Peak Chlorophyll Research Articles

Study of Natural Herbal Dyes Photodegradation Effect to Optical Properties for Dye-Sensitized Solar Cells

The stability of natural dyes for use in dye-sensitive solar cells is known from their photodegradation characteristics. Photodegradation effects using artificial light radiation on natural herbal dyes were investigated. Three natural herbal dyes, namely Fagraea acuminatissima, sappanwood, and kulit setong were used in this study. The stability of the natural herbal dyes under artificial light radiation was studied. The optical properties of the natural herbal dyes as indicators of their stability were characterized using FTIR and UV-VIS absorption. Stability testing of natural herbal dyes was conducted in a room with artificial lighting for 5 weeks. Observations of changes in their optical properties were performed weekly. It can be seen that all three natural herbal dyes contained anthocyanin. In addition to anthocyanin, Fagraea acuminatissima and sappanwood also contain chlorophyll. In contrast, the kulit setong contains beta-carotene in addition to anthocyanin. The degradation percentage showed that sappanwood degrade to all of its pigments. While an increase occurred in the chlorophyll peak of Fagraea acuminatissima and the beta-carotene peak of kulit setong. This clearly shows that Fagraea acuminatissima has the highest stability, and potentially increases the efficiency of solar cells.

Periodically asymmetric responses of deep chlorophyll maximum to light and thermocline in a clear monomictic lake: Insights from monthly and diel scale observations

Deep chlorophyll maximum (DCM), a chlorophyll peak in the water column, has important implications for biogeochemical cycles, energy flow and water surface algal blooms in deep lakes. However, how an observed periodically asymmetric DCM response to environmental variables remains unclear, limiting our in-depth understanding and effective eco-environmental management of deep lakes. Based on both monthly field investigations in 2021 and diel continuous observations in 2021–2023 in clear, monomictic Lake Fuxian, Southwest China, the temporal dynamics and drivers of DCM were examined and periodic features of DCM were found, with a formation period (FP, February–July) and a weakening period (WP, August–December). On the monthly scale, although DCM dynamics were partly attributed to thermocline structures, the role of light penetration depths varied with period. In the FP, the influence of light on DCM was direct, i.e., increased depth and thickness but decreased magnitude. Differently, the influence of light mainly occurred by affecting thermocline structures in the WP, where water quality was another important driver. On the diel scale, light was a major reason for a thicker and lower (magnitude) DCM during day than at night, and the response of DCM to environmental factors between the FP and WP differed also more during day. This periodically asymmetric response of daytime DCM not only being caused by light but possibly also related to other physical factors such as lake surface water temperature, wind speed and precipitation. Bayesian network modelling suggested that water darkening and stratification intensification may promote a shallower, thinner and larger (magnitude) DCM in both FP and WP, but achieving such changes in DCM requires different light and thermocline thresholds. Our findings provide new information valuable for modelling DCM and for predicting the related surface algal blooms in deep lakes under climate change and eutrophication.

Long-term measurements reveal a 100-day lag between peaks in phytoplankton chlorophyll and benthic bacterial abundance in the Fram Strait

Abstract Repeated measurements of benthic and pelagic parameters in the rapidly changing Arctic Ocean provide a unique insight into spatial and interannual trends and changes in the ecosystem. Here, we compiled biogenic and biogeochemical measurements collected from sediment cores at the Long-Term Ecological Research Observatory HAUSGARTEN located in the Fram Strait. A total of 21 stations were visited yearly over a period of 18 years (2002–2019). The time series highlighted an increase in bacterial numbers for samples collected 50 days after the peak phytoplankton bloom. Although bacterial abundances were not bathymetric depth-dependent when viewed across all years, we observed a seasonal trend in benthic microbial abundance closely related to the timing of the phytoplankton bloom with a time-lag of 100 days between the surface phytoplankton peak and the peak in bacterial abundance in the sediment. Considering the residence time of phytoplankton in the upper ocean and the water depth, we estimated an average settling velocity for phytodetritus of 30 m.d−1, which is similar to previous observations from Fram Strait. This suggests that settling organic matter promotes vertical microbial connectivity and benthic bacterial abundance in the deep ocean, shaping the microbial biogeography, diversity, and biogeochemical processes.

