Sources and Fates of Nitrogen in Virginia Coastal Bays

Anderson, Iris C.; Stanhope, Jennifer W.; Hardison, Amber K.; McGlathery, Karen J.

doi:10.1201/ebk1420088304-c3

Cited by 26 publications

(19 citation statements)

References 102 publications

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“…Boynton et al (1996) directly related higher areal nitrogen loading rates (gNm −2 waterbody year −1 ) in the MD bays to degraded water quality, as reflected by elevated concentrations of total nitrogen and chlorophyll-a. Land use surrounding Maryland's Coastal Bays is about 35% agriculture, 54% natural vegetation (including wetlands), and 9% developed (Anderson et al 2010). In contrast, land use throughout Virginia's Eastern Shore is less developed with roughly 38% agricultural area, 59% natural vegetation (including wetlands), and 2% developed (Stanhope et al 2009).…”

Section: Introductionmentioning

confidence: 94%

“…Available data (e.g., McGlathery et al 2007;Anderson et al 2010) show that a regional gradient of nutrient enrichment exists among the coastal bays of the Delmarva Peninsula driven by differences in land use, with generally higher areal nitrogen loading rates in the northern lagoons and lower areal loading rates in the southern lagoons (Table 1). Extensive agriculture and commercial and residential development in the DE and MD coastal watersheds contribute to large annual areal nitrogen loading rates to the receiving coastal lagoons (Boynton et al 1996; Table 1).…”

Section: Introductionmentioning

confidence: 98%

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Quantifying Annual Nitrogen Loads to Virginia’s Coastal Lagoons: Sources and Water Quality Response

Giordano

Brush

Anderson

2010

Estuaries and Coasts

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Coastal lagoons of the Delmarva Peninsula receive varying annual nitrogen loads because of differing land uses. Extensive development and agriculture contribute to elevated nutrient loads in Maryland and Delaware. Agriculture and forests dominate Virginia's landscape, suggesting these systems receive lower loads. We used a watershed model to achieve three objectives: (1) quantify loads to Virginia lagoons; (2) determine the sources of the loads; and (3) project changes in annual loads under different development scenarios. Model simulations indicated that some Virginia lagoons receive relatively high annual nutrient loads (kgNyear −1 ) due to intensive agriculture and a high watershed/lagoon areal ratio. Model projections also suggested that increased agricultural and residential development in Virginia could lead to annual loads (kgN year −1 ) typical of impacted Maryland systems. A comparison of Maryland and Virginia water quality responses to nutrient loading suggested that Virginia's lagoons exhibit a different response to nutrient loading, though the exact mechanism for this difference is unclear.

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Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 98%

Quantifying Annual Nitrogen Loads to Virginia’s Coastal Lagoons: Sources and Water Quality Response

Giordano

Brush

Anderson

2010

Estuaries and Coasts

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“…Median turbidities below 10 NTU were found only after the bed area exceeded 200 ha. At this point, bed expansion accelerated and turbidities continued to decrease to median levels of approximately 4 to 5 NTU in 2008and 2010. In Chesapeake Bay, Moore (2004 found that the effects of Z. marina vegetation on water column suspended sediments, chlorophyll, and light attenuation increased with bed development.…”

Section: Eelgrass Effects On Water Quality and Sedimentsmentioning

confidence: 99%

“…Higher levels (>10 to 15 NTU) have been found closer to the mainland , where R² = 0.9287 (Fig. 7), where there is more effect of watershed loadings (Stanhope et al 2009, Giordano et al 2011) that contribute to the gradient of organic and inorganic constituents observed in the water column (Anderson et al 2010). Higher turbidity levels were also found near the channels separating the different bays.…”

Section: Eelgrass Effects On Water Quality and Sedimentsmentioning

confidence: 99%

“…Here the watersheds are dominated by agriculture and forests, resulting in relatively low nutrient loadings (Anderson et al 2010), in contrast to other coastal bays in Maryland and Delaware, where extensive development and intensive agriculture contribute to elevated loadings (Giordano et al 2011) and enriched conditions (Boynton et al 1996). Similarly, in coastal bay systems including Pamlico Sound, North Carolina, to the south, human activities have resulted in nutrient enrichment and sedimentation (Paerl et al 2010), and in Barnegat Bay, New Jersey, to the north, increased loadings have been linked to seagrass declines (Kennish et al 2010).…”

Section: Eelgrass Effects On Water Quality and Sedimentsmentioning

confidence: 99%

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Seed addition facilitates eelgrass recovery in a coastal bay system

Orth¹,

Moore²,

Marion³

et al. 2012

Mar. Ecol. Prog. Ser.

