Document Type

Honors Thesis

Publication Date

Spring 5-2017

Abstract

The net primary productivity (NPP), also known as the net ecosystem metabolism, of an estuary is a value indicative of the growth and activity of an estuary’s primary producers, relative to the metabolic activity of its consumers. When NPP is high, estuaries exhibit autotrophic conditions that have the capacity to support fruitful bivalve aquaculture. For oyster farmers, the ability to monitor an estuary’s NPP would allow them to predict and prepare for seasonal changes to oyster growth that result from changes to their phytoplankton food source and access to dissolved oxygen (DO). Not only would this aid farmers on site at the location of current oyster culture operations, but measuring the NPP of potentially new locations for oyster farms could also aid farmers in informed site selection, saving them money down the road. NPP can be calculated using dissolved oxygen measurements applied to an equation for Net Ecosystem Metabolism (NEM) known as the Delta Method. This study aimed to create an easy-to-use, inexpensive model that oyster farmers can use on site to monitor the changes to biological activity, in terms of NEM, occurring in the estuary in which they grow their oysters. By using dissolved oxygen data collected from the Damariscotta River, an estuary that supports multiple productive oyster farms and hosts two data-gathering, remote-sensing buoys, I also determined the viability of using this tool for site assessment of future oyster farm locations. A comparison of NEM and net primary productivity (NPP) values generated by the model to values reported in the literature, NPP found using 14C radiocarbon analysis, and seasonal trends in other biological and physical variables at play in the estuary, such as chlorophyll, nitrate, PAR, and temperature, revealed that the model is capable of producing useful and relatively accurate values. An evaluation of DO as a measurement, compared to 14C, revealed that DO measurements have their limitations, but the NEM values they are used to calculate provide a more comprehensive picture of biological activity occurring among trophic levels in an estuary than any of the other measurements discussed in this study. The highest NEM values generated by the model were found at the location of current oyster farm operations in the Damariscotta River, indicating that the values generated by the model correctly reflect this site’s current, demonstrated capacity to support aquaculture. This suggests that the model could be used by oyster farmers as a viable, inexpensive tool for site assessment in the future.

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