A baseline study of the diversity and community ecology of crab and molluscan macrofauna in the Sematan mangrove forest, Sarawak, Malaysia

Abstract

Baseline ecological studies of pristine mangroves are important for monitoring, management and conservation of mangrove ecosystems. Diversity, density, biomass and community structure of crab and molluscan macrofauna were studied in a near-pristine mangrove forest in Sematan, Sarawak. In each of the nine 100-m2 plots, six 15-min catching periods were used to collect crabs and three 1-m2 quadrats were sampled for molluscan epifauna. Environmental variables and vegetation were also recorded in each 100-m2 plot. Thirty-one crab species and 44 molluscan species were recorded, including a few species not previously reported from Sarawak. Crab community structure was correlated with topographical height and surface water pH and salinity. Gastropod community structure was correlated with redox potential of water at depth, topographical height, surface water pH and leaf litter. Crab community structure and species number were positively correlated with tree and seedling community structure and diversity, suggesting that the mangrove vegetation is important to the crab fauna as a habitat and food supply. Molluscan abundance was positively correlated with sapling diversity and negatively correlated with the numbers of mangrove associates and tree species. The young leaves on mangrove saplings may provide a better food source than those on mature trees or mangrove associates. The data from this study provide a valuable baseline for future use at this site and for comparison with more degraded mangrove habitats elsewhere in South-East Asia.

Ecosystem-Wide Impacts of Deforestation in Mangroves: The Urabá Gulf (Colombian Caribbean) Case Study

“…Gastropods in the Caribbean and elsewhere have been pointed as key detritivores and sediment grazers, even outweighing the role of crabs [80][81][82]. Available assessments on the impacts of mangrove deforestation on benthos report that vegetation provides support and physical habitat that may reduce predation and desiccation (Asia: [83,84]; Africa: [85,86]; Australia: [87]). For instance, clearing pneumatophores in small-scale deforestations for building walkways and trails was correlated with a decline in density and species richness in the entire community, particularly on gastropods [87].…”

“…For instance, clearing pneumatophores in small-scale deforestations for building walkways and trails was correlated with a decline in density and species richness in the entire community, particularly on gastropods [87]. In addition, community and population metrics, otherwise uncorrelated with physicochemical variables under natural conditions [84], became significantly explained by temperature and pH in deforested mangroves [86].…”

Molluscs’ Composition and Distribution in Mangroves of the Cameroon Central Coast

“…Several studies have shown a correlation between changes in the diversity and abundance of macrobenthos and the obvious variability of the environment such as the variability of habits (plants, sediment, ...) or sediment characteristics (mud, sand) [34,37,38]. Overall molluscan species recorded were mostly epifaunal, and were divided into four occupied habitats (deadwood, plant root, plant stem and substratum).…”

Effect of Anthropogenic Activities on Mangrove Crab Diversity in Cameroon Atlantic Coast

“…In each station, 500 m line transect was established across the zone according to the vegetation spread. To assess the abundance and density of the crab populations, crab individuals were sampled in randomly selected 4×4 m plots along the transect, using three techniques (visual count [23], excavation [33] and crab harvest [34]) depending on species found. Harvested crabs were sedated in cold water for a few minutes, washed and stored into 70% alcohol or in a field freezer for later processing.…”

“…The consequences of deforestation on mangrove fauna have not yet been documented in West Africa. The significant role of crabs as a engineer species starts to be recognized, but their ecological answers with respect to human pressures are poorly known compared to other aspects of their life such as diversity, distribution, sex ratio, ecological roles, feeding ecology, plant periodical migrations, physiological adaptations, domestic wastewater effects,… [22,23,24,25,26,27,28,29,30]. So, the aim of this study is to determine the impact of human pressures on mangrove crab biodiversity in Cameroon.…”