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Chesapeake Bay News

Archives: October 2007


Fresh or Salty? Bay's Salinity Makes a Big Difference to Underwater Life

Have you ever noticed that the air smells salty in some places on the Chesapeake Bay, while in others it does not? The salt you smell has to do with the salinity, or amount of salt, in the water you're near.

On the upper Bay in Maryland, where the Bay's salinity is lowest, you probably won't smell that “ocean” smell. But near the mouth of the Bay in Virginia, where salinity is highest, the air may smell very salty.

Of course, this “salty air” test isn't exactly scientific. Salinity is scientifically defined as the number of grams of dissolved salts present in 1,000 grams of water. It is usually expressed in parts per thousand (ppt).

Fresh water contains few salts (less than 0.5 ppt) and is less dense than full ocean-strength sea water, which averages 25 to 30 ppt.

The Chesapeake Bay's salinity is highest at its mouth, where sea water from the Atlantic Ocean enters. As you head north in the Bay, salinity gradually decreases.

Water with salinity greater than 0.5 ppt but less than 25 ppt is called brackish, meaning a combination of salt water and fresh water. Most of the water in the Chesapeake Bay is brackish.

On a map, salinity contours called isohalines mark the salt content of surface waters. Isohalines tend to show a southwest-to-northeast tilt for two reasons:

The greatest volume of fresh water enters the Bay from its northern and western tributaries, such as the Susquehanna and Potomac rivers.

The earth's rotation causes a phenomenon called the Coriolis Force. Flowing water in the Northern Hemisphere deflects to the right, which means that saltier water moving up the Bay veers towards the Eastern Shore. Therefore, water near the Eastern Shore is saltier than water on the western side of the Bay.

Salinity in the Chesapeake Bay fluctuates depending on precipitation and the season. In drought years, such as 2007, salinity increases because less fresh water flows from the Bay's rivers. This can have both mixed effects on Bay species like oysters, blue crabs and underwater bay grasses.

Oysters have higher spat sets in years when salinity is high. However, MSX and Dermo, the two diseases that have ravaged Bay oyster populations, also flourish in saltier waters.

When more sea water enters the lower Bay and creeps northward, crabs migrate to the upper reaches of the Bay and the headwaters of rivers to escape the high salinity. This northerly migration can benefit crab reproduction, as females lay their egg masses further up the Bay rather than near the ocean. Their location, coupled with decreased fresh water flow, allows crab larvae to stay closer to the Bay, where they are more likely to survive than if they were swept out into the ocean.

Dramatic changes in Bay salinity can have adverse effects on bay grasses because most species specifically require either salty, brackish or fresh waters to grow. Since bay grasses cannot migrate with changing salinity, they ultimately die.

So the next time you're by the Bay — whether at the beach, on a boat or in your neighborhood — take a deep breath and enjoy the salty (or not-so-salty) smell of the air. While it may simply be a breeze for you, the amount of salt you smell means a lot to the critters living below the water's surface.

Keywords: salinity

EPA Inspector General Releases Evaluation on Growth in Bay Watershed

The U.S. Environmental Protection Agency, Office of Inspector General (IG) released on Sept. 10 an evaluation report stating that development growth in the Bay watershed is outpacing Bay restoration efforts. The report was written in response to Congressional requests to evaluate how well the EPA is assisting its Chesapeake Bay partners in restoring the estuary.

The Bay watershed's population is over 16.5 million and growing by more than 170,000 residents annually. The rapid rate of population growth and related residential and commercial development means that this is the only pollution sector in the Bay watershed that is still growing.

In the Bay Program's 2006 Bay Health and Restoration Assessment, it was estimated that increases in pollution due to development have surpassed the gains achieved to date from improved landscape design and stormwater management practices. This estimation from Bay Program scientists has now been corroborated by the IG report.

To combat the increase in pollution from development in the Bay watershed, Bay Program partners are focusing restoration efforts on reducing nutrient and sediment runoff from new development.

Pennsylvania and Virginia have been revising their stormwater regulations.

Maryland Gov. Martin O'Malley recently signed a new stormwater law, and the Maryland Department of the Environment is now working on regulatory actions it will need to put in place to comply with the new Maryland law.

The IG report listed two main recommendations for reducing nutrient and sediment loads from developing lands.

The Chesapeake Bay Program Office director should prepare a strategy to:

  • Demonstrate leadership to reverse the trend of increasing pollution from developing lands.
  • Work with Bay Program partners to set realistic, community-level goals for reducing pollution from developed and developing lands.
  • The EPA's Water Protection Division director, with delegated states, should establish a documented permitting approach to achieve greater nutrient and sediment reductions in Bay watershed Municipal Separate Storm Sewer System (MS4) permits.

Download the full IG evaluation report from the EPA website.


New Reports Detail Potential Impacts of Biofuel Production, Global Warming on Bay

Two reports released in September detail the wide-ranging potential effects of biofuel production and global warming on the future of the Bay and its watershed.

  • Earlier in the month, the Chesapeake Bay Commission released Biofuels and the Bay, which presents the possible effects of increased corn production for biofuels on the Bay's farms, forests and waters.
  • This week, the National Wildlife Federation released The Chesapeake Bay and Global Warming, which focuses on the effects that global warming could have on the Bay region's fish, bird, wildlife habitat and coastal lands.

Biofuels and the Bay: Getting it Right to Benefit Farms, Forests and the Chesapeake

America 's desire to reduce greenhouse gases and become energy independent has turned our attention toward biofuels, a category of alternative energy products made from crops, such as corn, and other organic sources. However, if increased corn production in the Bay watershed is not handled correctly, more nutrients could flow into our already over-enriched Bay and rivers.

Biofuels and the Bay discusses what needs to be done to develop a “best strategy” for biofuels in the Bay region, as well as:

  • The current focus on grain-based ethanol and the developing technology to produce cellulose-based ethanol.
  • The possibility of burning poultry litter to generate heat and electricity and capturing methane from hog and dairy waste to produce biofuel products.
  • The potential for producing biodiesel from soybeans, canola and poultry fat.

Download Biofuels and the Bay from the Chesapeake Bay Commission website.

The Chesapeake Bay and Global Warming: A Paradise Lost for Hunters, Anglers, and Outdoor Enthusiasts?

Over the past 25 years, billions of dollars have been invested in restoration activities across the Bay watershed. But global warming may make it harder for Bay restoration partners to reach their conservation goals. The National Wildlife Federation synthesizes the many ways that fish and wildlife in the Bay region will be affected by global warming, including loss of coastal habitat, altered migration patterns and more aquatic diseases.

The Chesapeake Bay and Global Warming offers solutions and recommendations to reduce the impact of global warming on the Bay's habitats and wildlife, including:

  • Reducing global warming pollution.
  • Providing adequate and dedicated funding for species and habitat conservation.
  • Conserving land and managing new development in the face of global warming.
  • Government and citizen action to protect the Bay's resources for future generations.

Download The Chesapeake Bay and Global Warming from the National Wildlife Foundation Web site.

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