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Title:	The habitat preferences and ecological role of fiddler crabs in Sungai Sepang mangrove ecosystems
Authors:	Mohammad Mokhtari Karchegani (P52833)
Supervisor:	Zaidi Che Cob, Prof. Dr.
Keywords:	Ecosystems Sediment Burrow effects Universiti Kebangsaan Malaysia -- Dissertations
Issue Date:	15-Jul-2017
Description:	Burrowing activity by fiddler crabs as dominant macrofauna in the mudflats of mangrove ecosystems, disturb an extensive amount of sediment. However, the burrows increase sediment surface area and create heterogeneous habitat for benthic infaunal organisms. The aim of this study is to determine the magnitude of burrow effects of different species of fiddler crabs and to identify the key environmental factors that control the crab abundances. To compare the burrow effects between seven species of fiddler crab found in the study area, the preferred habitats were determined by Canonical Discriminative Analysis (CDA). Sediment grain size which influences most sediment properties acts as a main factor responsible for sediment heterogeneity. Uca annulipes and Uca perplexa with the high number of spoon tipped setae on their second maxiliped are specialized to feed on the sandy sediments and therefore they commonly occupied sandy sediments with high amounts of grain size particles of 150 and 250 um. Uca paradussumieri was abundant at muddy substrate with low sediment density of low shore. Uca forcipata due to their sensitivity to high temperatures prefers muddy sediments under the shade of mangrove tree. Uca rosea and Uca triangularis choose muddy sediment with high density to construct their burrows. The results of this study revealed that crab burrows efficiently oxidized subsurface sediment down to 4cm depth. Through the oxidation effect, crab burrows stimulated iron reduction and reduce organic content of sediments. The effects of burrows varied according to their location on the intertidal gradient. In general, the thickness of oxidized layer around burrows was varied in accordance to depth and burrow diameter. By modifying sediment properties, fiddler crab burrows change the meiofaunal assemblages. Redundancy Analysis (RDA) indicated that most of the variability in meiofauna was related to sediment heterogeneity created by crab burrows. Meiofauna assemblages were significantly different between burrows and ambient sediments. These differences were attributed most to the abundance of Nematoda, Copepoda, Annelida, Gastrotricha, Ostracoda and Molluska. Higher abundance of Nematoda, Copepoda, Froaminifera, Annelida, Gastrotricha, Ostracoda and Molluska were recorded in burrows compared to the ambient sediment. Within foraminifera's assemblages, the genus Milliammina, Ammotium, Trochamina, Arenoparrella, Haplophragmidium and Textularia were more frequent in burrows. The densities of bacteria in burrows were almost twice as in the ambient sediments. In comparison to ambient sediment, burrows of U. rosea and U. forcipata contain a lower bacterial diversity whereas U. paradussumieri burrows clearly support a more diverse bacterial community. The results of this study demonstrated that crab burrows effectively modify the physical, chemical and biological properties of sediment. Nevertheless, burrow effect varied significantly among different species of fiddler crabs as results of different habitat characteristics, sediment texture and crab size.,Certification of Master's/Doctoral Thesis" is not available
Pages:	197
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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