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Bay Grasses

Overview

Bay grasses are plants that grow underwater. Also known as submerged aquatic vegetation or SAV, bay grasses can be found in the shallow waters of the Chesapeake Bay and its streams, creeks and rivers, and are a critical part of the Bay ecosystem. They provide wildlife with food and habitat, add oxygen to the water, absorb nutrient pollution, trap sediment and reduce erosion. Improving water clarity is the most important step in bay grass restoration, because bay grasses need sunlight to grow.

Because bay grasses are sensitive to pollution but quick to respond to improved water quality, their abundance is a good indicator of Bay health. You can watch changes in bay grass abundance take place over time using this interactive map.

What are bay grasses?

Bay grasses are plants that grow underwater. They can be found in the shallow waters of the Chesapeake Bay and its streams, creeks and rivers, and are a critical part of the Bay ecosystem.

Bay grasses are also known as submerged aquatic vegetation or SAV.

Why are bay grasses important?

Bay grasses provide food and habitat to a number of wildlife species and produce oxygen that underwater animals need to survive. Bay grasses keep water clear and healthy by absorbing nutrient pollution, trapping floating particles of sand, silt and sediment, and reducing erosion.

Bay grasses also act as an excellent measure of Chesapeake Bay health. Although bay grasses are sensitive to pollution, they respond fairly quickly to improvements in water quality. This means their abundance is a good indicator of restoration progress.

You can watch changes in bay grass abundance take place over time using this interactive map.

Bay grasses provide food, habitat and oxygen

Bay grass beds provide food and shelter to a number of wildlife species, many of which depend on each other for survival.

  • Microscopic zooplankton feed on decaying bay grasses, ridding grass beds of waste. In turn, these zooplankton become food for larger critters.
  • Small invertebrates–including barnacles, sponges, sea slugs and sea squirts–feed on and attach themselves to bay grass stems and leaves. Small crustaceans consume harmful algae that might otherwise grow on bay grasses and stunt their growth.
  • Young crabs and fish–including spot, croakers, weakfish, Atlantic menhaden, white perch and American shad–find protective nurseries in bay grass beds. Scientists have found 30 times more juvenile blue crabs in bay grass beds than in areas with no bay grasses.
  • Small fish dart between bay grasses as they hunt for prey and hide from predators.
  • Molting blue crabs seek refuge in bay grass beds while their soft shells make them vulnerable to predation.
  • Migratory waterfowl feed on bay grasses and the animals that live in bay grass beds.

Bay grasses also add oxygen to the water during photosynthesis. Underwater critters need oxygen to survive.

Bay grasses keep the water clear and healthy

Bay grass beds help keep the Chesapeake Bay clean and healthy.

  • Bay grasses absorb excess nutrients like nitrogen and phosphorous.
  • Bay grass beds trap floating particles of sand, silt and sediment, which might otherwise cloud the water and suffocate shellfish.
  • Bay grass beds reduce erosion by slowing water currents, anchoring bottom sediment in place and softening waves that break along the shoreline.

How do bay grasses grow?

Just like plants on land, bay grasses go through photosynthesis to convert sunlight into food. Sunlight, therefore, is the most important factor determining bay grass survival. Water must be clear enough for sunlight to pass through it and reach the bay grasses that grow on the bottom of rivers, streams and the Chesapeake Bay.

How does pollution affect bay grasses?

Bay grass growth is hindered by pollutants that cloud the water. These pollutants include excess nutrients, which fuel the growth of dense algae blooms, and suspended particles of sand, silt and sediment.

Healthy bay grass beds can trap and absorb some of this nutrient and sediment pollution, but too much of it can block sunlight from reaching the plants.

How does weather affect bay grasses?

Extreme weather, including high temperatures or excess rainfall, can harm bay grasses.

Temperature

Some bay grass species, including eelgrass, cannot grow in water that is too warm. In 2005, high temperatures caused large beds of eelgrass in the lower Chesapeake Bay to die. It can take several years for bay grass beds to recover from these kinds of large-scale losses.

Precipitation

Precipitation—and the water-clouding pollution it pushes into rivers and streams—is a big influence on bay grass growth.

  • Higher than average rainfall can push nutrient and sediment pollution into the Bay and its rivers and streams. In 2012, scientists recorded a 21 percent decline in bay grass abundance, attributed in part to the strong storms—like Hurricane Irene and Tropical Storm Lee—seen in the late summer and fall of 2011.
  • Lower than average rainfall can result in clearer water, which can boost bay grass growth.

