title: Benthic primary producers are key to sustain the Wadden Sea food web: stable carbon isotope analysis at landscape scale.
abstract: Coastal food webs can be supported by local benthic or pelagic primary producers and by the import of organic matter. Distinguishing between these energy sources is essential for our understanding of ecosystem functioning. However, the relative contribution of these components to the food web at the landscape scale is often unclear, as many studies lack good taxonomic and spatial resolution across large areas. Here, using stable carbon isotopes, we report on the primary carbon sources for consumers and their spatial variability across one of the world's largest intertidal ecosystems (Dutch Wadden Sea; 1460 km2intertidal surface area), at an exceptionally high taxonomic (178 species) and spatial resolution (9,165 samples from 839 locations). The absence of overlap in δ13C values between consumers and terrestrial organic matter suggests that benthic and pelagic producers dominate carbon input into this food web. In combination with the consistent enrichment of benthic primary producers (δ13C -16.3‰) relative to pelagic primary producers (δ13C -18.8) across the landscape, this allowed the use of a two-food-source isotope-mixing model. This spatially resolved modelling revealed that benthic primary producers (microphytobenthos) are the most important energy source for the majority of consumers at higher trophic levels (worms, molluscs, crustaceans, fish, and birds), and thus to the whole food web. In addition, we found large spatial heterogeneity in the δ13C values of benthic primary producers (δ13C -19.2 to -11.5‰) and primary consumers (δ13C -25.5 to -9.9‰), emphasizing the need for spatially explicit sampling of benthic and pelagic primary producers in coastal ecosystems. Our findings have important implications for our understanding of the functioning of ecological networks and for the management of coastal ecosystems.
authors.affiliation: Groningen Institute for Evolutionary Life Sciences, University of Groningen, P.O. Box 11103, Groningen, 9700 CC, The Netherlands.
authors.forename: M J A
authors.initials: MJA
authors.lastname: Christianen
authors.affiliation: Faculty of Geosciences, Department of Earth Sciences, Utrecht University, Utrecht, 3508 TA, The Netherlands.
authors.forename: J J
authors.initials: JJ
authors.lastname: Middelburg
authors.affiliation: Department of Coastal Systems, NIOZ Royal Netherlands Institute for Sea Research, Utrecht University, P.O. Box 59, Den Burg, 1790 AB, The Netherlands.
authors.forename: S J
authors.initials: SJ
authors.lastname: Holthuijsen
authors.affiliation: Groningen Institute for Evolutionary Life Sciences, University of Groningen, P.O. Box 11103, Groningen, 9700 CC, The Netherlands.|Department of Coastal Systems, NIOZ Royal Netherlands Institute for Sea Research, Utrecht University, P.O. Box 59, Den Burg, 1790 AB, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Jouta
authors.affiliation: Department of Coastal Systems, NIOZ Royal Netherlands Institute for Sea Research, Utrecht University, P.O. Box 59, Den Burg, 1790 AB, The Netherlands.
authors.forename: T J
authors.initials: TJ
authors.lastname: Compton
authors.affiliation: Groningen Institute for Evolutionary Life Sciences, University of Groningen, P.O. Box 11103, Groningen, 9700 CC, The Netherlands.|Institute for Wetland and Water Research, Radboud University Nijmegen, Heyendaalseweg 135, Nijmegen, 6525 AJ, The Netherlands.
authors.forename: T
authors.initials: T
authors.lastname: van der Heide
authors.affiliation: Groningen Institute for Evolutionary Life Sciences, University of Groningen, P.O. Box 11103, Groningen, 9700 CC, The Netherlands.|Department of Coastal Systems, NIOZ Royal Netherlands Institute for Sea Research, Utrecht University, P.O. Box 59, Den Burg, 1790 AB, The Netherlands.
authors.forename: T
authors.initials: T
authors.lastname: Piersma
authors.affiliation: Faculty of Geosciences, Department of Earth Sciences, Utrecht University, Utrecht, 3508 TA, The Netherlands.|Department of Marine Microbiology and Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, Utrecht University, P.O. Box 59, Den Burg, 1790 AB, The Netherlands.
authors.forename: J S
authors.initials: JS
authors.lastname: Sinninghe Damsté
authors.affiliation: Department of Coastal Systems, NIOZ Royal Netherlands Institute for Sea Research, Utrecht University, P.O. Box 59, Den Burg, 1790 AB, The Netherlands.
authors.forename: H W
authors.initials: HW
authors.lastname: van der Veer
authors.affiliation: Faculty of Geosciences, Department of Earth Sciences, Utrecht University, Utrecht, 3508 TA, The Netherlands.|Department of Marine Microbiology and Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, Utrecht University, P.O. Box 59, Den Burg, 1790 AB, The Netherlands.
authors.forename: S
authors.initials: S
authors.lastname: Schouten
authors.affiliation: Groningen Institute for Evolutionary Life Sciences, University of Groningen, P.O. Box 11103, Groningen, 9700 CC, The Netherlands.
authors.forename: H
authors.initials: H
authors.lastname: Olff
mesh_terms: D000818:Animals; D059001:Aquatic Organisms / Q000145:classification / Q000502:physiology*; D002244:Carbon; D002247:Carbon Isotopes; D017753:Ecosystem; D005399:Fishes; D020387:Food Chain; D009587:Nitrogen Isotopes
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D002244:Carbon
keywords: Dutch Wadden Sea; carbon subsidy; coastal food web; estuary; macrobenthos; stable carbon isotopes; tidal wetland ecosystem