Post-flood Conditions Research Articles

Evaluation of post extreme floods in high mountain region: A case study of the Melamchi flood 2021 ​at the Koshi River Basin in Nepal

Extreme precipitation events and associated hazards are becoming more frequent and intense due to climate change. On June 2021, a devastating flash flood occurred in the Melamchi River in Nepal causing immense destruction to lives and property. The flood event was cascading in nature and associated with multiple driving factors. This study evaluates the post-extreme flood conditions of the Melamchi Flood 2021 (MF21). Rainfall, streamflow (discharge), and gauge height (water level) data of the nearest stations were analyzed. Since there was a lack of reliable instantaneous river discharge during the disastrous MF21, this study developed the flow rating curves at hydrometric stations. Post-extreme flood was evaluated considering upstream catchment hydrology, glacial lake outbursts, landslide damming, and the hydrodynamic propagations using the Hydrologic Engineering Center's River Analysis System (HEC-RAS) model and gauge-to-gauge (G2G) correlation. The results were then compared to field observations. The HEC-RAS model was simulated for several flood frequency periods in different return periods (namely 2, 5, 10, 25, 50, 100, 200, 500, and 1000 years). Results showed that the average 24 ​h gauge height and discharge at Nakote station (a few km downstream of landslide damming) are 15.88 ​m and 169.18 ​m3/s, in which the model-based highest frequency of 1-h extreme flood and return period can reach 716 ​m3/s in 1000 years. During MF21, the discharge of the Nakote region at the 10 ​min intervals was estimated to be with a maximum of 7162.10 ​m3/s, an average of 2207.13 ​m3/s and a minimum of 237.44 ​m3/s.Additionally, the outburst discharge from glacial lake at high elevation was estimated to be 295.14 ​m3/s contributing to downstream flooding. The model-based discharge during the past flood period was also estimated in 9 cross-section points of the river in which discharge at the damming area was 63.81 ​m3/s and downstream Dumredovan was 1206.58 ​m3/s. This research provides valuable insights to post-extreme flood evaluation and the approach can be used for other watersheds in evaluating post flood conditions.

Evaluation of Soil Physico-Chemical Properties in Pre and Post Flood Conditions at Thatta Sindh Pakistan

The heavy rainfall caused biggest ever natural rain flood in River Indus in the history of Pakistan during 2010. The deltaic district Thatta of Sindh Pakistan hit by flood with breach came out at Dyke near Thatta city on right bank of River Indus. The soil sampling was carried out in month July 2010 prior to flood for routine soil analysis. After flood again soil samples from 13 same sites of pre flood spots were collected at two depths, 0-15 and 15-30 cm. Aim was to observe soil physic-chemical properties and nutrient status of pre-flood and post flood conditions. Soil sand pH and SAR were found significantly higher in post-flood conditions whereas clay and OM were found high in pre-flood conditions. The nutrients status of N, P, Ca and Mg were depleted however K remained satisfactory in post-flood conditions. In post flood conditions the pH and SAR were positive and significantly correlated with each other indicated disperse of soil. The information obtained from this study will be helpful to develop flood qualification strategies and proper management of soil.

IMPACT OF FLOOD AND PSYCHOLOGICAL ADAPTATION ON FLOOD SURVIVOR IN MOJOKERTO REGENCY, INDONESIA

Background: Flood is a hydrometeorological disaster that has an impact on all aspects of human life. Many complaints expressed by flood victims include feelings of sadness, fear, worry, loss of valuables, and difficulty in carrying out daily activities.
 Objectives: Researchers measure stress levels as a result of overflow floods that occur every year and assess coping mechanisms for flood survivors in Mojoanyar District, Mojokerto Regency.
 Methods: Researchers used a cross-sectional method with a sample of 144 respondents (225 families). Data were collected using the Jalowiec Coping Scale (JCS) and Depression on Anxiety Stress Scale (DASS) instruments and then tested for contingency coefficient statistics (significance level 0.05).
 Results: The results showed that there were 19 respondents (13.2%) who had maladaptive coping mechanisms experienced severe stress. Adaptive respondents experienced mild stress as many as 50 respondents (34.7%). The results of statistical tests show that there is a relationship between coping mechanisms and stress levels for flood survivors with a correlation value of 0.632 with a significance of 0.00 (p<0.05).
 Conclusion: Based on the findings, flood survivors need to improve their coping mechanisms in order to be able to adapt psychologically to post-flood conditions. Good cooperation between the community and the government, the business world, academia and the media is needed to address disaster complaints and reduce the risk of future disasters.

