Temporal and spatial changes in benthic invertebrate trophic networks along a taxonomic richness gradient

Species interactions underlie most ecosystem functions and are important
for understanding ecosystem changes. Representing one type of species
interaction, trophic networks were constructed from biodiversity
monitoring data and known trophic links to assess how ecosystems have
changed over time. The Baltic Sea is subject to many anthropogenic
pressures, and low species diversity makes it an ideal candidate for
determining how pressures change food webs. In this study, we used benthic
monitoring data from 20 years (1980-1989 and 2010-2019) from the Swedish
coast of the Baltic Sea and Skagerrak to investigate changes in benthic
invertebrate trophic interactions. We constructed food webs and calculated
fundamental food web metrics evaluating network horizontal and vertical
diversity, as well as stability that were compared over space and time.
Our results show that the west coast of Sweden (Skagerrak) suffered a
reduction in benthic invertebrate biodiversity by 32 % between the 1980’s
and 2010’s, and that the number of links, generality of predators, and
vulnerability of prey, have been significantly reduced. The other basins
(Bothnian Sea, Baltic Proper and Bornholm Basin) do not show any
significant changes in species richness or consistent significant trends
in any food web metrics investigated, demonstrating resilience at a lower
species diversity. The decreased complexity of the Skagerrak food webs
indicates vulnerability to further perturbations and pressures should be
limited as much as possible to ensure continued ecosystem functions.