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Long-term non-linear ecosystem-scale changes in water quality and biotic communities in coastal lagoons have been associated with intensification of anthropogenic pressures. In light of incipient changes in Johnson Bay (an embayment of Chincoteague Bay, Maryland-Virginia, USA), examination of nitrogen sources was conducted through synoptic water quality monitoring, stable nitrogen isotope signatures (deltaN-15) of in situ bioindicators, and denitrification estimates. These data were placed in the context of long-term and broader spatial analyses. Despite various watershed protection efforts, multiyear summer time studies (2004-2007) suggested that high levels of terrestrially derived nutrients still enter Johnson Bay. Total nitrogen concentrations in Johnson Bay were 132% the concentrations in the broader Chincoteague Bay during the late 1970s (mean 2004-2007 was 40.0 - 73.2 µM). Comparing total nitrogen concentrations in Johnson Bay to St. Martin River (consistently the most eutrophic region of these coastal bays), Johnson Bay has increased from 62.5% to 82.5% of the concentrations in St. Martin River during the late 1970s. Though specific sources of nitrogen inputs have not yet been definitively identified, the long-term increase in total nitrogen concentrations occurred despite increased and continued conservation and protection measures. We suggest that investigating nutrient sources can reveal potentially ineffective nutrient policies and that this knowledge can be applied towards other coastal lagoons.
', WIDTH, 630, LEFT, true, FONTSIZE, '0.8em', FONTCOLOR, '#000000', PADDING, 10)">Elucidating terrestrial nutrient sources to a coastal lagoon, Chincoteague Bay, Maryland, USAAnthropogenic nitrogen contributes to water quality degradation, but it is difficult to distinguish sources once they are mixed in coastal ecosystems. Natural abundances of stable nitrogen isotopes (deltaN-15) were measured in oyster (Crassostrea virginica) tissues (muscle, gills, and mantle) during summer 2006 to summer 2008 to identify nitrogen sources in Monie Bay (a subestuary of Chesapeake Bay) receiving freshwater inputs from three tributary creeks. The creeks (estimated flushing times: 3.5, 5.7, and 37.2 d) vary in size and potential nitrogen sources: septic systems and poultry operations (Monie Creek), crop fertilizer (Little Monie Creek), and wetlands, forest, or both (Little Creek). Grand mean oyster tissue deltaN-15 values (11.8 ± 0.4‰ in muscle, 10.4 ± 0.4‰ in gills, and 10.5 ± 0.3‰ in mantle) indicated a mixture of human and animal sources. Potential nitrogen loss from denitrification (15.1–24.5%) likely did not substantially modify isotopic values, and deltaN-15 values were greater than would be expected from atmospheric sources, refuting these alternative explanations. Though dilute, spatial patterns supported the inference that human waste, poultry waste, or both entered Monie Bay from its watershed and the adjacent Wicomico River watershed (via mixing). Calculated nitrogen generation from poultry manure in the watershed (containing 2.5 x 10ˆ3 people) was 2.9 x 10ˆ4 to 1.0 x 10ˆ6 kg of total nitrogen (TN) per year (equivalent to 6.8 x 10ˆ3–2.3 x 10ˆ5 people), whereas throughout Delmarva Peninsula (containing 1.2 x 10ˆ6 people) it was 3.9 x 10ˆ6 to 1.3 x 10ˆ8 kg TN yˆ1 (equivalent to 9.0 x 10ˆ5–3.1 x 10ˆ8 people). Conservatively estimated (based on 0.038 kg chickenˆ-1 yˆ-1), poultry in the Monie Bay watershed generated an amount of nitrogen equivalent to that generated by 263% of the human population. Throughout Delmarva Peninsula, poultry generated an amount of nitrogen equivalent to that generated by 76% of the human population. Estuaries commonly receive nutrients from both inside and outside their watersheds, and oyster deltaN-15 values elucidated this process locally.
', WIDTH, 630, LEFT, true, FONTSIZE, '0.8em', FONTCOLOR, '#000000', PADDING, 10)">Oyster deltaN-15 as a Bioindicator of Potential Wastewater and Poultry Farming Impacts and Degraded Water Quality in a Subestuary of Chesapeake Bay Cardinal after blizzard in Cambridge, MD Fallen treen from a blizzard in Cambridge, MD with cardinal (Cardinalis cardinalis) perched on branch ', WIDTH, -400, FONTSIZE,'12px', PADDING, 10)"> | Choptank River sunset with trees Sunset through trees over Choptank River in Maryland ', WIDTH, -400, FONTSIZE,'12px', PADDING, 10)"> | Choptank River sunset Sunset over Choptank River in Maryland ', WIDTH, -400, FONTSIZE,'12px', PADDING, 10)"> | HPL laboratory setup Laboratory setup for HPL open house in Cambridge, MD ', WIDTH, -300, FONTSIZE,'12px', PADDING, 10)"> | HPL open house with touch tank Open house event at HPL in Cambridge, MD with touch tank ', WIDTH, -400, FONTSIZE,'12px', PADDING, 10)"> | Plowed winter road in Cambridge, MD Plowed road during winter in Cambridge, MD ', WIDTH, -400, FONTSIZE,'12px', PADDING, 10)"> |
Acanthaster planci (Crown-of-Thorns starfish) Illustration of Acanthaster planci (Crown-of-Thorns starfish), which preys on corals. ', WIDTH, -400, FONTSIZE,'12px', PADDING, 10)"> | Fale: enclosed 1 (Samoa) Illustration of an enclosed fale. ', WIDTH, -400, FONTSIZE,'12px', PADDING, 10)"> | Gymnomyza samoensis (Ma\'o Ma\'o) Illustration of Gymnomyza samoensis (Ma\'o Ma\'o), which is endemic to Samoa and American Samoa. It is classified Endangered by the IUCN, most likely due to habitat loss, and the introduction of rats and other predators to the islands. ', WIDTH, -400, FONTSIZE,'12px', PADDING, 10)"> | Lontra canadensis (North American River Otter) Illustration of Lontra canadensis (North American River Otter). ', WIDTH, -340, FONTSIZE,'12px', PADDING, 10)"> | Merremia peltata Illustration of Merremia peltata, a common invasive on Pacific Island nations. ', WIDTH, -297, FONTSIZE,'12px', PADDING, 10)"> | Pluvialis fulva (Pacific Golden Plover) Illustration of Pluvialis fulva (Pacific Golden Plover). ', WIDTH, -365, FONTSIZE,'12px', PADDING, 10)"> | Tractor 5 Illustration of a tractor. ', WIDTH, -400, FONTSIZE,'12px', PADDING, 10)"> | Tridacna gigas (Giant Clam) Illustration of Tridacna gigas (Giant Clam), which is classified Vulnerable by the IUCN due to overharvesting. ', WIDTH, -400, FONTSIZE,'12px', PADDING, 10)"> | Urban: church 2 Illustration of a church. ', WIDTH, -400, FONTSIZE,'12px', PADDING, 10)"> | Urban: downtown (Fiji) Illustration showing the downtown of a community in Fiji. ', WIDTH, -400, FONTSIZE,'12px', PADDING, 10)"> | Deep sea mining: bulk cutter Illustration of a bulk cutter, used for deep sea mining. ', WIDTH, -389, FONTSIZE,'12px', PADDING, 10)"> | Deep sea mining: support vessel Illustration of a support vessel for deep sea mining. ', WIDTH, -400, FONTSIZE,'12px', PADDING, 10)"> |
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