ICHTHYOFAUNA FROM FRESHWATER OF KUMARAKOM REGION OF VEMBANAD LAKE, KOTTAYAM, KERALA, SOUTH INDIA - WITH SPECIAL REFERENCE TO POST FLOOD

The present study was carried out to better understand the variety of Ichthyofauna in the Kumarakom region of Vembanad Lake. Kumarakom is a popular tourist spot near Kottayam. Kumarakom is an area with abundant indigenous fishery resources and high level of biodiversity. The current study was carried out to identify the fishes of the Kumarakom region of Vembanad Lake following the flood condition for a period of 5 months (September 2019 to January 2020) at 15-day intervals and compared to ichthyofauna of preflood. During the survey, 15 fresh water species were identified.During post-flood conditions, the fish diversity in the Kumarakom Region of Vembanad Lake decreased.

Infectious Diseases Associated with Hydrometeorological Hazards in Europe: Disaster Risk Reduction in the Context of the Climate Crisis and the Ongoing COVID-19 Pandemic.

Hydrometeorological hazards comprise a wide range of events, mainly floods, storms, droughts, and temperature extremes. Floods account for the majority of the related disasters in both developed and developing countries. Flooding alters the natural balance of the environment and frequently establish a favorable habitat for pathogens and vectors to thrive. Diseases caused by pathogens that require vehicle transmission from host to host (waterborne) or a host/vector as part of their life cycle (vector-borne) are those most likely to be affected by flooding. Considering the most notable recent destructive floods events of July 2021 that affected several Central Europe countries, we conducted a systematic literature review in order to identify documented sporadic cases and outbreaks of infectious diseases in humans in Europe, where hydrometeorological hazards, mainly floods, were thought to have been involved. The occurrence of water-, rodent-, and vector-borne diseases in several European countries is highlighted, as flooding and the harsh post-flood conditions favor their emergence and transmission. In this context, strategies for prevention and management of infectious disease outbreaks in flood-prone and flood-affected areas are also proposed and comprise pre- and post-flood prevention measures, pre- and post-outbreak prevention measures, as well as mitigation actions when an infectious disease outbreak finally occurs. Emphasis is also placed on the collision of floods, flood-related infectious disease outbreaks, and the evolving COVID-19 pandemic, which may result in unprecedented multi-hazard conditions and requires a multi-hazard approach for the effective disaster management and risk reduction.

Framework for selection of temporary disaster waste management sites for post-flood recovery in Seoul, South Korea

In this study, a multi-criteria geographical information system (GIS) framework is proposed to address complicated decision-making problems associated with the selection of temporary disaster waste management sites (TDWMSs). Focusing on post-flood conditions, the framework considers potential limitations on vehicle access and transport based on flood depths and road widths. The usability of the framework was evaluated by applying it to Seoul, South Korea, the location chosen for this case study. Fourteen criteria were constructed, and TDWMS suitability was determined based on a weighted sum analysis. Compared with the existing TDWMSs in Seoul, the minimum, maximum, and mean suitability scores of the TDWMSs identified using the proposed framework improved by 27.27%, 11.54%, and 23.08%, respectively. The described approach can inform the decision-making of urban planners to improve resilience to flooding by identifying candidate sites with relatively superior suitability ratings. Our approach also serves as a starting point for the development of integrated models and solutions capable of addressing complicated decision-making problems for TDWMS selection that consider post-disaster conditions.

