**5.2.1 Phosphorous (P) and nitrogen (N) management**

Phosphorous compounds are measured as total phosphorous (TP) and soluble reactive phosphorous (SRP) and nitrogen is measured as total nitrogen (TN), ammonia (NH3+), nitrate (NO3-) and nitrite (NO2). Understanding the dynamics of P and N is essential whilst managing water quality. In shallow enriched lakes internal cycling of P can result in highly variable TP concentrations, often a strong seasonal variation occurs as well as this can usually be high in the summer when P is released from the sediment under anoxic conditions. Nitrogen concentrations however in summer are low in shallow temperate lakes due to an increased assimilation by algae. The high algal biomass leads to oxygen depletion and loss of biodiversity and fish mortality. Understanding of the environmental

Management Strategies for Large River

of salt into the system (Bos et al., 1999).

**5.2.4 Management of toxic substances** 

**5.2.3 Controlling salinisation** 

Floodplain Lakes Undergoing Rapid Environmental Changes 343

Salinity is becoming an increasingly challenging issue for managing water quality and ecosystems of many lowland riverine floodplain wetlands worldwide. Riverine floodplains of coastal zones are frequently inundated by saline water as a result of sea level rise (Schallenberg et al., 2003). Micro-crustaceans can be utilized to manage water quality in wetland since increased salinity in wetlands cause physiological stress in zooplankton resulting from limited osmoregulatory function influencing feeding rate, growth, reproduction, body size, life span and survival capacity. Cladocerans such as *Sida* and *Simocephalus* show optima very close to the mean value of salinity ranging between 0.2 and 17.4% (Aminsick et al., 2005). Amongst chydorids, *Acroperus harpae*, *Graptoleberis testudinaria*, *Alonella nana* and *E. lamellatus* prefer low salinity ranges while *Oxyurella* and *Leydigia* prefer high salinity ranges (Aminsick et al., 2005). Transfer function weighted averaging (WA) models for salinity show that cladoceran assemblages are excellent proxies for reconstructing salt concentration in wetlands and help identifying the timing of the release

Salinity in arid and semi-arid rivers is influenced by prolonged drought, river regulation, periodic low flows and intensive land use activities in river catchments (Nielsen et al., 2003a). Unlike lowland coastal zones, arid and semi-arid rivers receive salts from groundwater and terrestrial materials via the rock weathering or from the transboundary pollutants from the atmosphere. During low flows, the combination of evaporation and groundwater intrusions assist to increase the natural salinity levels (Jolly et al., 2001). In Murray Darling River, Australia, however, the natural processes have been significantly altered by humans following the European arrival (Jolly et al., 2001). There have been noticeable differences in species richness of micro-crustaceans in low-flows and high salinity periods (Nielsen et al., 2003b, 2007). Zooplankton sampled from longitudinal gradients of the South American arid rivers such as the Salado River (Buenos Aires Province, Argentina) indicates that they have species-specific variations in salinity optima and tolerances (Claps et al. 2009). Hatching of resting eggs of zooplankton is reported to have reduced in wetland with high salinity levels (Skinner et al., 2001). Variance partitioning of benthic cladocerans response to lake water salinity in Kenya suggest that salinity explained more than 51% of the observed variations (Verschuren et al., 2000). Recently Barry et al. (2005) assessed the hatching response of *Daphnia* ephippia to the diatom inferred salinity levels of a sediment core collected from a lake in southwest Victoria, Australia, where significant differences in ephippial densities and hatching were observed with respect to varying salinity levels. Given the increased sensitivity to salinity by cladocerans these organisms can be used to quantify a

threshold of salt that are appropriate for a healthy floodplain wetland ecosystems.

