Feeding Shift of Mangrove Crab Assemblages Revealed Through δ¹³C and δ¹⁵N Stable Isotope Ratios in Mangroves of Peninsular Malaysia (Early view)

Abstract

Crab feeding patterns in mangroves of Peninsular Malaysia were assessed using stable isotope analysis of δ¹³C and δ¹⁵N to identify carbon and nitrogen ratios in crabs, sediment and leaf litter. Sampling of crabs was done using a hand catch method in six chosen sites in Peninsular Malaysia. Three sites were characterized by coastal developments in Penang Island, and three sites from the less disturbed area of Merbok, Kedah. Data were analysed using Welch’s t-test to identify differences in δ¹³C and δ¹⁵N in samples between Penang and Merbok while Pearson’s correlation  test was used to determine significant correlations (if any) of isotope signatures  among crabs, sediment and leaf litter in SPSS v 27.0. The δ¹³C and δ¹⁵N in crabs, sediment and leaf litter differed between Penang and Merbok, except for δ¹³C in crabs. Findings showed that the δ¹³C and δ¹⁵N in sediment and leaf litter were significantly greater in Penang compared with Merbok, however the δ¹⁵N in crabs in Merbok was greater than the δ¹⁵N in crabs in Penang. These patterns suggest a feeding shift in crabs in Merbok, possibly caused by low nutrient content in the leaf litter and sediment. In Penang, δ¹³C in crabs was positively correlated with sediment, while δ¹⁵N was positively correlated with both sediment and leaf litter, while no significant correlations were found in Merbok.