Real-time and long-term monitoring of waves and suspended sediment concentrations over an intertidal algal reef

Abstract

Suspended sediment concentration (c) has been considered a critical environmental factor in reef habitats; however, the values and variations of c are not evident in a unique reef mainly created by crustose coralline algal concretions compared to abundant studies in coral reefs. The results of real-time and long-term monitoring of waves and c over the intertidal algal reef are reported because of the construction of an offshore industrial harbor near the reef. The real-time monitoring systems were based on techniques, including optical backscatter sensors (OBSs) for measuring c, pressure sensors for measuring waves, data loggers, and wireless networks for data transmission. The instruments sampled every hour and ran continuously and automatically for years. The OBS measurement was compared and validated with biweekly water sampling. A good correlation between the results of the two methods was observed. Nevertheless, more calibrations of OBSs in different seasons reduced the variance between the two methods over a year-long timescale. The year-long data showed a remarkable seasonal variation in c. The average c was approximately 140 mg/l during the winter season, while it was only approximately 70 mg/l during the summer season. The observed c was higher than that in other coral reef environments; the elevated and highly variable c, ranging from approximately 0 to 500 mg/l, may be one factor that creates the unique algae reef environment. The year-long measurement of waves and c showed that the variation in c was mainly due to the variation in waves in different seasons and was well correlated with the wave-induced bed shear stress. The real-time and long-term data measured by the system will aid in better understanding and providing useful environmental data for accessing future environmental changes and protecting reef habitats.

Numerical modeling on wave-current flows and bed shear stresses over an algal reef

“…Most of the in-situ field observations were conducted in the G1 area because conservation class organisms and significant changes in topography are found at G1 and G2. A long-term project was initiated in 2019 to measure waves and suspended sediment concentrations (Lý & Huang, 2022).…”

A Reliable Architecture for IoT-based Aquatic Monitoring System of Coral Reef and Algae

“…Traditionally, monitoring is done by collecting and analyzing water samples physically. Only simple analysis without being influenced by factors such as concentration, size and shape of grains is one of the advantages of this method [20]. However, it is unsuitable for continuous data and longterm studies because of the difficulty in collecting water samples during unpredictable weather [21].…”