild has been developed by U.S. Geological Survey researchers leading to more definitive answers about the status of coral reefs.

Corals and other marine organisms build their skeletons and shells through calcification, the biological process of secreting calcium carbonate obtained from ocean water. This new approach to measuring corals can provide finer-scale resolution than traditional linear measurements of coral growth. 

"A coral may grow two millimeters in height on the left side of the colony and five millimeters on the right, so linear measurements are inherently variable and require sampling hundreds of corals to detect changes in growth over time… our method requires only 10 corals per site," said Ilsa Kuffner, USGS scientist and lead author of the study.

Using the weight-based approach, Kuffner's team discovered that colonies of the Massive Starlet coral calcified about 50 percent faster in the remote Dry Tortugas National Park compared to three sites along the rest of the island chain from Miami to Marathon, Fla. The reasons behind this surprising pattern are not clear, leaving a mystery sure to pique the interest of many reef managers.

The new approach could be highly useful to managers because it can detect small changes over space and time due to its high level of precision. Also, the method uses inexpensive and easy-to-find materials, and no corals are harmed in the process.  

"This tool provides the kind of scientific information needed to manage coral reefs at the ecosystem scale by looking at the relationships between coral health, climate change, and water-quality. It provides partners and reef managers with better, more sensitive metrics to assess coral growth, identify the most important variables, and prioritize strategies to protect and preserve these valuable ecosystems," said Acting USGS Director, Suzette Kimball. "It is also one of the ways USGS science is advancing the National Ocean Policy by supporting a number of on-the-ground priority actions."

A next step in understanding declines in coral growth is discerning the different components of water-quality that are driving calcification rates, and this can only be achieved through the cooperation of reef managers and scientists around the world. The real power in the new approach will be realized if it is applied across many reefs that naturally have different temperature regimes, water quality, and pH conditions. 

"The study results suggest that we should pay more attention to different aspects of water-quality if we hope to understand and predict what will happen to coral reefs as oceans continue to change," said Kuffner. 

According to Kuffner, managers already know coral reefs are in decline, but they want to know why. They need a linkage between cause and effect that explains why reefs are not growing like they used to or are not recovering from disease or die-off events. Correlating finely measured coral growth rates with water quality and other environmental information is an important step to making these linkages so they can inform management decisions. 

Photo of coral: Massive Starlet coral, Siderastrea siderea Photo credit: Ilsa B. Kuffner (USGS) (High resolution image)

Coral reefs are in decline globally with the National Oceanic and Atmospheric Administration currently proposing to list 66 reef-building coral species under the Endangered Species Act. Identifying the cause of the decline is not straightforward. Oceanographic instruments have confirmed that the ocean is warming, acidifying, and changing in other aspects of water quality. The first two are a direct result of altered carbon distribution due to burning of fossil fuels; the latter stems largely from land-use changes. Laboratory studies demonstrate that all three of these environmental stressors can hinder coral growth, but linking the causative agents to reef decline in the natural environment requires dependable, precise methods to detect change over time. 

This study is part of a larger USGS Coral Reef Ecosystem Studies project aimed at understanding the status, construction, and resilience of shallow-water reef environments and forecasting future change to inform reef management strategies. Current areas of research include the Dry Tortugas, U.S. Virgin Islands and Biscayne National Parks, and selected areas of the Florida Keys National Marine Sanctuary.

To learn more about the Coral Reef Ecosystem Studies Project, please visit the website.