Zonations and oscillations via heterotrophic processes in tidal unvegetated aquifers. Issue 8 (3rd August 2022)

• Record Type: Journal Article
• Authors: Yao, Yuting; Kong, Jun; Zhang, Chenming; Tang, Zixuan; Shen, Chengji; Luo, Zhaoyang; Lu, Chunhui; Feng, Xuejun; Sun, Yang
• Is Part Of: Hydrological processes. Volume 36:Issue 8(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-08-03
• Subjects: bioclogging -- coastal aquifers -- groundwater circulation -- heterotrophic processes -- microbial accumulation -- tidal penetration; Hydrology -- Periodicals; Hydrology -- Research -- Periodicals; Hydrologic models -- Periodicals; Hydrological forecasting -- Periodicals; 631.432
• DOI: 10.1002/hyp.14654
• Languages: English
• ISSNs: 0885-6087

Abstract

Abstract: Global‐change drivers that alter tidal amplitude or sea level could directly impact coastal aquifers' seawater–microbe interactions. The semidiurnal or diurnal tide can have consequences for chemical redistribution, because it deepens oxygen and nutrients penetration depth, thereby increasing O2 depletion via microbial respiration in sediments during groundwater circulation. However, chemical and microbial distributions in tidal aquifers remain unclear, in deference to their link with depth and lateral location. By combining the microbes‐accumulated equation with the traditional groundwater flow model in coastal aquifers, we explicitly unravelled the heterotrophic zonation, the salinity zonation, and the oxic zonation of tidal aquifers. According to the model estimates, salt penetrates deeper than reactive chemicals, and the heterotrophic high biomass zone is presumably 2–3 m deep. Such depth of heterotrophic distribution is 2–3 orders of magnitude higher than phototrophic distribution. Additionally, heterotrophic biomass can exhibit faint oscillations, even under the tide forces, whereas dissolved chemicals fluctuate significantly with tidal pumps. Due to the transport of nutrients by tidal penetration, intertidal sediments have a higher respiration rate than subtidal sediments, converting more organic carbon from seawater to atmospheric CO2 via microbes. We demonstrate that heterotrophic biomass may play the dominant role in the chemical reactions of nearshore sediments. Our results confirm the efficacy of unvegetated tidal sediments that rely on ubiquitous heterotrophs as a driver of oxygen consumption and DOC transformation. These steps above will allow for better field investigations of coastal aquifers within a framework of zonations and oscillations. Abstract : Global‐change drivers that alter tidal amplitude or sea level could directly impact coastal aquifers' seawater–microbe interactions. Tide can have consequences for chemical redistribution by deepening oxygen and nutrients penetration depth, thereby increasing O2 depletion via microbial respiration in sediments during groundwater circulation. Due to the transport of nutrients by tidal penetration, intertidal sediments have a higher respiration rate than subtidal sediments. Therefore, heterotrophic biomass could not be neglected in nearshore sediments.