Project Topics
Get Complete Project Material File(s) Now! »
Biodiversity and Ecosystem Services (BES)
After reviewing biodiversity and ecosystem function relationships, this following section is dedicated to ecosystem services (ES), which can link the ecosystem functions to human society. Ecosystem services are the conditions and processes through which natural ecosystems, and the species that make them up, sustain and fulfil human life (Daily, 1997). Consequently, ES contribute to raise awareness of the importance of protecting ecosystems, and can also provide decision makers with quantitative data, enabling them to consider all aspects of the socio-economic-ecological system in which we live (Kremen, 2005; Cardinale et al., 2012).
A large number of studies concerning ecosystem services have been carried out over the last decade and major international search initiatives have formed and rapidly developed. The Millennium Ecosystem Assessment 2005 (MA 2005) firstly brought the concept and classification of ecosystem services into widespread use. Following MA, the Economics of Ecosystems and Biodiversity (TEEB, 2010) centring on economic valuation was launched. Then the Mapping and Assessment of Ecosystems and their Services (MAES) initiative aimed to produce a framework for ecosystem assessment to ensure a harmonised approach across the EU, which uses The Common International Classification of Ecosystem Services (CICES) for more detailed and more comprehensive classification of ES. The Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) was established in 2012 with the aim to assess ecosystem services on a global level. The number of articles including “Ecosystem services” and the four main categories of ES are shown in Figure I-2 and I-3 respectively.
Water purification service
At global scale, although a few provision ecosystem services have been improved (e.g. crop provision), many key ecosystem services are at risk of degradation, mainly regulating services, e.g. 70% of the regulating services are degraded or being used unsustainably (MA, 2005). Particularly, water purification, as a regulating service controlling water quality, is of great importance for the dense populated regions with heavy pressure on water resources, such as Europe (European Water Framework Directive, TEEB 2010). For example, water purification seems to be the most degraded service among all regulating services in Spain (Santos-Martín et al., 2013).
In general, the MA emphasizes the identification and use of indicators for ecosystem services survey and trends assessments (MA, 2005). An ecosystem service indicator is information which communicates the characteristics and trends of ecosystem services, making it possible for policy-makers to understand the conditions of delivery, as well spatial and temporal trends and rate of change in ecosystem services (Layke et al., 2012). A rather broad interpretation of this definition includes datasets and proxy indicators such as land cover and land use (Maes et al., 2016). Potential indicators used to map (or quantify) water purification service (i.e. biophysical indicator on the supply side) are nutrient retention capacity, denitrification, the area or proposition occupied by riparian forest, the amount of waste processed by ecosystems (volume/mass of water processes) and the naturalness of riverbeds and floodplains (Layke, 2009; Maes et al., 2012; La Notte et al., 2012 a, b; Albert et al., 2015). There are different approaches to conduct the biophysical assessment of water purification service delivery at different scales. For example, the nutrient retention capacity is commonly used in approaches to quantify the water purification capacity in laboratory experiments (microcosm), in situ measurements (e.g. nutrient enrichment experiments) and modelling approaches (e.g. The Soil and Water Assessment Tool (SWAT) models).
On the demand side, the contribution of ecosystem services to human well-being can be socio-cultural (Chan et al., 2012) or monetary (Wegner and Pascual, 2011).
1) The socio-cultural value i.e., the contributions to user’s cultural identity and heritage, spiritual values, or good social relationships or living security obtained through ecosystem services (Chan et al., 2012). It is given by users to ecosystem services was measured through indicators that express the importance users allocate to them in a non-market value elicitation context (de Groot et al., 2012). For instance, according to the investigation of 796 respondents in Spain during 2008-2009 (Martín-López et al., 2014), water purification was the service showing highest saliency (66.5% of respondents selected it as being of primary importance) of all ecosystem services.
2) The monetary value of ecosystem services can be estimated using contingent valuation and replacement methods. For instance, Martín-López et al. (2014) report the monetary values of water purification service (i.e. 210840 euros ha−1 year−1) based on contingent valuation. In total, provisioning services accounted for 65.6% to the monetary value of the sum of all the ES values, regulating services accounted for 7.7%, and cultural services accounted for 26.4% (Martín-López et al., 2014).
Concerning the demand side, one can see that human beings have very high demand of water purification service (socio-cultural aspect), but the estimated monetary value of this regulating service is relative low (economic aspect). One of the possible reasons could be the lack of accurate estimation and complementary understanding of the supply side of water purification (ecological aspect), which may underestimate its economic value. There may exist mismatching between the supply flow and demand of this service with time and/or space (Albert et al., 2014). Finally, the water purification service estimations in both supply and demand sides may be limited by the following uncertainties, like (i) the number of benefits considered (e.g. nitrogen, phosphorus and pesticide removal); (ii) the methods of quantification of biophysical units and valuations; (iii) the variables included in the valuation metrics (e.g. market price) (Boithias et al., 2016). Moreover, many valuations of ES, to date, do not integrate biophysical processes but focus on expert knowledge and spatial analyses (e.g. Burkhard et al., 2012; Nedkov and Burkhard, 2012). Biophysical processes could help to understand the mechanistic links by integrating biophysical indicators associated with the structure and the functionalities of the ecosystems to provide ecological services. More researches are needed to understand biophysical processes involved in the ES supply to realistically valuate them.
