Phytoplankton Community Structure of the Makassar Strait, Indonesia

Abstract

Makassar Strait is a unique oceanic ecosystem influenced by Indonesian Throughflow (ITF) and acted as a geographical barrier for Asian and Australasian ecozones. Those characteristics could form the diversity of phytoplankton in the strait. Thus, this research aimed to describe the phytoplankton community structures and determine the longitudinal or latitudinal shift in the Makassar Strait community. Specimen collection was carried out in 2013 from 20 stations along the Makassar Strait during the Widya Nusantara Expedition (EWIN). There were 165 phytoplankton species identified in this study, which consists of 1 cyanobacterium, 97 diatoms, and 67 dinoflagellates. The cyanobacteria, Trichodesmium spp. was dominating the phytoplankton communities, with a relative density of >60%. Aside from Trichodesmium spp, the diatoms, Chaetoceros lorenzianus, Thalassionema nitzschioides, Bacteriastrum furcatum, Chaetoceros curvisetus, and Chaetoceros dichaeta were also the most abundant species in Makassar Strait. There was no extreme species assemblage shifting along the latitudinal and longitudinal gradients in the Makassar Strait. The phytoplankton community structure in all stations was similar, with noticeable differences only found at stations 8, 21, and 29 that are located in proximity to the Kalimantan coastline. However, a southward decrease in the density and diversity of phytoplankton was noticed in this study. It was confirmed that Makassar Strait was not a barrier for phytoplankton dispersal, which is shown in an indistinct shift in the phytoplankton community structure both latitudinally and longitudinally. However, ITF might be an important factor that controls the latitudinal trend in phytoplankton diversity and cell density in this research.