Master's Thesis Summary
The communities of benthic macroinvertebrates of the freshwater and brackish water transition zone of the Mira estuary was studied to evaluate the composition and structure of the communities according to the salinity gradient and to assess potential for biological resources. Spatial variability of macrobenthos revealed two different areas: a freshwater area, with median annual salinities of 0.5, characterized by high abundances and taxa, mainly insects; and a brackish water region, with higher salinities, characterized by salinity tolerant taxa (Corophium orientale, Cyathura carinata. Lekanesphaera spp., Alkmaria romijni, Hediste diversicolor e Streblospio shrubsolii) and showing higher diversity and evenness. Seasonal variations were observed in both areas, although higher in the freshwater region. Nevertheless, spring was the season with higher abundances while autumn showed the lowest. The upper limit of the saline estuary of this water body was determined to be located 8 km upstream of Odemira village and the transition area between freshwater and brackish water extended approximately for 2.7 km upstream of this limit. The communities of benthic macroinvertebrates in this transition zone are distributed gradually along the saline gradient which is in accordance with the ecocline model. The potential biological resources to explore in the freshwater and brackish water zone in the Mira estuary was evaluated by inquiries and complemented with the information available in the bibliography. Only recreational fishing was practice, therefore fishing rod the only gear used. Ragworms and shrimp were the preferential bait for the capture of Dicentrarchus labrax, Anguilla anguilla, Diplodus sargus, Solea spp., and corn for Cyprinus carpio. Procambarus clarkii, Palaemon longirostris and Corbicula fluminea were found to be potential resources for human consumption or for bait.
Keywords: transition area, benthic macrofauna, spatial and temporal variations, saline gradient, potential biologic resources
Keywords: transition area, benthic macrofauna, spatial and temporal variations, saline gradient, potential biologic resources
PhD. Research
Summary
Freshwater-estuarine interface (FEI) is characterized by high structural heterogeneity and variations in water and sediment physicochemical conditions (Basset et al., 2001) that constrain organisms living in these areas and force them to develop various adaptations to cope with stressful environmental conditions. Benthic invertebrates are widely used as indicators of estuarine environmental status because they respond predictably to many kinds of natural and anthropogenic stress (Weisberg et al., 1997), reason why they were included in the Water Framework Directive (WFD) as a biological element. Spatial and temporal heterogeneity of benthic communities in FEI can be strongly determined by salinity range that is used as a discriminating factor (Wolf et al., 2009) and tidal influence, which changes condition in intertidal (e.g. temperature, humidity, desiccation and inundation) and subtidal habitats (e.g. wide-ranging levels of salinity, depth, light penetration, temperature) (Bate et al., 2002). The assessment of the Ecological Quality Status (EQS) in these areas with low salinity and tidal fluctuation is particularly challenging because benthic communities are mainly dominated by species that are tolerant both to natural and human induced pressures, plus these communities are still poorly known worldwide (Rundle et al., 1998).
Portuguese estuaries are relatively well-studied, with several studies addressing the benthic taxonomic composition, changes in the community structure in response to spatial gradients and seasonal variations in environmental conditions (Carvalho et al., 2006; Chainho et al., 2008; Patrício et al., 2009). Nevertheless, historical data on biological elements is not available for tidal freshwater and oligohaline stretches (Bettencourt et al., 2004). This knowledge is necessary so that a baseline of current conditions can be determined and an appropriate methodology to assess its EQS can be developed (McLuscky and Elliott, 2007). Before its EQS assessment, the boundary between freshwater and oligohaline stretches must be classified based on its typology and the different water bodies within this interface must be previously defined (Vincent et al., 2002; Perus et al., 2004). Within these stretches, there are however distinct habitats (Medeiros et al., 2012). While in the end the ecological status must be reported at the water body level (Vincent et al., 2002), reference conditions to determine the EQS need to be defined accounting for the type of habitat features that will influence biological communities (Muxika et al., 2007; de Paz et al., 2008; Teixeira et al., 2008). Thus, if within a water body different habitats are identified and monitored, then reference conditions that reflect the expected natural biological communities at each habitat should be defined (Teixeira et al., 2008).
