Publication Date

Spring 2026

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Moss Landing Marine Laboratories

Advisor

Michael Graham; Maxime Grand; Scott Hamilton

Abstract

As foundation species, kelps significantly influence the structure and composition of their surrounding habitat by modifying environmental conditions, including light levels, currents, nutrient availability, sedimentation, and seawater chemistry. Light, in particular, is a critical resource that varies greatly within kelp forests, affecting kelp reproductive processes such as gametogenesis, fertilization, and recruitment, which are vital to population persistence. Biological factors, such as density-dependent competition for resources and sexual competition with other kelps, can also affect such processes. To understand how environmental variables influence kelp populations, it is crucial to recognize their combined effects. This study investigated the impacts of light levels and density on sexual competition between kelp species. I assessed the timing of egg production and the maximum sporophyte production in giant kelp (Macrocystis pyrifera), bull kelp (Nereocystis luetkeana), and feather boa kelp (Egregia menziesii), based on light levels, density, and competition. Light significantly influenced these processes, whereas density had no significant effect. Macrocystis produced eggs more quickly and outcompeted Nereocystis across all light levels. Egregia consistently produced eggs faster than Macrocystis, but only outcompeted it under high light. My findings indicate that light modulates species interactions at the microscopic level and that sexual competition alone may not fully explain the observed patterns. These results emphasize that early-life-stage competition plays a critical role in shaping kelp forest composition, a key factor for predicting ecosystem responses to environmental change.

Download

Included in

Biochemistry Commons

Share

COinS