Longitudinal Chemical Gradients and the Functional Responses of Nutrients, Organic Matter, and Other Parameters to the Land Use Pattern and Monsoon Intensity

River water quality degradation is one of the hottest environmental issues worldwide. Therefore, monitoring water quality longitudinally and temporally is crucial for effective water management and contamination control. The main aim of this study was to assess the longitudinal variations in water quality in the mainstream of the Han River, Korea, from 2015 to 2019. The trophic state classification (TSC), microbial pollution indicator (MPI), and river pollution index (RPI) were calculated to characterize river water quality and revealed more serious pollution toward the downstream zone (Dz) due to agricultural and urban-dominated areas. The biodegradability index (BI) indicated that non-biodegradable organic pollutants are increasing in the water body from the urban and animal wastewater treatment plants. Nutrients, organic matter contents, total suspended solids, ionic factors, and algal chlorophyll were higher in the Dz than in any other zones and were markedly influenced by the summer monsoon. Empirical analysis showed that nutrients and organic matter had positive linear functional relations with agricultural and urban coverage and negative linear relations with forest coverage. The pollutant-transport function suggested that suspended solids act as TP and TN carriers. Regression analysis indicated that TP (R2 = 0.47) has more positive functional relations with algal growth than TN (R2 = 0.22). Our findings suggest that a combination of empirical models and pollution indices might be utilized to assess river water quality and that the resulting information could aid policymakers in managing the Han River.

A novel phage indirectly regulates diatom growth by infecting diatom-associated biofilm-forming bacterium

Algae and heterotrophic bacteria have close and intricate interactions, which are regulated by multiple factors in the natural environment. Phages are the major factor determining bacterial mortality. However, their impacts on the algae-associated bacteria and thus on the algae-bacteria interactions are poorly understood. Here, we obtained a diatom-associated bacterium Stappia indica SNL01 that could form biofilm and had an inhibitory effect on the growth of diatom Thalassiosira pseudonana . Meanwhile, the phage SI01 with a double-stranded circular DNA genome (44,247 bp) infecting S. indica SNL01 was isolated. Phylogenetic analysis revealed that phage SI01 represents a novel member of the Podoviridae family. The phage contained multiple lysis genes encoding for cell wall lysing muramidase and spore cortex lysing SleB, as well as depolymerase-like tail spike protein. By lysing the host bacterium and inhibiting the formation of biofilm, this phage could indirectly promote the growth of the diatom. Our results shed new insights into how phages indirectly regulate algal growth by infecting bacteria closely associated with algae or in the phycosphere. IMPORTANCE The impact of phage infection on the algae-bacteria relationship in the ocean is poorly understood. Here, a novel phage infecting the diatom-associated bacterium Stappia indica SNL01 was isolated. This bacterium could form biofilm and had a negative effect on diatom growth. We revealed that this phage contained multiple lysis genes and could inhibit the formation of bacterial biofilm, thus indirectly promoting diatom growth. This study implicates that phages are not only important regulators of bacteria but also have substantial indirect effects on algae as well as the algae-bacteria relationship.

A possible predictive mathematical model for the growth of a periphytic alga

Algae are photosynthetic organisms and have qualities that are very attractive for cultivation and industrial development for commercial purposes. When algal growth is analyzed for the production of biomass usually only the exponential phase of the growth curve is considered and the other phases are ignored. The objective of the work is to present a possible predictive mathematical model that allows a better understanding of the kinetic behavior of a periphytic microalgae by means of the use of the Smoluchowski discrete equation, with special emphasis on the lag phase. More specifically, unknown connection between the discrete Smoluchowski equation and the deterministic Baranyi model is shown in the present study. Analysis of this connection leads to a possible predictive mathematical model about of the kinetic behavior of a periphytic microalgae.

Controls on the epilimnetic phosphorus concentration in small temperate lakes

Phosphorus (P) is one of the key limiting nutrients for algal growth in most fresh surface waters. Understanding the determinants of P accumulation in the water column of lakes of...

