Primary production of microphytobenthos in mangrove forest: Spatial variations between inside and outside of mangrove

Abstract

Microphytobenthos (MPB) plays a key role in the food web of coastal ecosystems and is an important primary producer. While the ecological significance of MPB in shallow aquatic ecosystem has long been recognized, the role of MPB in mangrove habitat has received little attention. In order to understand the amount of MPB primary production (PP) in the mangrove forest, in situ measurement of microalgal PP was performed in Prek Tnout, Cambodia and David Fleay Wildlife Park, Australia, between June and August 2016. Because mangrove canopy can block sunlight directly, sediments were collected at locations both inside and outside of mangrove forest. MPB PP was measured in an aerated water bath using Field microsensor multimeter and oxygen microelectrode. The results showed somehow regional and site-specific variations on MPB PP between Cambodia and Australia. Forexample, PP values in Cambodia were slightly greater than those of Australia (Cambodia: 5.74-7.49 mmol O2 m-2 h-1, Australia: 3.51-6.56 mmol O2 m-2 h-1, respectively). Net PP in mangrove outside was found to be 1.4 times greater than that of mangrove inside (mangrove outside: 6.88 mmol O2 m-2 h-1, mangrove inside: 4.94 mmol O2 m-2 h-1, respectively), and the very difference might be explained by the light-shading effect by mangrove canopy. Of note, the in situ measured MPB PPs in mangrove forests in Cambodia and Australia were comparable to slightly smaller than t habitat has received little attention. In order to understand the amount of MPB primary production (PP) in the mangrove forest, in situ measurement of microalgal PP was performed in Prek Tnout, Cambodia and David Fleay Wildlife Park, Australia, between June and August 2016. Because mangrove canopy can block sunlight directly, sediments were collected at locations both inside and outside of mangrove forest. MPB PP was measured in an aerated water bath using Field microsensor multimeter and oxygen microelectrode. The results showed somehow regional and site-specific variations on MPB PP between Cambodia and Australia. Forexample, PP values in Cambodia were slightly greater than those of Australia (Cambodia: 5.74-7.49 mmol O2 m-2 h-1, Australia: 3.51-6.56 mmol O2 m-2 h-1, respectively). Net PP in mangrove outside was found to be 1.4 times greater than that of mangrove inside (mangrove outside: 6.88 mmol O2 m-2 h-1, mangrove inside: 4.94 mmol O2 m-2 h-1, respectively), and the very difference might be explained by the light-shading effect by mangrove canopy. Of note, the in situ measured MPB PPs in mangrove forests in Cambodia and Australia were comparable to slightly smaller than those in the Korean tidial flats. In anyhow, because MPB PPs in mangrove habitats are not well known, thus present study would provide certain range of common PP levels in the given areas or similar.