The definition of reference conditions are perceived as the set of conditions to be expected in the absence of or under minimal anthropogenic disturbances (Economu, 2002), which plays an essential role for the assessment of the EQS (Nijboer et al., 2004). The WFD states that type-specific reference conditions should firstly consider zoogeographic features and abiotic variables in order to derive strata of the highest possible ecological homogeneity. Biological attributes of ecological quality should then be selected accordingly to their sensitivity to particular types of environmental stress and reference conditions for the selected metrics and the appropriate strata should be specified (Economu, 2002). The use of existing reference conditions should be the preferred approach for setting baselines where it is possible to find current habitats in locations where anthropogenic influences are negligible (Economu, 2002). Although, the major impediment to the application of this approach is that locating genuinely unimpacted sites may be challenging (Bennion et al., 2004; Silvestri et al., 2005). So, WFD indicates several alternative methods for types where reference conditions are not currently available (such as the freshwater-estuarine interface of the Mira River estuary) (Medeiros et al., 2012). Historical data information, modelling and expert judgement are described by the WFD to set reference conditions (Directive 2000/60/EC) and alternative benchmark conditions have been indicated as a possible approach for such problem (Wolf et al., 2009). Several biological methodologies already developed have proven effective in the assessment of ecological conditions in variety of management settings and in distinct water types (e.g. Alba-Tercedor et al., 2002; Teixeira et al., 2008; Borja et al., 2011). For Portuguese transitional waters and for benthic invertebrates, one of the proposed and adopted methodologies is the Benthic Assessment Tool - BAT (Teixeira et al., 2009), a multimetric methodology based on the Margalef (1969), the Shannon-Wiener diversity (Shannon and Weaver, 1963) and AMBI (AZTI Marine Biotic Index, Borja et al., 2000) indices.
Nonetheless, due to the lack of physicochemical and biological data information and knowledge concerning the upper areas of the estuaries (particularly, the Mira River estuary) and the absence of reference conditions for habitats therein, existing ecological assessment tools have failed when applied to low salinity areas of transitional systems (de Paz et al., 2008), especially because diversity is a common denominator (Teixeira et al., 2008). These problems indicate the need to set reference conditions and adapt existing assessment tools and EQR thresholds in order to make them useful indicators in freshwater-estuarine transitional areas. The poor knowledge of the local fauna coupled with the traditional morphological approaches can cause difficulties in implementing large scale biomonitoring programs (Hajibabaei et al., 2011), limiting the adaptation of pre-existing benthic assessment tools to evaluate the EQS of an ecosystem. More than an adaptation, a considerable change in monitoring technologies is the new challenge for ecosystem monitoring and assessment, driven by the need for new tools which will support more rapid, accurate and timely observations of ecosystem structure and function (Baird and Hajibabaei, 2012). Molecular methods such as DNA barcoding are emerging as a tool for species identification and more recently, in environmental biomonitoring (Stein et al., 2013). DNA sequence-based analyses have provided evolutionary biologists and ecologists the opportunity to address questions that were not still answered using other types of data (Hajibabaei et al., 2011), since genomic approaches to taxon diagnosis exploit diversity among DNA sequences to identify organisms. According to Sweeney et al. (2011), DNA barcoding has much more to offer than the traditional taxonomic identification of benthic invertebrates, since a molecular approach can provide a finer resolution for evaluating environmental change associated with both natural and anthropogenic processes. Nevertheless, this methodology doesn’t replace morphological taxonomy but it can improve taxonomy and, eventually lead to a greater understanding of community structure, pollution tolerance at the species level and effective bioassessment of an aquatic ecosystem (Baird and Sweeney, 2011).
