A perspective on two decades of policies and regulations influencing the protection and restoration of submerged aquatic vegetation in Chesapeake Bay, USA (original) (raw)
Related papers
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.
2009
Broad declines in Chesapeake Bay submerged aquatic vegetation (SAV) populations that were first observed in the late 1960s and 1970s prompted the initiation of a comprehensive aerial mapping program to assess the status of the resource. This mapping program which began in 1978 has continued on an annual basis since 1984. The imagery used has primarily consisted of high resolution black and white photographs taken at a scale of 1:24,000. Mapping missions have been flown under guidelines addressing frame overlap, tidal stage, seasonal plant development, sun angle, atmospheric transparency, water turbidity and wind speed and direction to maximize SAV bed signatures. Currently 173 flight lines, which cover approximately 3,800 flight line km, are photographed and mapped for SAV each year. Scanned aerial photography images are geo-rectified and orthographically corrected to produce a series of aerial mosaics at 1 m resolution. The SAV beds are interpreted on-screen using in a GIS environment. Extensive ground survey data is also collected to verify the SAV photo-interpretation. A bay wide analysis of SAV distributions since the 1930s was also undertaken with archival aerial photographs using similar procedures to develop a composite historical coverage of SAV. Both the current and historical mapping results have been used for a variety of purposes. The composite historical coverages have been used to set SAV restoration goals and direct SAV restoration efforts. In addition, analyses of the historical SAV growth and bay bathymetry have been used to set seasonal water clarity targets for shallow water historically vegetated SAV areas throughout the bay. Comparisons of current SAV mapping results with historically based restoration targets are used annually to provide important indexes of bay condition and trends that are used to assess the effectiveness of nutrient and sediment reduction strategies for the bay and its watershed. In addition, the photographic imagery and the resultant SAV delineations have been widely used by managers to identify and minimize direct impacts to the SAV.
Estuaries and Coasts, 2010
Chesapeake Bay supports a diverse assemblage of marine and freshwater species of submersed aquatic vegetation (SAV) whose broad distributions are generally constrained by salinity. An annual aerial SAV monitoring program and a bi-monthly to monthly water quality monitoring program have been conducted throughout Chesapeake Bay since 1984. We performed an analysis of SAV abundance and up to 22 environmental variables potentially influencing SAV growth and abundance (1984–2006). Historically, SAV abundance has changed dramatically in Chesapeake Bay, and since 1984, when SAV abundance was at historic low levels, SAV has exhibited complex changes including long-term (decadal) increases and decreases, as well as some large, single-year changes. Chesapeake Bay SAV was grouped into three broad-scale community-types based on salinity regime, each with their own distinct group of species, and detailed analyses were conducted on these three community-types as well as on seven distinct case-study areas spanning the three salinity regimes. Different trends in SAV abundance were evident in the different salinity regimes. SAV abundance has (a) continually increased in the low-salinity region; (b) increased initially in the medium-salinity region, followed by fluctuating abundances; and (c) increased initially in the high-salinity region, followed by a subsequent decline. In all areas, consistent negative correlations between measures of SAV abundance and nitrogen loads or concentrations suggest that meadows are responsive to changes in inputs of nitrogen. For smaller case-study areas, different trends in SAV abundance were also noted including correlations to water clarity in high-salinity case-study areas, but nitrogen was highly correlated in all areas. Current maximum SAV coverage for almost all areas remain below restoration targets, indicating that SAV abundance and associated ecosystem services are currently limited by continued poor water quality, and specifically high nutrient concentrations, within Chesapeake Bay. The nutrient reductions noted in some tributaries, which were highly correlated to increases in SAV abundance, suggest management activities have already contributed to SAV increases in some areas, but the strong negative correlation throughout the Chesapeake Bay between nitrogen and SAV abundance also suggests that further nutrient reductions will be necessary for SAV to attain or exceed restoration targets throughout the bay.
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.
Distribution and abundance of submerged aquatic vegetation in the lower Chesapeake Bay, Virginia
1979
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.
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.