Exploring the Susceptibility of Turbid Estuaries to Hypoxia as a Prerequisite to Designing a Pertinent Monitoring Strategy of Dissolved Oxygen

Schmidt, Sabine; Diallo, Iris I.; Derriennic, Hervé; Fallou, Hélène; Lepage, Mario

doi:10.3389/fmars.2019.00352

Cited by 29 publications

(19 citation statements)

References 29 publications

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“…This could have increased the suspended matter load in the water, thereby decreasing the DO level. However, DO did not fall below the critical level that could be tolerated by aquatic organisms [20,21]. Station 7, which was the farthest from the demolition site, is at a broader point of the lake and close to the deep shipping channel that opens into the Arabian Sea through the bar mouth.…”

Section: Resultsmentioning

confidence: 99%

Citizen Science Tools Reveal Changes in Estuarine Water Quality Following Demolition of Buildings

et al. 2021

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Turbidity and water colour are two easily measurable properties used to monitor pollution. Here, we highlight the utility of a low-cost device—3D printed, hand-held Mini Secchi disk (3DMSD) with Forel-Ule (FU) colour scale sticker on its outer casing—in combination with a mobile phone application (‘TurbAqua’) that was provided to laymen for assessing the water quality of a shallow lake region after demolition of four high-rise buildings on the shores of the lake. The demolition of the buildings in January 2020 on the banks of a tropical estuary—Vembanad Lake (a Ramsar site) in southern India—for violation of Indian Coastal Regulation Zone norms created public uproar, owing to the consequences of subsequent air and water pollution. Measurements of Secchi depth and water colour using the 3DMSD along with measurements of other important water quality variables such as temperature, salinity, pH, and dissolved oxygen (DO) using portable instruments were taken for a duration of five weeks after the demolition to assess the changes in water quality. Paired t-test analyses of variations in water quality variables between the second week of demolition and consecutive weeks up to the fifth week showed that there were significant increases in pH, dissolved oxygen, and Secchi depth over time, i.e., the impact of demolition waste on the Vembanad Lake water quality was found to be relatively short-lived, with water clarity, colour, and DO returning to levels typical of that period of year within 4–5 weeks. With increasing duration after demolition, there was a general decrease in the FU colour index to 17 at most stations, but it did not drop to 15 or below, i.e., towards green or blue colour indicating clearer waters, during the sampling period. There was no significant change in salinity from the second week to the fifth week after demolition, suggesting little influence of other factors (e.g., precipitation or changes in tidal currents) on the inferred impact of demolition waste. Comparison with pre-demolition conditions in the previous year (2019) showed that the relative changes in DO, Secchi depth, and pH were very high in 2020, clearly depicting the impact of demolition waste on the water quality of the lake. Match-ups of the turbidity of the water column immediately before and after the demolition using Sentinel 2 data were in good agreement with the in situ data collected. Our study highlights the power of citizen science tools in monitoring lakes and managing water resources and articulates how these activities provide support to Sustainable Development Goal (SDG) targets on Health (Goal 3), Water quality (Goal 6), and Life under the water (Goal 14).

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Section: Resultsmentioning

confidence: 99%

Citizen Science Tools Reveal Changes in Estuarine Water Quality Following Demolition of Buildings

et al. 2021

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“…Instead of being a stratified estuary, Mahanadi estuarine water showed a good oxygen saturation of 78% to 89% throughout the year [9]. Oxygen concentration in both the estuarine waters were above the hypoxia (DO < 3mgL -1 , Schimdt et al, [41]). High turbidity probably helped the small celled chain forming species Skeletonema costatum to flourish in Saptamukhi estuarine water in monsoon.…”

Section: Discussionmentioning

confidence: 96%

Comparison of phytoplankton community structure in two tropical estuaries of East Coast of India

