This article has been peer reviewed and accepted for publication. It is in production and has not been edited, so may differ from the final published form.
Hydrographic maintenance of deep anoxia in a tidally-influenced saline lagoon
Low dissolved oxygen concentrations are of increasing concern in aquatic ecosystems, particularly at the interface between freshwater and marine environments. Oxygen depletion occurs naturally in many perennially stratified systems and it remains to be seen how climate change will impact upon these habitats. This is, in part, due to a lack of high-resolution, long-term data describing inter-annual variability in dissolved oxygen concentrations within stratified basins. Physicochemical parameters for Lough Furnace, an ecologically important tidal lagoon, were assessed using daily measurements (2009-14) from an undulating CTD profiler and observations of tidal exchange flow. Continuous vertical saline stratification existed, with anoxia (< 0.1 mg l-1) typically persisting below 6 m. Tidal inflows were generally restricted, with deep-water renewal events by intrusions of denser spring tidal water occurring episodically (3 times in 6 years), following prolonged periods of low freshwater input. While wind forcing alone was not sufficient to generate basin-scale mixing, the conditions that led to deep-water renewals may also be conducive to wind-driven upwelling events in nearshore areas. These findings have wider application to larger scale two-layered stratified systems with deep anoxia as the ability to forecast such dynamic events is important for assessing the ecological implications of dissolved oxygen depletion.
MF17199 Accepted 25 September 2017
© CSIRO 2017