Ecosystem functions and nitrate removal under stress in rivers
The biodiversity, ecosystem function and their relationships in riverine ecosystems could be modified by man-made pressures, including global change, chemical pollution for example, heavy metals, medical residues, pesticides or nutrient enrichment (eutrophication), physical changes (e.g. channelization and dam), loss or alteration of riparian zones (Wakelin et al., 2008). Such stresses can alter river characteristics, negatively impact ecological communities, disrupt river functions and related ecosystem services such as regulation for water quality (Bernot and Dodds, 2005; Schäfer et al., 2007; Simon et al., 2009; La Notte et al., 2012a; Rasmussen, 2012c; Dehedin et al., 2013; Elosegi and Sabater, 2013; Albert et al., 2014)(refer to Figure I-2).
In the literature, there is much focus on the influences of stressors on river characteristics, but few studies on how these stressors affect ecosystem functions (but see Meyer et al., 2005; Bott, 2006; Piscart et al., 2009; Simon et al., 2009; Izagirre et al., 2013), and rare studies on how the relationship between biodiversity and ecosystem functions evolves under stressors, especially in animal ecology and freshwater ecosystems (Piscart et al., 2009; Cornut et al., 2012; Steudel et al., 2012; Woodward et al., 2012; Colas et al., 2016). Despite the decline and change of biodiversity driven by anthropogenic impact, most BEF studies manipulated species richness or composition without considering anthropogenic stressors (Hooper et al., 2005; Hillebrand and Matthiessen, 2009; Reiss et al., 2009). In that case, the predictions of the relationship among biodiversity and ecosystem functions under stressful conditions might be unreliable when all the three components (biodiversity, ecosystem function and stress) are not simultaneously considered in a system (McMahon et al., 2012).
In particular, the nitrate removal function in rivers is assumed to be affected by these stressors in several ways. First, physical alteration, such as channelization that removes streambed heterogeneity and volume of the hyporheic sediment might decrease the water residence time, and thus decrease nitrate removal (Nogaro et al., 2013). Secondly, chemical pollution, by for example pesticides may cause direct toxic depression of microbial metabolic activity, reducing nitrate removal (Schäfer et al., 2011; Artigas et al., 2014). Also, elevated nitrate loads, representing another type of pollutants, may increase or ‘‘saturate’’ the ability of rivers to attenuate nitrate pollution (Mulholland et al., 2008). Finally, since it was previously stated that biodiversity is indirectly or directly involved in the nitrate removal processes, all stressors that affect this biodiversity (e.g. the loss or substitution of some species or functional groups) is supposed to change the capacity of nitrate removal in riverine ecosystems (Newbold et al., 2006; Flores et al., 2014).
Nutrient and DOC reduction rates
The definition of nutrient reduction rate is referred to the total quantity of nutrient that is removed from water when passing through the sediment of microcosms. It was estimated by the changes of nitrate and DOC quantities over time (time interval: 7 days) in the reservoir water. The nitrate reduction rate quantifies the sum of all the processes which transform the nitrate and that can happen during the water flow through the sediment column, mainly denitrification, DNRA and anammox pathways. DOC reduction rate referred to all the microbial metabolism processes of aerobic and anaerobic re-mineralization of DOC. It mainly occurred as an oxidation process of DOC.
Statistical analysis
The normal distribution and homoscedasticity of variances of nitrate reduction were verified. Before testing faunal influences, the homogeneity of the nutrient concentrations and nitrate reduction rates between intended treatments were examined by one-way ANOVA test.
O2 concentration, nitrate and DOC reduction rates were measured repeatedly in each microcosm at different times (P2, P3 and P4). The variations of these variables were examined by one-way repeated measures RM-ANOVA with treatment as a main factor and time as the repeated factor. The sphericity assumption was examined (Mauchly’s sphericity test). If RM-ANOVAs detected significant differences, pairwise post-hoc tests (Bonferroni multiple comparisons) were undertaken to examine the differences. Significance was determined at ɑ = 0.05 (95% confidence). Since O2 concentration, nitrate and DOC reduction rates at SBM treatment were only available in Phase 2, these data of SBM treatment were not included in RM-ANOVA analysis. Also, O2 concentration, nitrate and DOC reduction rates in Phase 1 were not included in the statistical analysis and were only performed as references in the Figure II.2-2, Figure II.2-3 and Figure II.2-4.
For comparing the variables that were only available at the end of the experiment (biofilm biomasses, denitrification and respiration rates) in two treatments (SB and SBMM), Mann-whitney test was used.
Table of contents :
Chapitre I: General introduction
I.1 Résumé du chapitre I
I.2 Biodiversity and ecosystem functions
I.3 Biodiversity and Ecosystem Services (BES)
I.4 Water purification service and nitrate removal
I.5 What are the links between invertebrates and the nitrate removal function?
I.6 Ecosystem functions and nitrate removal under stress in rivers
I.7 Objectives and organization of the thesis
Chapter II: The relationship between invertebrate community and the nitrate removal function
II.1 Résumé du chapitre II
II.2 Part 1: Effect of time and invertebrates on nitrate removal in laboratory experimental conditions
II.3 Part 2: Effects of macroinvertebrate traits on nitrate removal in stream sediments
II.4 Main discussion
Chapter III: The relationship between invertebrate community and the nitrate removal function in the condition of stress
III.1 Résumé du chapitre I III
III.2 Part 1: Effects of meiofauna and macrofauna on nitrate reduction in freshwater macro-porous sediment under pesticide stress
III.3 Part 2:Biodiversity and ecosystem purification service in an alluvial wetland
III.4 Main discussion
Chapitre IV: General discussion, conclusion and perspectives
IV.1 General discussion
IV.2 Conclusion
IV.3 Perspective
References
