Abstract
Abstract. Kelp forests are among the world's most productive marine ecosystems, yet little is known about their biogeochemistry. This study presents a 14-month time series (July 2013–August 2014) of surface and benthic dissolved inorganic carbon and total alkalinity measurements, along with accompanying hydrographic measurements, from six locations within a central California kelp forest. We present ranges and patterns of variability in carbonate chemistry, including pH (7.70–8.33), pCO2 (172–952 µatm), and the aragonite saturation state, ΩAr (0.94–3.91). Surface-to-bottom gradients in CO2 system chemistry were as large as the spatial gradients throughout the bottom of the kelp forest. Dissolved inorganic carbon variability was the main driver of the observed CO2 system variability. The majority of spatial variability in the kelp forest can be explained by advection of cold, dense high-CO2 waters into the bottom of the kelp forest, with deeper sites experiencing high-CO2 conditions more frequently. Despite the strong imprint of advection on the biogeochemical variability of the kelp forest, surface waters were undersaturated with CO2 in the spring through fall, indicative of the strong role of photosynthesis on biogeochemical variability. We emphasize the importance of spatially distributed measurements for developing a process-based understanding of kelp forest ecosystem function in a changing climate.
Highlights
Kelp forests are found along rocky coastlines in temperateto-subpolar coastal regions throughout the world’s oceans
The reserve was created in 2007 as part of the network of central California marine-protected areas designated under the California Marine Life Protection Act (Lovers Point-Julia Platt State Marine Reserve Fact Sheet, 2016)
Sample sets from July and August 2013 were collected over 2 days, with the samples from the protected transect typically collected a day before the samples from the exposed transect and the KFA site. We include these first 2 months of the time series when presenting the data as time series, but in order to avoid confounding variability from sampling on different days, any of the analyses presented here which require comparisons between the sites are limited to the period of September 2013–August 2014, when samples were all collected within approximately 90 min of one another
Summary
Kelp forests are found along rocky coastlines in temperateto-subpolar coastal regions throughout the world’s oceans. Kelp is an important foundation species that support diverse biological communities, including invertebrates, fishes, and marine mammals through their creation of complex, threedimensional biological habitat and the provisioning of carbon and nutrients which magnify secondary production in the coastal zone (Steneck et al, 2002). Kelp (including Ecklonia spp., Laminaria spp., and Macrocystis spp.) forests are among the most productive marine ecosystems (Mann, 1982), with linear extension rates of kelp fronds that can range from 2 to 14 cm d−1 (Graham et al, 2007).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
