Date of Award

Fall 12-2012

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Wildlife Ecology and Wildlife Conservation

Advisor

Cynthia S. Loftin

Second Committee Member

Joseph Zydlewski

Third Committee Member

William Halteman

Additional Committee Members

Jasmine Saros

Kevin Simon

Abstract

This research examined responses of Atlantic salmon ( Salmo salar) stream communities to experimental simulation of marine-derived nutrient input. Prior to construction of dams beginning in the early 1800s, Atlantic salmon and other anadromous species migrated from the ocean to spawn in Maine's extensive rivers and streams. Spawning fish transported marine-derived nutrients to these systems as carcasses, eggs, and waste products. These contributions may have influenced productivity in otherwise nutrient limited systems, bolstering growth and survival of young Atlantic salmon and other anadromous species and influencing other components of the stream communities.

This study involved a reach-scale experiment to explore assimilation of marine-derived nutrients supplied to small streams in Maine. Four headwater streams were stocked with Atlantic salmon fry in May 2009 and 2010, and marine-derived nutrient input was simulated with a carcass analog placed in treatment reaches to match timing of sea lamprey (Petromyzon marinus; July) and Atlantic salmon (October) spawning. Total dissolved nitrogen and phosphorus concentrations were greater in treatment reaches two days following carcass analog additions and returned to background concentrations approximately one month later. Periphyton biomass did not differ between control and treatment reaches for eight weeks following additions. Macroinvertebrate community assemblages differed between control and treatment reaches two and four weeks following additions. Macroinvertebrates and Atlantic salmon assimilated nitrogen (12-57% of total N) and carbon (21-65% of total C) from carcass analogs, and the magnitude and duration of enrichment varied temporally and by functional feeding group. Mass was 33-48% greater and length was 9-15% greater in young-of-the-year Atlantic salmon in treatment reaches for four months following nutrient additions. Percent total lipids in Atlantic salmon were twice as great in treatment reaches one month following carcass analog additions, and lipid levels remained elevated for two more months. Absolute growth rates, based on otolith microstructure analysis, correlated with water temperature fluctuations in all reaches and were elevated in treatment reaches for one month following carcass analog additions. Simulated sea lamprey spawning increased stream water nutrient concentrations, shifted macroinvertebrate community structure, and increased growth potential of juvenile Atlantic salmon, which may contribute to population persistence and ecosystem productivity.

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