Bay Lake Research Articles

Sexual dimorphism of invasive knifefish (Chitala ornata) in Laguna de bay, Philippines

Chitala ornata (J.E. Gray) (Osteoglossiformes: Notopteridae) has since established abundant and nuisance populations in Laguna de Bay. A fundamental prerequisite for the development of management strategies for invasive species like C. ornata is a full understanding of its life history characteristics including sexual dimorphism. In the present study, we examined the sexual dimorphism of C. ornata. Sexes of C. ornata can be distinguished through the examination of its genital papilla wherein females show distinct morphological adaptions for effective oviposition on a spawning substrate. Comparison of means and multivariate analysis of several morphometric characters showed that sexual size dimorphism in C. ornata is female-biased which is mainly attributed to the disparity of resource expenditure between sexes for reproduction and size-dependent advantages of females in the production of more progenies with better chances of survival.

Age Dynamics of Helminth Fauna in Longfin Baikal Sculpin Cottocomephorus inermis (Cottidae)

This is the first report on the infection of longfin Baikal sculpin Cottocomephorus inermis of Barguzinsky Bay (Lake Baikal) by helminths. A total of eight species of parasites belonging to five classes have been identified. The differences in the composition of the helminth fauna of longfin Baikal sculpin of different ages have been revealed.

Determination of Some Physico-Chemical Parameters and Water Quality Index (WQI) of Laguna de Bay, Philippines

Water quality monitoring activities is a vital part in assessing the status of certain bodies of water such as the Laguna de Bay. The lake has been a significant natural resource as a catchment of an expansive watershed providing various ecological and economic values. It is the largest inland water body in the Philippines and the third largest in South East Asia. Water quality monitoring network is a critical element in the assessment, restoration and protection of Laguna de Bay. This paper measured some important physico-chemical properties of four selected sites from Laguna de Bay such as temperature, pH, electrical conductivity, alkalinity, dissolved oxygen levels, and phosphate and ammonia concentrations. Water Quality Index (WQI) utilizing Weighted Arithmetic Water Quality Index Method was also evaluated.

ESTIMATION OF CHL-A CONCENTRATION IN LAGUNA LAKE USING SENTINEL-3 OLCI IMAGES

Abstract. The use of Sentinel-3 Ocean and Land Color Instrument (OLCI) images in estimating chlorophyll-a (total and class-differentiated)a concentration is promising owing to Sentinel-3’s 21 bands. This was investigated for the case of Laguna de Bay (or Laguna Lake), Philippines. Field surveys were conducted on 13–17 November 2018 using FluoroProbe, a submersible fluorimeter capable of quantifying concentrations of spectral classes of microalgae. These were regressed with reflectance data obtained from 10-day composite Sentinel-3 reflectance images as well as ten empirical algorithms (indices) for OLCI. Compared to band reflectance, the 10 indices yielded stronger correlations, especially with R665/R709, R674/R709, and (1/R665-1/R709)xR754 with the following respective correlation values: −0.623, −0.646, and 0.628. Multiple regression results indicates that 48% of the variability of total chl-a concentration is explained by five explanatory (reflectance) variables (R412, R443, R560, R681, and R754) with RMSE of 2.814 μg/l. In contrast, the two indices R674/R754 and (1/R665-1/R709)xR754 accounted for about 46% of the variability of total chl-a concentration with RMSE of 2.475 μg/l. For diatoms and bluegreen microalgae, R560/R665 and (1/R665-1/R709)xR754 constitute the models with R2 of 0.21 and 0.435, and RMSE of 2.516 and 2.163 ug/l, respectively. Green microalgal concentration is jointly described by three indices: R560/R665, R674/R754, and R709-R754, with R2 = 0.182 and RMSE = 1.219 μg/l. From cryptophytes, the model comprising of R560/R665, (1/R665-1/R709)xR754, and R709-R754 produced an R2 = 0.289 and RMSE = 0.767 μg/l. It can be said that the empirical algorithms can be used for Sentinel-3 OLCI data providing acceptable estimations of total and spectral class-differentiated chl-a concentration.