Spatial and temporal distribution of chlorophyll a concentration in the Sunda Shelf

The Sunda Shelf, characterized as an oligotrophic region, exhibits relatively low chlorophyll concentrations, with interannual variations primarily driven by winter chlorophyll levels exceeding 0.2 mg m−3. Utilizing multisensor satellite data spanning from 1999 to 2019, we harnessed the Data Interpolating Empirical Orthogonal Functions (DINEOF) method to perform a comprehensive reconstruction of chlorophyll a concentration in the southern South China Sea (SSCS). The findings reveal pronounced seasonal and interannual variations in chlorophyll levels, characterized by a peak in January and a subsequent decline until April. Additionally, under the prevailing southwest monsoon, a secondary chlorophyll peak was observed in August, followed by a slight decrease until October. Wind speed (WS) and sea surface temperature (SST) emerged as significant influencing factors at the seasonal scale, displaying notable correlations with spatial and temporal changes in chlorophyll concentrations. Importantly, the monsoon’s role outweighs that of SST in regulating seasonal chlorophyll dynamics on the Sunda Shelf within the SSCS. The study highlights a strong negative correlation between chlorophyll and SST, indicating that nutrient inputs from winter upwelling stimulate phytoplankton growth. The strength of the Sunda Shelf upwelling is influenced by cyclonic circulation in the South China Sea, while El Niño–Southern Oscillation events modulate monsoon intensity, impacting cold water masses and cyclonic circulation strength. These findings contribute to a better understanding of seasonal and interannual chlorophyll dynamics in the SSCS, particularly on the Sunda Shelf, and their ecological implications.

Collapse of scallop Nodipecten nodosus production in the tropical Southeast Brazil as a possible consequence of global warming and water pollution

Mollusc rearing is a relevant global socioeconomic activity. However, this activity has faced severe problems in the last years in southeast Brazil. The mariculture scallop production dropped from 51,2 tons in 2016 to 10,2 tons in 2022 in the Baia da Ilha Grande (BIG; Rio de Janeiro). However, the possible causes of this collapse are unknown. This study aimed to analyze decadal trends of water quality in Nodipecten nodosus spat and adult production in BIG. We also performed physical-chemical and biological water quality analyses of three scallop farms and two nearby locations at BIG in 2022 to evaluate possible environmental stressors and risks. Scallop spat production dropped drastically in the last five years (2018–2022: mean ± stdev: 0.47 ± 0.45 million). Spat production was higher in colder waters and during peaks of Chlorophyll a in the last 13 years. Reduction of Chlorophyll a coincided with decreasing spat production in the last five years. Warmer periods (>27 °C) of the year may hamper scallop development. Counts of potentially pathogenic bacteria (Vibrios) and Escherichia coli were significantly higher in warmer periods which may further reduce scallop productivity. Shotgun metagenomics of seawater samples from the five studied corroborated these culture-based counts. Vibrios and fecal indicator bacteria metagenomic sequences were abundant across the entire study area throughout 2022. The results of this study suggest the collapse of scallop mariculture is the result of a synergistic negative effect of global warming and poor seawater quality.

Multi-objective optimal reservoir operation considering algal bloom control in reservoirs

Reservoir operation strategies (ROSs) are considered an efficient and low-cost method to control algal blooms. However, reservoir operations must consider regular objectives, including flood prevention and power generation. To address this multi-objective optimization problem, we coupled the non-dominated sorting genetic algorithm-II (NSGA-II) model and the General Lake Model-Aquatic EcoDynamics library (GLM-AED) model to optimize reservoir operations. Taking the Zipingpu Reservoir as a case study, we found the peak of outflow discharge (POD) could be reduced from 1059.5 to 861.4 m3 s−1 (19%), the total power generation (TPG) could be increased from 6.6 × 108 to 7.1 × 108 kW h (8%), and the peak of chlorophyll a concentration (PCC) could be decreased from 42.7 to 27.2 μg L−1 (36%) compared with the original reservoir operation in the early flood period. The obtained Pareto frontier revealed the tradeoffs between algal bloom control, flood prevention, and power generation. Reservoir operation schemes that achieved low PCC were typically associated with large POD and moderate TPG. In particular, under fixed start and end water levels, maintaining a higher average water level during May and June could result in larger outflows, effectively inhibiting algal accumulation and bloom development, thereby leading to a lower PCC. Slight variations in average water age were found among the minimum PCC scheme, maximum TPG scheme, and minimum POD scheme, indicating that water exchange varied little and has not been responsible for the differences in PCC. Collectively, enhancing outflow was determined to play a vital role in reducing PCC, particularly when operating under constrained rules. These findings contribute new insights into optimal reservoir operations considering algal bloom control and emphasize the importance of enhancing outflow as a governing mechanism. Furthermore, the coupled model offers a transferable technical framework for reservoir managers to mitigate eutrophication through ROSs.