Pollution caused by toxic substances is becoming a major threat to diversity, composition and abundances of biota in large river floodplain lakes. Most trace metals have natural mineral origins and it is essential to understand the amount of mineral inputs into wetlands. Records of anthropogenic lead pollution in European lakes are reported to have determined by ratios of 206Pb/207Pb in sediment. Natural ratios of the isotope (206Pb:207Pb) are generally higher than those of anthropogenically induced lead pollution and can be determined by analysis of floodplain lake sediments. Recently pyrite pollution has become one of major issues of the organic metallic toxicity across the Murray Darling Basin, Australia due to the

perturbations of P and N and toxic algal blooms has been advanced through the use of the PCR-DNA technique on cladoceran eggs. Weider et al. (1997) reported that there is a link between changes in allozyme allele and eutrophication caused by increased nitrogen concentrations and algal bloom in the European lowland wetland systems. External nutrient loading in some wetlands from the point source has been controlled by external sewage treatment. However, recovery of the shallow floodplains wetland ecosystems has been delayed due to internal phosphorous loading. Cladoceran-inferred transfer function for TP has been developed in north Europe in order to examine the relationship between zooplankton assemblages and P-induced eutrophication in lowland lake system (e.g., Brodersen et al., 1998). Some benthic chydorid cladocerans are reported to have been predominantly occurring in lowland lakes with relatively high algal productivity. Ecological effect of pollution in interconnected shallow floodplain lakes of the River Erewash system in the UK suggest that significant P and N enrichment in the catchment over the past decades have resulted in a switch from submerged macrophytes to phytoplankton dominant system which have altered macro-and-micro-invertebrates communities over a range of time scales in the past (Sayer et al., 1999; Sayer & Roberts, 2001). Evaluation of P and N concentrations in lowland large river floodplain lakes at temporal and spatial scales using the micro-crustacean assemblages provides a crucial understanding of the land use activity and ecosystem change.

#### **5.2.2 Controlling acidification**

Unlike upland lakes the effects of acidification on water quality of large river floodplain lakes is relatively less studied. The impacts of acid deposition on upland rivers and lakes of Europe are shown to have influenced negatively on ecosystem structure and function as a result of sulphur-induced acid rain in the past. In order to improve water quality, attempts were made to reconstruct acidity (lake water pH) inferred by a range of biological proxies archived in lake sediment (Battarbee, 2000). Using modern remains of zooplankton, cladoceran-based pH transfer function was developed. Cladocerans responded very well to acidification of a range of lakes (N=22) distributed across Germany and Austria over the past. The reconstruction of pH using a sediment core derived from the Lake Groer Arbersee shows that a severe decrease in pH in this lake from about 6 to values of about 4.8 over the past decades (Krause-Dellin & Steinberg, 1986). Some acidobiontic species of cladoceran such as *Alonella exigua* preferring pH less than 5.5 are reported to have survived. Information regarding changes in micro-crustacean assemblages and diversity provides the timing of catchment modification of large river floodplain lakes by humans and help resource managers control acidification. Some endemic zooplankton species of copepods and cladocerans in Australian rivers and wetland systems are reported to have been associated with low water pH, which in turn is regarded as zooplankton preferring habitats with dominant granites and soil types (Tayler et al., 1996). Sulphidic acidification in the Murray Darling Basin is rapid (Baldwin & Mitchell, 2000). Sulpher present in floodplain sediments are exposed to reduce sulphide due to prolonged drought and river regulations enhancing acidification (Hall et al., 2006). A range of ecological effects of sulphidic acidification has been documented in the Murray River Basin. However, the timing for water quality change has not yet been tested using micro-crustaceans. Sulphidic sediment influence hatchability of micro-crustaceans and reduce diversity of acid-sensitive taxa. The use of these animals can help identifying habitat types that are exposed to sulphidic process and reconstructing acidification over various time scales.

#### **5.2.3 Controlling salinisation**

342 International Perspectives on Global Environmental Change

perturbations of P and N and toxic algal blooms has been advanced through the use of the PCR-DNA technique on cladoceran eggs. Weider et al. (1997) reported that there is a link between changes in allozyme allele and eutrophication caused by increased nitrogen concentrations and algal bloom in the European lowland wetland systems. External nutrient loading in some wetlands from the point source has been controlled by external sewage treatment. However, recovery of the shallow floodplains wetland ecosystems has been delayed due to internal phosphorous loading. Cladoceran-inferred transfer function for TP has been developed in north Europe in order to examine the relationship between zooplankton assemblages and P-induced eutrophication in lowland lake system (e.g., Brodersen et al., 1998). Some benthic chydorid cladocerans are reported to have been predominantly occurring in lowland lakes with relatively high algal productivity. Ecological effect of pollution in interconnected shallow floodplain lakes of the River Erewash system in the UK suggest that significant P and N enrichment in the catchment over the past decades have resulted in a switch from submerged macrophytes to phytoplankton dominant system which have altered macro-and-micro-invertebrates communities over a range of time scales in the past (Sayer et al., 1999; Sayer & Roberts, 2001). Evaluation of P and N concentrations in lowland large river floodplain lakes at temporal and spatial scales using the micro-crustacean assemblages

provides a crucial understanding of the land use activity and ecosystem change.

and reconstructing acidification over various time scales.

