Dark Bottles Research Articles

Unveiling primary production dynamics in the southern Bay of Bengal: Comparative analysis of in-situ measured data with multiple primary production models

In this study, marine water samples were collected at 18 sampling stations. The collected marine water samples were analysed using a well-calibrated UV spectrophotometer for chlorophyll-a estimation, and using a hyperspectral underwater radiometer, both buoy mode and profile mode in-situ data were collected. The study evaluated four different primary production models to study the dynamics of the southern Bay of Bengal. The simple Eppley model used in the study resulted in huge variations in the nearshore and frontal regions; the dark and light bottle methods showed enormous variations along all 18 sampling stations and underestimated the productivity of the southern Bay of Bengal. However, the VGPM model and its variants showed similar trends in near shore, frontal, and off-shore waters for all three transects, and the Kameda model closely matched the available literature for the primary production estimates of the southern Bay of Bengal. From the detailed analysis of the Kameda model, it is found that the average primary production for the Southern Bay of Bengal for the post monsoon season (February 2023) is estimated as 339.08 mgC/m2/d.

Uji stabilitas penyimpanan RC A amlodipine dengan metode kromatografi cair tingkat tinggi

Background: One of the important components of health is the availability of drugs as part of public health services. This is because drugs are used to save lives, restore or maintain health. The pharmaceutical industry as a drug-producing industry has a strategic role in health service efforts to the community. Findings: Along with increasing education and public awareness of the importance of health, the pharmaceutical industry is required to provide drugs in adequate types and quantities and of good quality. Therefore, public access to drugs including availability and affordability for the entire community must be expanded. Access to drugs, especially essential drugs, is an obligation for the government and health service institutions, both public and private. Methods: Add with mobile phase to the limit mark, then homogenize (Solution S1 0.04 mg/ml). The solution to be tested for stability during the RC A Amlodipine area is stable. Storage is carried out in dark glass bottles and stored in a refrigerator at a temperature of 2-8 °C. Conclusion: This indicates that each new batch analysis can use the RC Amlodipine stock for a period of 4 months with a storage temperature of 2-8 °C. In this study, RC A Amlodipine which was weighed before the study each time the test was carried out was weighed once and made into a stock solution for 4 months. This study also carried out the potential for cost saving because every year 3 bottles are now 1 bottle, which is 96.5%.

Evaluation of the fermentative activity of Saccharomyces cerevisiae HG1.3 and condition for threeleaf cayratiawine preservation

Threeleaf cayratia(Cayratia trifolia L.) is a wild climbing vine species that has potential raw material for wine production. Berries are green and turn purple when ripe, widely distributed in the Mekong delta provinces of Vietnam. This study aimed to investigate the threeleaf cayratiawine fermentation activity of Saccharomyces cerevisiae HG1.3 at the volumes of 1, 2, and 4 litres, along with examining the colour stability of the wine under different storage temperatures and packaging methods. The results showed that the fermentation volumes of 2 and 4 litres contained 12.37 and 12.45% (v/v) of ethanol contents, respectively. At the storage conditions of cool temperature (2-4°C)in the dark bottle, threeleaf cayratiawine has a stable colour and good sensory evaluation for colour and taste clarity after 4 weeks, with the optical transmittance value at 550 nm is 0.419%. In addition, threeleaf cayratiawine was clarified by the addition of 0.5% pectinase for 6 days after the fermentation period, then filtered and supplemented with 0.2% citric acid. The final product meets the Vietnamese standards (TCVN 3217-79 and TCVN 7045:2002).

