Complex Aquatic Ecosystems Research Articles

Spatial Analysis of Aquatic Ecological Health under Future Climate Change Using Extreme Gradient Boosting Tree (XGBoost) and SWAT

Climate change not only affects the water resource system but also has a great impact on the aquatic ecosystem, which is complexly linked to various organic and inorganic matter. It is difficult to simulate the current aquatic ecosystem and predict the future system due to the immensity and complexity of aquatic ecosystems; however, a spatial analysis of future aquatic ecological health is necessary if we are to adapt and take action against future climate change. In this study, we evaluated the aquatic ecological health of the Han River basin under the future climate change RCP4.5 and RCP8.5 scenarios using three indices: fish assessment index (FAI), trophic diatom index (TDI), and benthic macroinvertebrate index (BMI). For this, we developed the SWAT-XGBoost linkage algorithm, and the algorithm accuracy for the FAI, TDI, and BMI was 89.3~95.2%. In the case of the FAI and BMI assessment of aquatic ecological health, the upstream Han River was classified as a hot spot. In the case of the TDI, the downstream area of the Han River was classified as a cold spot. However, as the current TDI downstream was classified as grades D and E, continuous management is needed.

Watershed features shape spatial patterns of fish tissue mercury in a boreal river network

Freshwater mercury (Hg) contamination is a widespread environmental concern but how proximate sources and downstream transport shape Hg spatial patterns in riverine food webs is poorly understood. We measured total Hg (THg) in slimy sculpin (Cottus cognatus) across the Kuskokwim River, a large boreal river in western Alaska and home to subsistence fishing communities which rely on fish for primary nutrition. We used spatial stream network models (SSNMs) to quantify watershed and instream conditions influencing sculpin THg. Spatial covariates for local watershed geology and slope accounted for 55 % of observed variation in sculpin THg and evidence for downstream transport of Hg in sculpins was weak. Empirical semivariograms indicated these spatial covariates accounted for most spatial autocorrelation in observed THg. Watershed geology and slope explained up to 70 % of sculpin THg variation when SSNMs accounted for instream spatial dependence. Our results provide network-wide predictions for fish tissue THg based largely on publicly available geospatial data and open-source software for SSNMs, and demonstrate how these emerging models can be used to understand contaminant behavior in spatially complex aquatic ecosystems.

A Review of the Conservation Status of Shorebirds in Mongolia

We present the first comprehensive review of 62 migratory shorebird species in Mongolia, covering their ecological status, IUCN assessments at regional or national levels, population trends, threats, and conservation measures. Mongolia hosts a total of 62 shorebird species from twenty-two genera and seven families, with six species classified as globally threatened: the Critically Endangered Sociable Lapwing, the Endangered Siberian Sandplover, the Far Eastern Curlew, the Great Knot, and the Vulnerable Sharp-Tailed Sandpiper. Both national and global IUCN Red List assessments highlight Mongolia’s significance as a breeding and passage migrating site for globally threatened and Near-Threatened shorebirds. Species richness is higher in northern regions compared to the south, with the highest diversity found in areas with complex aquatic ecosystems. Global population trends indicate a decline in 61% of species, with 18% remaining stable, 16% of unknown status, and 5% increasing. At the national level, most species are stable (61%), 34% status is unknown, and 5% are decreasing. Anthropogenic-induced threats, including habitat loss and degradation, pollution, disturbance, and harvesting, pose significant risks to 69% of species, while natural disasters affect 11%. Additionally, 8% of species are impacted by accidental mortality and intrinsic factors, and 5% by changes in native species. Despite these threats, no specific conservation action plans exist for shorebirds in Mongolia. However, general conservation measures are in place, such as environmental and fauna protection laws, regulations on foreign trade in endangered species, and the establishment of protected areas under governmental resolutions. Mongolia also participates in international conventions like the Convention on Biological Diversity (CBD), Ramsar, and Migratory Species (CMS), and has developed national red lists, red books, and publications such as “A Summary Conservation Action Plan for Mongolian Birds”, “Important Bird Areas” to support conservation efforts.