Increased sea ice melt as a driver of enhanced Arctic phytoplankton blooming.

Phytoplankton primary production in the Arctic Ocean has been increasing over the last two decades. In 2019, a record spring bloom occurred in Fram Strait, characterized by a peak in chlorophyll that was reached weeks earlier than in other years and was larger than any previously recorded May bloom. Here, we consider the conditions that led to this event and examine drivers of spring phytoplankton blooms in Fram Strait using in situ, remote sensing, and data assimilation methods. From samples collected during the May 2019 bloom, we observe a direct relationship between sea ice meltwater in the upper water column and chlorophyll a pigment concentrations. We place the 2019 spring dynamics in context of the past 20 years, a period marked by rapid change in climatic conditions. Our findings suggest that increased advection of sea ice into the region and warmer surface temperatures led to a rise in meltwater input and stronger near-surface stratification. Over this time period, we identify large-scale spatial correlations in Fram Strait between increased chlorophyll a concentrations and increased freshwater flux from sea ice melt.

Effects of the 2018 European heatwave and drought on coastal biogeochemistry in the German Bight

In 2018, Europe experienced an unprecedented heatwave and drought, especially in central and northern Europe, which caused decreased terrestrial production and affected ecosystem health. In this study, the effects of this event on the marine environment are investigate, with a focus on the biogeochemical response in the German Bight of the North Sea. Using time series data from FerryBoxes, research cruises, monitoring programs and remote sensing we compare conditions in 2018 to climatological values. We find that (1) the heatwave caused rapid warming of surface waters, (2) the drought reduced river discharge and nutrient loads to the coast, and (3) these combined effects altered coastal biogeochemistry and productivity. During 2018, both water discharge and nutrient loads from rivers discharging into the German Bight were below the seasonally variable 10th percentile from March onward. Throughout the study domain, water temperature was near or below that threshold in March 2018, but higher than in other years during May 2018, representing not only a heat wave, but also the fastest spring warming on record. This extreme warming period saw concurrent high peaks in chlorophyll a, dissolved oxygen and pH, consistent with the development of a strong spring bloom. It appears that productivity was above 75th percentile of the 21-year record in most of the nearshore region, while offshore it was widely below the 25th percentile in 2018. The drought-related low discharge limited nutrient supply from the rivers, but likely increased water residence time nearshore, where a surge in primary production with efficient nutrient utilization during the spring depleted nutrients available for transport offshore. There, the heatwave-related rapid warming of surface water resulted in the establishment of a stable thermal water column stratification, hindering vertical nutrient supply to the surface layer during the summer.

Post-heating Fluorescence-based Alteration and Adulteration Detection of Extra Virgin Olive Oil

Olive oils are more expensive compared with other vegetable oils. Therefore, adulterating such expensive oil is prevalent. The traditional methods for olive oil adulteration detection are complex and require pre-analysis sample preparation. Therefore, simple and precise alternative techniques are required. In the present study, the Laser-induced fluorescence (LIF) technique was implemented for detecting alteration and adulteration of olive oil mixed with sunflower or corn oil based on the post-heating emission characteristics. Diode-pumped solid-state laser (DPSS, λ = 405 nm) was employed for excitation and the fluorescence emission was detected via an optical fiber connected to a compact spectrometer. The obtained results revealed alterations in the recorded chlorophyll peak intensity due to olive oil heating and adulteration. The correlation of the experimental measurements was evaluated via partial least-squares regression (PLSR) with an R-squared value of 0.95. Moreover, the system performance was evaluated using receiver operating characteristics (ROC) with a maximum sensitivity of 93%.