Evaluation of Flexural Strength and Microhardness of Different Type Glass Ionomer Cements

Abstract Purpose: The aim of this study is to evaluate and compare flexural strength and microhardness of different types of glass ionomer cements (Fuji IX GP® Fast, Riva LC HV, EQUIA Forte Fil). Materials and Methods: A total of 30 samples (n = 10) were prepared for microhardness test, and an additional total of 30 samples (n = 10) were prepared for the flexural strength test. Customized stainless steel molds (25×2×2 mm³) were produced for the flexural strength test, and 10 mm and 2 mm plexiglass molds were produced for the microhardness test. The prepared samples were stored in distilled water in a dark bottle at 37 °C (±1 °C) for 24 hours. A three-point bending test was performed using a universal testing device, and the maximum force values required to fracture the samples were determined in Newton by the device after the fracture. For the Vickers microhardness test measurements were made from different areas of the upper surfaces of each sample and the average of five measurements was calculated in MPa. Results: When comparing the flexural strength values, EQUIA Forte Fil group observed the highest flexural strength value, while Riva LC HV group had lowest flexural strength value. When comparing the microhardness values, EQUIA Forte Fil group showed the highest microhardness value, whereas Riva LC HV group observed the lowest microhardness value. Conclusion: The use of EQUIA Forte Fil, which has the highest microhardness and flexural strength values, and similarly strengthened glass ionomer cements may enhance clinical success. Key Words: glass ionomer cements; microhardness; flexural strength

Rethinking some roots of ecosystem approach in aquatic ecology: between the food cycle and lake metabolism.

The present study provides new insight into the key aspects of the early formative period of the ecosystem concept in aquatic ecology. Raymond Lindeman's trophodynamics is known to be a starting point for the development of the modern concept of ecosystem. The trophodynamic approach in ecology was proposed by Lindeman in his widely cited paper of 1942. Lindeman's views are analyzed in comparison with the contemporary production studies in aquatic ecology. It is shown that a similar theoretical system has been proposed in the USSR at the end of the 1930s by Georgiy G. Vinberg. He introduced the concept of biotic balance based on the wide appraisal of the dark and light bottles method. The study shows that both Lindeman's trophodynamics and Vinberg's concept of biotic balance relied on an energy-based approach in considering the wholeness of a water body. The two scientists, however, differed in several important aspects concerning the interpretation of the role of living organisms. The holistic interpretation of ecosystem by Lindeman and Vinberg can be seen as part of the dilemma between physicalism and organicism. At the same time, the main emphasis in the concepts of both Vinberg and Lindemann was on the primary production component, a feature that was common to the first holistic systems in production hydrobiology (e.g., E. Naumann's regional limnology). It is clear that modern problems of aquatic ecology should be addressed from the perspective of the organismocentric understanding of the ecosystem, but undoubtedly at the new level of development of this view.

Evaluation of three physical mixing methods of nanoparticles to orthodontic primer

Background: Demineralization and white spot lesions are the most common complications in fixed orthodontic treatment. It is useful to enhance the remineralization properties of the orthodontic primer by the addition of remineralizing agents. Fluoride and calcium are regarded as the main component of enamel fluorohydroxyapatite crystals. This pilot study compared three mixing methods of calcium fluoride nanoparticles (nCaF2) with conventional orthodontic primer (Transbond XTTM) to develop a primer with enamel remineralization properties. Materials and methods: The nanoparticles were added to Transbond XTTM primer to form 20% (w/w) of the final solution. Three dark plastic bottles were prepared and stored until mixing. The first sample was mixed by a Vortex machine, the second was mixed with an electric agitator, and the third one was mixed with a customized plastic spatula adapted to a dental engine and a straight handpiece. Cured blocks of the developed primer were prepared and were examined for homogeneity, cracks, and agglomeration of the nanoparticles within the primer using Field Emission Scanning Electron Microscopy (FESM). Results: The third Sample showed a continuous distribution of nanoparticles with no apparent cracks or agglomeration of nanoparticles. In contrast, a higher agglomeration was seen in the first sample than in the other two. Conclusion: Mixing of nCaF2 with Transbond XTTM orthodontic primer was best achieved by the customized plastic spatula adapted to a dental engine compared to Vortex and electric agitator machines.

