Oxygen drives benthic-pelagic decomposition pathways in shallow wetlands

Gea H Van Der Lee,Piet F M Verdonschot,Michiel H S Kraak,J Arie Vonk,Ralf C M Verdonschot

doi:10.1038/s41598-017-15432-3

Gea H Van Der Lee, Piet F M Verdonschot + Show 3 more

Open Access

https://doi.org/10.1038/s41598-017-15432-3

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Abstract

Oxygen availability is perceived as an important environmental factor limiting POM decomposition. In shallow wetlands, however, the impact of commonly observed anoxic conditions in the benthic layer on the relative contribution of microbes and invertebrates to POM decomposition remains largely unknown. Therefore, the aim of this study was to determine if dissolved oxygen drives benthic-pelagic decomposition pathways in shallow wetlands. Dissolved oxygen concentration, invertebrate community composition, microbial decomposition and invertebrate consumption were measured in the benthic and pelagic layer of 15 permanent drainage ditches. We showed that an increased duration of anoxic conditions in the benthic layer of the ditches was related to increased microbial decomposition in this layer, while invertebrate consumption decreased in the benthic layer and increased in the pelagic layer. The increased invertebrate consumption in the pelagic layer was related to the presence of amphipods. We concluded that anoxic conditions in the benthic layer of shallow wetlands relate to an increase in microbial decomposition and a decrease in invertebrate consumption, as detritivorous invertebrates move to the pelagic layer to consume particulate organic matter. This illustrates that environmental conditions, such as dissolved oxygen, may drive the relative importance of aquatic organisms to ecosystem functioning.

Highlights

Dead particulate organic matter (POM) fuels shallow wetland food webs by serving as a food source for interacting microbes and invertebrates[1,2]
We determined microbial decomposition and invertebrate consumption in permanent drainage ditches, characterized by different dissolved oxygen conditions in the benthic layer compared to the pelagic layer
Similar dissolved oxygen patterns have been observed in shallow wetland environments other than drainage ditches[9,26]

Summary

Introduction

Dead particulate organic matter (POM) fuels shallow wetland food webs by serving as a food source for interacting microbes and invertebrates[1,2]. Considerable differences in daily and seasonal dissolved oxygen concentrations have been measured along depth gradients in the water column[7,8,9,10] This may alter the relative importance of microbes and invertebrates for POM decomposition in each layer, as they are differently adapted to function under low dissolved oxygen conditions[3,11]. We hypothesized that low dissolved oxygen concentrations in the benthic layer I) do not change microbial decomposition rates, as other functional groups adapted to low oxygen become active and dominant[24], and II) lead to lower invertebrate consumption, as they die[18,19] or move to the pelagic layer[20]. We performed a field study in which we continuously monitored dissolved oxygen concentrations, determined invertebrate community composition, and quantified microbial decomposition and invertebrate consumption in the benthic and pelagic layer of 15 permanent peat drainage ditches in The Netherlands

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