How are bay grasses being restored to the Chesapeake Bay?

Modern science allows researchers to target bay grass restoration to those areas where grasses once grew. But poor water quality, irregular weather and a lack of funding have slowed restoration progress.

Chesapeake Bay Program partners use four initiatives to restore and maintain the health of bay grass beds: improving water clarity, planting bay grasses, protecting existing bay grass beds and enhancing bay grass-related education and outreach.

Improving water clarity

Improved water clarity is critical to bay grass restoration because clouded water can block sunlight from reaching aquatic plants. When water is clear, more sunlight can reach the bottom of rivers, streams and the Chesapeake Bay, fueling the growth of new bay grasses and the expansion of existing grass beds.

Maryland, Virginia and the District of Columbia have outlined water clarity standards for the shallow waters where bay grasses grow or once could be found. These standards list the amount of sunlight that must be able to pass through the water.

Pollution reduction efforts—including the Bay “pollution diet”—aim to slow the flow of nutrients and sediment into the Bay and its waterways. Upgrades to wastewater treatment plants and on-farm conservation practices, for example, are expected to improve water clarity.

Planting bay grasses

Although bay grasses can naturally colonize an area faster than we can spread them through planting, planting bay grasses can lead to restoration success, enhancing the natural expansion of healthy grass beds.

The Maryland Department of Natural Resources (DNR), for instance, led two large-scale eelgrass restoration projects on the Patuxent and Potomac rivers between 2003 and 2007. Scientists found that distributing seeds collected from healthy grass beds elsewhere could accelerate the natural expansion of weaker eelgrass beds. Scientists need sustained funding and adequate plant and seed supplies to continue this kind of work.

Protecting existing bay grass beds

Bay grass beds can be damaged by a number of things, including human activities, invasive species and climate change.

  • Shellfish dredges and boat propellers can pull bay grasses up from the bottom of rivers, streams and the Bay. In shallow waters, “scars” from these human activities are often visible across grass beds.
  • Invasive species can threaten existing bay grass beds. Mute swans, for instance, can eat more than eight pounds of bay grasses in a single day, pulling plants up from their roots and depleting entire grass beds. Water chestnut floats on the water’s surface, blocking sunlight from reaching grasses growing underneath.
  • The rising temperatures that accompany climate change could make the Bay an unsuitable habitat for certain bay grass species. The flooding and shoreline erosion that accompany sea level rise could lead to a further decline in water clarity.

Enhancing bay grass education and outreach

A number of organizations are teaching citizens about bay grass importance.

Take Action

For Chesapeake Bay restoration to be a success, we all must do our part. Our everyday actions can have a big impact on the Bay. By making simple changes in our lives, each one of us can take part in restoring the Bay and its rivers for future generations to enjoy.

To support bay grasses in the Bay watershed, boaters can follow posted speed limits and no-wake laws to avoid harming bay grass beds. Boaters can also steer clear of bay grasses growing in shallow waters.

Photos



 

Chesapeake Bay News

In The Headlines


Underwater Bay Grass Abundance (Baywide)

In 2013, there were an estimated 59,927 acres of underwater grasses in the Chesapeake Bay. This marks an increase of almost 12,000 acres since 2012 and an achievement of 32 percent of the 185,000-acre goal.


Underwater Bay Grass Density

In 2013, there were an estimated 59,927 acres of underwater grasses in the Chesapeake Bay. High-density beds accounted for 60 percent of the total acreage, which is a 12 percent increase from 2012.

The densities of the grass beds growing in 2013 are as follows:

  • 60 percent of the beds had densities of 70 to 100 percent
  • 19 percent of the beds had densities of 40 to 70 percent
  • 13 percent of the beds had densities of 10 to 40 percent
  • Eight percent of the beds had densities of less than 10 percent

Planting Underwater Bay Grasses

In 2013, 1 acre of underwater bay grass was planted, bringing the total to 173 acres planted since 2003.



Bay 101: Bay Grasses



September 08, 2010

Bay grasses, also known as submerged aquatic vegetation, are an integral part of the Chesapeake Bay ecosystem. Lee Karrh from the Maryland Department of Natural Resources (DNR) explains what bay grasses need to grow and why their survival is important to Bay critters.

Produced by Matt Rath
Music: “A Moment of Jazz” by Ancelin

Chesapeake Unscripted: What is Submerged Aquatic Vegetation? (Baltimore, Md.)



