Structure and energy demand of the benthic soft-bottom communities in the Java Sea and around the islands of Madura and Bali,Indonesia

In July 1984 benthic research was carried out in the Java Sea and around the islands of Madura and Bali.The aim was to describe the structure of the benthic communities in terms of numerical density (numbers of dominant macrofaunal groups and meiofauna per square metre) and biomass (g ashfree dry weight (AFDW) per square metre), and in relation to geographical position and main ambient factors, i.e. water depth, bottom temperature and sediment characteristics.In addition attempts were made to estimate the activity of these benthic ecosystems, and to show their relation to the pelagic.Box-core samples, collected along west-east axis in the Java Sea and in the Strait of Madura, showed relatively poor benthic communities. The average densities of macrofaunal organisms (> 1 mm) did not exceed 250 specimens·m⁻²; the total biomass was below 1 g AFDW·m⁻²; small polychaetes and crustaceans were the dominant groups.A number of larger organisms have developed very remarkable adaptations to the muddy environment. Meiofaunal organisms (nematodes being the dominant group) numbered 0.06·10⁶ to 0.46·10⁶ specimens·m⁻². In general there is a trend from west to east towards somewhat richer communities. The actual carbon demand of the benthic ecosystem in the area investigated is tentatively estimated at an average of 38 g C·m⁻²·y⁻¹, which amounts to about 40% of the primary production.Both the very soft fluid-mud bottoms in the central Java Sea and in Strait Madura, and the relatively low amount of energy available for growth, probably prevent the establishment of well developed benthic communities.