The response of submerged plants to different environmental factors and hydrologic regime in West Lake Dongting

沉水植物是湖泊生态系统的重要组成部分，其生产力和分布格局受环境因子特别是水文情势决定.洞庭湖是长江流域重要的大型通江湖泊，近年来受人为干扰和气候变化影响，水文节律与水质等环境因子发生改变，导致沉水植物出现衰退现象，急需开展科学恢复，因此有必要对洞庭湖沉水植物深入研究.本研究选取西洞庭湖为研究区域，于2018年和2019年夏季调查了12处典型生境、98个样点的沉水植物与水深、透明度等11个环境因子，采用独立样本T检验和冗余分析方法对沉水植物与环境因子的关系进行分析，对比年际水文情势变化的影响.结果表明：1）西洞庭湖沉水植物主要在水深较浅、水质更优、水体更为稳定的半阻隔子湖和自由连通的湖湾区分布，在河道及水位波动较大的区域分布较少，有、无沉水植物分布样点间存在显著差异的环境因子为水深、透明度、底泥总磷和pH；2）在有沉水植物分布的样点，沉水植物生物量与pH、水深和水体总磷呈显著相关关系；3）自然连通的季节性淹没湖泊沉水植物生物量在2018年高于2019年，可能与2019年5—8月沉水植物关键生长期出现的涨水过程有关，持续的高水位对沉水植物的生长产生了不利影响.维持自然水文节律、湖泊生境异质性与自由连通性、健康的水质等是恢复西洞庭沉水植物的关键，建议在水深低于3 m、营养盐浓度适中、流速及风浪较小的湖湾区或半阻隔湖泊开展沉水植物恢复.;Submerged plants are important components in lake ecosystems, their production and distribution pattern are affected by environmental factors, especially the hydrologic regime. Lake Dongting is an important large lake in the Yangtze River Basin with free hydrologic connection to the main stream. In recent years, due to influences of human disturbances and climate change, environmental factors such as hydrologic regime and water quality of Lake Dongting have been changed dramatically, resulting in the decline of submerged plants, which calls urgent science-based rehabilitation. Thus, there is a need to have further study on submerged plants at Lake Dongting. In this study, West Lake Dongting was selected as the research area. Submerged plant communities and 12 environmental indicators were investigated in 98 sampling plots at 11 sites in West Lake Dongting during summer in 2018 and 2019. Independent t-test and redundancy analysis were used to evaluate the relationship between the submerged plants and environmental factors, and to explore the effects of hydrologic regime change on submerged plants between years. Results showed that: 1) Submerged plants in West Lake Dongting were mainly distributed at semi-isolated sub-lakes or free flooding lake bays where with shallower water depth, better water quality and more stable water body, whilst there is less distribution at sites in major flowing channels and with high water fluctuation. Water depth, transparency, total phosphorus in bottom sediment and water pH showed significant differences between sites with and without appearance of submerged plants in West Lake Dongting; 2) Biomass of submerged plants was significantly correlated with pH, water depth and total phosphorus in water; 3) At free flooding lake bay, biomass of submerged plants was higher in 2018 than it in 2019. It is supposed to be the result of water level raising processes during May to August 2019 when was key growing stage of submerged plants. A continuously high-water level adversely impacted plant growth. Maintaining natural hydrologic regime, habitat heterogeneity with free flow in the lake, and healthy water quality were proposed to be the key factors to rehabilitate submerged plants in the West Lake Dongting. Sites at free flooding lake bay or semi-isolated sub-lakes those with water depth less than 3 meters, appropriate water nutrients, low water flow rate and less waves were recommended to be rehabilitated in priority.

The Administrative Performance of the Laguna Lake Development Authority on the Small Lakes of the Laguna de Bay Region, Philippines

The Administrative Performance of the Laguna Lake Development Authority on the Small Lakes of the Laguna de Bay Region, Philippines