Primary Productivity of Phytoplankton in Mandalika Coastal Area, Central Lombok Regency

The research entitled "Primary Productivity of Phytoplankton in Mandalika Coastal Area, Central Lombok Regency" was conducted from March to August 2023. This study aims to analyze the primary productivity of phytoplankton and physical and chemical parameters in Mandalika Coastal waters at three different stations (Kuta Beach, Tanjung Aan, and Gerupuk Bay) using dark and light bottles. Based on the results of the study, it is known that Mandalika Coastal waters have phytoplankton primary productivity values ranging from 122.619 - 329.166 mgC/m2/day. The lowest productivity value (122.619 mgC/m2/day) occurs at station III classified as mesotrophic. Station III also has relatively lower physical and chemical parameter values such as an average pH of 7.7 mg/L and an average temperature of 29ºC compared to other stations. The highest productivity value (329.166 mgC/m2/day) occurred at Station II classified as eutrophic and Station I (189.285 mgC/m2/day) also classified as eutrophic. This is supported by pH worth 7.8 mg/L and temperatures ranging from 29.3 - 29.7 ºC, where the value is relatively higher than station III.

Application of Citric Acid and Packaging Type Selection in Preserving Stability of Homemade Tomato Sauce

Tomatoes are horticultural product widely grown in Indonesia and consumed by societies. They contain minerals, vitamins, and bioactive compounds beneficial for health. Unfortunately, tomatoes quickly decline in quality, causing their post-harvest shelf life to be short. One attempt to prevent the wastage of tomatoes is to process them into sauce products. To extend the stability of tomato sauce, food-grade preservatives such as citric acid need to be added. Furthermore, different packaging also affects the stability of tomato sauce. This study used citric acid with varying concentrations of 0.05%, 0.10% and 0.15%. The packaging used included Clear Glass Bottles, Dark Glass Bottles, Clear Plastic Bottles, and Dark Plastic Bottles. The tomato sauce was evaluated by room storage for 30 days to investigate the stability of water content, acidity level, and total microbes. Adding 0.15% citric acid may be considered in preserving tomato sauce with a difference in increasing water content of 1.7%, a difference in decreasing pH of 0.1, and a difference in increasing total microbes of 1.4 cfu/g. Using a dark glass bottle may better protect tomato sauce from quality degradation.

Phytoplankton primary production in Chascomus pond (Provincia de Buenos Aires, Argentina)

In situ phytoplankton primary production in Chascomús pond (eutrophic Pampasic “laguna”) was studied by the oxygen method (light and dark bottle) between.January 1984-January 1985. Valúes obtained ranged from37,9 to 981,6 mg C • m-1 • d-1. Factors influencing it, as suspended particulate matter and hydrological changes, are discussed. Parallel determinations of the artificial light photosynthesis response proved to be useful,almostqualitatively under the experimental conditions applied, to follow the behaviour obtained by incubations in natural environment.

Interference of glitter with the photosynthetic rates of a submerged macrophyte, Egeria densa

ABSTRACT Thousands of glitter particles are potentially daily released into aquatic ecosystems, but their effects on the ecological processes of aquatic species remain unknown. The metallic coating of glitter could potentially reflect light and interfere with photosynthesis, so this study analysed the photosynthetic rates of the macrophyte Egeria densa in the presence and absence of 0.04 g/L glitter using the light and dark bottle method. We collected 400 individuals of E. densa and separated them into four equal-sized treatment groups (with and without glitter under iluminated and dark conditions). We found that the presence of glitter reduced the rates of net photosynthesis (P N) and gross photosynthesis (P G) of E. densa by 34.61%, and 29.65%, respectively, compared with the control treatment without glitter, and also decreased the light intensity inside the bottles. These results suggest that the metal coating of glitter particles attenuates light penetration and increases water reflectance, wich interferes with underwater radiation and light absorption for photosynthetic processes.

Seasonal variation of gross ecosystem productivity of periphyton in three post-mining lakes in the Czech Republic, Europe