Keywords: benthic macroinvertebrates, biotic indices, low salinity areas, ecological quality status, DNA barcoding
Freshwater-estuarine interface (FEI) is characterized by high structural heterogeneity and variations in water and sediment physicochemical conditions (Basset et al., 2001) that constrain organisms living in these areas and force them to develop various adaptations to cope with stressful environmental conditions. Benthic invertebrates are widely used as indicators of estuarine environmental status because they respond predictably to many kinds of natural and anthropogenic stress (Weisberg et al., 1997), reason why they were included in the Water Framework Directive (WFD) as a biological element. Spatial and temporal heterogeneity of benthic communities in FEI can be strongly determined by salinity range that is used as a discriminating factor (Wolf et al., 2009) and tidal influence, which changes condition in intertidal (e.g. temperature, humidity, desiccation and inundation) and subtidal habitats (e.g. wide-ranging levels of salinity, depth, light penetration, temperature) (Bate et al., 2002). The assessment of the Ecological Quality Status (EQS) in these areas with low salinity and tidal fluctuation is particularly challenging because benthic communities are mainly dominated by species that are tolerant both to natural and human induced pressures, plus these communities are still poorly known worldwide (Rundle et al., 1998).
Portuguese estuaries are relatively well-studied, with several studies addressing the benthic taxonomic composition, changes in the community structure in response to spatial gradients and seasonal variations in environmental conditions (Carvalho et al., 2006; Chainho et al., 2008; Patrício et al., 2009). Nevertheless, historical data on biological elements is not available for tidal freshwater and oligohaline stretches (Bettencourt et al., 2004). This knowledge is necessary so that a baseline of current conditions can be determined and an appropriate methodology to assess its EQS can be developed (McLuscky and Elliott, 2007). Before its EQS assessment, the boundary between freshwater and oligohaline stretches must be classified based on its typology and the different water bodies within this interface must be previously defined (Vincent et al., 2002; Perus et al., 2004). Within these stretches, there are however distinct habitats (Medeiros et al., 2012). While in the end the ecological status must be reported at the water body level (Vincent et al., 2002), reference conditions to determine the EQS need to be defined accounting for the type of habitat features that will influence biological communities (Muxika et al., 2007; de Paz et al., 2008; Teixeira et al., 2008). Thus, if within a water body different habitats are identified and monitored, then reference conditions that reflect the expected natural biological communities at each habitat should be defined (Teixeira et al., 2008).
The definition of reference conditions are perceived as the set of conditions to be expected in the absence of or under minimal anthropogenic disturbances (Economu, 2002), which plays an essential role for the assessment of the EQS (Nijboer et al., 2004). The WFD states that type-specific reference conditions should firstly consider zoogeographic features and abiotic variables in order to derive strata of the highest possible ecological homogeneity. Biological attributes of ecological quality should then be selected accordingly to their sensitivity to particular types of environmental stress and reference conditions for the selected metrics and the appropriate strata should be specified (Economu, 2002). The use of existing reference conditions should be the preferred approach for setting baselines where it is possible to find current habitats in locations where anthropogenic influences are negligible (Economu, 2002). Although, the major impediment to the application of this approach is that locating genuinely unimpacted sites may be challenging (Bennion et al., 2004; Silvestri et al., 2005). So, WFD indicates several alternative methods for types where reference conditions are not currently available (such as the freshwater-estuarine interface of the Mira River estuary) (Medeiros et al., 2012). Historical data information, modelling and expert judgement are described by the WFD to set reference conditions (Directive 2000/60/EC) and alternative benchmark conditions have been indicated as a possible approach for such problem (Wolf et al., 2009). Several biological methodologies already developed have proven effective in the assessment of ecological conditions in variety of management settings and in distinct water types (e.g. Alba-Tercedor et al., 2002; Teixeira et al., 2008; Borja et al., 2011). For Portuguese transitional waters and for benthic invertebrates, one of the proposed and adopted methodologies is the Benthic Assessment Tool - BAT (Teixeira et al., 2009), a multimetric methodology based on the Margalef (1969), the Shannon-Wiener diversity (Shannon and Weaver, 1963) and AMBI (AZTI Marine Biotic Index, Borja et al., 2000) indices.