Detection and identification of a mixed cyanobacteria and microalgae culture using derivative spectrophotometry.

Early detection and monitoring of algal blooms and potentially toxic cyanobacteria in source waters are becoming increasingly important with rising climate change and industrialization. There is a growing need to measure the mixed microalgae cultures sensitively and accurately, as multiple algae species are present in natural source waters. This study investigated the detection of an equal concentration, mixed-culture of cyanobacteria (Microcystis aeruginosa) and a common green algae (Chlorella vulgaris) in water using UV-Vis spectrophotometry while employing longer pathlengths and derivative spectrophotometry to improve the detection limit. A strong linear relationship (R2>0.99) was found between the concentration and absorbance of the mixed-culture at 682nm using 50 and 100mm pathlengths. This study showed that the cyanobacterial (phycocyanin) peak could be separately identified in mixed-culture setting, while the chlorophyll peaks of both algae overlapped each other. The lowest detection limit of the mixed algal culture using traditional spectrophotometry and derivative spectrophotometry was calculated to be 25,997 cells/mL and 5505 cells/mL using a 100mm cuvette pathlength. Lastly, the performance of mixed-culture and individual algal cultures were compared, and analyses were carried out to evaluate differences in slopes which can be used for quantification purposes. The results indicate that derivative spectrophotometry significantly improved the detection limit making the method potentially viable for the early detection of mixed algal cultures.

Effects of LED Red and Blue Light Component on Growth and Photosynthetic Characteristics of Coriander in Plant Factory

Coriander is a whole-plant edible micro vegetable frequently used in the food industry. Its fresh eating features give it a flavor that is both tasty and refreshing, as well as potentially dangerous due to the bacteria (e.g., Shigella sonnei) it may contain. Artificial light-based plant factories are becoming increasingly popular due to the development of light-emitting diodes (i.e., LEDs). These plant factories employ artificial light to recreate the ideal lighting conditions for photosynthesis, ensuring plant yield and safety. Red (R) light and blue (B) light are essential for crop development and photosynthesis because R light and B light correspond to the wavelength absorption peaks of chlorophyll. However, the sensitivity of various crops to the light of varying wavelengths varies. Here, we determined the ideal R to B light ratio for cultivating coriander in plant factories by evaluating the photosynthetic characteristics of coriander (‘Sumai’) under different red–blue ratios. Specifically, we used monochrome red (R) and blue (B) light as controls and evaluated a total of seven different ratio treatments of R and B light (R, R:B = 5:1 (R5B1), R:B = 3:1 (R3B1), R:B = 1:1 (R1B1), R:B = 1:3 (R1B3), R:B = 1:5 (R1B5), B) under the background of uniform light intensity (200 ± 10 μmol m−2 s−1) and photoperiod (16-h/8-h light/dark). The results showed that the total yield of R:B = 3:1 (R3B1) was 16.11% and 30.61% higher than monochrome R and B treatments, respectively, the photosynthetic rate (Pn) and stomatal density were increased, and the nitrate content was decreased. Monochromatic light has adverse effects on crops. Monochromatic R light reduces the CO2 assimilation amount. Monochromatic blue light treatment lowers chlorophyll concentration and net photosynthetic rate.