Changes of fluvial processes caused by the restoration of an incised mountain stream

The construction of a high check dam on mountain Krzczonówka Stream, Polish Carpathians, in the mid-20th century caused numerous detrimental changes to the downstream reach. In 2014 the check dam was lowered to make the structure passable for river biota. Before that, several block ramps were constructed in the deeply incised downstream reach to facilitate entrapment of the sediment expected to be released from the lowered check dam. When the check-dam lowering was underway, a flood flushed out from the dam reservoir a considerable amount of sediment that was efficiently trapped by the block ramps. To determine to what extent the environmental problems caused by the long-term sediment starvation of the stream were mitigated by the restoration works, one-dimensional hydraulic modelling of flood flows was performed for pre- (2013) and post-flood conditions (2015) in ten study cross-sections. Moreover, hydromorphological quality of the stream was determined before the onset of restoration activities (2012) and after their completion (2015). The flood of 2014 deposited about 15,650 m3 of bed material in the downstream reach, which re-established an alluvial channel bed and increased bed elevation by 0.50 m on average. Bed aggradation reduced flow capacity of the channel and increased water stages attained at given flood discharges. This significantly decreased bed shear stress and entrainable grain size of bed material. The proportion of the total flow conveyed over the floodplain and retention potential of the floodplain increased, although these effects were largely dependent on the amount of bed aggradation in the study cross-sections. The hydromorphological quality of the stream improved in 4 out of the 5 evaluated cross-sections, with 3 cross-sections being upgraded from moderate to good quality class. The study demonstrated effectiveness of block ramps in mitigating problems in the physical functioning of an incised mountain stream.

СТРАТЕГІЧНИЙ РОЗВИТОК МІЖНАРОДНОГО РИНКУ ТРАНСПОРТНИХ ПЕРЕВЕЗЕНЬ

The current state of the international transport market is considered in the article. It has been established that the transport industry has been significantly affected by quarantine restrictions through Covid-19. At present, in a harsh crisis environment caused by quarantine restrictions through Covid-19, all sectors of the world economy have been affected. As expected, passenger turnover decreased in January and May to half of last year and will resume in direct dependence on quarantine measures. The most serious losses are in the railways and aviation, while road transport and public transport in the cities feel somewhat better. Significant reductions are expected in terms of traffic. Thus, international transportation will be reduced by 30–40% due to quarantine restrictions and falling industrial production. Currently, the international transportation market is in crisis. The use of the main strategies of modern transport enterprises operating in the market of international transport was studied. Such strategies are: offensive strategy; adaptation strategy; defense strategy; survival strategy. It is established that these strategies do not fully satisfy the activity of transport enterprises in modern conditions. Analysis of the economic aspect of the external environment allows us to understand how economic resources are formed and distributed at the state level. For most companies, this is the most important condition for their business activity. The main problems of the modern transport industry in the current crisis are identified. It was also determined that the strategies that are popular in the activities of international transport companies, after quarantine restrictions do not perform their function and require careful rethinking. This makes it necessary to use the strategy of “Innovative development of the transport industry and global investment design”. It is proposed to use the strategy of innovative development of the transport industry and global investment design in post-flood conditions, which will create a favorable investment climate in the international transport market.

Settlement Landscape Planning based on Flood Mitigation in Pinang Sub-district Tangerang City

