Brine Disposal Impact Assessment and Quantification of Ecosystem Health by Network Environ Analysis (NEA) In the Strategic Petroleum Reserve

Network Environ Analysis (NEA) is a set of input-output methods designed to quantify dynamic characteristics of the within-system environments of a system's component-level compartments.  We employed this methodology to conduct an environmental impact assessment of brine disposal from the Strategic Petroleum Reserves offshore in the Gulf of Mexico. We formulated a steady-state model of the water-column/benthic ecosystem complex of the continental shelf and subjected it to various hypersaline scenarios.  Compartments were classified into four sectors: Plankton, Nekton, Benthos, and Organic Complex. Changes in the output and input environs of commercially important penaeid shrimp were explored. The order of output and input environ impacts to this compartment was Benthos > Organic Complex > Plankton > Nekton, clearly reflecting each group's capacity for avoidance of epibenthic hypersaline lenses projected to accumulate near the sea bottom.  Under elevated salinities the number of times substance cycled through the compartments increased, and reciprocally, residence times in the compartments decreased.  Just as physicians take vital signs of patients to assess extent of illness, the health of an ecosystem may also be reflected in increased process rates quantifiable in environs.  NEA offers promise as a modeling-based approach to quantitative environmental impact and whole-ecosystem health assessment.