Distribution and abundance of submerged aquatic vegetation in the lower Chesapeake Bay, Virginia (original) (raw)
Related papers
Estuaries, 1984
An historical summary of the distribution and abundance of submerged aquatic vegetation (SAV) in the Chesapeake Bay is presented. Evidence suggests that SAV has generally been common throughout the bay over the last several hundred years with several fluctuations in abundance. The decline of Zosrera marina (eelgrass) in the 1930's and the rapid expansion of Myriopl?yZlum spicutum (watermilfoil) in the late 1950's and early 1960's were two significant events involving a single species. Since 1965, however, there has been a significant reduction of all species in most sections of the bay. Declines were first observed in the Patuxent, Potomac and sections of other rivers in the Maryland portion of the Bay between 1965 and 1970. Dramatic reductions were observed over the entire length of the bay from 1970 to 1975. Particularly severe losses were observed at the head of the bay around Susquehanna Flats as well as in numerous rivers along Maryland's eastern and western shores. Changes in the lower, Virginia portion of the bay occurred primarily in the western tributaries. Greatest losses of vegetation occurred in the years following Tropical Storm Agnes in 1972. Since 1975 little regrowth has been observed in the Chesapeake Bay. Other areas along the Atlantic Coast of the U.S. during the same period have experienced no similar widespread decline. It thus appears that the factors affecting the recent changes in distribution and abundance of submerged vegetation in the bay are regional in nature. Causes for this decline may be related to changes in water quality, primarily increased eutrophication and turbidity. ' Contribution No.
Chesapeake Bay: An Unprecedented Decline in Submerged Aquatic Vegetation
Science, 1983
Data on the distribution and abundance of submerged aquatic vegetation in Chesapeake Bay indicate a significant reduction in all species in all sections of the bay during the last 15 to 20 years. This decline is unprecedented in the bay's recent history. The reduction in one major species, Zostera marina, may be greater than the decline that occurred during the pandemic demise of the 1930's.
Distribution of Submerged Aquatic Vegetation in the Chesapeake Bay and Tributaries - 1984
1985
Crown density scale for estimating SAV bed density Location of 3 zones and 21 major sections in the Chesapeake Bay for delineation of SAV. •. • •. .. • •. Location of quadrangles along transition of Potomac River for SAV study conducted by NVCC. •. • Location of vegetation sampling transects in the tidal and transition portion of the Potomac River conducted by uses in 1983 and 1984. . •. .. .. • • .
Analysis of the Abundance of Submersed Aquatic Vegetation Communities in the Chesapeake Bay
Estuaries, 2000
A procedure was developed using aboveground field biomass measurements of Chesapeake Bay submersed aquatic vegetation (SAV), yearly species identification surveys, annual photographic mapping at 1:24,000 scale, and geographic information system (GIS) analyses to determine the SAV community type~ biomass~ and area of each mapped SAV bed in the bay and its tidal tributaries for the period of 1985 through 1996. Using species identifications provided through over 10,900 SAV ground survey observations, the 17 most abundant SAV species found in the baywere clustered into four species associations: ZOSTERA, RUPPIA~ POTAMOGETON, and FRESHWATER MIXED. Monthly aboveground bioula~ values were then assigned to each bed or bed section based upon monthly biolnass models developed for each COUllnunity. High salinity colnulunities (ZOSTERA) were found to dominate total bay SAV aboveground biomass during winter, spring, and snlnlner. Lower salinity communities (RUPPIA, POTAMOGETON, and FRESHWA-TER MIXED) dominated in the fall. In 1996~ total bay SAV standing stock was nearly 22,800 metric tons at annual maximum biomass in July encompassing an area of approximately 25~670 hectares. Minimum biomass in December and January of that year was less than 5,000 metric tons. SAY annual maximum biomass increased baywide from lows of less than 15~000 metric tons in 1985 and 1986 to nearly 25~000 metric tons during the 1991 to 1993 period, while area increased from approximately 20,000 to nearly 59,999 hectares duriug that same period. Year-to-year comparisons of UlaXiUlUUl annual colnulnuity abundance froul 1985 to 1996 indicated that regrowth of SAV in the Chesapeake Bay froln 1985-1993 occurred principally in the ZOSTERA COUllnunity~ with 85% of the baywide increase in biolna~ and 71% of the increase in area occurring in that COUllnunity. Maximum bioula~ of FRESHWATER MIXED SAV beds also increased from a low of 3,200 inetric tOllk~ in 1985 to a high of 6,650 metric tons in 1993, while inaxiulnul biolnas~ of both RUPPIA and POTAMOGETON beds fluctuated between 2,450 and 4,600 metric tons and 60 and 600 metric tons~ respectively, during that same period with net declines of 7% and 43%~ respectively, between 1985 and 1996. During the July period of annual, baywide, maximum SAV biomass, SAV beds in the Chesapeake Bay typically averaged approximately 0.86 metric tons of aboveground dry mass per hectare of bed area.
Distribution of Submerged Aquatic Vegetation in the Chesapeake Bay and Tributaries - 1985
1986
Effective cooperation by so many different types of governmental agencies in arranging, during a comparatively short developmental time frame, a comprehensive survey-mapping project of this scope is noteworthy. More and more emphasis is being placed on tracking SAV because of its perceived usefulness as an indicator of potential and actual improvement in the Chesapeake Bay's water quality and the correlated balance of living resources. Acknowledgement would not be complete without high commendation for the citizens and Maryland charterboat captains who took part in an unusual pilot program to provide "groundtruthing" of SAV beds to be used in conjunction with interpretation of the 1985 photography. The Citizens' Program for the Chesapeake Bay and the Chesapeake Bay Foundation, together with the U.S. Fish and Wildlife Service, organized nearly 150 citizens to report locations of grass beds around the Bay. In addition, about fifteen members of the Maryland Charterboat Association, funded by Maryland DNR, participated in the ground truthing program and contributed valuable information on location of grassbeds. The entire 1985 program, though arranged on relatively short notice, promised great potential benefits (from both informational and participational standpoints) that an expanded 1986 ground truthing program was organized. vi There are certain people who have made a project like this a real possibility. In addition, the production of such a report required the dedication of numerous technicians, artists and photographers. The following people deserve a note of thanks: Bert Brun,
Submersed Aquatic Vegetation in Chesapeake Bay: Sentinel Species in a Changing World
BioScience, 2017
Chesapeake Bay has undergone profound changes since European settlement. Increases in human and livestock populations, associated changes in land use, increases in nutrient loadings, shoreline armoring, and depletion of fish stocks have altered the important habitats within the Bay. Submersed aquatic vegetation (SAV) is a critical foundational habitat and provides numerous benefits and services to society. In Chesapeake Bay, SAV species are also indicators of environmental change because of their sensitivity to water quality and shoreline development. As such, SAV has been deeply integrated into regional regulations and annual assessments of management outcomes, restoration efforts, the scientific literature, and popular media coverage. Even so, SAV in Chesapeake Bay faces many historical and emerging challenges. The future of Chesapeake Bay is indicated by and contingent on the success of SAV. Its persistence will require continued action, coupled with new practices, to promote a healthy and sustainable ecosystem.