High potential in synergizing the reduction of dissolved organic carbon concentration and carbon dioxide emissions for submerged-vegetation-covered river networks

Various technologies and projects have been explored and developed for the synergetic control of environmental pollution and carbon emissions in aquatic ecosystems. Planting submerged vegetation in shallow waters was also expected to achieve this purpose. However, the magnitude and mechanism of carbon dioxide (CO2) emission affected by submerged vegetation is not clear enough in complex aquatic ecosystems. This study investigated the influences of submerged plants on CO2 emission, ecosystem metabolism features, and microbial community traits based on observations in river networks on the Changjiang River Delta. The results showed that CO2 emission from planted waters accounted for 73% of unplanted waters. Meanwhile, planted waters had higher dissolved organic carbon removal capacity in overlying water and higher potential of carbon sequestration in sediment at the same time. These distinctions between the two habitats were attributed to (1) improved CO2 and bicarbonate consumption in water columns via enhancing photosynthesis and (2) inhibited CO2 production by reconstructing the benthic microbial community. Additional eco-advantages were found in planted sediments, such as a high potential of methane oxidation and xenobiotics biodegradation and a low risk of becoming black and odorous. In brief, submerged vegetation is beneficial in promoting pollution removal and carbon retention synchronously. This study advances our understanding of the feedback between aquatic metabolism and CO2 emission.

Anodic Electrodepositing Bioinspired Cu-BDC-NH2@Graphene Oxide Membrane for Efficient Uranium Extraction.

The challenge of removing trace levels of heavy metal ions, particularly uranium, from wastewater is a critical concern in environmental management. Uranium, a key element in long-term nuclear power generation, often poses significant extraction difficulties in wastewater due to its low concentration, interference from other ions, and the complexity of aquatic ecosystems. This study introduces an anodic electrodeposited hierarchical porous 2D metal-organic framework (MOF) Cu-BDC-NH2@graphene oxide (GO) membrane for effective uranium extraction by mimicking the function of the superb-uranyl-binding protein. This membrane is characterized by its hierarchical pillared-layer structures resulting from the controlled orientation of Cu-BDC-NH2 MOFs within the laminated GO layers during the electrodeposition process. The integration of amino groups from 2D Cu-BDC-NH2 and carboxylate groups from GO enables a high affinity to uranyl ions, achieving an unprecedented uranium adsorption capacity of 1078.4 mg/g and outstanding selectivity. Our findings not only demonstrate a breakthrough in uranium extraction technology but also pave the way for advancements in water purification and sustainable energy development, proposing a practical and efficient strategy for creating orientation-tunable 2D MOFs@GO membranes tailored for high-efficiency uranium extraction.

Investigation of Plankton Ecology in Chinnamuttom and Colachel Fishing Harbor in Southeast Coast of India

Water quality parameters and plankton were analysed in two fishing harbors (Chinnamuttom and Colachel), waters along the complex aquatic ecosystem at Kanyakumari district during July 2021 - June 2022. Seasonal variations of physico-chemical parameters such as AT (27-34oC), SST (24.3-31oC), pH (7.46 -8.12), salinity (28.0-33.5 psu) ,DO (3.4-5.6 mg/l) and the inorganic nutrients such as NO3 (0.042-0.14 mg/l), NO2 (0.074-0.088 mg/l), PO4 (0.078-0.193 mg/l), SiO4 (0.480-0.797 mg/l) and NH3 (0.054-0.127 mg/l) were estimated in selected study site i.e. harbor waters. A total of 74 species of phytoplankton was recorded in Chinnamuttom harbor water and 59 species were recorded in Colachel harbor water during the study period. Bacilariophycea were dominantly recorded in both ststions.Totally 56 species of zooplankton were observed in Chinnamuttom harbor whereas 46 species were found in colachel harbour. Calanoid groups were dominantly recorded in both stations during the study period. Also the physicochemical parameters influence was correlated.Statistical tools PRIMER (Ver. 6.1.11) and Origin Pro 8.0. were employed to find the species diversity, richness and evenness were calculated.

