Document Type

Honors Thesis

Major

Marine Science

Advisor(s)

Amanda Klemmer

Committee Members

Robert Steneck, Joseph Zydlewski

Graduation Year

May 2024

Publication Date

Spring 5-2024

Abstract

The intertidal coastlines of Maine are dominated by a near monoculture of Ascophyllum nodosum. This species of macroalgae is foundational to the ecosystems in which it inhabits, so what controls the Ascophyllum nodosum controls the coasts. A. nodosum has been documented as a steady-state species in terms of biomass, canopy height, and primary productivity. Algal biomass results from algal recruitment, primary productivity (growth rate), and environmental disturbance (rate of biomass loss). My study estimated the abiotic disturbance of the environment on biotic factors ofAscophyllum nodosum. Physical forcings of the environment, ice, water motion, and light, drive Ascophyllum nodosum abundance, distribution, and primary productivity. Within the Damariscotta River, biotic factors of Ascophyllum nodosum (canopy height, age, density, biomass, productivity) and abiotic factors (ice scour, wave exposure, current intensity) were quantified or estimated for several sites along a uniform tidal elevation. The Damariscotta River was chosen for the large gradient of productivity and disturbance potentials of the environment. Apparent thallus longevity and canopy height were highest where the disturbance potential of the environment was lowest. Ice scour and plucking remove fronds resulting in an increase in thallus density. Water motion and wave exposure drove an increase in primary productivity but only to a point where crashing waves removed Ascophyllum thalli. As a result, algal biomass was highest in areas with relatively high rates primary productivity but low rates of disturbance. In conclusion, the abundance of Ascophyllum nodosum is driven heavily by the physical forcings of the environment.

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