Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Underwater grass comeback bodes well for Chesapeake Bay

03.09.2014

The Susquehanna Flats, a large bed of underwater grasses near the mouth of the Susquehanna River, virtually disappeared from the upper Chesapeake Bay after Tropical Storm Agnes more than 40 years ago. However, the grasses mysteriously began to come back in the early 2000s. Today, the bed is one of the biggest and healthiest in the Bay, spanning some 20 square miles. A new study by scientists at the University of Maryland Center for Environmental Science explores what's behind this major comeback.

"This is a story about resilience," said Donald Boesch, president of the University of Maryland Center for Environmental Science. "It's a powerful example of how organisms in ecosystems once given a chance can make themselves resistant to stresses and changes."


After a decades long absence, the under water grasses in the upper Chesapeake Bay are back.

Credit: University of Maryland Center for Environmental Science

Underwater grasses are important to the Bay because they provide habitat for juvenile fish and enhance water clarity by trapping and removing sediment from the water. Historically extolled by trophy fisherman and waterfowl enthusiasts as prime wildlife habitat, researchers believe that the underwater grass beds at the shallow Susquehanna Flats began to decline in the 1960s when polluted runoff from a rapidly developing watershed overwhelmed the Bay's waters with nutrients, causing algae blooms that blocked out much-needed sunlight for underwater plants.

"Underwater grasses are sensitive to water quality so they are a direct indicator of the Bay's health," said lead-author Cassie Gurbisz of the Center's Horn Point Laboratory. "The fact that they came back means something good is happening. It's important, however, for us to understand how they came back so we can use that information to support restoration in other areas."

With SAV already stressed by nutrient pollution, it was Tropical Storm Agnes in 1972—a three-day weather event in June that dumped up to 19 inches of rain on the region and an estimated 30 million tons of sediment into the Chesapeake Bay—that was the final blow that destroyed the bed. A torrent of polluted floodwaters and sediment overwhelmed the beds, and the submerged plants virtually disappeared for nearly three decades. That is until the early 2000s when the underwater grasses, also called submerged aquatic vegetation (SAV), rapidly recolonized nearly the entire region.

"This was a large and abrupt resurgence. The Susquehanna Flats SAV bed is gigantic--the largest in the Chesapeake, with multiple species of grasses," said Professor Michael Kemp. "When you're out on the Flats in summer at low tide, you see these plants at the water surface all around you, and it's a truly awe inspiring scene."

It was clear that the extreme flood event following Tropical Storm Agnes triggered the historic demise of the grasses at Susquehanna Flats, however the extended absence of SAV for over 30 years—and the rapid comeback in the last decade—was puzzling to scientists. Researchers analyzed recent and historical data to try to develop a model that explains this resurgence. Monitoring programs throughout the years provided a wealth of information on underwater grasses (since 1958), water quality (since 1984) and even climate-related variables, such as temperature and rivers discharge dating back to the late 1800s.

Researchers found that modest reductions in nutrient pollution to the Bay beginning in the late 1980s had led to long-term improvements to water clarity and the amount of light available for plants to grow underwater. A dry period from 1997-2002 combined with the absence of major storm events provided ideal conditions for new plant growth, and a critical threshold for the amount of light reaching the plants was crossed. As a result, the bed began to expand and colonize deeper water.

"Exceptional growing conditions during the drought period allowed the system to overcome turbid water and served to kick start a rapid resurgence," said Cassie Gurbisz. "Light availability is the most important factor in the growth of submersed plants."

Then the plants took over with a process called positive feedback. That is, once given a chance, grass beds can improve their own growing conditions by helping sediment drop to the bottom and stay there (increasing the amount of sunlight that can reach their leaves), and using excess nutrients in the water to grow. The researchers found lower nitrogen concentrations and less turbidity in the grass beds than the surrounding waters.

These feedbacks also affect a plant bed's resilience, or its ability to resist disturbances such as storms and rebound after they pass. The researchers note that in the decade before Tropical Storm Agnes, the bed was deteriorating. As a result, feedbacks were not very strong and the bed was unable to stand up to Agnes. The present bed is, evidently, more resilient. When major floodwaters flowed from the Susquehanna River in Fall 2011, a portion of the bed was lost. However, the remaining bed has continued to thrive and expand.

"These processes and patterns are not unique to Susquehanna Flats. Similar trends have been suggested for the Mid-Atlantic Coastal Bays and Northern Europe alike," said Kemp. "Our broader motivation lies in the idea that the methods and models used here can be applied elsewhere to explore similar plant bed dynamics around the world."

The paper, "Unexpected resurgence of a large submersed plant bed in Chesapeake Bay: Analysis of time series data," by Cassie Gurbisz and Michael Kemp of the University of Maryland Center for Environmental Science's Horn Point Laboratory, was published in the March 2014 issue of Limnology and Oceanography.

###

Univertsity of Maryland Center for Environmental Science The University of Maryland Center for Environmental Science unleashes the power of science to transform the way society understands and manages the environment. By conducting cutting-edge research into today's most pressing environmental problems, we are developing new ideas to help guide our state, nation, and world toward a more environmentally sustainable future through five research centers—the Appalachian Laboratory in Frostburg, the Chesapeake Biological Laboratory in Solomons, the Horn Point Laboratory in Cambridge, the Institute of Marine and Environmental Technology in Baltimore, and the Maryland Sea Grant College in College Park. http://www.umces.edu

Amy Pelsinsky | Eurek Alert!

More articles from Ecology, The Environment and Conservation:

nachricht Bioinvasion on the rise
15.02.2017 | Universität Konstanz

nachricht Litter Levels in the Depths of the Arctic are On the Rise
10.02.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Switched-on DNA

20.02.2017 | Materials Sciences

Second cause of hidden hearing loss identified

20.02.2017 | Health and Medicine

Prospect for more effective treatment of nerve pain

20.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>