ESTIMATION OF CHLOROPHYLL-A CONCENTRATION IN LAGUNA DE BAY USING SENTINEL-3 SATELLITE DATA

Abstract. The mission of the European Space Agency’s Sentinel-3 satellite is to provide data for land and ocean monitoring purposes. Sentinel- 3’s Ocean and Land Colour Instrument (OLCI) data are being used largely for monitoring offshore and coastal waters but can also be used for inland waters including lakes. It has a spatial resolution of 300 meters, a temporal resolution of 2–3 days and contains 21 spectral bands. Laguna de Bay, with a surface area of around 930 km2, suffers from periodic algal blooms resulting from excessive nutrient inputs from surrounding watersheds. This study aims to assess the applicability of Sentinel-3 OLCI for estimating chlorophylla (chl-a) concentration in Laguna Lake. Several chl-a estimation algorithms (i.e., band ratios and indices) were tested for Sentinel 3 OLCI images and compared with in-situ data obtained using a chl-a sensor. A regression model comprising of individual spectral bands, band ratios, and band indices for chl-a estimation as independent variables was developed, yielding an adjusted R2 of 0.759 and RMSE of 1.19 ug/L. The model consists of R620, R674/R708, and RED/NIR. A map was produced showing the spatial distribution of chl-a in Laguna Lake, with most of the portion of the lake having a concentration ranging from 7.5 ug/L to 15 ug/L. This shows that Sentinel 3 OLCI images can be utilized for accurately estimating chl-a in Laguna Lake.

Nutrient loadings and deforestation decrease benthic macroinvertebrate diversity in an urbanised tropical stream system

Lotic ecosystems in urban areas are severely impacted by anthropogenic environmental stressors, such as deforestation and nutrient pollution, due to socioeconomic activities in the catchment. To work out measures for identification and mitigation of concurrent multiple stressors to a stream system, it is necessary to assess the relative importance of impacts by the individual stressors. Here we aimed to discriminate the covarying effects of nutrient pollution and deforestation on benthic macroinvertebrate communities in an urbanised tropical stream system. In the Silang-Santa Rosa Subwatershed (SSRS) of Laguna de Bay, benthic macroinvertebrates and physicochemical environments were investigated at 13 sites varying in human population density, riparian canopy, and land-use pattern as indicated by geographic information systems in the catchment. Regression and multivariate analyses were performed to identify the drivers of the biodiversity loss and understand its underlying mechanisms. In the SSRS, where rapid economic growth took place without updating poorly installed wastewater treatment plants (WWTPs), domestic activity indicated by human population density in the catchment was the primary factor in generating heavy phosphorous loadings (mean total phosphorus = 0.91; range = 0–1.50 mg/l) that caused hypoxia (mean dissolved oxygen = 2.98; range = 0.13–6.27 mg/l) in stream waters and subsequently reduced macroinvertebrate diversity (mean H’ = 0.91; SD ± 0.61). Nutrient and organic pollution and riparian deforestation explained 53.5% and 9.7% of the variation of benthic macroinvertebrate communities in SSRS, respectively. Given such scenario, additional WWTPs servicing urban developments and improved riparian canopy cover in the SSRS can be both strategic and cost-effective in the initial steps of environmental mitigation in urbanised streams, especially in rapidly developing countries.

Village Level Provisioning Ecosystem Services and Their Values to Local Communities in the Peri-Urban Areas of Manila, The Philippines

This study investigates different provisioning services in the peri-urban landscapes of Manila conurbation through a case study of two villages in the Jala-Jala municipality of the Laguna de Bay area in the Philippines. Laguna de Bay is an ecologically productive and important watershed for the urban and peri-urban areas of Manila for the provision of food, freshwater, and other materials. However, the lake and its ecosystem are under threat because of rapid urbanization and associated land-use changes. This study is based on a semi-quantitative survey conducted with 90 households in two villages: Special District and Paalaman. It was aimed to capture how provisioning services in the locality are connected with local livelihoods. The results obtained from the study suggest that landscapes in this peri-urban area still has considerable provisioning ecosystem services associated with local biodiversity and that this dependence on provisioning services and their relationship to peri-urban landscapes and biodiversity should be addressed for sustainable landscape management. The results have important implications for the conservation potential of biodiversity on which local livelihoods depend, in urban and peri-urban ecosystems.