We investigated the seasonal variation of gross ecosystem productivity (GEP) of periphyton biomass in three post-mining lakes in the Czech Republic. These lakes were established as part of recultivation efforts after coal mining activities and resulted in a unique series of anthropogenic oligotrophic lakes of gradual successional age. Periphyton is ubiquitous in aquatic habitats and performs numerous environmental functions such as nutrient cycling and self-purifying of aquatic ecosystems. Well-developed periphyton mat can be formed within a few weeks, so it can quickly become the dominant of littoral zone of newly established lakes. In studied post-mining lakes, the highly developed periphytic community covers the littoral zone of each lake to the depth of 2m (Bešta et al. 2022, Konopáčová et al. 2023) Fig. 1. We aimed to shed some new light on the processes controlling the dynamics of primary productivity in oligotrophic lakes. The accurate estimation of primary productivity is crucial for understanding the functioning of aquatic ecosystems, as primary productivity serves as the primary source of autochthonous carbon in these systems. In addition to phytoplankton, periphyton can significantly contribute to primary productivity in littoral zones, known for their high productivity and biodiversity. Conducting in situ measurements provides the most accurate means of inferring the metabolic activity of primary producers in littoral zones. We conducted detailed seasonal in-situ periphyton gross primary production (GPP) measurements in three post-mining lakes with different successional ages (Čapková et al. 2022). GPP and NPP of periphytic biomass were determined using direct in-situ measurement of O2 fluxes. O2 production and consumption were measured over 5 hours of in-situ light and dark gas-tight glass bottle incubation. Bottles were filled with the lake water from the corresponding depth, and a similar amount of periphytic biomass was enclosed Fig. 2. We used the Fibox3 fibre-optic oxygen meter coupled with a PSt3 oxygen sensor (PreSens, Regensburg, DE) to measure changes in O2 concentration. The O2 fluxes were normalized to periphytic biomass in each bottle (measured as total organic carbon). Data were corrected for O2 concentration changes in dark and light gas-tight bottles containing lake water without periphytic communities. This setup enabled us to monitor online oxygen flux, therefore, insights into metabolic activities. The primary productivity was measured in real-time, allowing us to capture the quantitative effect of various environmental drivers on periphyton productivity, i.e. phosphorus concentration and light intensity, as they are known to play significant roles in primary productivity. We showed that the primary production of periphyton mats exhibited seasonal variations, with higher productivity observed in spring compared to other seasons. This observation could be attributed to the occurrence of winter/spring upwelling events and vertical mixing, which resupply nutrients from the deeper strata. Furthermore, the physiological activity of periphyton was strongly influenced by the seasonal changes in light intensity, temperature, and nutrient concentration. We provided the first insight into the seasonal variation of primary productivity of the periphyton assemblage dominating the littoral zone of newly established post-mining lakes. We stress the importance of periphyton in aquatic ecosystems, particularly in anthropogenic oligotrophic lakes.

Influences of zonation on water fertility and structure communities of phytoplankton and benthos in Batukaras Mangrove Forest, Pangandaran District, Indonesia

Abstract. Pratiwi D, Oktavia D, Sumiarsa D, Sunardi S. 2023. Influences of zonation on water fertility and structure communities of phytoplankton and benthos in Batukaras Mangrove Forest, Pangandaran District, Indonesia. Biodiversitas 24: 4978-4988. Mangrove forests are coastal areas with several advantages, including access to natural resources that other regions do not provide. Pangandaran has mangrove forest areas, namely Batukaras mangroves, located in Batukaras Village, Pangandaran, West Java, Indonesia. This study aims to identify the primary productivity and community structure of phytoplankton and benthos as one of the natural resources in the Batukaras mangrove with different zone patterns of mangrove (seaward and landward). The purposive sampling method determined the observation stations based on the vegetation density. The obtained data of Net Primary Productivity (NPP) was analyzed with the light and dark bottle (Winkler method). In addition, the data community structure of phytoplankton and benthos was analyzed using the Shannon Wienner diversity index (H'), equitability index (E), and Simpson dominance index (D). The results show that the NPP in seaward and landward are mesotrophic with values of 105.833 mgC/m3/h and 36.463 mgC/m3/h. The abundance of phytoplankton and benthos in seaward is 560 ind/m3 and 387 ind, while landward ranges from 1140 ind/m3 and 135 ind. Planktoniella sp. and Faunus ater dominated the community structure of phytoplankton and benthos seaward, while the landward location consisted of Oscillatoria sp. and Terebralia sulcata. The community structure of phytoplankton and benthos in seaward and landward has significant differences (<0.05). The seaward and landward zone shows relatively stable and non-polluted waters.