Unlike upland lakes the effects of acidification on water quality of large river floodplain lakes is relatively less studied. The impacts of acid deposition on upland rivers and lakes of Europe are shown to have influenced negatively on ecosystem structure and function as a result of sulphur-induced acid rain in the past. In order to improve water quality, attempts were made to reconstruct acidity (lake water pH) inferred by a range of biological proxies archived in lake sediment (Battarbee, 2000). Using modern remains of zooplankton, cladoceran-based pH transfer function was developed. Cladocerans responded very well to acidification of a range of lakes (N=22) distributed across Germany and Austria over the past. The reconstruction of pH using a sediment core derived from the Lake Groer Arbersee shows that a severe decrease in pH in this lake from about 6 to values of about 4.8 over the past decades (Krause-Dellin & Steinberg, 1986). Some acidobiontic species of cladoceran such as *Alonella exigua* preferring pH less than 5.5 are reported to have survived. Information regarding changes in micro-crustacean assemblages and diversity provides the timing of catchment modification of large river floodplain lakes by humans and help resource managers control acidification. Some endemic zooplankton species of copepods and cladocerans in Australian rivers and wetland systems are reported to have been associated with low water pH, which in turn is regarded as zooplankton preferring habitats with dominant granites and soil types (Tayler et al., 1996). Sulphidic acidification in the Murray Darling Basin is rapid (Baldwin & Mitchell, 2000). Sulpher present in floodplain sediments are exposed to reduce sulphide due to prolonged drought and river regulations enhancing acidification (Hall et al., 2006). A range of ecological effects of sulphidic acidification has been documented in the Murray River Basin. However, the timing for water quality change has not yet been tested using micro-crustaceans. Sulphidic sediment influence hatchability of micro-crustaceans and reduce diversity of acid-sensitive taxa. The use of these animals can help identifying habitat types that are exposed to sulphidic process

**5.2.2 Controlling acidification** 

Salinity is becoming an increasingly challenging issue for managing water quality and ecosystems of many lowland riverine floodplain wetlands worldwide. Riverine floodplains of coastal zones are frequently inundated by saline water as a result of sea level rise (Schallenberg et al., 2003). Micro-crustaceans can be utilized to manage water quality in wetland since increased salinity in wetlands cause physiological stress in zooplankton resulting from limited osmoregulatory function influencing feeding rate, growth, reproduction, body size, life span and survival capacity. Cladocerans such as *Sida* and *Simocephalus* show optima very close to the mean value of salinity ranging between 0.2 and 17.4% (Aminsick et al., 2005). Amongst chydorids, *Acroperus harpae*, *Graptoleberis testudinaria*, *Alonella nana* and *E. lamellatus* prefer low salinity ranges while *Oxyurella* and *Leydigia* prefer high salinity ranges (Aminsick et al., 2005). Transfer function weighted averaging (WA) models for salinity show that cladoceran assemblages are excellent proxies for reconstructing salt concentration in wetlands and help identifying the timing of the release of salt into the system (Bos et al., 1999).

Salinity in arid and semi-arid rivers is influenced by prolonged drought, river regulation, periodic low flows and intensive land use activities in river catchments (Nielsen et al., 2003a). Unlike lowland coastal zones, arid and semi-arid rivers receive salts from groundwater and terrestrial materials via the rock weathering or from the transboundary pollutants from the atmosphere. During low flows, the combination of evaporation and groundwater intrusions assist to increase the natural salinity levels (Jolly et al., 2001). In Murray Darling River, Australia, however, the natural processes have been significantly altered by humans following the European arrival (Jolly et al., 2001). There have been noticeable differences in species richness of micro-crustaceans in low-flows and high salinity periods (Nielsen et al., 2003b, 2007). Zooplankton sampled from longitudinal gradients of the South American arid rivers such as the Salado River (Buenos Aires Province, Argentina) indicates that they have species-specific variations in salinity optima and tolerances (Claps et al. 2009). Hatching of resting eggs of zooplankton is reported to have reduced in wetland with high salinity levels (Skinner et al., 2001). Variance partitioning of benthic cladocerans response to lake water salinity in Kenya suggest that salinity explained more than 51% of the observed variations (Verschuren et al., 2000). Recently Barry et al. (2005) assessed the hatching response of *Daphnia* ephippia to the diatom inferred salinity levels of a sediment core collected from a lake in southwest Victoria, Australia, where significant differences in ephippial densities and hatching were observed with respect to varying salinity levels. Given the increased sensitivity to salinity by cladocerans these organisms can be used to quantify a threshold of salt that are appropriate for a healthy floodplain wetland ecosystems.

