Study on seasonal hydrology and biogeochemical variability in a tropical estuarine system, Central Mozambique Coast, Africa

• Published in: Marine pollution bulletin 2018-06, Vol.131 (Pt A), p.674-692
• Main Author: Miguel, Lucas Lavo António Jimo
• Format: Article
• Language: English
• Subjects: 3D CAEDYM; Aquatic ecosystems; Bathymetry; Biogeochemical flow; Biogeochemistry; Brackish water; Brackishwater environment; Chlorophyll; Chlorophyll - analogs & derivatives; Chlorophyll - analysis; Chlorophyll a; Coastal management; Coastal zone management; Computer applications; Computer simulation; Data; Dissolved oxygen; Doppler sonar; Dynamics; Ecosystem; Ecosystem dynamics; Elevation; Environmental Monitoring - instrumentation; Environmental Monitoring - methods; Estuaries; Estuarine dynamics; Estuarine environments; Flooding; Hydrology; Hydrology - methods; Morphology; Mozambique; Nitrates; Nitrates - analysis; Ocean currents; Organic matter; Oxygen - analysis; Photometers; Policies; Rain; Rainy season; River discharges; Rivers; Runoff; Seasonal variation; Seasonal variations; Seasons; Silicates; Silicon dioxide; Silicon Dioxide - analysis; Sustainability; Temperature; Three dimensional models; Tidal currents; Tidal energy; Tidal power; Tidal prism; Tropical Climate; Water depth; Water discharge; Wet season
• ISSN: 0025-326X; 1879-3363
• DOI: 10.1016/j.marpolbul.2018.04.071

Little is known about the dynamics of particulate inorganic and organic matter in brackish water controlled by tidal prism and seasonal river discharges in Macuse estuary, on central Mozambique coast, southern Africa. This manuscript illustrates seasonal variation of biogeochemical flow dynamics in a tropical estuarine system in Zambézia province. The data were collected at 42 stations, including tidal current measurements with an Acoustic Doppler Current Profiler, tidal elevation with a tidal-gauge and nitrate, silicate (SiO2), dissolved oxygen and chlorophyll-a with a photometer device system and tidal currents with multisensory instrument device (Current, Temperature and Depth device). These field data helped to calibrate a twelve months simulation of a 3D Computational Aquatic Ecosystem Dynamics Model (3D CAEDM) in 2014. The results emphasize a tidal elevation of 4-m height that generated tidal currents of 120 cm/s. They combination with seasonal runoff of ~500 m3/s from Namacurra River and averaged bathymetry morphology of 10-m depth, led on to the seasonal concentration flux of dissolved oxygen, nitrate, SiO2 and chlorophyll-a during the ebbing and flooding. In addition, the river discharges were found to be the main source of nitrate and SiO2, while the tidal prism led on the hydrological flow of the brackish-waters during the rainy season with maximum salinity anomaly of 16%. Besides the data obtained, the 3D model matches in reproducing the biogeochemical data flow have considerable potential possess of a valuable information in long- and short-term and large- and small-scale that may allow policy-makers to determine political decisions for bio-conservation, sustainability and coastal management. •This research has shown that seasonal tidal prism and runoff led on the biogeochemical flow in Macuse estuary, central Mozambique coast;•The seasonal river's discharges increased the suspended particulate matter supply including nitrate, silicate and suspended sediments;•ELCOM-CAEDYM module matched the field data emphasizing the ability to reproduce well the biochemical processes in natural waters;•The simulated biogeochemical data obtained possess a valuable information that may allow policy-makers to determine decisions for suitable bio-conservation, sustainability and coastal management.