The Impact of the Mass Mortality of Ochre Stars (Pisaster ochraceus) and Sunflower Stars (Pycnopodia helianthoides) on Intertidal and Subtidal Communities in Puget Sound

Abstract

Severe Sea Star Wasting Disease (SSWD) outbreaks were reported between Alaska and Baja California, including Puget Sound (Eisenlord et al 2016). Eisenlord et al 2016’s results from intertidal surveys in Tacoma and on the San Juan Island are shown in Figure 1a and b. The affected intertidal and subtidal communities were reported in those locales, excluding Puget Sound (Fuess et al 2015). The severe SSWD epidemic has killed very large abundances of sea stars, which are important keystone predators of the marine ecosystem and food web, causing abundances of sea stars’ prey to increase and out-complete other species. This has shifted the communities and ecosystem (Schultz 2016, Montecino-Laterro 2016, Paine & Trimble 2004, Fuess et al 2015). However, the study of the affected communities in Puget Sound was very limited and further studies are necessary. My goals in research are to recognize similar influences in Puget Sound and gain more understanding of the changes in the ecosystem. My two hypotheses are: First, the decline in ochre star populations in Puget Sound due to SSWD causes mussel (Mytilus trossulus) populations to increase and take up space to prevent species from settling down (Menge et al, 2016 and MARINe 2016). Second, the decline in sunflower star populations in Puget Sound due to SSWD outbreaks causes the prey rate in herbivorous invertebrate populations (such as green sea urchins) to increase immediately and consume the kelp forest in Puget Sound (Fuess et al 2015). To achieve my research goals, I was counted and identified species in sea stars’ prey populations through a quadrat method in the intertidal zone (Documenting Plants & Animals in Each Habitat 1999). Sea Stars’ radii were measured in radius with a ruler, counted, and categorized as to the severity of the disease (Eisenlord et al 2014) in transects in the method intertidal zone (J. Engle 2008). The environments the intertidal zone were also identified. I explored MARINe (2016)’s historical data from her intertidal surveys through from between 2009 and 2010 to between 2015 and 2016. Also, I explored ROV (Remote Operated Vehicle) data from Washington Department of Fish and Wildlife (WDFW). I counted Sunflower stars (Pyconpodia helianthoides) and their prey, and identified the environments in subtidal zones.