DETERIORATION KINETICS OF NEUTRALIZED RED FRUIT (Pandanus conoideus L.) OIL DURING STORAGE

This study’s goal was to obtain a kinetics model of neutralized red fruit oil (NRFO) quality change during storage. The NRFO was stored in dark bottles at 60 °C, 75 °C and 90 °C for ± 15 days to evaluate the quality. The results showed that the quality of NRFO decreased along with the increase in temperature and storage time. This was indicated by increasing moisture content, Free Fatty Acid (FFA), peroxide number, as well as decreasing of the total carotenoids and total tocopherols. The FFA content and peroxide number of NRFO increase followed the kinetics zeroth order model, with activation energy (Ea) of 6372 cal/moloK and 9954 cal/moloK, respectively. Meanwhile, the decrease in carotenoid and tocopherol content followed the kinetics first order model, with Ea 9581 cal/moloK and 14242 cal/moloK, respectively. Estimation of shelf life of NRFO was based on peroxide number equation. The shelf life of NRFO is 398.5 days or 13.3 months if it is stored at 20 °; and the shelf life is 277.6 days or 9.3 months if it is stored 30 °C.

Effects of ohmic heat processing and ascorbic acid on antioxidant compounds and colour of red‐fleshed dragon (Hylocereus polyrhizus) fruit juice during storage

SummaryRed‐fleshed dragon fruit is a promising source of antioxidants and natural colour compounds. This study examined the effects of ohmic heating (OH) and ascorbic acid addition on total phenolic content (TPC), betacyanin (BC), antioxidant activity and colour changes in the juice during storage. The juice was treated from 20 to 85 °C and stabilised at 85 °C for 60 s by OH at 60 Hz and 30 V cm−1. The treated samples were stored at 4 °C in dark bottles for 8 weeks, and BC, TPC, antioxidant activity and colour were determined weekly. After 1 week of storage, there was no degradation of TPC or BC (P > 0.05). However, after 8 weeks of storage, BC decreased by 47%, TPC decreased by 60% and antioxidant activity decreased by 39% in the OH juice. The colour changes of the juice during the 8‐week storage period were strongly correlated with the BC (r (correlation coefficient) > 0.98). A comparison of the OH process with conventional heating (CH) showed that OH resulted in less degradation to BC, TPC and antioxidant activity than CH. OH is a suitable technology for processing red‐fleshed dragon fruit juice. Adding 0.25% AA to the juice helped reduce changes in colour, BC, TPC and antioxidant activity (P < 0.05).

Interactions of bioactive trace metals in shipboard Southern Ocean incubation experiments

AbstractIn the Southern Ocean, it is well‐known that iron (Fe) limits phytoplankton growth. Yet, other trace metals can also affect phytoplankton physiology. This study investigated feedbacks between phytoplankton growth and dissolved Fe, manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), and cadmium (Cd) concentrations in Southern Ocean shipboard incubations. Three experiments were conducted in September–October 2016 near the West Antarctic Peninsula: Incubations 1 and 3 offshore in the Antarctic Circumpolar Current, and Incubation 2 inshore in Bransfield Strait. Additions of Fe and/or vitamin B12 to inshore and offshore waters were employed and allowed assessment of metal (M) uptake relative to soluble reactive phosphorus (P) across a wide range of initial conditions. Offshore, treatments of >1 nmol L−1 added Fe were Fe‐replete, whereas inshore waters were already Fe‐replete. Results suggest Mn was a secondary limiting nutrient inshore and offshore. No Fe‐vitamin B12 colimitation was observed. Overall, M:P uptake in the incubations was closely related to initial dissolved M:P for Fe, Mn, Co, Ni, and Cd, and for Cu inshore. Final concentrations of Fe and Zn were similar across light treatments of the experiments despite very different phytoplankton responses, and we observed evidence for Co/Cd/Zn substitution and for recycling of biogenic metals as inventories plateaued. In dark bottles, the absence of Mn oxidation may have allowed more efficient recycling of Fe and other trace metals. Our results provide insight into factors governing trace metal uptake, with implications for phytoplankton community composition locally and preformed micronutrient bioavailability in Southern Ocean water masses.

