Mangrove outwelling: a review
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- Lee, S.Y. Hydrobiologia (1995) 295: 203. doi:10.1007/BF00029127
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The export of detritus and faunal biomass from mangroves has long been considered as an important support for offshore biological production and has been widely used as an argument for mangrove conservation. This functional role of the mangroves, like many other paradigms in mangrove ecology, has seldom been put to rigorous test since the hypothesis was postulated about 25 years ago. Past studies on which the hypothesis was based were mostly carried out in mangrove or other wetland environments, little is known about the fate and effects of outwelled detritus on oceanic, offshore, communities. Mass balance studies carried out in the last 15 years tend to suggest that export is common from tidal mangroves, the direction of flow depends, however, on the identity of the chemical species in question. Pore water and groundwater flow can affect tidal material exchange but are poorly studied. Generally, tracer methods using stable isotope ratios or other signatures have suggested that outwelling may be much less significant than expected. Further, most past studies have focussed on particulate matter while it is increasingly apparent that dissolved organics may play a more important role in matter exchange between offshore and mangrove communities. There is also evidence that benthic biomass and richness may not bear any positive or significant relationship with detritus availability.