『Abstract
　Long term measurements of NO3^- concentrations in two estuaries on Buzzards Bay, Massachusetts, USA, coupled with a large, step-wise increase in the groundwater NO3^- to one of those estuaries, have allowed the effects on the estuary to be isolated and quantified. The results show that prior to the abrupt increase, the estuary responded in a linear manner of NO3^- input, as suggested in the literature. After the abrupt increase, the estuary initially absorbed the greatly increased groundwater input, and after a year the response became a fluctuating variable with periods of less than 1 year. It is proposed that this indicates increased recycling from the sediments. This behavior is consistent with models of nutrient-induced regime shift in its early stages, as described in the literature. Further isotopic analysis is suggested as a means to confirm the estuary mechanism.』

1. Introduction
2. Methods
　2.1. Quality control
3. Results
　3.1. Nitrate in Squeteague Harbor, Scotch House Cove and the groundwater
4. Discussion
　4.1. Source of abrupt nitrate increase to Squeteague Harbor
　4.2. SQT response
　4.3. Comparison with published estuary responses to nitrogen loading
　4.4. Prior investigations of regime shift
　4.5. SQT high frequency response
5. Conclusions
Acknowledgements
References