E-Nose Quality Evaluation of Extra Virgin Olive Oil Stored in Different Containers

The degradation process of virgin olive oil (VOO) is related to storage time and the type of storage container used. The aim of this work is to explore the evolution of the VOO quality stored in different container types over a defined storage period in order to predict the organoleptic characteristics using a non-destructive technique such as the electronic-nose (E-nose). The “Picual” variety VOO was stored in different containers over a period of 21 months and monitored using sensory analysis, volatile compounds, and an E-nose. The panelists showed that oil stored in dark glass bottles and in green polyethylene bottles began to show defects after 12 and 15 weeks, respectively. However, oil stored in tin containers retained its quality throughout the 21 months studied. A total of 31 volatile compounds were identified, and the evolution of the volatile profile in the different containers during the storage period was studied. The E-nose data were able to classify oil quality by container using principal component analysis (PCA). Furthermore, the E-nose data combined with partial least squares (PLS) regression enabled the building of a predictive model to quantify sensory defect values (RCV2 = 0.92; RCV2 = 0.86), evidencing that this technique would be an appropriate screening tool to support a sensory panel.

Primary production and destruction of organic matter in Lake Arakhley (Eastern Transbaikalia, Russia)

Global climate changes affect water ecosystems. Long-term observations of climatic variables are indicative of cyclic climate changes. The fluctuations result in changes in water levels in lakes, which, in turn, alter primary production processes. Planktonic algae are the main drivers of primary production. This research continues long-term studies on hydroecology of Lake Arakhley. The lake is used for fishery and recreation. This work aims to estimate production and destruction processes in Lake Arakhley during the current transitional period between dry and wet years. To this end, we performed field studies on Lake Arakhley in August from 2016 to 2021, during the season of maximum precipitation, in the central and littoral zones of the lake. Primary production of phytoplankton in water was estimated by the oxygen light and dark bottle method. Sampling was carried out to assess physical and chemical parameters of water using a multiparameter water quality instrument. Lake Arakhley features the low level of mineralization under alkali conditions and relatively stable level of mineralization registered from 2016 to 2021. Macrophytes zone expanded after the massive flooding of the shore in 2021 hence alterating the values of such environmental factors as oxygen levels, total and mineral phosphorus, with destruction prevailing over organic matter production. Depth and transparency however contribute to significant production of organic matter in the lake. The findings can be used as the groundwork for the sustainable management of the lake.

Characterization of Spatiotemporal Variations in Mert Stream Water Quality by Phytoplankton Community and Biological Indices

In order to determine the water quality of the Mert Stream, algal indicators and some biological indices (TDI, IDG, PTI, Palmer, DAIpo) based on phytoplankton species were used. Phytoplankton samples were performed monthly from six different sites at a depth of 0.5 meter using a one-litre water sampler between July 2011 and June 2012. After phytoplankton samples were placed in 250-mL dark bottles and fixed with Lugol’s solution until processed in the laboratory, they were identified and counted in the tubular plankton counting chambers using an inverted microscope according to Utermöhl method. Bacillariophyta members became the dominant division in the phytoplankton with an abundance rate of 83.3% and 71 taxa. Lindavia glomerata, Navicula cryptocephala, Cyclotella planctonica, and Navicula veneta were determined as the most dominant species among phytoplanktonic taxa of Mert Stream. Trophic diatom index (TDI) and Generic diatom index (IDG) based on planktonic diatoms were used to determine the trophic status of the Mert Stream. Pollution tolerance index (PTI), Diatom assemblage index (DAIPo) and Palmer index were also included to assess the organic load-based sabrobity level of the Mert Stream. According to the results of mean TDI and IDG (55 and 13, respectively), the trophic status of the Mert Stream is a mesotrophic structure with moderate nutrients and good water transparency. According to the average PTI result (2.7), Mert Stream is in the β-mesosaprobic class, which corresponds to moderate pollution. Considering DAIpo indice, the saprobity of Mert stream is α-oligosaprobic level and the stream is not exposed to a serious organic-based pollution. However, according to the Palmer index, all stations of the Mert Stream except the 6th station are under the threat of high organic pollution. In present study, it was seen that the best biological index that reflects the station-based trophic structure of the stream is IDG, and the best biological index that reflects the station-based organic pollution of the stream is PTI.