January 05, 2011

What is submerged aquatic vegetation, and why is it important to the Chesapeake Bay?  Commonly known as “bay grasses” they among the most critical inhabitants of the Bay’s ecosystem.  Find out more about submerged aquatic vegetation, and see what people around Baltimore’s Belvedere Square had to say about it.

Produced by Matt Rath
Music: “Neapolitan song” by Astrid & Ruediger Kramer
“2 percenter” by Williamson
“All of Me” by Double F


Publications

Underwater Bay Grasses in the Chesapeake Bay and Rivers in 2011

Publication date: March 28, 2012 | Type of document: Backgrounder | Download: Electronic Version

In 2011, 57,956 acres of underwater bay grasses in Chesapeake Bay and its tributaries were mapped via aerial survey.
However, while the entire Bay was flown, some portions of the Bay were not mapped since SAV signatures were
masked by…

Underwater Bay Grasses in the Chesapeake Bay and Rivers in 2010

Publication date: April 21, 2011 | Type of document: Backgrounder | Download: Electronic Version

In 2010, 79,675 acres of underwater bay grasses were mapped in Chesapeake Bay and its tributaries.

Underwater Bay Grasses in the Chesapeake Bay and Rivers in 2009

Publication date: April 27, 2010 | Type of document: Backgrounder | Download: Electronic Version

In 2009, 85,899 acres of underwater bay grasses were mapped in Chesapeake Bay and its tributaries. This is a 12 percent increase from 2008, when 76,860 acres were mapped.

Underwater Bay Grasses in the Chesapeake Bay and Rivers in 2008

Publication date: April 29, 2009 | Type of document: Backgrounder | Download: Electronic Version

Backgrounder: Underwater Bay Grasses in the Chesapeake Bay and Rivers in 2008

Strategy to Accelerate the Protection and Restoration of Submerged Aquatic Vegetation in the Chesapeake Bay

Publication date: December 01, 2003 | Type of document: Policy Memorandum | Download: Electronic Version

This document presents a strategy to accelerate the protection and restoration of submerged aquatic vegetation, or SAV, in the Chesapeake Bay and its tidal tributaries.

Chesapeake Bay Underwater Grasses

Publication date: September 22, 2003 | Type of document: Backgrounder | Download: Electronic Version

Bay grasses are a unique yardstick for measuring the progress of Chesapeake Bay restoration efforts because they are not under harvest pressure and their health is closely linked to water quality. In recent years both the health and…

2002 Chesapeake Bay SAV Abundance and New Baywide Restoration Goal

Publication date: September 22, 2003 | Type of document: Backgrounder | Download: Electronic Version

In 2002, SAV coverage reached a record 89,658 acres - more than twice the level first recorded in 1978. While this increase is impressive, a great deal more needs to be done to reach the Bay Program’s new 185,000-acre baywide restoration…

SAV 2000 Survey: Preliminary Executive Summary

Publication date: May 01, 2001 | Type of document: Backgrounder | Download: Electronic Version

The distribution of submerged aquatic vegetation (SAV) in Chesapeake Bay, its tributaries, and the coastal bays of the Delmarva Peninsula, was mapped from 2,033 black and white aerial photographs. These were taken between May and October…

SAV 2000 Survey: Preliminary River Segment Data

Publication date: May 01, 2000 | Type of document: Backgrounder | Download: Electronic Version

Number of Hectares of SAV in 1999 and 2000 and Percent Change for Chesapeake Bay Segments and Zones




From Around the Web

Bay FAQs

  • How does a loss of bay grasses affect other parts of the Chesapeake Bay?
  • How do people cause bay grasses to die?
  • Why do bay grasses die?
  • How do bay grasses grow underwater?
  • How do animals depend on bay grasses?
  • How can people save bay grasses?
  • How does temperature affect the growth of bay grasses?
  • How many types of bay grasses grow in the Chesapeake Bay?
  • Why are bay grasses important?
  • What are bay grasses?

 

Bay Terms

  • Ecosystem
  • Erosion
  • Molt
  • Nutrients
  • Photosynthesis
  • Precipitation
  • Sediment
  • Submerged aquatic vegetation (SAV)
  • Zooplankton

 

Bay-Friendly Tips

  • Avoid Bay Grass Beds
  • Steer clear of bay grass beds in shallow waters to avoid harming this critical habitat and food source.
  • Fertilize in the Fall
  • If you need to fertilize your lawn, do it in the fall. Spring rains wash fertilizer off lawns and into local waters.
  • Observe Wake Laws
  • Follow speed limits and no-wake laws to avoid churning up sediment, harming underwater grasses and speeding up erosion on nearby shorelines.

 

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