Effects of different nutrient loadings on planktonic primary production in embayments of Indonesia

Abstract

A study on planktonic primary production was conducted in three Indonesian embayments subjected to different levels of eutrophication. The three embayments are Jakarta, Lampung and Semangka Bay. A previous study revealed that Jakarta Bay is heavily eutrophied while Lampung Bay is moderately eutrophied and Semangka Bay is close to pristine conditions. The eutrophication state in the three bays studied was closely related with respective nutrient loading of the embayments. Annual primary production in Jakarta Bay ranged from 47 to 503 g C m-2 y-1, in Lampung Bay from 31 to 196 g C m-2 y-1 and in Semangka Bay from 14 to 40 g C m-2 y-1. Spatial gradients in primary productivity were closely related to spatial nutrient gradients in the bays, except in Semangka Bay, due to the high turbidity of the river mouth. Temporal variability in primary productivity was small, consistent with small changes in environmental parameters across seasons. Jakarta Bay which has the most eutrophied waters was the highest in terms of primary productivity, followed by Lampung Bay and Semangka Bay. The primary productivity levels in the three bays was closely related with levels of nutrient loadings. This research is of importance for the development of primary production measurement in Indonesia since it is among that uses the radiocarbon technique.