Researcher ORCID Identifier

Graduation Year


Date of Submission


Document Type

Open Access Senior Thesis

Degree Name

Bachelor of Arts



Reader 1

Branwen Williams

Reader 2

Diane Thomson

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2023 Sadie R Heckman


Clathromorphum compactum, a species of crustose coralline algae (CCA), is incredibly valuable for the future of high latitude ocean health, both as a comprehensive archive of changing ocean conditions, and ecologically as a foundational species for promoting biodiversity. Previous work establishes C. compactum as an effective climate proxy, and its life history provides several advantages for this use. C. compactum grow in nongeniculate, generally radial formations on hard substrates, over a wide distribution in mid-to-high latitude oceans and at subtidal depth ranges. Indeterminate growth leads to extreme longevity in C. compactum (Halfar et al., 2008), and growth rates are relatively constant over its life span, resulting in well-defined increments. A high-Mg calcite skeleton provides an elemental ratio of Mg/Ca that directly correlates with SST; as temperatures rise, Mg manifestation levels in skeletal material rise (Adey et al., 2015; McCoy & Kamenos, 2015; Williams et al., 2018). The species is thus an established, specific, and accurate climate proxy. C. compactum also acts as an indicator of broader ecosystem health, where its presence serves as a foundation for subtidal ecological communities and as a binding agent for broader reefal ecosystems. Its decay indicates ocean conditions are unfit for upkeep of marine calcifiers. Because past research has established several methods for acquiring proxy temperature data from marine calcifiers, my goal was to find evidence of recent warming trends at a high latitude (53⁰ 17.6' N) ocean site in C. compactum skeletal material, and to connect its value as a vital ecosystem foundation to its value as a climate archive. I found that Mg/Ca and d18O content of specimen 10-21_15-17_1 both reflected SST increase in the past 22 years. Despite increased Mg manifestation, growth rates did not correlate with SST or time. This outcome reaffirms C. compactum’s effectiveness in manifesting changes in ocean temperature, but lack of growth rate correlation suggests that C. compactum may be reaching its threshold of heat and acidity tolerance.