IMPACT OF INDUSTRIAL DYES ON ALGAL GROWTH

The deterioration of water quality because of industrial dye discharges is becoming an emerging environmental problem throughout the world. Dyes are directly discharged into nearby water bodies which in turn affect the aquatic ecosystem and human health. Dyes were degraded by means of biological methods. This study involves the application of two algae (Chlorella vulgaris and Spirulina) and oxidation pond in the decolourisation of dyes. The UV spectromax M3 spectrophotometer was used in reading absorbance values. Methylene blue (MB) (20 mg/l, 50 mg/l and 100mg/l), Eriochrome Black T (EBT) (20mg/l, 50mg/l and 100mg/l) and Melanoidin (100mg/l, 250mg/l and 500mg/l) at different concentrations were used for this study. Decolourisation was recorded in a 10-day experiment. In Spirulina, maximum dye removal was 92.37 percent (20mg/l) in methylene blue dye, 54.24 percent (20 mg/l) in EBT and 45.89percent (100mg/l) in melanoidin while in oxidation pond, the maximum dye removal was 91.84 percent (20mg/l) in methylene blue dye, 93.22percent (20mg/l) in EBT and 46.1 percent (100mg/l) in melanoidin and in Chlorella vulgaris, the maximum dye removal was 91.3 percent (20mg/l) in methylene blue dye, 79.25 percent (20mg/l) in EBT and 57 percent (100mg/l) in melanoidin. The dye removal was dependent on algal concentration and dye concentration. Gel puncture method was used to determine the toxicity of individual dyes on algae (Mixed sample, Scenedesmus and Lake Sample) at varying concentration of dyes.

Effects of Caprolactam Wastewater on Algal Growth and Nutrients Removal by Arthrospira platensis

Caprolactam wastewater (WCP), which is generated during the production of caprolactam, contains high contents of NO3− and inorganic P and is considered to be difficult to treat. In this study, Arthrospira platensis was used to remove N and P from WCP. Culture conditions and wastewater addition were optimized to relieve the inhibition effects of WCP. The results show that A. platensis growth and photosynthetic activity were inhibited depending on WCP concentrations. The inhibition rates were enhanced as the culture time increased under batch mode. However, the fed-batch mode significantly minimized the negative impact on A. platensis, which is beneficial for removing N and P from WCP by Arthrospira. After 10 d of cultivation of A. platensis in a 25 L circular photobioreactor in fed-batch addition of WCP (1.25% mixed WCP (v/v) each day), the average biomass productivity reached 17.48 g/(m2·d), the maximum protein content was 69.93%, and the N and P removal ratios were 100%. The accumulation effect of WCP inhibition on algal growth was not observed under this culture condition. Fed-batch cultivation of A. platensis is a promising way for bioremediation of WCP with high N and P removal efficiencies and high value-added biomass production.

The Water Quality and Nutrients Status in the Dungun River Basin, Terengganu

This study investigated the spatial variation of nitrogen (N)-based and phosphorus (P)-based nutrients together with water quality parameters (temperature, pH, dissolved oxygen, biological oxygen demand, chemical oxygen demand and total suspended solids) in the Dungun River basin, Terengganu. The Water Quality Index (WQI) of the river was applied according to the Malaysian Department of Environment (DOE-WQI) and classified based on the Malaysian National Water Quality Standard (NWQS). Results showed that the major source of nutrients and water quality deterioration in the basin was most likely due to the effluent discharged from the nearby palm oil factory. The overall WQI mean value obtained was 85.44%, which indicated that the Dungun River basin was in a clean condition and categorised into Class II based on the NWQS classification. The overall mean mass N:P ratio was 19.8:1 which indicated that the algal growth was generally controlled by the P-based nutrients. Based on this study, it is suggested continuous monitoring necessary to be carried out for proper management of this river basin.