The Pinang sub-district is one of the sub-districts in Tangerang City. Along with the access road development, the residential areas in The Pinang Sub-district has also increased. But behind the development activities of residential areas in Pinang sub-district, there is a flood disaster in the residential landscape as a landscape hazard. Flood disaster in Pinang sub-district, is a disaster that occurs almost every year, especially during the rainy season. Pinang sub-district itself belongs to the Angke River Basin. According to the BNPB 2016, the potential for flood disasters in Pinang District also played a role in the magnitude of the impact of flooding in Banten Province, such as social impacts of 10,476,016 people and economic impacts of 3,611,576 million rupiahs. Settlement landscape planning based on flood disaster mitigation needs to be done to prevent loss and loss of life in Pinang District. The purpose of this study is to identify the physical, biophysical, and social aspects of settlements in Pinang sub-district, analyze the risk of flood disasters and the land suitability of the residential landscape in Pinang sub-district, and develop a landscape plan of settlement based on flood mitigation in Pinang Sub-district. This research conducted at eleven villages in Pinang sub-district, from January to May 2019. The methods used in this research are preparation, inventory, analysis, synthesis, and landscape planning. The analysis conducted the legality analysis, flood disaster risk analysis, and land suitability analysis for settlement development. The analysis results then become a reference in landscape plan preparation. The landscape plan is prepared based on spatial, activity, evacuation, facility plan, circulation plan, and vegetation plan. The basic concept in this research is the settlement landscape of Pinang sub-district based on flood disaster mitigation to reduce the impact that can occur due to disasters by considering pre-disaster, disaster, and post-flood conditions.

Epizootics of epizootic ulcerative syndrome among estuarine fishes of Kerala, India, under post-flood conditions.

Epizootic ulcerative syndrome (EUS), primarily caused by the water mold Aphanomyces invadans, is an OIE-notifiable disease, having potential impacts on fisheries. We report EUS epizootics among estuarine fishes of Kerala, India, during 2018, under post-flood conditions 3 decades after its primary outbreak. Six fish species (Mugil cephalus, Platycephalus sp., Scatophagus argus, Arius sp., Planiliza macrolepis and Epinephelus malabaricus) were infected, including the first confirmed natural case in E. malabaricus and P. macrolepis. Salinity, surface temperature, dissolved oxygen and pH of resident water during the epizootic were <2 ppt, 25°C, 4.1 ppm and 7.0. The presence of zoonotic bacterial pathogens (Aeromonas veronii, Shewanella putrefaciens, Vibrio vulnificus and V. parahaemolyticus) in tissues of affected fish indicates that EUS-infected fish may pose a public health hazard if not handled properly. Lack of clinical evidence in the region during the last 3 decades, a high number of affected fishes, including 2 new fish species, the severity of skin lesions and very low water salinity (<2 ppt) during the outbreak in contrast to historical water salinity records suggest relatively recent invasion by A. invadans. Phylogenetic analysis based on the internal transcribed spacer region of the rRNA gene showed that the same clone of pathogen has spread across different continents regardless of fish species and ecotypes (fresh/estuarine environments). Altogether, the present study provides baseline data which can be applied in EUS management strategies within brackish-water ecosystems. We recommend strict surveillance and development of sound biosecurity measures against the disease.

Spring flood induced shifts in Fe speciation and fate at increased salinity

Rivers have traditionally been viewed as negligible sources of iron (Fe) to marine waters, as most Fe gets lost during estuarine mixing. However, recent findings demonstrate that Fe from boreal rivers display a higher resistance towards salinity-induced aggregation, presumably due to stabilizing interactions with organic matter. Previous studies have shown that Fe (oxy)hydroxides are selectively removed by aggregation processes, and that organic Fe complexes are less affected by increasing salinity. It has been further proposed that Fe speciation varies in response to seasonal differences in hydrology. In this study X-ray absorption spectroscopy (XAS) was used to determine the temporal variation in Fe speciation and the connection to Fe stability in response to increasing salinity in two boreal rivers (Kalix and Råne River), with the purpose to better understand the fate of riverine Fe export. Sampling was done from winter pre-flood, over the spring flood, to post-flood conditions (early April until mid June). In addition, parallel analyses for Fe speciation and isotope composition (δ56Fe relative to IRMM-14) were made on river samples, as well as salinity-induced aggregates and the fraction remaining in suspension, with the main objective to test if δ56Fe reflect the speciation of Fe.The contribution of organically complexed Fe increased during spring flood compared to the pre- and post-flood, as did Fe transport capacity. However, since Fe (oxy)hydroxides were dominating throughout the sampling period, the seasonal variability was small. Interestingly, salinity-induced aggregation experiments revealed that Fe (oxy)hydroxides, which dominated aggregates, displayed lower δ56Fe than in the river samples Fe, while organic Fe complexes in suspension had higher δ56Fe values. The seasonal variability in Fe isotope signature could not be simply linked to Fe speciation, but was probably also influenced by variation in source areas of Fe and processes along the flow-path that alter both Fe speciation and isotopic composition.

