Date of Award

Summer 8-20-2021

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Marine Biology

Advisor

Rhian Waller

Second Committee Member

Kevin Eckelbarger

Third Committee Member

Jay Lunden

Additional Committee Members

Seth Tyler

Nishad Jayasundara

Abstract

Cold-water corals are important habitat builders in the deep ocean worldwide. Despite being known for centuries, recent technological advances and deep-sea exploration has revealed cold-water corals thriving at depths of up to 6000m. Similar to their warm-water relatives, cold-water corals are hotspots of diversity, with their structures creating habitat for thousands of associated species. Some cold-water corals create bioherms that stretch for tens of kilometers, while others come together to form vast undersea forests. These habitats are often home to commercially important fisheries species, and conservation efforts have recently begun to regulate fishing in cold-water coral ecosystems to protect them from damaging fishing practices. Slow-growing cold-water corals disturbed by fishing gear may need decades or even centuries to recover. Also, cold-water corals are threatened by impending climate change in the form of warming and changes to ocean chemistry and circulation.

Given their importance to deep sea communities and vulnerability to anthropogenic impacts, research to understand cold-water coral ecology is urgently needed. One of the foundational processes of any organism is its reproduction. In the case of cold-water corals, understanding their reproductive ecology is both crucial for making recommendations to policymakers charged with stewarding sustainable fisheries, and extremely challenging to study. The remote deep-water habitat of many cold-water corals makes life history studies costly and often impossible. In the past several decades, scientists have worked to piece together descriptions of cold-water coral reproduction using comparisons to shallow-water relatives as context to identify patterns, but there are still very few cold-water species whose reproductive biology is truly well understood.

In this dissertation, we report three studies that each focused on one stage of reproduction – gametogenesis, early embryogenesis, and larval health and settlement – in three cold-water corals from the North Pacific, North Atlantic, and Southern Oceans, and asked how those stages were affected by temperature using a combination of histology, electron microscopy, and experimental techniques. Learning how vulnerable stages of cold-water corals will respond to environmental change is critical for sustaining healthy, productive deep-sea ecosystems going forward.

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