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Front. Mar. Sci. | doi: 10.3389/fmars.2019.00224

Sandbar breaches control of the biogeochemistry of a micro-estuary

  • 1School of marine sciences, Ruppin Academic Center, Israel
  • 2Morris Kahn Marine Research Station, Charney School of Marine Sciences, University of Haifa, Israel
  • 3School of Earth and Environment, Faculty of Environment, University of Leeds, United Kingdom
  • 4Soil and Water Sciences, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Israel

Micro-estuaries in semi-arid areas, despite their small size (shallow depth of few meters, length of few kilometers and a surface area of less than one square kilometer) are important ecosystem services providers. Despite their high abundance, tendency to suffer from eutrophication and vulnerability to other anthropogenic impacts, such systems are among the least studied water bodies in the world. In low tidal amplitude regions, micro-estuaries often have limited rate of sea-river water exchange, somewhat similar to fjord circulation, caused by a shallow sandbar forming at the coastline. The long-term study we report here was inspired by the idea that, due to their small size and low discharges regime, relatively small interventions can have large effects on micro-estuaries. We used a stationary array of sensors and monthly detailed water sampling to characterize the Alexander estuary, a typical micro-estuary in the S.E. Mediterranean, and to identify the main stress factors in this aquatic ecosystem. The Alexander stream is stratified throughout the year with median bottom salinity of 18 PSU. Prolonged periods of hypoxia were identified as the main stress factor. Those were alleviated by breaching of the sandbar at the estuary mouth by sea-waves or floods (mostly during winter) that flush the anoxic bottom water. Analysis of naturally occurring sandbar breaches, and an artificial breach experiment indicate that the current oxygen consumption rate of the Alexander micro-estuary is too high to consider sandbar breaches as a remedy for the anoxia. Nevertheless, it demonstrates and provides the tools to assess the feasibility of small-scale interventions to control micro-estuaries hydrology and biogeochemistry.

Keywords: Eutrophication, Anthropogenic pollution, Coastal streams, Mediterranean, sandbar, sill, Micro-estuaries

Received: 22 Nov 2018; Accepted: 10 Apr 2019.

Edited by:

Isabel Iglesias, Interdisciplinary Center for Marine and Environmental Research (CIIMAR), Portugal

Reviewed by:

José Pinho, University of Minho, Portugal
Perran Cook, Monash University, Australia  

Copyright: © 2019 Suari, Amit, Gilboa, Sade, Krom, Gafni, Topaz and Yahel. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Yair Suari, Ruppin Academic Center, School of marine sciences, Hadera, Israel, yairsuari@gmail.com