Patterns of Growth and Erosion of blades of the kelp Saccharina latissima

Kelp, large seaweeds of the Phylum Ochrophyta (or Phaeophyta), Order Laminariales \nprovide many essential functions to intertidal habitats all over the world, yet the factors that \ngovern their productivity are understudied. This is becoming an increasingly important issue as \nkelp productivity and population sizes have decreased over time due to an overabundance of \npredation and changes in the environment, resulting in kelp deforestation with decreased \nresilience (Steneck et al. 2002; Krumhansl and Scheibling 2012, Wernberg et al. 2019). Kelp \ndeforestation not only posits a biological problem to its surrounding ecosystem but also an \neconomic problem as they are an important aspect of aquaculture, are utilized in many \ncommercial products and support many commercial fisheries by providing habitats and food web \nsupport. The increasing vulnerability of these kelp forests has become a growing problem, \nespecially as we find out more about the vital role that kelp plays in its ecosystem. \nKelp forests play in important role in fighting climate change; they sequester carbon and \nprovide blue carbon sinks, ameliorate ocean acidification, and provide complex habitats that \nencourage intertidal biodiversity. This suggests that kelp aquaculture is key to fighting climate \nchange as well (Duarte et al. 2017).They are autotrophic and are primary producers that serve as \na food source, both for herbivores as live plants that are fed on as well as through the detritus that \nthey shed (Mann 1973). They exude dissolved organic material (DOM) from their blades that contribute to both the biotic composition of their surroundings as well as to epiphyte activity (James et al. 2020). Kelp provide structural \nfunctions as well; their detritus often forms complex habitats that allow for greater biodiversity of micro-organisms that live on the ocean floor, and the kelp beds can provide a similar function as well for macro-organisms such as juvenile fish (Figure 1, Branch and Griffiths 1988). \n \nAs we increasingly discover the ways in which kelp are essential contributors to its local \necosystems, it becomes more important that further studies are conducted to learn more about \ntheir rates of growth and erosion and to study which factors may affect these rates. In this study \nwe looked specifically at Saccharina latissima (sugar kelp), a brown alga that grows along the \nwestern coast of the US and is ecologically important to its surrounding habitat in the Salish Sea \nwhere this experiment took place. This experiment was conducted over the course of 6 years as a \npart of a spring quarter class at Friday Harbor Labs and we used a simple but effective method \nthat can measure growth and erosion of S. latissima that was used at different depths and thus at \ndifferent light levels. With this data we ask what the patterns of growth and erosion are in S. \nlatissima and estimate the rate of growth and erosion in April and May.