Multi-scale analysis of functional plankton diversity in floodplain wetlands: Effects of river regulation

Riverine floodplains are among the most diverse and dynamic ecosystems, but river regulation measures have altered the natural hydrological regime threatening their ecological integrity. We compared spatial patterns of phyto- and zooplankton functional diversity and of environmental heterogeneity between floodplain wetlands located in free-flowing and impounded stretches of the Danube River (Austria). We included two nested spatial scales (different habitats and water sections within wetland areas) and two contrasting hydrological conditions (post-flood, no flood). Environmental heterogeneity was lower in the wetland in the impounded stretch than in the free-flowing ones. At post-flood conditions, increased alpha diversity of rotifers and microcrustaceans and decreased beta diversity of phytoplankton and rotifers occurred in the impounded stretch as compared to the wetlands in free-flowing one. Beta diversity was higher between water sections than between habitats in free-flowing wetlands and similar across scales in the wetland in the impounded stretch. Regarding functional composition, the wetland in the impounded stretch hosted more homogeneous communities, as some ecological traits were nearly absent. Our results indicate that patterns of functional diversity in floodplain wetlands affected by river regulation are altered, highlighting the major role of the gradient of lateral connectivity and dynamic water level fluctuations as drivers for planktic diversity in river floodplains. This study contributes with essential knowledge to optimize restoration and diversity conservation measures in riverine ecosystems.

Environmentally Driven Changes in Fatty Acid Profiles of a Commercially Important Penaeid Prawn

Rainfall, runoff and estuary inflow link catchment conditions to the physical, chemical and biological properties of estuaries. Commercially exploited penaeid prawn species often rely on estuarine nurseries, and thus, the productivity of penaeid fisheries can be enhanced or diminished by catchment conditions. We conducted an initial investigation into changes in the fatty acid composition of school prawn Metapenaeus macleayi following freshwater inflow, under natural environmental conditions. Juvenile school prawns were collected from two south-eastern Australian estuaries during non-flood (normal) and post-flood conditions, and fatty acid concentrations quantified. Total fatty acid concentrations were significantly higher during post-flood conditions, and constrained ordination showed clear separation of samples collected under normal and post-flood conditions on the basis of their fatty acid composition. Docosahexaenoic acid (DHA), docosapentaenoic acid (DPA) and linoleic acid made a significant contribution to the dissimilarity among these groups. There was a significant negative relationship between salinity and linoleic acid concentrations post-flood. Changes observed in fatty acid profiles likely reflect both changes in the estuarine food web, as well as physiological responses to stress. These changes have implications for prawn condition, growth and survival.

Plankton metacommunities in floodplain wetlands under contrasting hydrological conditions.

Species diversity is affected by processes operating at multiple spatial scales, although the most relevant scales that contribute to compositional variation and the temporal shifts of the involved mechanisms remain poorly explored. We studied spatial patterns of phytoplankton, rotifers and microcrustacean diversity across scales in a river floodplain system of the Danube in Austria under contrasting hydrological conditions (post‐flood versus low water level).The species turnover between water sections (β2) and between wetlands (β3) was the major components of regional diversity for all studied groups, with species turnover between habitats (β1) as a minor contributor. β1 diversity and β2 diversity were lower than expected by chance in most cases, suggesting that communities are more homogeneous than expected at these scales. β3 diversity was higher than expected by chance in many cases, indicating more distinct communities at the wetland level. Patterns were highly similar under different hydrological conditions, indicating no major immediate effect of flood events.Local environmental and spatial factors were similarly important in structuring phytoplankton, rotifer and microcrustacean communities in both hydrological conditions. Relevant environmental factors were spatially structured in post‐flood conditions especially between sections, suggesting flood‐driven homogenisation within the wetlands. Under low water level, spatial structuring of environment decreased and pure environmental factors gained relevance for phytoplankton and rotifers.Our results suggest that although β2 diversity between water sections is a major component of regional diversity, long‐term spatial processes responding to connectivity across the wetland structure phytoplankton, rotifer and microcrustacean communities. Aquatic sections within the limited spatial extent of the remaining floodplain areas appear more homogeneous than expected probably due to flood recurrence over the years.These results highlight that adequate planning of restoration and conservation strategies of floodplain wetlands should consider environmental heterogeneity together with long‐term spatial processes.

