The study was performed in Mahakam Delta, East Kalimantan Province, Indonesia. The samples were taken from
4 stations representing plain delta and front delta. Station 1 (ST1) is categorized to delta plain which consists of
active and inactive river channel, while ST2, ST3, and ST4 belong to delta front in center, north and south direction
of Mahakam Delta. Delta front is sub-environments with high energy and sediments are constantly influenced by
tidal currents, ocean currents along the shore, and the wave action [13].
Plankton sampling was carried out by filtering water samples as much as 50 liters by plankton net. Filtered water
samples were stored in the sample bottle, and then preserved with Lugol solution of 10%. The samples were brought
to be identified and classified by a binocular microscope and identification book [13, 14, 15]. The abundance of each
plankton was calculated.
Univariate analysis approach was used to describe some ecological indicators through diversity index. The
indicators were diversity and dominance index of the identified plankton species. Diversity index was based on
Shannon and Wiener index [16] with the following formula: