The influence of mouth status on pH variability in small temporarily closed estuaries

Omarjee, Aadila; Taljaard, Susan; Weerts, S P; Adams, Janine B.

doi:10.1016/j.ecss.2020.107043

Cited by 9 publications

(3 citation statements)

References 33 publications

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“…Perched estuaries, lagoons, and enclosed bays with long residence times have recorded extremely high pH values similar to those found in this study, including instances of reduced TA: correlated to the proximity of oceanic influence 52 , 55 , 56 . In these systems, biological metabolism and evaporation become the dominate mechanisms that modify pH 5 , 56 , 57 . It would be remiss to note, however, that the thermodynamic controls on carbonate chemistry also become enhanced at long residence times as was seen in this study.…”

Section: Discussionsupporting

confidence: 85%

Alkalinity cycling and carbonate chemistry decoupling in seagrass mystify processes of acidification mitigation

Miller

Kelley

2021

Sci Rep

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The adverse conditions of acidification on sensitive marine organisms have led to the investigation of bioremediation methods as a way to abate local acidification. This phytoremediation, by macrophytes, is expected to reduce the severity of acidification in nearshore habitats on short timescales. Characterizing the efficacy of phytoremediation can be challenging as residence time, tidal mixing, freshwater input, and a limited capacity to fully constrain the carbonate system can lead to erroneous conclusions. Here, we present in situ observations of carbonate chemistry relationships to seagrass habitats by comparing dense (DG), patchy (PG), and no grass (NG) Zostera marina pools in the high intertidal experiencing intermittent flooding. High-frequency measurements of pH, alkalinity (TA), and total-CO2 elucidate extreme diel cyclicity in all parameters. The DG pool displayed frequent decoupling between pH and aragonite saturation state (Ωarg) suggesting pH-based inferences of acidification remediation by seagrass can be misinterpreted as pH and Ωarg can be independent stressors for some bivalves. Estimates show the DG pool had an integrated ΔTA of 550 μmol kg−1 over a 12 h period, which is ~ 60% > the PG and NG pools. We conclude habitats with mixed photosynthesizers (i.e., PG pool) result in less decoupling between pH and Ωarg.

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Section: Discussionsupporting

confidence: 85%

Alkalinity cycling and carbonate chemistry decoupling in seagrass mystify processes of acidification mitigation

Miller

Kelley

2021

Sci Rep

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show abstract

“…Perched estuaries, lagoons, and enclosed bays with long residence times have recoded extremely high pH values similar to those found in this study, including instances of reduced TA: correlated to the proximity of oceanic influence 43,47,48 . In these systems, biological metabolism and evaporation become the dominate mechanisms that modify pH 5,48,49 . It would be remiss to note, however, that the thermodynamic controls on carbonate chemistry also become enhanced at long residence times as was seen in this study.…”

Section: Discussionsupporting

confidence: 81%

Alkalinity Cycling And Carbonate Chemistry Decoupling in Seagrass Mystify Processes of Acidification Mitigation

Miller

Kelley

2021

Preprint

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The adverse conditions of acidification on sensitive marine organisms has led to the investigation of bioremediation methods as a way to abate local acidification. This phytoremediation, by macrophytes, is expected to reduce the severity of acidification in nearshore habitats on short timescales. Characterizing the efficacy of phytoremediation can be challenging as residence time, tidal mixing, freshwater input, and a limited capacity to fully constrain the carbonate system can lead to erroneous conclusions. Here, we present in situ observations of carbonate chemistry relationships to seagrass habitats by comparing dense (DG), patchy (PG), and no grass (NG) Zostera marina pools in the high intertidal experiencing intermittent flooding. High-frequency measurements of pH, alkalinity (TA), and total-CO2 elucidate extreme diel cyclicity in all parameters. The DG pool displayed frequent decoupling between pH and aragonite saturation state (Ωarg) suggesting pH-based inferences of acidification remediation by seagrass can be misinterpreted as pH and Ωarg can be independent stressors for some bivalves. Estimates show the DG pool had an integrated ΔTA of 550 μmol kg-1 over a 12 h period, which is ~60 % > the PG and NG pools. We conclude habitats with mixed photosynthesizes (i.e., PG pool) result in less decoupling between pH and Ωarg.

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“…The relationship is however not statistically significant. DO concentrations could therefore be a reflection of both pelagic and benthic microalgae activity, that of filamentous macroalgae which bloom on occasion (this study, Omarjee et al, 2020), and in addition be influenced by the organic and bacteria load from the wastewater treatment works into the system.…”

Section: Discussionmentioning

confidence: 93%

How drought affects range and variability of environmental conditions in subtropical South African estuaries

Scharler

Bownes

Jerling

2022

Preprint

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Globally estuaries are under increasing pressure from human development impacts as well as the growing effects of climate change that is already, and increasingly so, causing major changes in events such as droughts. Although droughts are regular occurrences and are projected to become progressively more significant in many parts of the world, their potential impacts on estuaries requires better understanding and quantification. This study aims to quantify environmental and phytoplankton parameter changes in two contrasting subtropical estuary types in South Africa; the temporarily closed uMdloti Estuary and the predominantly open to the sea uMlalazi Estuary during a hydrological drought event and subsequent non-drought period. Drought caused lower salinities, almost exclusively freshwater, throughout the temporarily closed estuarine type uMdloti. The marine-estuarine salinity environment of the predominantly open uMlalazi during drought expanded to include lower salinities in the non-drought period. Dissolved oxygen levels were more variable during drought conditions including periods of hypoxia, but more stable at elevated levels in both estuaries during the non-drought period. Temperature measurements included higher values during drought, especially in the dry season. Chl-a concentrations were overall higher and more variable during drought in uMdloti, with periods of bloom formation as well as decay. Drought-induced conditions can span several generations for estuarine and estuarine associated organisms. The results from the study provide quantitative support for the hypothesis that extended periods of drought conditions lead to a decrease in niche availability to estuarine organisms in a range of estuary types.

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The influence of mouth status on pH variability in small temporarily closed estuaries

Cited by 9 publications

References 33 publications

Alkalinity cycling and carbonate chemistry decoupling in seagrass mystify processes of acidification mitigation

Alkalinity cycling and carbonate chemistry decoupling in seagrass mystify processes of acidification mitigation

Alkalinity Cycling And Carbonate Chemistry Decoupling in Seagrass Mystify Processes of Acidification Mitigation

How drought affects range and variability of environmental conditions in subtropical South African estuaries

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