Chapter Eleven Fine sediment dynamics in the mangrove-fringed, muddy coastal zone

• Published in: Muddy Coasts of the World: Processes, Deposits and Function Vol. 4; pp. 279 - 292
• Main Authors: Wolanski, Eric, Spagnol, Simon, Lim, Eng B.
• Format: Book Chapter
• Language: English
• Published: The Netherlands Elsevier Science & Technology 2002
• Subjects: Fishes (ichthyology); Hydraulic engineering
• ISBN: 0444510192; 9780444510198
• ISSN: 1568-2692
• DOI: 10.1016/S1568-2692(02)80085-7

This chapter discusses the fine sediment dynamics in the mangrove-fringed muddy coastal zone. Studies of the fate of fine sediment at the mouth of muddy rivers have revealed that the sediment generally falls rapidly out of suspension and does not follow the brackish water in the river plume. The Amazon river plume is a well-documented example. This observation has been attributed to the formation in coastal waters of large flocs, also called micro-aggregates that accelerate the settling of the fine sediment. The shallow, mangrove-fringed coastal waters, including the intertidal areas, were extremely turbid at spring tides. The state of the fine sediment in suspension varied greatly from inshore to offshore from the turbidity front. The microphotographs reveal the presence of plankton-generated marine snow on which mud particles were attached. These flocs visually resembled the marine snow-mud aggregates where the bacteria, plankton detritus, and mucus acted as a coagulant for the fine sediment. The mathematical model enables one to understand the pathways of the fine sediment in a mangrove-fringed, muddy coastal zone at spring tides. It is found that at spring tides the suspended sediment concentration in the water, leaving the mangrove creeks, to enter Hinchinbrook Channel at ebb tides peak at about 1–5 kg m−3 ,respectively, during calm weather and south-easterly trade winds.