Channelling of basal resources and use of allochthonous marine carbon by soil arthropods of the Wadden Sea salt marsh

Salt marshes are located between the marine and terrestrial systems.
Because they form as sediment accumulates, they comprise a gradient of
shore height with differing inundation frequencies and associated abiotic
soil conditions. Along this gradient, both autochthonous vascular plant
resources and allochthonous marine algal or detrital resources are
available, with the availability of both varying with season and salt
marsh zone. However, little is known about the importance of either
resource for the soil animal food web. We investigated both spatial and
temporal resource use of the soil macro- and mesofauna of the salt marsh
using neutral lipid fatty acids (NLFAs). Generally, irrespective of season
and zone the soil animal food web relied on carbon originating from
autochthonous vascular plants and associated bacteria and fungi, with the
role of bacteria generally exceeding that of fungi. However, the
channelling of fungal resources consistently peaked in October, whereas
seasonal changes in the channelling of plant and bacterial resources
varied among salt marsh zones. Further, variations in the channelling of
resources with season and zone varied among salt marsh animal species.
Although being only minor, allochthonous resources of marine origin
contributed to soil food web nutrition across salt marsh zones and
seasons. The contribution of algae to soil food web nutrition depended on
inundation frequency and season, i.e. algal productivity. Overall, the
results demonstrate that the salt marsh soil fauna predominantly relies on
autochthonous vascular plant resources, with the contribution of
allochthonous marine resources being minor and restricted to few taxa.