INFAUNAL MANGROVE SWAMP FORAMINIFERA IN THE SETIU WETLAND, TERENGGANU, MALAYSIA

Abstract

The distribution and abundance of live (rose Bengal-stained) and dead infaunal foraminifera have been documented in short cores taken at four locations representing a narrow range of salinity settings in the mangrove swamps of the Setiu wetland, Terengganu, peninsular Malaysia. Cores were taken at mud-rich sites, two in the mid-swamp and two in the high swamp, from mainland-fringing mangrove swamps characterized by generally sandy substrates. Twenty-four taxa were recorded as live. Of these, two were restricted to the mid-swamp, eight were restricted to the high swamp, seven were restricted to shallow-infaunal depths (0–16 cm), and three were restricted to deep-infaunal depths (>16 cm). Thirteen taxa occurred both shallow and deep infaunally and 13 occurred at both high- and mid-swamp sites. Only six taxa, Ammobaculites exiguus, Bruneica clypea, Caronia exilis, Haplophragmoides wilberti, Siphotrochammina lobata, and Trochammina inflata were found live in all four cores. The down-core patterns of foraminiferal data in high swamp core SET10 SET1, high-swamp core SET09 TR2 15A and mid-swamp core SET09 TR3 7A are not significantly impacted by deep-infaunal contribution, down-core taphonomic loss, or bioturbation. This suggests that all three cores could record sea-level changes. In contrast, mid-swamp core SET 09 TR1 7A exhibits significant enrichment of down-core assemblages by deep-infaunal foraminifera and extensive down-core taphonomic loss of tests, thus precluding its use for sea-level reconstructions. It is arguable whether the basis for down-core sea-level reconstructions should be surface samples of transects across the mangrove swamp because an average of only 7% of the total number of live foraminifera in the four cores occurs in the 0–2 cm depth interval; most of the standing crop occurs in the 0–16 cm interval. However, because all abundant taxa occur both shallow (16 cm) infaunally and assemblages in the 0–2 cm interval are very similar to those in the 0–16 cm interval, down-core sea-level reconstructions based on 0–2 cm surface samples, with a calculated error range of ca ±18 cm, could be attempted. Thus, it is possible that a sea-level signal could be preserved in foraminiferal assemblages from the mangrove swamps of Setiu, Malaysia, albeit with a relatively low resolution.