River flow pattern and heavy metals concentrations in Pasig River, Philippines as affected by varying seasons and astronomical tides

This study explored the transport of metal pollutants in Pasig River, an important source of water for different uses in the National Capital Region of the Philippines. In particular, the study investigated the effect of varying seasons and varying levels of tides on the flow pattern and heavy metals concentrations in Pasig River. Pasig River is one of the main outlets which drain directly into the Manila Bay and Laguna de Bay. Four sampling sites were chosen along the 27 km-stretch of Pasig River which includes the following: Delpan, Lambingan, Guadalupe and Kalawaan sampling locations. Series of water samplings were conducted during the months of April, 2007 copping the dry season and November 2007 covering the wet season. Sampling design was primarily based on the height of tide at Manila Bay. Flow rate as computed from surface flow velocity was measured at each station. Concentration of heavy metals such as cadmium, copper, lead and nickel, were also measured. Results indicate that an observable backflow occurred during the dry season when the tide was high, that is, saline water from Manila Bay, intruding into the Pasig River. Further, this study established that the highest flow rate was noted during the wet season at low tide, particularly at the Kalawaan station. On the other hand, low flow rate was observed during the dry season when the tide was high. With regard to the levels of heavy metals, concentrations were found to be elevated during the dry season and also, when high tide occurs. Water samples collected from Delpan station yielded high metal concentrations with lead (Pb) as the dominant heavy metal among the four metals analysed in this study. Variability in the metal concentration due to seasonal changes, varying flow patterns and tide may indicate water quality problems not only in Pasig River but also to coastal areas such as Manila Bay.

Recognizing Crucial Aquatic Factors Influencing Greenhouse Gas Emissions in the Eutrophication Zone of Taihu Lake, China

Greenhouse gas (GHG) emissions, which are closely related to climate change and serious ecological instability, have attracted global attention. The estimation of crucial aquatic factors for the flux of GHGs in lakes is a key step in controlling and reducing GHG emissions. The importance of 14 aquatic factors for GHG emissions was estimated in Meiliang Bay, which is an eutrophication shallow bay in Taihu Lake in eastern China. The random forest (RF) method, which is an improved version of the classified and regression tree (CART) model, was employed. No distribution assumption on variables was required in this method and it could include nonlinear actions and interactions among factors. The results show significant positive correlations among the fluxes of CO2, CH4, and N2O. The most crucial factor influencing CO2 emissions is the water temperature (WT) followed by sulfate (SO42−), alkalinity (Alk), dissolved oxygen (DO), and nitrate (NO3−–N). The important factors for CH4 emissions are WT, SO42−, DO, Alk, and NO2−–N. The outcome for N2O, in which the key factor is NO2−–N, was slightly different from those of CO2 and CH4. A comprehensive ranking index (CRI) for the fluxes of all three GHGs was also calculated and showed that WT, NO2−–N, SO42−, DO, and Alk are the most crucial aquatic factors. These results indicate that increasing DO might be the most effective means of controlling GHG emissions in eutrophication lake bays. The role of SO42− in GHG emissions, which has previously been ignored, is also worth paying attention to. This study provides a useful basis for controlling GHG emissions in eutrophication shallow lake bays.

SOME ASPECTS ON THE REPRODUCTIVE BIOLOGY OF AN ENDEMIC CATFISH, ARIUS MANILLENSIS VALENCIENNES, 1840 (SILURIFORMES: ARIIDAE), OF LAGUNA DE BAY, PHILIPPINES

Arius manillensis is an endemic and economically important catfish of Laguna de Bay, Philippines. This study generated data on some aspects of its reproductive biology that are vital for the enhancement of propagation efforts for inland fisheries in the Southeast Asian region. Monthly assessments were conducted for one whole year to establish the distinct spawning season(s) through determinations of gonadosomatic index (GSI), fecundity through counting the number of two classes of follicles, and size at sexual maturity. Sex ratio was taken into account. Peaks in GSI occurred in March to April and July to August. These peaks correspond with months of peaks in fecundity. The parallel patterns of these reproductive aspects strengthen the occurrence of two distinct spawning seasons. GSI did not show significant correlation with body parameters while fecundity was significantly correlated with body weight (BW) and length (BL) and gonad weight (GW). Size and weight of apparent sexual maturity or peak reproductive capacity is about 20 cm and 200 g, respectively. Sex ratio was female-biased (2.11: 1). Female dominance indicates a unique reproductive behavior of A. manilensis where males could have evolved survival mechanism(s) to elude capture during breeding seasons and evidently during spawning on the cold months.

