Success of lake restoration depends on spatial aspects of nutrient loading and hydrology

Annette B.G Janssen,Dianneke Van Wijk,Luuk P.A Van Gerven,Elisabeth S Bakker,Robert J Brederveld,Donald L Deangelis,Jan H Janse,Wolf M Mooij

doi:10.1016/j.scitotenv.2019.04.443

Annette B.G Janssen, Dianneke Van Wijk + Show 6 more

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https://doi.org/10.1016/j.scitotenv.2019.04.443

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Abstract

Many aquatic ecosystems have deteriorated due to human activities and their restoration is often troublesome. It is proposed here that the restoration success of deteriorated lakes critically depends on hitherto largely neglected spatial heterogeneity in nutrient loading and hydrology. A modelling approach is used to study this hypothesis by considering four lake types with contrasting nutrient loading (point versus diffuse) and hydrology (seepage versus drainage). By comparing the longterm effect of common restoration measures (nutrient load reduction, lake flushing or biomanipulation) in these four lake types, we found that restoration through reduction of nutrient loading is effective in all cases. In contrast, biomanipulation only works in seepage lakes with diffuse nutrient inputs, while lake flushing will even be counterproductive in lakes with nutrient point sources. The main conclusion of the presented analysis is that a priori assessment of spatial heterogeneity caused by nutrient loading and hydrology is essential for successful restoration of lake ecosystems.

Highlights

The water quality of aquatic ecosystems is increasingly degraded by excessive nutrient loading and changes in natural hydrology (Fink et al, 2018; Kroeze et al, 2013; Tong et al, 2019; Tonkin et al, 2018)
Results of this first step are used to interpret the effect of nutrient loading and hydrology types on the success of lake-wide restoration measures
Since we demonstrated that the effectiveness of all three lake measures is inextricably linked with the lake type, we propose that a priori assessment of spatial heterogeneity caused by the nutrient loading and hydrology is essential for successful restoration of lake ecosystems

Summary

Introduction

The water quality of aquatic ecosystems is increasingly degraded by excessive nutrient loading and changes in natural hydrology (Fink et al, 2018; Kroeze et al, 2013; Tong et al, 2019; Tonkin et al, 2018). Human-alterations to the natural hydrology and changed pathways of allochthonous nutrient input are underlying this widespread degradation of aquatic ecosystems (Beusen et al, 2016; Doughty et al, 2016; Tonkin et al, 2018). Sources of allochthonous nutrient inputs are numerous and include atmospheric wet and dry deposition, loading via water flows such as groundwater, rivers and tide (Beusen et al, 2016). An often overlooked source of nutrients originates from animal motility such as fish and bird migration (Doughty et al, 2016) These various sources of allochthonous nutrient inputs are commonly categorised into two main load types; point and diffuse nutrient sources (Rissman and Carpenter, 2015). This difference affects the spatial heterogeneity in resource availability within ecosystems, which in turn creates spatial patterns in the aquatic food web (Doi, 2009)

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