James River a Bright Spot in Disappointing Year for Bay Grasses

By Bill Street, Executive Director

The Virginia Institute of Marine Science (VIMS) has just issued its latest report on submerged aquatic vegetation or SAV in the Chesapeake Bay region. This report is based on aerial photos and comparisons over time. The news for the Bay is fairly disappointing: the total area of grass is down 22 percent throughout the Chesapeake Bay. This marks the second consecutive year that grasses have declined. To put it in perspective, according to the report, more then a quarter of the 85,500 acres of submerged grasses tracked in a 2009 survey no longer exist.

However, there is also good news on our home river: grasses in the tidal portion of the James River are up 14 percent. This is the highest level since the annual surveys started in 1978 and represents 54 percent of the restoration goal for grasses in the James.

A couple factors are worth noting. First, the James did not receive as much torrential rain and flooding as the Chesapeake waters to the north. In fact, the annual average flow for the James was 14 percent below the long-term average. This means that the river did not receive the same level of polluted runoff as the other parts of the bay and tributaries. Also, the grasses on the James continue to be concentrated in the tidal creeks and tributaries to the river where the surrounding land use is largely forest, wetlands and agricultural lands where farmers are practicing continuous no-till farming.

We are encouraged to note that for the first time in the survey, grass beds were found on the main stem of the tidal James above Newport News. This appears to be an expansion of the beds in the adjacent tidal creeks and provides hope that if water quality on the main stem of the river can be improved that we can get more grasses growing throughout the river.

These underwater grasses are important for a number of reasons. Submerged grasses provide habitat and food for aquatic animals; trap sediment and nutrients; and add oxygen to the water. Therefore, underwater grasses represent one of the most critical elements of the Chesapeake’s diverse ecosystem.  And, like any plant, aquatic grasses require sunlight to grow. Because grasses can only get sufficient sunlight if the water is relatively clear and free of sediment, the presence of grasses is a positive indicator of current river health.

The following graph shows that underwater grasses have made steady and significant progress over the past decade.  Clean water = more grasses = more fish and crabs!