A molecular-based method to estimate the risk associated with cyanotoxins and odor compounds in drinking water sources

A biomolecular-based monitoring approach for the assessment of water quality hazards and risks associated with cyanobacteria was developed and validated in drinking reservoirs in Taiwan and the Philippines. The approach was based upon the measurement of gene abundances of toxigenic Microcystis and Cylindrospermopsis; for cyanotoxins; and for aesthetically offensive earthy-musty odor compounds. This was compared to conventional monitoring approaches, which included cell enumeration by microscopy, and toxin and odor compound analysis by instrumental analytical methods and immunoassays as appropriate for the metabolites. The validation involved samples from ten major reservoirs on Taiwan's main island, nineteen reservoirs on the offshore islands, and Laguna de Bay in the Philippines. The gene-based approach was successfully validated statistically and compared to conventional widely utilized risk assessment schemes which have employed ‘Alert Levels’ for toxic cyanobacteria. In this case a new integrated scheme of ‘Response Levels’ is proposed which incorporates odor metabolite hazards in addition to cyanotoxins and is based upon gene copy numbers to derive quantitative triggers. The comprehensive scheme evaluated from these locations is considered to be more precise and efficient for both monitoring and as a risk assessment diagnostic tool, given that it offers the capacity for analysis of the abundance of genes for cyanobacterial metabolites in large numbers of natural water samples in a significantly reduced period of time compared to the approaches of cell enumeration by microscopy or metabolite analytical techniques. This approach is the first time both the hazard and risk for both odors and cyanotoxins from cyanobacteria have been considered together in a monitoring scheme and offers an improved means for determining the Response Levels in the risk assessment process for cyanobacteria and their metabolites in drinking water sources.

Origin, distributions, and environmental significance of ubiquitous humic-like fluorophores in Antarctic lakes and streams

This study characterized dissolved organic matter (DOM) obtained from 47 lakes and 2 streams on ice-free areas at Lützow-Holm Bay and Amundsen Bay in East Antarctica (n = 74), where few biogeochemical studies have been historically conducted. Samples were analyzed for basic water chemistry and by resin fractionation, UV–vis spectroscopy, and excitation emission matrix spectroscopy combined with parallel factor analysis (EEM-PARAFAC). Salinity of the samples ranged very broadly from fresh to hypersaline as a result of evaporative concentration. There was a clear positive correlation between log-salinity and the spectral slopes of DOM (S275–295), an indicator of photodegradation. Thus, we interpreted the correlation as a progression of photodegradation by prolonged water retention time. Of the identified seven PARAFAC components, three ubiquitous humic-like components decreased as photodegradation progressed, while a photorefractory UVC humic-like component increased its relative abundance. A non-humic component, traditionally defined as Peak N, did not show a trend depending on photodegradation, and its level was high in nutrient-rich lakes, presumably due to high in-situ production. We found robust correlations between the relative abundance of the ubiquitous humic-like components and that of the Peak N component in the bulk DOM irrespective of water types or ice-free areas. We proposed there were common processes that generated the ubiquitous humic-like components from the Peak N component in the Lützow-Holm Bay and Amundsen Bay lakes and streams, such as bacterial processing of primary production-derived DOM and photochemical transformation of microbial DOM.

Identifying the Driving Factors of Black Bloom in Lake Bay through Bayesian LASSO.