Chowdhury¹

2020

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Phytoplankton community of two tropical river estuaries of the North-east coast of India was different due to dissolved nutrients concentration in those estuarine waters. The first study site was the Saptamukhi river estuary which is located in the Indian Sundarban (inside mangrove forest) and the second study site was Mahanadi estuary located in Orissa coast (adjacent to industrial and coastal fishing zone). The Saptamukhi estuary was mostly devoid of any anthropogenic influence and here the nutrient source was auto-generated. In Mahanadi estuarine water, the source of the major nutrients was industrial effluent and fishing waste. The Saptamukhi estuarine water had less dissolved phosphorus concentration but huge dissolved nitrogen available for phytoplankton uptake. A sufficient amount of dissolved silicate encouraged the diatom growth over other phytoplankton groups here. Due to the availability of the high amount of dissolved phosphorus and the low amount of dissolved nitrogen in the Mahanadi estuary the phytoplankton community was a mixed population of Bacillariophyceae, Cyanophyceae, Chlorophyceae and Dinophyceae and seasonal Chlorophycean bloom observed during the study period. In both the estuarine water primary productivity was high but the community respiration was higher and the estuaries were heterotrophic. Monsoonal runoff from land considerably changed the community in both estuarine water. Dissolved silicate concentration in both the estuarine water was sufficient for Diatom growth. Dissolve inorganic nitrogen and dissolved inorganic phosphate ratio played a major role for the community change of phytoplankton in two estuarine waters.

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“…Microbial community dwelling in the aquatic ecosystem degrades the organic matter present at the bottom through DO consumption (Moresco et al 2012 ; Fuhrman et al 2015 ). First, turbidity affects dissolved oxygen (DO) sources by limiting light penetration and hence photosynthetic activity, as well as gas exchange with the atmosphere (Schmidt et al 2019 ; Newport et al 2021 ).…”

Section: Discussionmentioning

confidence: 99%

Pre-to-post COVID-19 lockdown and their environmental impacts on Ghoghla beach and Somnath beach, India

Sahoo

Sonpal

Chanchpara

et al. 2022

Environ Sci Pollut Res

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Environmental impact of COVID-19 imposed lockdown (2020) and the new normal condition (2021) on two different beaches of India (Ghoghla beach, Diu and Somnath beach, Veraval) were compared with the pre-lockdown era, 2013. The lockdown phase favored the natural restoration of the beaches and showed infinitesimal values of the parameters tested when compared with the pre-lockdown regime. However, the new normal situation in 2021 opened up the accessibility of these beaches to the tourists and pilgrims resulting in significant changes of water quality. The release of diluted sewage mixed with freshwater from the Somnath town to the sea has led to the drastic change in beach water quality. The mean cadmium concentration increased drastically in beach waters (Ghoghla: 1.35, 0.28 and 7.09 μg/L; Somnath: 0.45, 0.28 and 0.58 μg/L) during pre-to-post lockdown, respectively. However, post-lockdown resulted in the rise of toxic heavy metals in the sediments of Somnath beach but Ghoghla beach remained to be pristine which may be due to the Blue Flagship status. The total number of marine bacteria was higher during 2013 and 2021 when compared during lockdown describing greater human interventions. For instance, Vibrio spp. count in Ghoghla beach water during pre-lockdown phase was 7733 CFU/mL and this value reduced to 70 and 5 CFU/mL in the lockdown and post-lockdown phases. Interestingly, the diversity of planktonic and benthic components showed a different trend from pre-to-post lockdown due to significant change in the inorganic nutrients and metal bioaccumulation. To our knowledge, this will be the first comprehensive assessment to report the environmental and ecological health of Ghoghla beach and Somnath beach during the pre-to-post lockdown. Supplementary Information The online version contains supplementary material available at 10.1007/s11356-022-21586-z.

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Exploring the Susceptibility of Turbid Estuaries to Hypoxia as a Prerequisite to Designing a Pertinent Monitoring Strategy of Dissolved Oxygen

Cited by 29 publications

References 29 publications

Citizen Science Tools Reveal Changes in Estuarine Water Quality Following Demolition of Buildings

Citizen Science Tools Reveal Changes in Estuarine Water Quality Following Demolition of Buildings

Comparison of phytoplankton community structure in two tropical estuaries of East Coast of India

Pre-to-post COVID-19 lockdown and their environmental impacts on Ghoghla beach and Somnath beach, India

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