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Publication Date

2024-5

First Advisor

Paulette Peckol

Second Advisor

Jess Gersony

Document Type

Honors Project

Degree Name

Bachelor of Arts

Department

Biological Sciences

Keywords

climate change, macroalgae, sea surface temperature, invasive species, dissolved inorganic carbon

Abstract

Temperature plays a significant role in shaping marine ecosystems. Recent rises in the frequency and intensity of marine heatwave (MHW) events and warming oceans associated with climate change necessitate a better understanding of the effects of climatic events on marine organisms. The Gulf of Maine is one of the world's most rapidly warming bodies of water. Interactions among native and introduced macroalgae will be affected by current and future warming; thus, their importance as food and habitat may shift with rising temperatures. Native Fucus vesiculosus has been under threat of displacement by an introduced red alga, Gracilaria vermiculophylla, in some locations. In this study, I investigated inter- and intraspecific interactions of F. vesiculosus and G. vermiculophylla at 15°C and 25°C and two biomass densities. I measured growth rates under various enrichment conditions (ambient, + nutrient enrichment (+N), and + nutrients/+ dissolved inorganic carbon enrichment (+N/+DIC)). Both species showed higher growth rates under 25°C and lower densities, and G. vermiculophylla grew faster than F. vesiculosus across all treatments. Growth did not vary between the ambient and +N treatments; only +N/+DIC resulted in consistently enhanced growth. F. vesiculosus demonstrated an apparent density effect under both intra- and interspecific conditions. In contrast, G. vermiculophylla showed significantly lower growth rates under interspecific pairings, suggesting adverse effects of F. vesiculosus. Grazing preference experiments using dominant gastropods (Littorina littorea and L. obstusata) showed 2X higher combined grazing rates on F. vesiculosus. Thus, while both species may survive under warming water temperatures, higher growth rates by G. vermiculophylla and lower grazing pressure may result in greater success of this introduced species, particularly in dense mats. This may result in a shift in species dominance across the intertidal region, with significant trophic implications.

Rights

©2024 Leah Harries. Access limited to the Smith College community and other researchers while on campus. Smith College community members also may access from off-campus using a Smith College log-in. Other off-campus researchers may request a copy through Interlibrary Loan for personal use.

Language

English

Comments

vi, 50 pages: color illustrations, charts. Includes bibliographical references (pages 38-50).

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