Black blooms are a serious and complex problem for lake bays, with far-reaching implications for water quality and drinking safety. While Fe(II) and S(−II) have been reported as the most important triggers of this phenomenon, little effort has been devoted in investigating the relationships between Fe(II) and S(−II) and the host of potentially important aquatic factors. However, a model involving many putative predictors and their interactions will be oversaturated and ill-defined, making ordinary least squares (OLS) estimation unfeasible. In such a case, sparsity assumption is typically required to exclude the redundant predictors from the model, either through variable selection or regularization. In this study, Bayesian least absolute shrinkage and selection operator (LASSO) regression was employed to identify the major influence variables from 11 aquatic factors for Fe(II), S(−II), and suspended sediment concentration (SSC) in the Chaohu Lake (Eastern of China) bay during black bloom maintenance. Both the main effects and the interactions between these factors were studied. The method successfully screened the most important variables from many items. The determination coefficients (R2) and adjusted determination coefficients (Adjust R2) showed that all regression equations for Fe(II), S(-II), and SSC were in good agreement with the situation observed in the Chaohu Lake. The outcome of correlation and LASSO regression indicated that total phosphorus (TP) was the single most important factor for Fe(II), S(-II), and SSC in black bloom with explanation ratios (ERs) of 76.1%, 37.0%, and 12.9%, respectively. The regression results showed that the interaction items previously deemed negligible have significant effects on Fe(II), S(−II), and SSC. For the Fe(II) equation, total nitrogen (TN) × dissolved oxygen (DO) and chlorophyll a (CHLA) × oxidation reduction potential (ORP), which contributed 10.6% and 13.3% ERs, respectively, were important interaction variables. TP emerged in each key interaction item of the regression equation for S(−II). Water depth (DEP) × Fe(II) (30.7% ER) was not only the main interaction item, but DEP (5.6% ER) was also an important single factor for the SSC regression equation. It also indicated that the sediment in shallow bay is an important source for SSC in water. The uncertainty of these relationships was also estimated by the posterior distribution and coefficient of variation (CV) of these items. Overall, our results suggest that TP concentration is the most important driver of black blooms in a lake bay, whereas the other factors, such as DO, DEP, and CHLA act in concert with other aquatic factors. There results provide a basis for the further control and management policy development of black blooms.

Spatial and Seasonal Variations in the Abundance of Nitrogen-Transforming Genes and the Microbial Community Structure in Freshwater Lakes with Different Trophic Statuses.

Identifying nitrogen-transforming genes and the microbial community in the lacustrine sedimentary environment is critical for revealing nitrogen cycle processes in eutrophic lakes. In this study, we examined the diversity and abundance of ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA), denitrifying bacteria (DNB), and anammox bacteria (AAOB) in different trophic status regions of Lake Taihu using the amoA, Arch-amoA, nirS, and hzo genes as functional markers. Quantitative Polymerase Chain Reaction (qPCR) results indicated that the abundance of the nirS gene was the highest, while the amoA gene had the lowest abundance in all regions. Except for the primary inflow area of Lake Taihu, Arch-amoA gene abundance was higher than the hzo gene in three lake bays, and the abundance of the nirS gene increased with decreasing trophic status. The opposite pattern was observed for the amoA, Arch-amoA, and hzo genes. Phylogenetic analyses showed that the predominant AOB and AOA were Nitrosomonas and Nitrosopumilus maritimus, respectively, and the proportion of Nitrosomonas in the eutrophic region (87.9%) was higher than that in the mesotrophic region (71.1%). Brocadia and Anammoxoglobus were the two predominant AAOB in Lake Taihu. Five novel unknown phylotypes of AAOB were observed, and Cluster AAOB-B was only observed in the inflow area with a proportion of 32%. In the DNB community, Flavobacterium occurred at a higher proportion (22.6–38.2%) in all regions, the proportion of Arthrobacter in the mesotrophic region (3.6%) was significantly lower than that in the eutrophic region (15.6%), and the proportions of Cluster DNB-E in the inflow area (24.5%) was significantly higher than that in the lake bay (7.3%). The canonical correspondence analysis demonstrated that the substrate concentration in sedimentary environments, such as NOx--N in the sediment, NH4+-N in the pore water, and the total organic matter, were the key factors that determined the nitrogen-transforming microbial community. However, the temperature was also a predominant factor affecting the AOA and AAOB communities.

Occurrence and the first report of Naegleria australiensis presence in a major lake in the Philippines.

Laguna de Bay or Laguna Lake is one of the six major lakes in the Philippines to be in close contact with population activities due to the expansion of urban settlements in the immediate cities surrounding the lake, thus pushing the population to settle upon its shores. To date, there are no data showing the biodiversity of free-living amoebae (FLA) present in this lake. The present study aims to isolate and identify the FLA present in Laguna de Bay, Philippines. Thirty subsurface water samples were taken from Laguna De Bay using random purposive sampling in May 2018 and were examined for amoebic growth under light microscopy (LM). Results show that 8 out of 30 (26.6%) water samples were positive for amoebic growth and were further tested for more advanced data and genetic variation of the species. Initial molecular analysis using polymerase chain reaction (PCR) and sequencing showed the presence of potentially pathogenic FLA Naegleria australiensis (MK418954). The detection of potential pathogenic FLA in lakes and dams may prove useful in preventing and controlling possible human infections in the country. More data from this study will aid in public awareness and establishing safety guidelines and control programs.