Cyanate dynamics under algal blooms and sediment resuspension events in a shallow micro-tidal estuary in the lower Chesapeake Bay

Although an emerging component in the marine nitrogen (N) cycle, cyanate concentrations and cycling have not been examined in estuarine systems to date. To better understand controls on cyanate concentrations in estuaries, time series data of cyanate and nutrient concentrations in the Lafayette River, a micro-tidal, sub-tributary of the lower Chesapeake Bay, were examined between June and September 2018, and May to September 2019. Cyanate concentrations ranged from near the detection limit (0.4 nmol L−1) to 82.9 nmol L−1 in 2018, and 6.8–207.4 nmol L−1 in 2019. Variations in cyanate concentrations were highly correlated with chlorophyll biomass in the summer, biomass degradation in early fall, and sediment resuspension that occurred in response to meteorological forcing. Cyanate concentrations increased after Chl a concentrations decreased suggesting algal decomposition as a source of cyanate. High cyanate concentrations in bottom waters, corresponded to wind-induced sediment resuspension events in the Lafayette River, again suggesting organic matter decomposition as a source of cyanate. Cyanate concentrations in sediment pore water varied between years; in summer 2018, cyanate concentrations were up to 150 nmol L−1, while in 2019, they were three times lower. To confirm an algal source for cyanate, a degradation experiment was conducted using Lafayette River water collected during a bloom of Margalefidinium polykrikoides in 2018. In dark incubation bottles, cyanate was one of the first labile organic nitrogen products produced, suggesting the contention that high concentrations of cyanate in late summer and fall were the result of organic matter decomposition. Neither cyanate nor ammonium accumulated in light bottles suggesting production and uptake are tightly coupled and microbes have a high affinity for cyanate in the light. In dark bottles, cyanate production rates were 6.8 nmol L−1 d−1, while microbial removal rates during the late phase of degradation were 1.5 nmol L−1 d−1, suggesting that cyanate may not be a preferred nitrogen substrate for microbes (including nitrifiers) in dark bottles or that microbes have a lower affinity for cyanate in the dark, allowing cyanate to reach steady state at concentrations greater than the detection limit.

Assessment of Primary Parameters in Sawa Lake and Their Impact on Productivity

Sawa Lake is one unique enclosed water system situated in southwest Iraq. The current study intends to track the change in water level and analyse the reasons and consequences of the shift in the lake’s physicochemical qualities and primary productivity. Monthly samples were taken from three study sites from February to July 2021. The study found that air and water temperatures increased and decreased at all sites, which were evaluated during the study period. The mean salinity values ranged from 85.92 to 19.67‰, with the highest value (52.20‰) occurring before the drought in February and the lowest value (19.67‰) occurring after the drought in July. The pH level ranged from 7.57 to 8.77. The current study’s nutrient concentration (nitrite, nitrate, and phosphate) was 1.04-19.91, 21.51-251.79, 0.26 - 2.37μg/L, respectively, and there was a reverse correlation between nitrite and nitrate with salinity. The productivity measured by the light and dark bottle method recorded the lowest level (0.25 mg/m3/h) before the drought, and the highest level (3.25 mg/m3/h) was observed after the drought period. Chlorophyll concentration decreased during a drought due to lowered nutrient inputs. These data demonstrate that primary productivity in the lake’s waters is relatively low. And, the drought for the lake occurred as a result of a series of reasons that were strongly influenced by human activities. Traditionally, groundwater is extracted for agricultural purposes in this region. Thus, the rate of groundwater flows into the lake decreases, which negatively affects the physical and chemical parameters and thus affects the productivity of the lake. One of the ways of management is to form a national campaign that adopts exceptional measures to meet the challenges related to groundwater by reformulating and developing water systems, in addition to the proposal to reduce the area of the lake basin industrially to one-third, because the water, even if it returns to flood the lake, does not return to the previous quantities. Thus, when the water quality will be good, it will create the appropriate conditions to increase the productivity of the lake.