#### **5.2.4 Management of toxic substances**

Pollution caused by toxic substances is becoming a major threat to diversity, composition and abundances of biota in large river floodplain lakes. Most trace metals have natural mineral origins and it is essential to understand the amount of mineral inputs into wetlands. Records of anthropogenic lead pollution in European lakes are reported to have determined by ratios of 206Pb/207Pb in sediment. Natural ratios of the isotope (206Pb:207Pb) are generally higher than those of anthropogenically induced lead pollution and can be determined by analysis of floodplain lake sediments. Recently pyrite pollution has become one of major issues of the organic metallic toxicity across the Murray Darling Basin, Australia due to the

Management Strategies for Large River

time (e.g., Lotter et al., 1997; Kattel et al., 2008).

**6. Conclusion** 

**7. References** 

360-368.

Floodplain Lakes Undergoing Rapid Environmental Changes 345

ranges. Subfossil cladocerans assemblages can help identifying climate change in a range of time scales in the past (Battarbee, 2000). Climate change such as amount of rainfall causes enlargement and contraction of wetland habitats leading to distinct variations in the relative abundances of littoral and planktonic cladoceran assemblages (Alhonen, 1970). The ratio of littoral:planktonic (L:P) cladocerans serves as significant indicator of climateinduced hydrological regime shifts in shallow floodplain lakes (Ogden, 2000). Cladoceran assemblages and resting eggs have responded to the termination of the last glacial maximum (LGM) and the Holocene sea level rise in coastal regions (Kattel & Augustinus, 2010). Development of a cladoceran-inferred calibration model for temperature is useful to understand the impacts of climate change on ecosystems over a range of time scales in the past and help developing effective management strategies to reduce vulnerability on

Management of large river floodplains lake ecosystems have become increasingly challenging in recent decades as a result of coupled human-climate disturbances. A range of theoretical models being developed in large river systems, have become useful to understand floodplain lake ecosystems processes and develop effective management strategies for restoration of these lakes. However, unprecedented impacts such as river regulation, land use activity, introduction of exotic species and rapid climate warming in recent decades on floodplains lake ecosystems together have intensified the effects and made the ecosystem processes complex to understand. The use of micro-crustaceans particularly the cladocerans are increasingly useful indicator to infer the changes occurring in large river floodplain lakes. Cladocerans play an invaluable role in food web structure and dynamics and they have a wide range of optima and tolerances to temperature as well as other environmental perturbations in floodplains systems. The use of cladoceran subfossils and their ephippia has further reformed our understanding of ecological processes of floodplains lakes of large river system. A long term investigation of the changes in a range of abiotic and biotic assemblages including micro-crustaceans is important to achieve conservation and management goals of large river floodplain lakes ecosystems effectively. Appropriate quantitative and qualitative assessments of these ecosystems can help understanding the past changes and developing future prediction models that provide appropriate information of risks of environmental vulnerabilities and enhances mitigation measures. However, such effort can only be achieved through wider collaborations amongst

scientific communities, governments and international organisations.

review. *Hydrobiologia,* Vol. 267, pp. 1-12.