Succession of protistan functional traits is influenced by bloom timing

Surface ocean eukaryotic phytoplankton biogeography can be determined as chlorophyll-a using remote sensing techniques yet evaluating its community composition remains limited. Given our ability to track site-specific chlorophyll-a concentration, we tested which factors influenced protistan functional trait distribution, and whether the distributions can be inferred from bloom succession. Here we surveyed the Labrador Sea during spring over three consecutive years, sequenced 18S data over 15 stations and collected satellite-derived chlorophyll-a concentration from March to July for each year. We evaluated changes in distribution of taxonomic composition as well as the functional traits of protistan size, trophic strategy (defined as phototrophy, phagotrophy, and mixotrophy as capable of both), motility and dimethylsulfoxide or dimethylsulfoniopropionate production by building a functional trait database after an extensive literature review. More variability in the biogeography of protistan functional traits was explained across water masses, and among years than taxonomic composition and patterns in trait variability were more apparent when site-specific timing of peak chlorophyll-a was considered. We found that reconstructing bloom phenology using days before peak (DBP) chlorophyll explained a significant amount of variability in functional trait community structure that was previously attributed to water masses or years, suggesting that spatial and interannual variations can be explained by the sampling moment during succession. Approximately 30 days prior to peak, mixotrophy as a trophic strategy was replaced by phototrophic protists of typically larger size classes. Our work suggests DBP influences protistan community trait succession that could inform biogeochemical models, and likely acts a proxy for the onset of stratification.

Dissolved organic carbon affects the occurrence of deep chlorophyll peaks and zooplankton resource use and biomass

Abstract Concentrations of dissolved organic carbon (DOC) are increasing in many parts of the world and vary considerably among lakes. As a result, it is important to understand the effects of DOC on zooplankton, which are a key component of freshwater food webs. Deep chlorophyll maxima (DCMs) also are common in many lakes and numerous studies suggest that they may be an important resource for zooplankton. In a survey of eight boreal lakes spanning a gradient of DOC (3.5–9.2 mg/L), we assessed variations in the occurrence of DCMs, zooplankton biomass and their use of basal resources using stable isotopes of carbon (C), nitrogen (N) and hydrogen (H). DCMs occurred only in lakes with lower DOC concentrations and Bayesian stable isotope mixing models indicated that they contributed between 22% and 72% of the assimilated diet of zooplankton. Food quality as indicated by C:P and chlorophyll a: C ratios increased with depth and in DCMs. The proportion of C ultimately derived by zooplankton from terrestrial sources increased from 6% to 27% with DOC. Zooplankton biomass among lakes declined with increasing DOC concentrations, the absence of DCMs and with increasing allochthony. Our results suggest that increasing inputs of DOC may suppress zooplankton in many lakes by affecting both resource quality and the availability of metalimnetic phytoplankton resources. Because zooplankton occupy a central position in freshwater food webs, declines in their biomass may further affect phytoplankton dynamics and fish productivity.

Stable isotopes demonstrate seasonally stable benthic-pelagic coupling as newly fixed nutrients are rapidly transferred through food chains in an estuarine fish community.

Seasonal differences in the availability of resources potentially result in the food web architecture also varying through time. Stable isotope analyses are a logistically simple but powerful tool for inferring trophic interactions and food web structure, but relatively few studies quantify seasonal variations in the food web structure or nutrient flux across multiple trophic levels. We determined the temporal dynamics in stable isotope compositions (carbon, nitrogen and sulphur) of a fish community from a highly seasonal, temperate estuary sampled monthly over a full annual cycle. Sulphur isotope values in fish tissues discriminated among consumers exploiting pelagic and benthic resources but showed no seasonal variation. This implied limited change in the relative consumption of pelagic and benthic resources by the fish community over the study period despite major seasonal changes in phytoplankton biomass. Conversely, carbon and nitrogen isotope values exhibited seasonality marked by the commencement of the spring phytoplankton bloom and peak chlorophyll concentration, with δ13 C values following expected trends in phytoplankton growth physiology and variation in δ15 N values coinciding with changes in major nitrogen sources to plankton between nitrate and ammonium. Isotope shifts in fish muscle were detected within 2 weeks of the peak spring phytoplankton bloom, suggesting a rapid trophic transfer of carbon and nitrogen along food chains within the estuarine food web during periods of high production. Therefore we caution against the assumption that temporal averaging effectively dampens isotopic variability in tissues of higher trophic-level animals in highly dynamic ecosystems, such as temperate estuaries. This work highlights how stable isotope analyses can be combined with environmental data to gain a broader understanding of ecosystem functioning, while emphasising the need for temporally appropriate sampling in stable isotope-based studies.

