The abundance of total underwater seagrass in the Chesapeake Bay is up 27% from last year. Underwater grasses increased by thousands of acres across all four water ranges (from freshwater, slightly salty, moderately salty, to very salty) in the Bay watershed. There are currently an estimated 75,000 acres of underwater grasses in the Bay, up from 59,711 acres in 2013. The increase in acreage in each salinity zone (amount of salt in the water) is represented in a table below.
While this increase is a vast improvement from previous years, the Bay needs to have an additional 15,000 acres of underwater seagrass to meet 2017 restoration goals, and a further 40,000 acres to meet 2025 goals, set by the Chesapeake Bay Program (CBP). Beyond 2025, the CBP ultimately aims to restore 185,000 acres of underwater grasses in the Bay. Underwater seagrass acreage is gradually increasing in the Bay, but over 100,000 additional acres must be restored to meet CBP standards.
|Zone||2013 Seagrass Acreage||2014 Seagrass Acreage||Zone Goal Achievement (%)|
|Tidal Fresh Salinity||1,320||15,305||74%|
|Oligohaline Salinity (Slightly Salty)||1,800||7,413||72%|
|Mesohaline Salinity (Moderately Salty)||11,850||37,260||31%|
|Polyhaline Salinity (Very Salty)||1,154||15,857||47%|
Bay grass acreage can fluctuate from year to year, due to die-offs from heat waves or major storms, such as Tropical Storm Lee in 2011. Long-term threats to underwater grasses, which have resulted in decades of declining seagrass abundance in the Bay, include nutrient and sediment pollution. Nitrogen, phosphorus, and sediment runoff from agricultural activity and urban stormwater runoff contribute to the declining health and die-off of Bay grasses.
Underwater seagrass plays an important role in the Chesapeake Bay ecosystem. Seagrass provides habitat and sanctuary to various underwater species, such as juvenile blue crabs and finfish. Grasses are able to improve water quality by filtering runoff in the Bay and taking up nutrients that would otherwise contribute to pollution in the watershed. Seagrass protects shorelines from erosion by absorbing wave energy and keeping sediment in place.
The 16,000-acre increase in underwater seagrass abundance in the Bay between 2013 and 2014 is great news. This is a trend that I hope to see continue in years to come. However, restoration, at levels expected by 2025, will not be possible without the Bay states’ cooperation in implementing and enforcing regulations that reduce nitrogen and sediment runoff into the watershed. While 2014 numbers are an improvement from previous years, Bay acreage will continue to fluctuate in years to come, and the only way to create a long-term positive trend in future seagrass abundance is to significantly reduce nitrogen and sediment pollution in the Bay.
Recent findings on Bay seagrass acreage come from the Virginia Institute of Marine Science (VIMS), which has released their annual report on underwater seagrass abundance in the Chesapeake Bay for 2014, (http://www.vims.edu/newsandevents/topstories/sav_2014_report.php).
For more information on underwater seagrass, please see Part III of our Phosphorus in the Chesapeake paper here: https://beyondthebayblog.com/2015/05/07/phosphorus-in-the-chesapeake-part-iii/.