A Multitracer Approach to Quantifying Resource Utilization Strategies in Lake Trout Populations in Lake Huron.

Lake ecosystems are threatened by an array of stressors. An understanding of how food webs and bioaccumulation dynamics respond to these challenges requires the quantification of energy flow. We present a combined, multitracer approach using both polychlorinated biphenyls (PCBs) and stable isotopes to trace energy flow, and to quantify how lake trout feeding strategies have adapted to changes in food web structure in 3 basins of Lake Huron (ON, Canada). This combined tracer approach allows the quantification of dietary proportions (using stable isotopes), which are then integrated using a novel PCB tracer approach that employs knowledge of PCB bioaccumulation pathways, to estimate consumption and quantify energy flow between age cohorts of individual fish across Lake Huron. We observed basin-specific differences in ultimate energy sources for lake trout, with Georgian Bay lake trout deriving almost 70% of their energy from benthic resources compared with 16 and 33% for Main Basin and North Channel lake trout, respectively. These differences in resource utilization are further magnified when they are contrasted with age. The dependency on pelagic energy sources in the Main Basin and North Channel suggests that these populations will be the most negatively affected by the ongoing trophic collapse in Lake Huron. Our study demonstrates the utility of a multitracer approach to quantify the consequences of food web adaptations to changes in aquatic ecosystems. Environ Toxicol Chem 2019;38:1245-1255. © 2019 SETAC.

Species Composition of Algal Epiphyton of Pink Lotus (Nymphaea pubescens Willd) Found in Laguna de Bay (Philippines)

In spite of the fact that epiphytic algae are considered an important component of freshwater ecosystems, our knowledge of their diversity and distribution is still rather poor. Taxonomic study on the composition of epiphytic algae living on submerged leaf and root tissues of macrophyte Nymphaea pubescens Willd, found at Laguna de Bay (Philippines), was conducted. In total, 21 algal taxa were identified: 10 Cyanophyceae, 6 Trebouxiophyceae, and 5 Bacillariophyceae. The taxa described in this study represent 13 orders, 16 families, 18 genera, and 21 species based on the recent combined taxonomical approach. Of these taxa, the occurrence of a rare cyanobacteria, Chroococcus schizodermaticus West, is reported for the first time in the Philippines. One species is also reported here for the first time in the Philippines, based on current taxonomic nomenclature, and this is Cyanothece aeruginosa (Nägeli) Komárek, which is based on the former name of Synechococcus aeruginosus Nägeli. These taxonomic records are considered important basal information in enriching the knowledge about the diversity and habitat distribution of cyanobacteria and microalgae in macrophytes found in freshwater habitats in the Philippines.

Optimization and Effect of Inner Water Diversion and Distribution in the West Lake of Hangzhou

West Lake is a world-famous landscape in Hangzhou, listed on the World Heritage list. In 2003, Hangzhou municipal government implemented the project of water diversion project, which diverted 400,000t/d water from Qiantang River into West Lake, thus, improved the overall water quality of West Lake significantly. However, due to the zigzag lakeshore line and the inlake embankment separation, the diverted water could not fully exchange among different regions of the lake, therefore, high concentration region of nutrient and cyanobacteria outbreak risk still existed in some lake bays. On the basis of spatial water quality analysis, this study put forward the internal water diversion and distribution scheme of the West Lake. Total phosphorus (TP) model with Environmental Fluid Dynamic Code (EFDC) was built to study the optimum water diversion quantity and distribution layout. According to the numerical result, the recommended water diversion scale was 70,000t/d, the layout of diversion and distribution recommended was “2 in 3 out”. The internal water diversion and distribution project was complemented in October 2015. According to the comparison of water quality before and after the project construction, the improvement rates of TP, TN and Chlorophyll A were 26.0%, 8.9% and 25.9% respectively, and the dead water area was reduced from 35% to 13%, which greatly improved the water environment of the water diversion area.