Unraveling ecosystem functioning in intertidal soft sediments: the role of density-driven interactions

Abstract

Although they only occupy a relatively small portion of the surface of the planet, coastal habitats are some of the most productive and valued ecosystems in the world. Among these habitats, tidal flats are an important component of many harbours and estuaries, but their deterioration due to human activities poses a serious threat to biodiversity and ecosystem function. Benthic communities are usually arranged in patches dominated by key species with overlapping distributions. Understanding the ecological consequences of interactions between these species in transition zones where their habitats overlap is necessary in order to quantify their contribution to overall ecosystem functioning and to scale-up and generalize results. Spatial transition in abundance and the interaction of multiple factors that drive ecosystem function are complex processes that require real-world research. Through a multi-site mensurative experiment, we show that transition areas drive non-linear effects on biogeochemical fluxes that have important implications for quantifying overall functioning. In our study the main drivers of ecosystem function were the abundance of two large but functionally very different species rather than biodiversity per se. Furthermore, we demonstrate that the use of the biogenic features created by specific infaunal species at the sediment–water interface is a better predictor of ecosystem functioning than the density of the species per se, making this approach particularly appealing for large scale, mapping and monitoring studies.

Species identity drives ecosystem function in a subsidy-dependent coastal ecosystem

“…The highest functioning species must also be the dominant species for process rates to be high at the ecosystem scale (Creed et al 2009, Treplin et al 2013. Our finding that an important ecological function was maximized when the two highest functioning species were the dominant species adds to the growing evidence supporting the role of species identity and dominance in the provisioning of key ecosystem functions, especially in soft-sediment ecosystems (Henderson et al 2019, Schenone andThrush 2020).…”

Modelled broad-scale shifts on seafloor ecosystem functioning due to microplastic impacts on bioturbation

“…In this study, changes of D b reflect a potentially different impact of MP on the sediment reworking in the areas dominant with maldanid worm M. stewartensis and tellinid bivalve M. liliana separately, as well as their transition zones (co-occur of these species) in the seafloor habitats. The bioturbation of M. liliana and M. stewartensis creates distinct microtopographic features on the sediment surface that influence the nutrient fluxes 53 . In MP-contaminated habitats, the maldanid worm can loss advantage in deep-particle mixing and maintaining the nutrient cycling.…”

Identifying “vital attributes” for assessing disturbance–recovery potential of seafloor communities

“…Species replacement was low in recovering communities at Tvarminne, indicating that community recovery could be linked to the recovery of the original ecosystem functions, but homogenous biotic landscapes and low species richness can also imply limited multifunctionality (Villnäs et al, 2018), and functional recovery may take considerable time with high disturbance frequency impeding development of pre-disturbance functions (Norkko et al, 2013). However, the implications for Kawau are more difficult to assess, because variation in species distributions across landscapes and variation in community composition can influence functional performance and multifunctionality (Schenone & Thrush, 2020;Siwicka & Thrush, 2020). Thus, new research investigating how these recovery traits are tied to traits that are linked to multiple ecosystem functions represents a new research focus for ecosystem dynamics.…”