Seed bank of seasonally flooded grassland: experimental simulation of flood and post-flood

Wetland seed banks comprise the propagules of plant species that have species-specific germination requirements for germination in either flooded or dry conditions. At the community level, wetland structure and succession during and after a seasonal flooding event depends upon the early life-history requirements of species, including germination under flooded and dry conditions. We examined the effects of simulated flood and post-flood scenarios on seedling emergence from a seed bank of seasonally flooded grassland in the Pantanal, Brazil. Field samplings were conducted in both wet and dry seasons, both of which were subject to flood and post-flood conditions. A total of 70 species emerged from the seed bank, dominated by Poaceae and Cyperaceae. Sixteen species were exclusive to the wet and one exclusive to the dry season. The richness of perennial species was higher under flood conditions, while the richness of annuals was greater post-flood. In general, the aquatic and amphibious species exhibited a significant germination response to flooding. Terrestrial species only germinated in post-flood conditions, with higher richness in the dry season. Four species had high seedling abundance in both treatments. The capacity of regeneration by seeds is high in these grasslands and can be increased by seasonal flooding and drawdown. In these seasonally flooded grasslands, we observed three main germination strategies: under flooded conditions, aquatic and amphibious species; post-flood conditions, an explosion of annual amphibious and terrestrial species; and in moist soil, perennial terrestrial species. The differential responses to flooding versus post-flood conditions help to maintain the structure and species richness in the community over time.

Assessing groundwater-surface water connectivity using radon and major ions prior to coal seam gas development (Richmond River Catchment, Australia)

Coal seam gas (CSG, or coal bed methane) mining is rapidly growing, with poorly understood impacts on groundwater and surface water systems. Here, we use chemical tracers to investigate groundwater-surface water connectivity in an Australian river system (Richmond River Catchment, New South Wales) prior to CSG extraction but after ∼ 50 exploratory CSG wells were drilled. We performed four surveys of 29 interconnected creek and river sites, over contrasting hydrological conditions. Radon was used to determine if a surface water segment was gaining groundwater. Radon observations over four seasons revealed that 28 out of 77 surface water segments were clearly gaining groundwater, 5 were possibly gaining groundwater and 44 were undetermined. This is equivalent to gaining segments in 333 km (39%) of surface water from the 864 km being investigated. High spatial and temporal variability in groundwater gaining segments was found. Na/Cl ratios were used to determine the fraction of groundwater in surface water. Overall, the groundwater contribution in surface waters was 14–24% higher in post flood conditions than during the other three surveys of baseflow and moderate flow conditions. The results serve as a regional baseline assessment of river water chemistry and groundwater-surface water connectivity prior to the planned development of CSG fields. Our geochemical tracer approach allows for a quick qualitative assessment of groundwater-surface water connectivity in poorly gauged river systems and can define priority locations where groundwater extraction for CSG mining should be carefully managed.

