Analysis of Stressors Contributing to Hypoxia in Lake Erie Using Deterministic Models.

Hypoxia;Lake Erie;Eutrophication;Natural Resources and Environment;Engineering;Science;Natural Resources and Environment

Rucinski, Daniel KennethBeletsky, Dmitry ;

University of Michigan

关键词: Hypoxia;    Lake Erie;    Eutrophication;    Natural Resources and Environment;    Engineering;    Science;    Natural Resources and Environment;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/102411/dkrucins_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Lake Erie continues to experience hypoxia (dissolved oxygen concentrations < 2 mg/L), despite basin-wide reductions in total phosphorus loads intended to limit or eliminate hypoxia, as outlined in the Great Lakes Water Quality Agreement (GLWQA) in 1978. Despite initial success, periodic hypoxia in the central basin of Lake Erie persisted, and more recently, hypoxic area has enlarged and reemerged as a potential hazard to ecosystem health.The consequences of hypoxic conditions (e.g., loss of suitable fish habitat and decrease in fish abundance and growth rates) have therefore led to a renewal in interest in understanding the relative contributions to the stressors contributing to hypoxia in Lake Erie.This dissertation focuses on the impacts of nutrients and hydro-meteorological forcingsTo analyze these stressors, a group of models was developed and applied in multiple management frameworks.First, a simple dissolved oxygen model was applied in a 1-dimensional, vertically stratified domain.Meteorological forcings determined temperature and mixing conditions, while the oxygen depletion rate within the water column was adjusted to match observed spatial and temporal dissolved oxygen concentrations, therefore determining if the water column oxygen demand has varied inter-annually.The model required an annually varying water column oxygen demand, suggesting that hypoxia is a function of variations in biological activity within the water column, and not strictly a meteorological phenomenon.Second, a more robust lower-food web model was developed, using the same 1-dimensional temperature and mixing conditions, but including nutrient loads and internal cycling to assess the effects of inter-annual variation in loading magnitude. The analysis suggests that a 46% reduction from the 2003-2011 average total phosphorus load and a 56% reduction from the current GLWQA target would be required to reduce hypoxic area to 2,000 km2.Finally, several hypothetical scenarios were explored with the lower-food web model, representing variations in load seasonality and meteorological conditions; including two climate warming scenarios. This work suggests that while there has been significant variation in seasonal patterns of nutrient loads, meteorological conditions play an important role due to the impact on stratification.