Friday, July 22, 2022

Bay Grasses Up a Little for 2021

Chesapeake Bay Program, Chesapeake Bay Program notes slight increase in underwater grass abundance

In 2021, an estimated 67,470 acres of underwater grasses were mapped in the Chesapeake Bay and its tidal tributaries, achieving 37% of the ultimate restoration goal of 185,000 acres. However, it is likely that more underwater grasses grew in the Bay in 2021 than the mapped acreage suggests. Adverse weather conditions, such as frequent rain and cloudy water, prevented researchers from successfully collecting imagery over the Mattaponi and Pamunkey rivers.

While underwater grass abundance did increase by almost 9% from 2020 to 2021, the preliminary acreage observed in 2021 is still a slight decrease from the long-term average of 69,623 acres, and approximately a 38% decline from 2018, when it was estimated that the Bay might have supported up to 108,078 acres.

Underwater grass abundance can vary from species to species and river to river. In 2021, local highlights included:

Northern Maryland: Underwater grass abundance in and around the Susquehanna Flats region increased from 9,200 acres in 2020 to 10,331 acres in 2021. However, the Elk River decreased from 613 acres in 2020 to 190 acres in 2021.

Middle and Eastern Chesapeake Bay: Underwater grass acreage in the Little Choptank River continued to decline, dropping from 551 acres in 2020 to 175 acres in 2021. Likewise, the Choptank River to its north decreased its acreage from 4,562 acres in 2020 to 4,132 acres in 2021. The Eastern Bay did not fare much better, declining from 840 acres in 2020 to 507 acres in 2021. On the middle Western shore of the Bay, the Severn and Magothy rivers both saw significant decreases in underwater grass acreage. The Severn declined from 294 acres in 2020 to 227 acres in 2021, while the Magothy decreased from 124 acres in 2020 to 59 acres in 2021.

Mid-to-Lower Chesapeake Bay: In the Virginia portion of the mid-to-lower Bay, underwater grasses did particularly well in the Corrotoman and Rappahannock rivers, as well as in Mobjack Bay. The Rappahannock, which includes the Corrotoman, increased from 2,204 acres in 2020 to 3,235 acres in 2021. In Mobjack Bay, underwater grass acreage increased from 7,440 acres in 2020 to 8,355 acres in 2021.

Grass is quite variable from year to year, with, as usual, weather, not long-term water quality trends  being the culprit in most cases. It is also complicated by the fact that there are numerous grass species in different area, and they are clearly to different factors. That being said, if the long term goal is 180,000 acres, and in a 'good' year, we're achieving 67,000, we're a long way from getting to the 2025 goals for fixing the Bay.

I would like to add, that by personal observation, and comments from Pete, this year, large areas of the middle Bay are showing less grass cover than in a few previous years, so next year might be a set back.

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