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Beaching and Natural Removal Dynamics of Pelagic Sargassum in a Fringing‐Reef Lagoon
Author(s) -
Rutten Jantien,
Arriaga Jaime,
Montoya Leonardo D.,
MariñoTapia Ismael J.,
EscalanteMancera Edgar,
Mendoza E. Tonatiuh,
Tussenbroek Brigitta I.,
Appendini Christian M.
Publication year - 2021
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1029/2021jc017636
Subject(s) - sargassum , berm , reef , pelagic zone , oceanography , environmental science , fishery , ecology , geology , algae , biology
Massive quantities of the pelagic brown macroalgae Sargassum spp. (sargassum) have been invading the Caribbean and West African shores since 2011, causing devastating effects on the coastal ecosystem and local economy. Little is known about sargassum beaching dynamics and the capacity of the coastal system to naturally remove beached sargassum. Here, we characterize the temporal variation in arriving and beached sargassum in a reef lagoon using a 5.2‐year data set of hourly optical imagery, and identify the governing hydrometeorological conditions. Image classification reveals interannual variability in the start, duration, and intensity of the sargassum arrival season. Arrivals are associated with relatively low energy onshore directed winds and waves, and offshore abundance of sargassum. Furthermore, nearshore sargassum mat size is found to decrease with decreasing wave/wind energy. Once sargassum beaches, a berm of wrack is formed. Natural wrack removal was observed under elevated water levels and increased wave action. Three types of wrack removal were distinguished, depending on the water level η with respect to the berm crest heightz cand berm crest toez t : gradual berm destruction with gaps developing in the seaward berm edge that grow larger with time (Type I;z t < η < z c ) and abrupt berm destruction with part of the wrack depositing on the upper beach (Type II; η > z c ) or in the dunes (Type III; η ≫ z c ). Higher energy waves activate the reef circulation, which is suspected to flush part of the wrack out of the reef lagoon. We propose a conceptual model of nearshore sargassum dynamics in a reef lagoon system.