Using resiliency, redundancy, and representation in a Bayesian belief network to assess imperilment of riverine fishes

AbstractConservation prioritization frameworks are used worldwide to identify species at greatest risk of extinction and to allocate limited resources across regions, species, and populations. Conservation prioritization can be impeded by ecological knowledge gaps and data deficiency, especially in freshwater species inhabiting highly complex aquatic ecosystems. Therefore, we developed a flexible approach that calculates a species' imperilment risk based on the conservation principles of resiliency, redundancy, and representation (i.e., the “three R's”). Our approach organizes data on species traits, distributions, population connectivity, and threats within a Bayesian belief network capable of predicting resiliency and redundancy within representative ecological settings. Empirical data and expert judgment inform the model to provide robust and repeatable risk assessments for rare and data‐deficient species. The model calculates resiliency at hierarchical spatial scales from distributional trends and population strength. Redundancy is estimated from the connectivity and quantities of extant populations. Resiliency, redundancy, and species' inherent vulnerability based on species traits collectively estimate extirpation risk within each unique ecological setting. Extirpation risks across ecological settings characterize representation and are aggregated to estimate global imperilment risk. We demonstrate the model's utility with Piebald Madtom (Noturus gladiator), a species petitioned for listing under the U.S. Endangered Species Act. Our results revealed that resiliency, redundancy, and extirpation risks can vary spatially across the species' range while identifying populations where additional sampling could disproportionally reduce uncertainty in estimated global imperilment risk. Our approach could standardize and expedite conservation status assessments, identify opportunities for early management intervention of at‐risk species and populations, and strategically reduce uncertainty by focusing monitoring and research on priority information gaps.

Investigating students’ development of mechanistic reasoning in modeling complex aquatic ecosystems

IntroductionThis study reports on a classroom intervention where upper-elementary students and their teacher explored the biological phenomena of eutrophication using the Modeling and Evidence Mapping (MEME) software environment and associated learning activities. The MEME software and activities were designed to help students create and refine visual models of an ecosystem based on evidence about the eutrophication phenomena. The current study examines how students utilizing this tool were supported in developing their mechanistic reasoning when modeling complex systems. We ask the following research question: How do designed activities within a model-based software tool support the integrations of complex systems thinking and the practice of scientific modeling for elementary students?MethodsThis was a design-based research (DBR) observational study of one classroom. A new mechanistic reasoning coding scheme is used to show how students represented their ideas about mechanisms within their collaboratively developed models. Interaction analysis was then used to examine how students developed their models of mechanism in interaction.ResultsOur results revealed that students’ mechanistic reasoning clearly developed across the modeling unit they participated in. Qualitative coding of students’ models across time showed that students’ mechanisms developed from initially simplistic descriptions of cause and effect aspects of a system to intricate connections of how multiple entities within a system chain together in specific processes to effect the entire system. Our interaction analysis revealed that when creating mechanisms within scientific models students’ mechanistic reasoning was mediated by their interpretation/grasp of evidence, their collaborative negotiations on how to link evidence to justify their models, and students’ playful and creative modeling practices that emerged in interaction.DiscussionIn this study, we closely examined students’ mechanistic reasoning that emerge in their scientific modeling practices, we offer insights into how these two theoretical frameworks can be effectively integrated in the design of learning activities and software tools to better support young students’ scientific inquiry. Our analysis demonstrates a range of ways that students represent their ideas about mechanism when creating a scientific model, as well as how these unfold in interaction. The rich interactional context in this study revealed students’ mechanistic reasoning around modeling and complex systems that may have otherwise gone unnoticed, suggesting a need to further attend to interaction as a unit of analysis when researching the integration of multiple conceptual frameworks in science education.

Sediments are important in regulating the algae-derived off-flavor (β-cyclocitral) in eutrophic lakes