Aladin, N. V. & Plotnikov, I. S. (1993). Large saline lakes of former USSR: a summary

Alhonen, P. (1970). On the significance of the planktonc/littoral ratio in the cladoceran

Alpert, P., Griggs, F. T. & Peterson, D. R. (1999). Riparian forest restoration along large

rivers: initial results from Sacramento River Project. *Restoration Ecology*, vol. 7, pp.

stratigraphy of lake sediments. *Community Biology*, vol. 35, pp. 1-9.

exposure of sulpher contained sediments following the river regulations and prolong drought. The processes controlling the FeS pollution in the Murray Darling Basin floodplain lakes is unknown. Establishing a macrophyte colony tolerant to sulphur-induced acidification can be useful. Engelhardt & Ritchie (2001) examined the role of aquatic macrophytes diversity in ecosystem functioning. Greater species richness and biomass of macrophytes tend to lower the chemical activities by filtering the particulate elements from the water and assisting ecosystem functioning and enhancing the wetland management practices. Phytophylous zooplankton such as *Eurycercus* and *Graptoleberis* (Quade, 1969) are proven to be useful for reconstructing past macrophyte cover in some billabongs in Australia (Ogden, 2000). Information regarding macrophyte cover in the past can help elucidating organometallic toxicity in lakes over time. Earliest records of POPs in lake sediments are generally limited, but the PAHs are produced from the combustion of organic matter, and generally have a long term record of past events (e.g. forest fires) in sediment. Sedimentary ratio of 1,7-dimethylphenanthrene and 2,6-dimethylpheanthrene has been used as indicator of wood combustion (Fermàndez et al. 2000). Recently Kattel and Sirocko (2011) have used cladocerans subfossils to identify the range of past anthropogenic regimes including the alteration of forest catchments in a European maar lake.

#### **5.3 Management of invasive species**

The endemic floodplain lake ecosystems of the North America were invaded by exotic flora and fauna soon after their introduction (e.g., Mooney & Cleland, 2001). The invading microcruastaceans, *Daphnia lumholtzi* also colonised the Upper Paraná River floodplain lakes of South America soon after their introduction. Favourable temperature, water transparency and decreased nutrient concentrations supported the expansion of *D. lumholtzi* in South American wetland system (Simões et al., 2009). The actual effects of alien species on microcrustacean assemblages are not known, but micro-crustacean assemblages are useful for understanding the impacts and timing of invasion on endemic ecosystems. Less *Daphnia* ephippia are deposited in sediments derived from introduced plants such as *Plantago* and *Pinus* in the Murray Darling River floodplain wetlands in Australia (Reid et al., 2007). Caudal remains of exotic zooplankton *Bythotrephes* sp. in sediment of a Canadian lake were useful to track the energy flow toward the higher trophic level as *Bythotrephes* sp. consistently reduced endemic crustacean populations that were important diet of fish (Hall & Yan, 1997). The timing of geographic distribution pattern of exotic *Daphnia* in North America such as *D. galeata* is unnoticed as a result of extensive hybridization with native *Daphnia.* Allozyme analysis of *Daphnia* ephippia in Europe and North America have become useful for reconstructing timing of invasion (Taylor & Hebert, 1993) and a genetic analysis of cladoceran fossil ephippia have advanced further the knowledge of global distribution patterns and impacts of exotic species on endemic ecosystems (Hairston et al., 1999).

#### **5.4 Mitigation of climate change**

Climate change exacerbates the ecological effects of large river floodplain lakes by altering the dynamics of nutrients, pH, salinity and organic toxics compounds such as PAHs and POPs. Mitigation is an action to reduce the risk and hazards of climate associated impacts on ecosystems (IPCC, 2007). Micro-crustacean assemblages are useful for understanding these impacts on large river floodplain lakes ecosystems and help configuring appropriate mitigation strategies. Cladocerans show variation in temperature optima and tolerance ranges. Subfossil cladocerans assemblages can help identifying climate change in a range of time scales in the past (Battarbee, 2000). Climate change such as amount of rainfall causes enlargement and contraction of wetland habitats leading to distinct variations in the relative abundances of littoral and planktonic cladoceran assemblages (Alhonen, 1970). The ratio of littoral:planktonic (L:P) cladocerans serves as significant indicator of climateinduced hydrological regime shifts in shallow floodplain lakes (Ogden, 2000). Cladoceran assemblages and resting eggs have responded to the termination of the last glacial maximum (LGM) and the Holocene sea level rise in coastal regions (Kattel & Augustinus, 2010). Development of a cladoceran-inferred calibration model for temperature is useful to understand the impacts of climate change on ecosystems over a range of time scales in the past and help developing effective management strategies to reduce vulnerability on time (e.g., Lotter et al., 1997; Kattel et al., 2008).