Nonetheless, due to the lack of physicochemical and biological data information and knowledge concerning the upper areas of the estuaries (particularly, the Mira River estuary) and the absence of reference conditions for habitats therein, existing ecological assessment tools have failed when applied to low salinity areas of transitional systems (de Paz et al., 2008), especially because diversity is a common denominator (Teixeira et al., 2008). These problems indicate the need to set reference conditions and adapt existing assessment tools and EQR thresholds in order to make them useful indicators in freshwater-estuarine transitional areas. The poor knowledge of the local fauna coupled with the traditional morphological approaches can cause difficulties in implementing large scale biomonitoring programs (Hajibabaei et al., 2011), limiting the adaptation of pre-existing benthic assessment tools to evaluate the EQS of an ecosystem. More than an adaptation, a considerable change in monitoring technologies is the new challenge for ecosystem monitoring and assessment, driven by the need for new tools which will support more rapid, accurate and timely observations of ecosystem structure and function (Baird and Hajibabaei, 2012). Molecular methods such as DNA barcoding are emerging as a tool for species identification and more recently, in environmental biomonitoring (Stein et al., 2013). DNA sequence-based analyses have provided evolutionary biologists and ecologists the opportunity to address questions that were not still answered using other types of data (Hajibabaei et al., 2011), since genomic approaches to taxon diagnosis exploit diversity among DNA sequences to identify organisms. According to Sweeney et al. (2011), DNA barcoding has much more to offer than the traditional taxonomic identification of benthic invertebrates, since a molecular approach can provide a finer resolution for evaluating environmental change associated with both natural and anthropogenic processes. Nevertheless, this methodology doesn’t replace morphological taxonomy but it can improve taxonomy and, eventually lead to a greater understanding of community structure, pollution tolerance at the species level and effective bioassessment of an aquatic ecosystem (Baird and Sweeney, 2011).
Keywords: benthic macroinvertebrates, biotic indices, low salinity areas, ecological quality status, DNA barcoding
Mira River, SW Portugal
The Mira River is a Portuguese river located in southwestern Alentejo. Its meander length is 145 km. It has its sources on the northern slopes of the Serra do Caldeirão and pursues a southeast-northwest course with a generally mild inclination to the Atlantic Ocean, where it discharges through a small calm delta near the town of Vila Nova de Milfontes, 115 km south to Lisbon. It is one of the two only rivers in Portugal with a chiefly south-north orientation (the other being its neighbour Sado) and one of the few rivers in Europe with this orientation. Mira basin borders Sado River basin at north and Guadiana River basin eastwards.
Main tributaries in the right bank: Torgal Rivulet, Luzianes River and Perna Seca River. Main tributaries in the left bank include rivers Macheira, Guilherme and Telhares.
Distributary streamlines run perpendicularly along the coastline and discharge directly to the Atlantic Ocean.
Main tributaries in the right bank: Torgal Rivulet, Luzianes River and Perna Seca River. Main tributaries in the left bank include rivers Macheira, Guilherme and Telhares.
Distributary streamlines run perpendicularly along the coastline and discharge directly to the Atlantic Ocean.
Keywords
Aquatic Ecosystems
Benthic Invertebrates Taxonomy
Benthic Macroinvertebrates
Biotic Indices
DNA Barcoding
Ecological Quality Status
Monitoring Programmes
Benthic Invertebrates Taxonomy
Benthic Macroinvertebrates
Biotic Indices
DNA Barcoding
Ecological Quality Status
Monitoring Programmes