Peak chlorophyll a concentrations in the lower Mississippi River from 1997 to 2018

AbstractLarge and turbid rivers have varying temperatures, light conditions, nutrient availability, and nutrient ratios that may affect phytoplankton communities and occur within a changing world of point and nonpoint source nutrient loadings. We investigated how these physical and chemical factors affect Chlorophyll a (Chl a) concentrations in the Mississippi River, the largest river in North America, by sampling 878 times from February 1997 to December 2018 near its terminus at Baton Rouge, Louisiana. We hypothesized that nutrient concentrations and ratios were significant factors limiting phytoplankton biomass accumulations in this turbid river. The Chl a concentrations were in the “poor” water quality category when above 20 μg Chl a L−1 12% of the time. Two percent of the samples were > 40 μg Chl a L−1 and occurred on declining discharges. Results from graphical analysis and a principal component regression analysis showed that the highest Chl a values were constrained to when dissolved silicate: dissolved inorganic nitrogen (DIN) molar ratios < 1 : 1 and dissolved DIN : phosphate molar ratios < 16 : 1, which is when the phytoplankton community likely consists of non‐siliceous phytoplankton. Increasing light conditions and reducing turbulence, which happens when river water is diverted into calmer and shallower waters, will create a phytoplankton bloom—perhaps becoming a harmful algal bloom—as has happened previously.

Episodic shifts of phytoplankton community and biomass during a restricted summer coastal upwelling event off the Southeast China

Upwelling supports a diversity of organisms in marine ecosystems. Wind-driven upwelling occurs off the southeast China during summertime. Interannual variability in the intensity, extent and central location of this upwelling presented, resulting in spatial heterogeneity in surrounding environment. A restricted coastal upwelling event visible in satellite contours and concave isolines of temperature, phosphate and silicic acid was observed across a geographical area with weak intensity, accompanied by spatial heterogeneity of nutrients in June 2009. Peaks in depth-averaged chlorophyll a (Chl a, 0.62 and 0.83 mg/m3) and phytoplankton abundance (10.51 and 9.23 × 103 cells/L) in two patches near the upwelling center were consistently exhibited, with maxima at 10 m and 30 m, respectively. A total of 122 species from 41 genera of diatoms and 33 species in 14 genera of dinoflagellates were identified by the Utermöhl method, as well as 4 species in Cyanobacteria and Chrysophyta. Rhizosolenia alata was the most dominant species, followed by Thalassionema nitzschioides, Pseudonitzschia pungens, R. alata f. gracillima, T. frauenfeldii and Paralia sulcata. The restricted upwelling caused an upward transport of deep-water associated flora including Heterodinium blackmanii, Pyrocystis pseudonoctiluca, Ceratium gravidum and C. incisum to the surface, and the dispersal of dominant species across the surveyed area. Cluster analysis was performed across three phytoplankton assemblages in relation to upwelling intensity and continental influence. Redundancy and Spearman correlation analyses revealed that phytoplankton variability was mainly associated with phosphate. Furthermore, transect profiles of Chl a and phytoplankton abundance confirmed the origination of summer upwelling was the transportation of deep cold water in South China Sea to the surface layer along the coastline. These results indicate that the spatial variability of the phytoplankton community and biomass were highly controlled by the changes in upwelling location and intensity.

Importance of winds, freshwater discharge and retention time in the space–time variability of phytoplankton biomass in a shallow microtidal estuary

In the present study, we analyze the effects of the hydrodynamics induced by action of wind and river discharge on the space–time variability of chlorophyll a concentration in estuary of Patos Lagoon. The study was carried out through the analysis of time series of winds, currents, salinity and chlorophyll a concentration, all measured in the narrow channel that connects the lagoon to Atlantic Ocean. In addition, we also analyze spatial data collected during eight cruises performed in the estuarine area during 2012. Results reveal two patterns of maximum of chlorophyll a concentration in the time series. The most prominent peak, was related to microalgae resuspension due to strong inflow currents. The second pattern, indicated by a less intense peak that occurs after seaward flows, at time salinity starts to decrease. The analysis of longitudinal estuarine profiles suggests an increase in chlorophyll a after saltwater intrusion up to 50 km inside the estuary associated to vertical stabilization caused by freshwater input from the only nearby tributary. Results also indicate that the peaks of chlorophyll a are linked to longer retention time and the vertical salinity stratification of water column.