In recent years, due to global warming and water eutrophication, cyanobacterial blooms have occurred frequently worldwide, resulting in a series of water quality problems, among which the odor problem in lakes is one of the focuses of attention. In the late stage of the bloom, a large amount of algae accumulated on the surface sediment, which will be a great hidden danger to cause odor pollution in lakes. β-Cyclocitral is one of the typical algae-derived odor compounds that cause odor in lakes. In this study, an annual survey of 13 eutrophic lakes in the Taihu Lake basin was investigated to assess the effects of abiotic and biotic factors on β-cyclocitral in water. Our results showed that high concentrations of β-cyclocitral in the pore water (pore-β-cyclocitral) were detected in the sediment and far exceeded that in the water column, with an average of about 100.37 times. Structural equation modeling indicated that algal biomass and pore-β-cyclocitral can directly regulate the concentrations of β-cyclocitral in the water column, and total phosphorus (TP) and temperature (Temp) promoted the algal biomass which further enhanced the production of β-cyclocitral both in the water column and pore water. It was worth noting that when Chla ≥30 μg/L, the effects of algae on pore-β-cyclocitral were significantly enhanced, and pore-β-cyclocitral played a major role in the regulation of β-cyclocitral concentrations in water column. Overall, our study facilitated a comprehensive and systematic understanding of the effects of algae on odorants and the dynamic regulatory processes in complex aquatic ecosystems, and revealed a long-neglected process, that was, the important contribution of sediments to β-cyclocitral in the water column in eutrophic lakes, which would conduce to a more accurate understanding of the evolution of off flavors in lakes and also useful for the management of odors in lakes in the future.

Using an affinity analysis to identify phytoplankton associations.

Phytoplankton functional traits can represent particular environmental conditions in complex aquatic ecosystems. Categorizing phytoplankton species into functional groups is challenging and time‐consuming, and requires high‐level expertise in species autecology. In this study, we introduced an affinity analysis to aid the identification of candidate associations of phytoplankton from two data sets comprised of phytoplankton and environmental information. In the Huaihe River Basin with a drainage area of 270,000 km2 in China, samples were collected from 217 selected sites during the low‐water period in May 2013; monthly samples were collected during 2006–2011 in a man‐made pond, Dishui Lake. Our results indicated that the affinity analysis can be used to define some meaningful functional groups. The identified phytoplankton associations reflect the ecological preferences of phytoplankton in terms of light and nutrient acquisition. Advantages and disadvantages of applying the affinity analysis to identify phytoplankton associations are discussed with perspectives on their utility in ecological assessment.

Swimming behavior of emigrating Chinook Salmon smolts

Swimming behavior of Chinook Salmon (Oncorhynchus tshawytscha) smolts affects transit time, route selection and survival in complex aquatic ecosystems. Behavior quantified at the river reach and junction scale is of particular importance for route selection and predator avoidance, though few studies have developed field-based approaches for quantifying swimming behavior of juvenile migratory fishes at this fine spatial scale. Two-dimensional acoustic fish telemetry at a river junction was combined with a three-dimensional hydrodynamic model to estimate in situ emigration swimming behavior of federally-threatened juvenile Chinook salmon smolts. Fish velocity over ground was estimated from telemetry, while the hydrodynamic model supplied simultaneous, colocated water velocities, with swimming velocity defined by the vector difference of the two velocities. Resulting swimming speeds were centered around 2 body lengths/second, and included distinct behaviors of positive rheotaxis, negative rheotaxis, lateral swimming, and passive transport. Lateral movement increased during the day, and positive rheotaxis increased in response to local hydrodynamic velocities. Swim velocity estimates were sensitive to the combination of vertical shear in water velocities and vertical distribution of fish.

Aquatic Ecosystems of the Anthropocene: Limnology and Microbial Ecology of Mine Pit Lakes.

Mine pit lakes (‘pit lakes’) are new aquatic ecosystems of the Anthropocene. Potentially hundreds of meters deep, these lakes are prominent in the landscape and in the public consciousness. However, the ecology of pit lakes is underrepresented in the literature. The broad goal of this research was to determine the environmental drivers of pelagic microbe assemblages in Australian coal pit lakes. The overall experimental design was four lakes sampled three times, top and bottom, in 2019. Instrument chains were installed in lakes and measurements of in situ water quality and water samples for metals, metalloids, nutrients and microbe assemblage were collected. Lakes were monomictic and the timing of mixing was influenced by high rainfall events. Water quality and microbial assemblages varied significantly across space and time, and most taxa were rare. Lakes were moderately saline and circumneutral; Archeans were not prevalent. Richness also varied by catchment. Microbial assemblages correlated to environmental variables, and no one variable was consistently significant, spatially or temporally. Study lakes were dominated by ‘core’ taxa exhibiting temporal turnover likely driven by geography, water quality and interspecific competition, and the presence of water chemistry associated with an artificial aquifer likely influenced microbial community composition. Pit lakes are deceptively complex aquatic ecosystems that host equally complex pelagic microbial communities. This research established links between microbial assemblages and environmental variables in pit lakes and determined core communities; the first steps towards developing a monitoring program using microbes.

