Abstract: Anthropogenic 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.

Abstract: 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.

Abstract: One of the most important goals of a coastal assessment program is to increase the knowledge of individuals and agencies who make management decisions. Information must be presented in an easy-to-understand format and supported by quantitative analyses. Quantitative analyses often involve applying statistical techniques that are used to visualize, describe, and model data. Statistics allow scientists and managers to distill data into useful information and increase the amount of confidence they have in their conclusions (Figure 8.1). This chapter describes how to use statistics to strike a balance between explanatory power and complexity (Figure 8.2). This brief introduction should provide some guidance in using statistics to analyze data.

Abstract: Chapter 4 discussed how selecting an appropriate communication product can affect an audience and persuade opinions. This chapter discusses how using another tool, an indicator (Figure 5.1), not only can persuade opinions, but also can be used to evaluate the health of an ecosystem. It starts by introducing what an ecological indicator is and why it is important and then describes different kinds of indicators, the process of selecting an indicator, how indicators are used to aid in management decisions, and how to structure indicators. Selecting, developing, and communicating ecological indicators are perhaps the most important, yet challenging aspects of a coastal assessment program and, therefore, should be given appropriate effort and resources.