Real-time analysis of multicomponent dissolved inorganic carbon in the air-sea exchanging process using gas-liquid Raman spectroscopy

Carbon cycle in coastal water is a significant dynamic component of global carbon budget, however, the diverse sources, carbon sinks and their complex interactions remained poorly understood. In order to detect the dissolved inorganic carbon (DIC) and their interactions, gas-liquid Raman spectroscopy was built and applied to simultaneously detect the constituents of air, dissolved CO2, HCO3- and chlorophyll in coastal water. The linear fitting curve between peak intensity and concentration was built for the quantitative analysis of HCO3- and CO2, meanwhile, the fluorescence peaks of chlorophyll at 679 nm were detected for the qualitative analysis. For the multi-components analysis, typical Raman spectra of the constituents of air, dissolved CO2, HCO3- in seawater, and the fluorescence spectra of chlorophyll in seawater were detected. Results showed that the time dependent change of CO2 and O2 in the air exhibited a contrary tendency, while that of dissolved CO2 and O2 was curved like a cosine. The changing tendency of relative concentrations of dissolved CO2 was about 2 h earlier than CO2 in air, due to the life activity of microorganisms driving the gas exchange at the air-sea interface. Furthermore, the study makes a study on the relationship between DIC and chlorophyll based on the detection of HCO3- and chlorophyll in coastal water, indicating that this gas-liquid Raman spectroscopy could successfully provide real-time analysis of multicomponent DIC in the air-sea exchanging process.

Smoke from regional wildfires alters lake ecology

Wildfire smoke often covers areas larger than the burned area, yet the impacts of smoke on nearby aquatic ecosystems are understudied. In the summer of 2018, wildfire smoke covered Castle Lake (California, USA) for 55 days. We quantified the influence of smoke on the lake by comparing the physics, chemistry, productivity, and animal ecology in the prior four years (2014–2017) to the smoke year (2018). Smoke reduced incident ultraviolet-B (UV-B) radiation by 31% and photosynthetically active radiation (PAR) by 11%. Similarly, underwater UV-B and PAR decreased by 65 and 44%, respectively, and lake heat content decreased by 7%. While the nutrient limitation of primary production did not change, shallow production in the offshore habitat increased by 109%, likely due to a release from photoinhibition. In contrast, deep-water, primary production decreased and the deep-water peak in chlorophyll a did not develop, likely due to reduced PAR. Despite the structural changes in primary production, light, and temperature, we observed little significant change in zooplankton biomass, community composition, or migration pattern. Trout were absent from the littoral-benthic habitat during the smoke period. The duration and intensity of smoke influences light regimes, heat content, and productivity, with differing responses to consumers.

Photocatalytic reduction of Cr(VI) within mesoporous TiO2 templated and confined with chlorophyll

AbstractBiomimetic light‐harvesting architecture has been proposed as an alternative for existing solar conversion systems. Chlorophyll‐sensitized TiO2 have been identified as promising catalyst for photocatalytic reduction system, but it is largely limited to complicated process for purification of chlorophyll and adding extra hole scavenger in system. In sharp contrast to conventional photosensitization methods in which the organic dyes were often adsorbed after photosensitization, herein mesoporous TiO2 incorporated with chlorophyll extract was synthesized in situ (TiO2/Chl). Interestingly, TiO2 incorporated with chlorophyll exhibited two distinct absorption bands around 407 and 668 nm which are closed to the characteristic absorption peak of chlorophyll. TiO2 incorporated with chlorophyll kept at 185°C for 1.5 hours (TiO2/Chl‐185) achieved a high photoreduction rate of 86.1% for the photocatalytic reduction of Cr(VI), which was approximately 29 and 20 times higher than that of TiO2 and TiO2 adsorbing chlorophyll (TiO2/ads Chl), respectively. The significant enhancement was due to the confinement of chlorophyll. This demonstrates that mesoporous TiO2 templated and confined with chlorophyll could offer a new approach for synergistic photoreduction of Cr(VI).