Study on the Evaluation of (Heavy) Metals in Water and Sediment of Skadar Lake (Montenegro), with BCF Assessment and Translocation Ability (TA) by Trapa natans and a Review of SDGs

Skadar Lake is a crypto-depression, a shallow lake, near to the Adriatic coast; the largest in the Balkan Peninsula and in southeastern Europe. The Lake is a very complex aquatic ecosystem in which anthropogenic activities have a long history in terms of the impact on wildlife and the overexploitation of natural resources. Such consequences related to heavy metals represent a global problem. Heavy metal pollution can cause severe ecological consequences in aquatic ecosystems. These pollutants accumulate in the aquatic biota from water, sediment and through the food chain, the impact can magnify. Aquatic macrophytes are good indicators of the health of a water body. This research was carried out to evaluate heavy metals concentration in water, sediment and in the aquatic macrophyte Trapa natans (water chestnut), with BCF (bio-concentration factor), BSAF (biota sediment accumulation factor) and TA (translocation ability), in order to determine the water quality of this specific part of the aquatic ecosystem of Skadar Lake near to the settlement of Vranjina, a fishing village. The determination of heavy metals was carried out by ICP-OES. (Inductively coupled plasma-optical emission spectrometry). Statistical analysis was established by R statistical computing software, version 3.5.3. The metal concentration in the water decreases in the following sequential order: As > Pb > Zn > Cu = Al = Cr > Cd = Hg. Meanwhile in the sediment, the descending sequence is as follows: Cr > Zn > Cu > Pb > As > Cd > Hg. The ability of plants to absorb and accumulate metals from the aqueous growth medium was assessed using a bio-concentration factor. The BCF in the stem, leaf and fruit has high values, mainly, of Al, Cr, Cu and Zn, while for the biota sediment accumulation factor, the highest values were recorded for the following elements: Hg, Cd, Cu and Zn. Analysis of the translocation ability of TA shows the dominance of four metals: Pb, Cd, Hg and As. A significant positive Kendall’s correlation coefficient between sediment and stem (R = 0.73, p < 0.05), stem and leaf (R = 0.87, p < 0.05) and leaf and fruit (R = 1, p < 0.05) was established.

The expanding repertoire of immune‐related molecules with antimicrobial activity in penaeid shrimps: a review

AbstractShrimps live in a complex aquatic ecosystem with numerous other biotic and abiotic factors, especially pathogenic microorganisms, which require the adaptation of prudent protective and survival strategies. As invertebrates, shrimps reply on humoral and cellular innate immune response mechanisms for protection against pathogens. One integral part of the humoral innate immune defence mechanism involves many biomolecules that are constitutively expressed or induced by pathogens. Shrimps, therefore, produce various biomolecules and secondary metabolites for physiological and pathophysiological purposes, most of which also act as effector molecules in immune‐related functions. A growing number of molecules have been identified as essential constituents of the immune arsenal of biomolecules in penaeid shrimps. This review provides a synthesis of important information on penaeid shrimp‐encoded immune‐related molecules with antimicrobial activities, their molecular regulation and importance in shrimp innate immune response. Research gaps would be identified and proposed research themes emphasized for future studies.

Seasonal cycles of phytoplankton biomass and primary production in a tropical temporarily open-closed estuarine lagoon — The effect of an extreme climatic event