Residence times and mixing of water in river banks: implications for recharge and groundwater–surface water exchange

Abstract. Bank exchange processes within 50 m of the Tambo River, southeast Australia, have been investigated through the combined use of 3H and 14C. Groundwater residence times increase towards the Tambo River, which suggests the absence of significant bank storage. Major ion concentrations and δ2H and δ18O values of bank water also indicate that bank infiltration does not significantly impact groundwater chemistry under baseflow and post-flood conditions, suggesting that the gaining nature of the river may be driving the return of bank storage water back into the Tambo River within days of peak flood conditions. The covariance between 3H and 14C indicates the leakage and mixing between old (~17 200 years) groundwater from a semi-confined aquifer and younger groundwater (&lt;100 years) near the river, where confining layers are less prevalent. It is likely that the upward infiltration of deeper groundwater from the semi-confined aquifer during flooding limits bank infiltration. Furthermore, the more saline deeper groundwater likely controls the geochemistry of water in the river bank, minimising the chemical impact that bank infiltration has in this setting. These processes, coupled with the strongly gaining nature of the Tambo River are likely to be the factors reducing the chemical impact of bank storage in this setting. This study illustrates the complex nature of river groundwater interactions and the potential downfall in assuming simple or idealised conditions when conducting hydrogeological studies.

Climate-driven changes in diet composition and physiological stress in an arboreal folivore at the semi-arid edge of its distribution

Species, particularly foliovores, at the trailing edge of their geographical range are likely to be most vulnerable to climate change as they respond to physiological stress and the decline in the nutrient richness of their food source. We investigate the effect of environmental conditions on diet composition, resource use, and physiological stress of koalas (Phascolarctos cinereus) in the semi-arid landscapes of southwest Queensland, Australia, across three different biogeographic regions. Fresh faecal pellets were collected to measure cortisol metabolites and assess diet. Regression analyses were used to relate the diet composition and physiological stress of wild koalas to environmental variables. The impact of drought was apparent, with higher faecal cortisol metabolites (FCM) levels recorded during drought conditions compared with post-flood conditions. Diet composition also changed between drought and post-flood conditions, with diets during drought being mainly composed of species with high leaf-moisture content. Low minimum temperatures increased FCM concentrations, and these effects were greater during drought conditions. The results demonstrate the importance of integrating physiological assessments into ecological studies to identify stressors that have the potential to compromise the long-term survival of threatened species, as well as the need to identify the resources required for their continued survival.

Flood effects on trophic linkages of selected fish species in the littoral zone of the St Lucia estuarine system, South Africa

The St Lucia Estuary, a UNESCO World Heritage Site, has experienced prolonged mouth closure since 2002. Until recently it was hypersaline, but heavy rainfall between October 2010 and January 2011 led to a large overall decrease in salinity. A stable isotope study was conducted in March 2011 on selected fish species from the nearshore environments at Charter's Creek and the estuary mouth region to determine the influence of flooding events on their diet. Oreochromis mossambicus, the dominant fish species at both sites, had a generalised diet and occupied the lowest trophic level both before and after flooding. Monodactylus argenteus, Leiognathus equula and Gerres acinaces from the mouth area displayed a largely zooplanktivorous diet and showed some changes in prey species between drought and post-flood conditions.

Sources and emission of greenhouse gases in Danube Delta lakes

Production of methane and carbon dioxide as well as methane concentrations in surface waters and emissions to the atmosphere were investigated in two flow-through lake complexes (Uzlina-Isac and Puiu-Rosu-Rosulet) in the Danube Delta during post-flood conditions in May and low water level in September 2006. Retained nutrients fueled primary production and remineralization of bioavailable organic matter. This led to an observable net release of methane, particularly in the lakes Uzlina, Puiu and Rosu in May. Input from the Danube River, from redbuds and benthic release contributed to CH(4) concentrations in surface waters. In addition to significant river input of CO(2), this trace gas was released via aerobic remineralization within the water column and in top sediments. Emission patterns of CO(2) widely overlapped with those of CH(4). Generally, greenhouse gas emissions peaked in the lake complex adjacent to the Danube River in May due to strong winds and decreased with increasing hydrological distance from the Danube River. Intense remineralization of organic matter in the Danube Delta lakes results in a net source of atmospheric greenhouse gases.