Assessing Herbivorous Impacts of Apohale sp. on the Ulva prolifera Green Tide in China

An epiphytic gammarid species, Apohyale sp., was abundant in the floating Ulva prolifera (U. prolifera), which forms large-scale green tides in the Yellow Sea (YSGT). Field observation and laboratory experiments were subsequently conducted to study the species identity, abundance, and grazing effects on the floating algal biomass. The abundance of Apohyale sp. showed great spatial variation and varied from 0.03 to 1.47 inds g−1 in the YSGT. In average, each gram of Apohyale sp. body mass can consume 0.43 and 0.60 g algal mass of U. prolifera per day, and the grazing rates varied among the algae cultured with different nutritional seawaters. It was estimated that grazing of Apohale sp. could efficiently reduce ~0.4 and 16.6% of the algal growth rates in Rudong and Qingdao, respectively. The U. prolifera fragments resulting from gnawing of Apohyale sp. had a higher growth rate and similar photosynthetic activities compared to the floating algae, indicating probably positive feedback on the floating algal biomass. This research corroborated the significant impact of Apohyale sp. on the floating algal mass of YSGT through the top-down control. However, further research is needed to understand the population dynamics of these primary predators and hence their correlation with the expansion or decline of YSGT, especially under the complex food webs in the southern Yellow Sea.

Chlorophyll-a growth rates and related environmental variables in global temperate and cold-temperate lakes

Lakes are key ecosystems within the global biogeosphere. However, the bottom-up controls on the biological productivity of lakes, including surface temperature, ice phenology, nutrient loads and mixing regime, are increasingly altered by climate warming and land-use changes. To better understand the environmental drivers of lake productivity, we assembled a dataset on chlorophyll-a concentrations, as well as associated water quality parameters and surface solar irradiance, for temperate and cold-temperate lakes experiencing seasonal ice cover. We developed a method to identify periods of rapid algal growth from in situ chlorophyll-a time series data and applied it to measurements performed between 1964 and 2019 across 357 lakes, predominantly located north of 40°. Long-term trends show that the algal growth windows have been occurring earlier in the year, thus potentially extending the growing season and increasing the annual productivity of northern lakes. The dataset is also used to analyze the relationship between chlorophyll-a growth rates and solar irradiance. Lakes of higher trophic status exhibit a higher sensitivity to solar radiation, especially at moderate irradiance values during spring. The lower sensitivity of chlorophyll-a growth rates to solar irradiance in oligotrophic lakes likely reflects the dominant role of nutrient limitation. Chlorophyll-a growth rates are significantly influenced by light availability in spring but not in summer and fall, consistent with a switch to top-down control of summer and fall algal communities. The growth window dataset can be used to analyze trends in lake productivity across the northern hemisphere or at smaller, regional scales. We present some general trends in the data and encourage other researchers to use the open dataset for their own research questions.

Silicon Concentrations and Stoichiometry in Two Agricultural Watersheds: Implications for Management and Downstream Water Quality

Agriculture alters the biogeochemical cycling of nutrients such as nitrogen (N), phosphorus (P), and silicon (Si) which contributes to the stoichiometric imbalance among these nutrients in aquatic systems. Limitation of Si relative to N and P can facilitate the growth of non-siliceous, potentially harmful, algal taxa which has severe environmental and economic impacts. Planting winter cover crops can retain N and P on the landscape, yet their effect on Si concentrations and stoichiometry is unknown. We analyzed three years of biweekly concentrations and loads of dissolved N, P, and Si from subsurface tile drains and stream water in two agricultural watersheds in northern Indiana. Intra-annual patterns in Si concentrations and stoichiometry showed that cover crop vegetation growth did not reduce in-stream Si concentrations as expected, although, compared to fallow conditions, winter cover crops increased Si:N ratios to conditions more favorable for diatom growth. To assess the risk of non-siliceous algal growth, we calculated a stoichiometric index to quantify biomass growth facilitated by excess N and P relative to Si. Index values showed a divergence between predicted algal growth and what we observed in the streams, indicating other factors influence algal community composition. The stoichiometric imbalance was more pronounced at high flows, suggesting increased risk of harmful blooms as environmental change increases the frequency and intensity of precipitation in the midwestern U.S. Our data include some of the first measurements of Si within small agricultural watersheds and provide the groundwork for understanding the role of agriculture on Si export and stoichiometry.