Exploring the Relationship Between Bull Kelp (Nereocystis luetkeana) and Northern Kelp Crabs (Pugettia producta)

Abstract

Kelps are a vital primary producer which have been found along 25% of the world’s coastlines in temperate and subpolar regions (Teagle et al. 2017; Rogers-Bennett and Catton 2019). Kelps form dense canopy forests maintaining high biodiversity, supporting both coastal communities and marine life as a foundational species and food source (Teagle et al. 2017). A single kelp can serve as three separate habitats: the blade, the stipe, and the holdfast (Teagle et al. 2017). Within the canopy there are juvenile salmonids, forage fish, and many invertebrates ranging in size from zooplankton to crustacean herbivores (Teagle et al. 2017; Shaffer et al. 2020). As a food source, kelps are consumed by humans and a variety of marine organisms ranging from sea urchins, mollusks, decapods, and fish (Springer et al. 2010; Dobkowski 2017). Here in the Salish Sea, bull kelp (Nereocystis luetkeana) is the dominant kelp forest (Dobkowski 2017). N. luetkeana is an annual kelp that must complete its life cycle within a single year, so its canopy is greatest during the summer and later senesces in the fall and winter (Siddon et al. 2008). With this, kelps are extremely vulnerable under changing ocean conditions as their abundance is dependent on sea surface temperature, salinity, and nutrient availability (Pfister et al. 2018). Previous studies indicate that the kelp beds throughout the Strait of Juan de Fuca and the coast of Washington State are persistent, but the beds around south Puget Sound are declining (Pfister et al. 2018).