Temporarily open-closed estuaries and estuarine lagoons are among the most complex aquatic ecosystems, prone to undergo rapid changes in response to global change and other anthropogenic impacts. Nonetheless, studies on the factors that control annual cycles of phytoplanktonic biomass and primary production in such systems, especially tropical ones, are still scarce. Even less information exists on the effect increasingly frequent extreme climatic events (ECE) might have on their dynamics. For this purpose, we monitored the changes in ecological conditions in the Los Micos estuarine lagoon (Honduras) by sampling monthly during an annual cycle that included several changes in the lagoon's mouth phase and attempted to understand which environmental factors affect phytoplanktonic biomass and primary production. We also evaluated the impact of, and recovery from, a tropical storm ECE. Annual mean net production (Pn), integrated for the euphotic zone, (4.3 ± 2.8 gC m−2 d−1) and Chlorophyll a (27.1 ± 19.1 mg m−3) values in Los Micos place it as one of the more productive estuaries worldwide. The physico-chemical characteristics of the lagoon clearly depended on mouth phase; however, the values of Chla and Pn did not show significant differences between the open and closed phases. The application of distance-based multivariate linear models did not show any clear dominant model being able to explain the observed Chla and Pn patterns. The most parsimonious models included among others, salinity, particulate organic carbon and PO43−, which suggests that primary production is controlled by multiple factors. During the ECE, about 19% of DIN, 91% of DSi and PO43−, 60% of particulate organic carbon and nitrogen, and 86% of Chla were exported to the sea, greatly reducing Pn. However, Chla and Pn values recovered to pre-storm levels within 30 days, indicating that these biological variables are highly resilient in Los Micos Lagoon.

Coupled reservoir-river systems: Lessons from an integrated aquatic ecosystem assessment

Sustainable reservoir-river management requires balancing complex trade-offs and decision-making to support both human water demands and ecological function. Current numerical simulation and optimization algorithms can guide reservoir-river operations for optimal hydropower production, irrigation, nutrient management, and municipal consumption, yet much less is known about optimization of associated ecosystems. This ten-year study demonstrates an ecosystem assessment approach that links the environmental processes to an ecosystem response in order to evaluate the impact of climatic forcing and reservoir operations on the aquatic ecosystems of a coupled headwater reservoir-river system. The approach uses a series of numerical, statistical, and empirical models to explore reservoir operational flexibility aimed at improving the environmental processes that support aquatic ecosystem function. The results illustrate that understanding the seasonal biogeochemical changes in reservoirs is critical for determining environmental flow releases and the ecological trajectory of both the reservoir and river systems. The coupled models show that reservoir management can improve the ecological function of complex aquatic ecosystems under certain climatic conditions. During dry hydrologic years, the high post-irrigation release can increase the downstream primary and macroinvertebrate production by 99% and 45% respectively. However, this flow release would reduce total fish biomass in the reservoir by 16%, providing management tradeoffs to the different ecosystems. Additionally, low post-irrigation flows during the winter season supports water temperature that can maintain ice cover in the downstream river for improved ecosystem function. The ecosystem assessment approach provides operational flexibility for large infrastructure, supports transparent decision-making by management agencies, and facilitates framing of environmental legislation.

A lab-scale study on heterotrophic nitrification-aerobic denitrification for nitrogen control in aquatic ecosystem.

Nitrogen (N) loss is generally caused by denitrification under anaerobic conditions and the N loss in the heterotrophic nitrification_aerobic denitrification (HN_AD) system is of recent research interest. However, previous studies are generally focused on pure cultures-based system and the information on HN_AD in the complex aquatic ecosystem is limited. In this study, HN-AD system was established in the mixed cultures of the sediments and the performances of HN-AD were evaluated under different conditions. Further, the N loss mechanism in HN_AD system was explored. The study found that the N was lost in the sediment cultures with ammonium-N (NH4+_N) (or) and nitrate-N (NO3-_N) as N source under aerobic conditions. The highest N loss rate was achieved under the TOC/TN mass ratio of 10 with citrate as the carbon source. Under this condition, the N loss percentages of NH4+_N (201.91mg/L) and NO3-_N (130.00mg/L) reached 99.61% and 100.00%, respectively, which were higher than those in the pure HN_AD strains reported in the literature. High NH4+_N removal efficiencies were also achieved at low C/N mass ratio and high NH4+_N concentration (493.12mgL-1). The N loss pathway in the system was investigated by adding Na2WO4 as the nitrate reductase inhibitor. The study found that the N was not lost via partial nitrification/denitrification pathway, i.e., NH4+ → NH2OH → NO2- → N2O (N2), instead via full nitrification/denitrification pathway, i.e., NH4+ → NH2OH → NO2- → NO3- → NO2- → N2O (N2), since nitrate was a key intermediate. The variation in NH4+_N, NO3-_N, and NO2-_N concentrations in the HN_AD processes further confirmed the N transformation pathway. Therefore, HN_AD may occur and cause N loss in natural aquatic ecosystems. The results of this study demonstrate that N was lost through HN-AD and that the well-cultured HN-AD sediments could be useful biological tool to remediate eutrophic water bodies.

