DOI: 10.5061/dryad.n02v6wwxd
title: Isotopic data of kelps and particulate organic matter (POM) from relevant studies and estimated contributions of kelps to local consumers

description: Kelp forests are highly productive coastal habitats that serve as
 biodiversity hotspots and provide valuable ecosystem services. Despite
 being one the largest marine biomes, kelp forests have been drastically
 understudied relative to other marine systems. Notably, while the role of
 kelp as habitat-forming, or ‘foundation species’, is well-documented, a
 comprehensive understanding of kelp forest food web structure is lacking,
 particularly regarding the importance of kelp-derived energy/nutrients to
 consumers. Here, we provide a biogeographic perspective on the energetic
 underpinning of kelp forests based on published literature. We targeted
 studies which used geochemical proxies – stable isotope analysis – to
 examine the transfer of carbon from kelp to local consumers. These studies
 (n=94) were geographically skewed, with &gt;40% from Northern European
 Seas and Temperate Northeast Pacific. Quantitative estimates for the
 percentage of kelp energy (or kelp+macroalgae if sources were pooled)
 incorporated by local consumers came from 43 publications, which studied
 141 species and 35 broader taxonomic groups. We examined these data for
 trends among functional groups and across upwelling regimes. No patterns
 are evident at present, perhaps due to the paucity or variability of
 available data. However, energetic subsides from kelps clearly support a
 wide range of diverse taxa around the globe. We also characterized
 biogeographic patterns in d13C values of kelps and particulate organic
 matter (POM, a phytoplankton proxy), to evaluate potential limitations of
 stable isotope analysis in disentangling the relative contributions of
 pelagic vs. benthic resources to coastal food webs. Globally, kelps and
 POM differed by &gt;4.5‰, but there was substantial variation among
 regions and kelp species. Accordingly, we discuss advances in stable
 isotope techniques which are facilitating more precise analysis of these
 complex energetic pathways. We end by proposing four main avenues of
 critical future research that will shed light on the resilience of these
 communities to global change.
description: This dataset is a compilation of isotopic data from published
 literature. See manuscript for literature review and data processing
 methods.
description: Data A1. This file contains
 all of the data compiled by the authors for the current review and used to
 produce the analyses in the described manuscript. For a full reference
 list refer to the main text as well as Supplementary materials Appendix
 1. The file
 “Kelp_POM.csv” presents all isotope values, including the bulk tissue
 d<sup>13</sup>C and d<sup>15</sup>N values as they
 are originally presented in the cited manuscripts. Where spreadsheet cells
 are left blank indicates data that was not reported in the original
 citation. The
 file “Kelp_Consumer.csv” presents the estimated mean or median
 contribution from kelp (or a combined kelp and macroalgae endmember) for
 consumers from all cited manuscripts. This includes associated metadata
 and methodological details for each species and study. Where spreadsheet
 cells are left blank indicates data/methods that was not reported in the
 original citation. As described in the main text, to avoid biasing
 analyses based on repeated measures from a small number of studies, where
 multiple values were recorded for the same species, we averaged the
 contribution estimates based on the ecological/geographic distinctions
 made in the original study. For example, Markel and Shurin (2015) and
 Ramshaw (2012) present estimates for various species in different
 ecological regions of British Columbia: Kyuquot Sound, an area with sea
 otters present, and Barkley Sound where sea otters are absent. For these
 studies we thus binned species data separately for Kyuquot and Barkley
 Sound. Details for all such bins can be found in the ‘Notes’
 column.