Department or Program

Geology

Abstract

In the process of their annual spawning migration, anadromous alewives (Alosa Pseudoharengus) act as nutrient vectors. While adults import marine derived nutrients (MDNs) to their lacustrine spawning grounds, juveniles export nutrients as they emigrate seaward. Monitoring of lake water quality parameters and carbon and nitrogen stable isotopic signatures of particulate organic matter and fauna in a coastal Maine lake during two annual alewife migrations was paired with a model predicting alewife nutrient fluxes. The combination aimed to detect any current loading and predict the outcome of alewife runs of varying escapement. Water quality data were largely consistent between years and no correlation was found between nutrient or chlorophyll concentrations and daily fish passage. Stable isotope analyses were unable to concretely identify the presence of MDN’s, likely due to low concentrations. Modeled adult alewife phosphorous inputs for the 2012 and 2013 migration were similar to juvenile export, while upper estimates of nitrogen contribution to the lake exceeded 75 kg . These imports currently represent an estimated 0.45% of the lakes annual N budget. Historical fish migrations, however, may have contributed as much as 12% of the annual N and 25% of the annual P load to the lake. Incorporating annual alewife flux estimates into a landscape loading model indicated that the study lake may be capable of receiving escapements of nearly 7 million (16x current) before critical water quality degradation. However, a new model describing the daily release and sequestration of lake nutrients by adult and juvenile alewife populations indicates that such annual approaches may be inapropriately blunt for water quality estimations as the result of spatiotemporal complexity in the alewife nutrient fluxes. The model additionally shows that complete nutrient import and export may be temporally separated by a month or more. This may decrease the efficiency of juvenile nutrient export. Implications for joint fishery and lake management are discussed.

Level of Access

Open Access

First Advisor

Beverly Johnson

Date of Graduation

5-2014

Degree Name

Bachelor of Science

Number of Pages

47

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