Fine-scale population structure and ecotypes of anadromous Hilsa shad (Tenualosa ilisha) across complex aquatic ecosystems revealed by NextRAD genotyping

The anadromous Hilsa shad (Tenualosa ilisha) live in the Bay of Bengal and migrate to the estuaries and freshwater rivers for spawning and nursing of the juveniles. This has led to two pertinent questions: (i) do all Hilsa shad that migrate from marine to freshwater rivers come from the same population? and (ii) is there any relationship between adults and juveniles of a particular habitat? To address these questions, NextRAD sequencing was applied to genotype 31,276 single nucleotide polymorphism (SNP) loci for 180 individuals collected from six strategic locations of riverine, estuarine and marine habitats. FST OutFLANK approach identified 14,815 SNP loci as putatively neutral and 79 SNP loci as putatively adaptive. We observed that divergent local adaptations in differing environmental habitats have divided Hilsa shad into three genetically structured ecotypes: turbid freshwater (Western Riverine), clear freshwater (Eastern Riverine) and brackish-saline (Southern Estuarine-Marine). Our results also revealed that genes involved in neuronal activity may have facilitated the juveniles’ Hilsa shad in returning to their respective natal rivers for spawning. This study emphasized the application of fundamental population genomics information in strategizing conservation and management of anadromous fish such as Hilsa shad that intersect diverse ecotypes during their life-history stages.

A comprehensive integrated catchment-scale monitoring and modelling approach for facilitating management of water quality

Predicting change of water quality in complex aquatic ecosystems is always challenged by accurate prediction of changes in hydrological, hydraulic and hydrodynamic behaviours at catchment scales. Therefore, developing a fully integrated catchment-wide modelling and monitoring framework is particularly important. In this paper, we introduce a comprehensive and integrated catchment-scale monitoring and modelling approach that consists of: 1) input datasets either from real-time sensors or sampling measurements or modelling; 2) a coupled catchment-scale modelling system including 1D-hydrological/hydraulic models, 1D-emission and transport models as well as 3D-hydrodynamic and water quality models; 3) data assimilation techniques; and 4) an operational management system (OMS). Results from various case studies demonstrate that this integrative system can be used not only for long-term predictions of water quality levels and scenario tests, but also for event predictions and real-time forecasting of water quality. This approach produces synergistic effects in modelling capability for facilitating research and management applications.

A simple modelling approach to simulate the effect of different climate scenarios on toxic cyanobacterial bloom in a eutrophic reservoir

Toxic cyanobacterial blooms are of major concern in eutrophic inland waters due to their water quality deterioration capabilities. Understanding their dynamics and driving factors is of great importance to manage bloom events and their consequences. Ecosystem models enable us to simulate, analyze and understand ecological processes in complex aquatic ecosystems. In this work, we examined the ability of the General Lake Model-Aquatic EcoDynamics (GLM-AED), an open-access one dimensional hydrodynamic-ecological model to simulate physical variables and the dynamics of two cyanobacterial species in 2016. The effect of possible hydrological and climatic scenarios on cyanobacterial blooms occurrence was also investigated. Results indicate that the model was able to accurately reproduce changes in water level (MAPE of 0.4%), water temperature profiles (MAPE of 5 to 7%) and the biomass of Microcystis aeruginosa and Chrysosporum (Aphanizomenon) ovalisporum at the study area. Dramatic changes were observed under warming trends including increase in both the length of the stratification period and in cyanobacteria bloom dynamics. Data analysis revealed that while water temperature was the primary factor determining cyanobacterial succession and occurrence, other factors such as water level fluctuations and irradiance are also important. Our findings suggest that any further increase in temperature would promote the development of potentially toxic cyanobacterial blooms at Karaoun Reservoir. The good performance of the model will provide essential insights required for deeper ecological understanding and water quality management.