Date

Fall 2020

Document Type

Master's Thesis (Open Access)

Degree Name

Master of Science (M.S.)

Department

Moss Landing Marine Laboratories

Abstract

The stalked kelp, Pterygophora californica, is an important secondary canopy- forming species of coastal kelp forests from Alaska to Baja. It has long been thought that due to its long-lived, perennial thallus structures, seasonal growth and reproduction, and compound translocation capabilities, Pterygophora creates nutrient reserves. However, many aspects of Pterygophora have been understudied, including this theorized storage mechanism. This study addressed its storage capabilities by identifying nutrient compartmentalization, monitoring thalli over time, and examining allocation through biomass removals. Compartmentalization was observed among thallus regions of control thalli. All regions of the stipe and the reproductive sori had a higher mean %C than the holdfast, sporophyll, and vegetative blade regions. Isotopic fractionation illustrated that on average, the vegetative blade and sporophylls were more enriched in 13C than the lower stipe, potentially suggesting that the high bulk carbon in the stipe is a reserve that allocates carbohydrates to the blades. However, carbon fractionation due to photosynthesis and respiration was not measured, and therefore it is unknown how much impact those processes have on the 13C enrichment among thallus regions. A pattern of decreasing mean %N was seen from the base to top of the thallus. The holdfast region on average was the region of highest %N, and lowest C:N. A pattern of increasing C:N was seen from the base to the top of the stipe, and the ratio in the sporophylls was more similar to the lower and mid stipe regions than to the other blade tissues. Seasonality of nutrient compartmentalization in the thallus was not seen, meaning time had no effect on the chemical distribution among thallus regions (“compartments”). However, some seasonal variability of chemicals was observed for the thallus as a whole and within thallus regions individually. The only thallus regions that were significantly affected by blade manipulations were the lower, mid, and upper stipe. Changes within these regions were significantly impacted by the removal of sporophylls. Overall, the evident patterns in this study have uncovered a consistent nitrogen reserve in the holdfast, carbon reserve in the stipe, and allocation of carbon to the blades.

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