Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Supplemental Files
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Project Information
• Funding

Coincident with monthly sampling of seawater for nutrient concentrations (see related dataset "Nutrient monitoring" https://www.bco-dmo.org/dataset/882057), we collected surface blades from M. pyrifera in the Breast Is. giant kelp bed from July 2018 - July 2019 to analyze for carbon (C) and nitrogen (N) content. On one frond from each plant (N = 3), we identified and removed the second intact blade closest to the frond’s scimitar blade. To capture seasonal variation in C and N content in kelp species in July 2018, January 2019, and August 2019, we collected blades from M. pyrifera plants (N = 5) at  ~1 m above their holdfasts and blades (N = 5) of N. fimbriatum and H. nigripes between 4 - 7 m depth (MLLW) at Samsing Pinnacle. We also opportunistically collected blades (N = 3-5) representing all kelp species present at Harris Is. in summer 2018 and 2020 and at Samsing Pinnacle in summer 2020. For all macroalgal tissue field collections, we immediately drained collected samples of excess seawater and kept them on ice in a covered cooler for transport to the lab. Within 2 hours of collection, we cleaned collected tissue of epiphytes and rinsed it briefly in fresh seawater. From all collected blades we excised 1 - 5 g of tissue immediately adjacent to the intercalary meristem where the blade meets the stipe. We spun tissue samples 10 times in a salad spinner before drying at 60 ℃ for at least 24 hrs. Dried samples were analyzed for C and N content (% dry mass) by the University of California Santa Cruz Stable Isotope Laboratory using a CE Instruments NC2500 elemental analyzer coupled to a Thermo Scientific DELTAplus XP isotope ratio mass spectrometer via a Thermo-Scientific Conflo III (routine measurement error ≤ 1.0 %C and ≤ 0.2 %N). 

Additional Funding Details:
In addition to primary funding from the NSF award OCE-1752600 additional funding was provided from The David and Lucile Packard Foundation and the North Pacific Research Board’s Graduate Student Research Award (1748-01) to Lauren Bell, PhD University of California Santa Cruz, Award title: "Fish Habitat, Fishes and Invertebrates, Lower Trophic Level Productivity Effect of substrate on herring roe response to global change."

BCO-DMO Data Manager Processing Notes:
* File “Sitkakelps_CN.csv” imported into the BCO-DMO data system.
​* Date format changed to ISO format
* ISO_DateTime_UTC added from local date and time (AKT/AKST)
* Species list with codes and scientific names extracted from parameter information. Matched to known taxon ids using WoRMS taxa match (2022-09-06). The spelling of "Laminaria setchelii" changed to "Laminaria setchellii" with two Ls after confirming the change with the data submitter. Species list along with identifiers attached as a supplemental data table.
* Latitude and Longitude added to main data table from the provided site list.

NSF Award Abstract:
High latitude kelp forests support a wealth of ecologically and economically important species, buffer coastlines from high-energy storms, and play a critical role in the marine carbon cycle by sequestering and storing large amounts of carbon. Understanding how energy fluxes and consumer-resource interactions vary in these kelp communities is critical for defining robust management strategies that help maintain these valuable ecosystem services. In this integrated research and education program, the project team will investigate how consumer populations respond to variability in temperature, carbonate chemistry and resource quality to influence the food webs and ecosystem stability of kelp forests. A comprehensive suite of studies conducted at the northern range limit for giant kelp (Macrocystis pyrifera) in SE Alaska will examine how kelp communities respond to variable environmental conditions arising from seasonal variability and changing ocean temperature and acidification conditions. As part of this project, undergraduate and high school students will receive comprehensive training through (1) an immersive field-based class in Sitka Sound, Alaska, (2) intensive, mentored research internships, and (3) experiential training in science communication and public outreach that will include a variety of opportunities to disseminate research findings through podcasts, public lectures and radio broadcasts.

Consumer-resource interactions structure food webs and govern ecosystem stability, yet our understanding of how these important interactions may change under future climatic conditions is hampered by the complexity of direct and indirect effects of multiple stressors within and between trophic levels. For example, environmentally mediated changes in nutritional quality and chemical deterrence of primary producers have the potential to alter herbivory rates and energy fluxes between primary producers and consumers, with implications for ecosystem stability. Moreover, the effects of global change on primary producers are likely to depend on other limiting resources, such as light and nutrients, which vary seasonally in dynamic, temperate and high latitude ecosystems. In marine ecosystems at high latitude, climate models predict that ocean acidification will be most pronounced during the winter months, when primary production is limited by light. This project is built around the hypothesis that there could be a mismatch in the energetic demands of primary consumers caused by warming and ocean acidification and resource availability and quality during winter months, with cascading effects on trophic structure and ecosystem stability in the future. Through complementary lab and field experiments, the project team will determine 1) how temperature and carbonate chemistry combine to affect primary consumer bioenergetics across a diversity of species and 2) the indirect effects of ocean acidification and warming on primary consumers via environmentally mediated changes in the availability, nutritional quality and palatability of primary producers across seasons. Using the data from the laboratory and field experiments, the project team will 3) construct a model of the emergent effects of warming and ocean acidification on trophic structure and ecosystem stability in seasonally dynamic, high latitude environments.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.