Biogeomorphic impact of oligochaetes (Annelida) on sediment properties and Salicornia spp. seedling establishment

Abstract

Citation: van Regteren, M., R. ten Boer, E. H. Meesters, and A. V. de Groot. 2017. Biogeomorphic impact of oligochaetes (Annelida) on sediment properties and Salicornia spp. seedling establishment. Ecosphere 8(7):e01872. 10.1002/ecs2.1872Abstract. Oligochaetes (Annelida) are active bioturbators that can be present in high densities in the transition zone between intertidal flats and salt marshes, though their occurrence and functional role remain understudied. This study aimed to clarify the biogeomorphic role of oligochaete bioturbation in facilitating or hindering vegetation establishment. Two microcosm experiments were performed to assess the effect of oligochaete bioturbation on sediment properties, oxidation depth, algal biomass, seed distribution, and germination success of pioneer species Salicornia spp. Oligochaetes created burrow networks in the sediment matrix, which, together with upward conveyor belt feeding, lead to substrate mixing. Sediment reworking rates of oligochaetes were compared with those of polychaete macrofauna. Bioturbation and bio-irrigation of burrows can stimulate resource flows into the sediment. Oxidation depth increased almost tenfold in the presence of oligochaetes. Their bioturbation did not seem to affect sediment properties such as dry bulk density, porosity, and organic matter content. Sediment reworking, however, significantly reduced algal biomass at the surface with possible cascading effects on sediment stability and erodibility. Oligochaete conveyor belt feeding buried Salicornia spp. seeds until below the critical germination depth, thus negatively affecting Salicornia spp. germination and seedling establishment. Our study indicates that small, though numerous, oligochaete bioturbators may reduce lateral expansion potential of salt marshes by hindering the establishment of pioneer vegetation in the transition zone. Additionally, in dynamic fine-grained habitats, these oligochaetes have the feature to quickly oxygenate the sediment top layer.

Limited seed retention during winter inhibits vegetation establishment in spring, affecting lateral marsh expansion capacity

“…Salicornia procumbens was present, up to 3 cm deep (March) in significantly higher abundances than the control (Figure ). We hypothesize that downward transport of these seeds into the soil occurred through benthic bioturbation (van Regteren, Boer, Meesters, & Groot, ; Zhu, Belzen, et al, ). Burial of seeds through bioturbation may increase seed retention and create a mechanism for seed bank formation.…”

“…A higher seed abundance with a higher viability below 1 cm found in the March treatment (Table and Figure A1) is an indication that these seeds originated from the experimental seed addition. They have moved downwards into the soil, most likely through bioturbation (van Regteren et al, ). Natural S. procumbens seed abundance increased at a depth of 4–9 cm, while viability remained low (between 10% and 40% viability).…”

The Effect of Shading and Nutrient Addition on the Microphytobenthos, Macrofauna, and Biogeochemical Properties of Intertidal Flat Sediments

“…These changes in the physical composition of the sediment would act in an antagonistic fashion to the stabilizing effect of the microphytobenthos. Oligochaetes were more abundant in lightly shaded sediment and less abundant in heavily shaded sediment and have been shown to significantly reduce algal biomass at the sediment surface (van Regteren et al, 2017), probably with cascading effects causing a reduction in sediment stability and increase in erodibility. Thus, an increase in oligochaetes would also act in an antagonistic fashion to the stabilizing effect of the microphytobenthos and could explain why the effect of shading on microphytobenthos and related sediment properties were not as large as otherwise might be expected.…”

Evaluatie van OSPAR aanbevelingen voor bedreigde en/of achteruitgaande soorten en habitats in Nederland

“…Ook lopen er pilot projecten in de Waddenzeehavens waarbij geëxperimenteerd wordt met een slibmotor. Dit onderzoek draagt bij aan de ontwikkeling van kennis over de verspreiding van zand en slib en de ontwikkeling van getijdenplaten (Baptist, 2015;de Vriend et al, 2015;Baptist et al, 2016;Baptist et al, 2017;van Regteren et al 2017 Goudswaard et al, 2009;van der Wal & van Dalfsen, 2008; Bos et al, 2014;Troost et al, 2014;. Een overzicht van vindplaatsen door duikers en in surveys is gemaakt in (Meun, 2008).…”