Publication Date

Spring 2026

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Moss Landing Marine Laboratories

Advisor

Michael Graham; Diana Steller; Scott Hamilton; Thomas Connolly

Abstract

Population replenishment is vital for species survival and depends on reproductive output and recruitment success. Many marine organisms rely on both short- and long-distance dispersal to sustain and expand their populations. Marine dispersal involves microscopic or planktonic stages that are influenced by currents, physical processes, and biological traits such as planktonic duration and sinking behavior. Depth and light gradients affect primary producer growth, impacting reproduction, especially in morphologically plastic seaweeds. This study examined how depth-related factors influence reproductive morphology, reproductive output, and dispersal of the subtidal brown seaweed Stephanocystis osmundacea in central California. Using field, lab, and computational methods, depth-driven trends appeared across all sectors. A kelp bed survey revealed two reproductive depth-specific ecomorphs: shallow individuals invest in dense, bushy reproductive fronds. In contrast, deep individuals focus on longer fronds but often face reproductive growth limits. Modeling field data showed population ecomorphs lead to reduced zygote output at greater depth. Zygotes released from greater depths were transported farther, contributing to long-distance dispersal. In contrast, zygotes from shallower depths contributed more to within-population replenishment. This study suggests that greater depth correlates with lower growth and output, but the implications for population dispersal are less clear. As rare subtidal East Pacific fucoids, Stephanocystis populations maintain deeper metapopulations but are limited in providing upper-water-column habitat to shallow water.

Download

Share

COinS