153

142

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Eleven years of eelgrass Zostera marina seed additions conducted in a coastal bay system where Z. marina had not been reported since 1933 have resulted in rapid Z. marina expansion beyond the initially seeded plots. From 1999 through 2010, 37.8 million viable seeds were added to 369 individual plots ranging in size from 0.01 to 2 ha totaling 125.2 ha in 4 coastal bays. Subsequent expansion from these initial plots to approximately 1700 ha of bay bottom populated with Z. marina through 2010 is attributable to seed export from the original plots and subsequent generations of seedlings originating from those exports. Estimates of annual patch vegetative expansion showed mean estimated diameter increasing at varying rates from 10 to 36 cm yr −1 , consistent with rhizome elongation rates reported for Z. marina. Water quality data collected over 7 yr by spatially intensive sampling, as well as fixed-location continuous monitoring, document conditions in all 4 bays that are adequate to support Z. marina growth. In particular, median chlorophyll levels for the entire sampling period were between 5 and 6 µg l −1 for each of the bays, and median turbidity levels, while exhibiting seasonal differences, were between 8 and 9 NTU. The recovery of Z. marina initiated in this coastal bay system may be unique in seagrass recovery studies because of how the recovery was initiated (seeds rather than adult plants), how rapidly it occurred (years rather than decades), and the explicit demonstration of how one meadow modulated water clarity and altered sediments as it developed and expanded. Our results offer a new perspective on the role seeds can play in recovery dynamics at large spatial scales.

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Seagrass restoration reestablishes the coastal nitrogen filter through enhanced burial

Aoki

McGlathery

Oreska

2019

Limnology & Oceanography

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Seagrass meadows perform an important ecological function as filters for incoming nutrients from surrounding watersheds, especially nitrogen (N). By enhancing N removal processes, including N burial in sediments and denitrification, seagrass meadows improve water quality. With accelerating losses of seagrass meadows worldwide, seagrass restoration plays a key role in reestablishing these coastal ecosystem functions. However, few measurements exist of N burial rates in temperate seagrass meadows and none have been published for restored meadows. In this study, we measured N burial rates in a large (6.9 km2) restored eelgrass (Zostera marina) meadow and compared N removal through burial to previous measurements of removal via denitrification. We also compared N removal to inputs from external loading and fixation and to N assimilation in seagrass biomass. We found that, in this meadow, burial was the dominant process of N removal; the burial rate of 3.52 g N m−2 yr−1 was comparable to rates in natural meadows within 10 yr after seeding and was more than 20× the rate in adjacent bare sediments (0.17 g N m−2 yr−1). We also found that the high rates of N assimilation (2.62 g N m−2 yr−1) created a substantial though temporary sink for nitrogen during the growing season. Our results highlight how seagrass meadows mediate N cycling through high rates of burial, which to date has been understudied in the literature. The successful return of the N filter function after restoration, shown here for the first time, can motivate continued efforts for seagrass restoration and conservation.

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Sources and Fates of Nitrogen in Virginia Coastal Bays

Cited by 26 publications

References 102 publications

Quantifying Annual Nitrogen Loads to Virginia’s Coastal Lagoons: Sources and Water Quality Response

Quantifying Annual Nitrogen Loads to Virginia’s Coastal Lagoons: Sources and Water Quality Response

Seed addition facilitates eelgrass recovery in a coastal bay system

Seagrass restoration reestablishes the coastal nitrogen filter through enhanced burial

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