Characterisation of pH variations along the Ba River in Fiji utilising the GEF R2R framework during the 2019 sugarcane season

Nicholas Metherall,Elisabeth Holland,Adi Mere Dralolo Vinaka,Sara Beavis

doi:10.1007/s10661-021-09423-1

Nicholas Metherall, Elisabeth Holland + Show 2 more

Open Access

https://doi.org/10.1007/s10661-021-09423-1

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Abstract

Within Pacific Small Island Developing States (Pacific SIDS), the ridge-to-reef (R2R) approach has emerged as a framework for monitoring river connectivity between terrestrial and marine ecosystems. The study measured water quality, including pH, over 88.40 km of the Ba River in Fiji. The sampling design focused on measuring spatio-temporal variability in pH throughout the sugarcane season with three rapid sampling periods (RSP1, 2 & 3) along the Ba River, together with continuous measurement of temperature and pH using stationary data loggers at two locations upstream and downstream of the sugar mill. Spatial variability in pH and water quality was characterised before (RSP1 and RSP2) and during (RSP3) the sugarcane season. Mean pH measured before the sugarcane crushing season for RSP1 and RSP2 were 8.16 (± 0.49) and 8.20 (± 0.61) respectively. During the sugarcane crushing season (RSP3), mean pH declined by 3.06 units to 6.94 within 42 m downstream of the sugar mill (P ≤ 0.001). The 3.06 unit decline in pH for RSP3 exceeded both the mean diurnal variation in pH of 0.39 and mean seasonal variation in pH of 2.01. This decline in pH could be a potential source of acidification to downstream coastal ecosystems with implications for coral reefs, biodiversity and fishery livelihoods.

Highlights

Environmental monitoring in water management programs has often been singularly focused: either at the catchment scale of the terrestrial realm or at the coast to reef scale of the marine realm
The results of this study add to the emerging literature on water quality sampling in R2R contexts in Pacific Small Island Developing States (SIDS)
The study demonstrated the success of a focused rapid sampling

Summary

Introduction

Environmental monitoring in water management programs has often been singularly focused: either at the catchment scale of the terrestrial realm or at the coast to reef scale of the marine realm. 2013; Fidelman et al, 2012; Christie et al, 2011; Veitayaki, 1998) These siloed approaches have often struggled with assessing the complex interplay across the land-sea boundary. A range of studies have advocated for the development of institutional capacity that focuses on adaptable water quality monitoring of ecological connectivity in rivers extending to reefs and coastal ecosystems (McCauley et al, 2019; Zinabu, et al, 2019; Beavis, 2005). By focusing on river corridor waterways through to coasts and reefs (or ocean), the R2R approach provides a framework for monitoring the river and its function in providing ecological connectivity between terrestrial and marine ecosystems

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