Palynomorph assemblages dominated by heterotrophic marine palynomorphs in tropical coastal shallow-water sediments from the southern Myanmar coast

Abstract

The goal of this study was to characterize palynomorph assemblages in tropical marine coastal shallow-water sediments collected from the southern coast of Myanmar, and possibly find them as useful tools for reconstructing changes in the tropical coastal environment. These sediment samples were dominated by heterotrophic marine palynomorphs, particularly in microforaminiferal linings and heterotrophic dinoflagellate cysts. In addition, these tropical marine palynomorph assemblages were characterized by low cell/grain concentrations, especially in photo/mixotrophic dinoflagellate cysts. These marine palynomorph characteristics are common to other tropical coastal surface sediments collected from Southeast Asia. These assemblages may reflect a diagnostic food web that characterizes tropical coastal shallow waters. For example, benthic foraminifers (microforaminiferal linings) that are always dominated usually consume prey organisms composed of bacteria, diatoms, dinoflagellates and amorphous organic substances. And bacteria can utilize dissolved organic matter delivered from terrestrial and marine environments via various organisms that inhabit water and sediment surfaces. The dominance of microforaminiferal linings appears to result from both microbial and grazing food webs in tropical coastal shallow-water sediments.