The existence of benthic animals on a body of water, is strongly influenced by various environmental factors, both biotic and abiotic. Biotic factors that influence them is a manufacturer, which is a food source for benthic animals. The abiotic factors are physical-chemical water such as: temperature, flow, dissolved oxygen (DO), biological oxygen demand (BOD) and chemical (COD), and the amount of nitrogen (N), water depth, and the base substrate.
Zoobentos an animal that part or all of their life cycle in the bottom waters, either sessile, crawling and digging holes (Odum 1993). Animals holds several important roles in water as in the process of decomposition and mineralization of organic material into surface waters, as well as occupying several trophic levels in the food chain (Odum, 1993). Benthos holds several important roles in water as in the process of decomposition and mineralization of organic material into surface waters and occupying several trophic levels in the food chain.
Suwondo et al, (2004) also suggested that Benthos an aquatic organism whose presence can be used as indicators of changes in the biological quality of river waters. In addition, benthic organisms can also be used as a biological indicator in studying the river’s ecosystem. This is due to different responses to an incoming pollutants in river waters and is immobile.
Benthos itself has various characteristics which include, according Sudarjanti and Wijarni (2006) are:
a) have a different tolerance to various types of pollution and have an immediate reaction.
b) found abundant in the waters, especially in the river ecosystem, affected by various types of pollutants that exist.
c) have a high diversity and have a response to environmental stress.
d) attached to the bottom of the aquatic life.
e) have a long life cycle.
Based on its size, the animal organism classified on the benthos:
a) Makrobentos (0, 425-15 mm)
b) Meiobentos (0.05 to 1 mm)
c) Mikrobentos (<50 μ, for example protozoa, rotifers and nematodes)
Organisms which includes macrozoobenthos are: Crustacea, Isopoda, Decapoda, Oligochaeta, molluscs, nematodes and annelids. Taxa-taxa that has a very important function in aquatic communities because most of it occupies the second or the third trophic level. While others have an important role in the mineralization process and recycling of organic materials, both from aquatic and from the mainland.
Mahmudi, et al, (1999), also confirm that the macrozoobenthos has an important role in the ecosystem of the river, namely:
(1) can provide information regarding the transfer and use of energy in the ecosystem of the river,
(2) possession of a role in the process of self-purification of the river, and
(3) can be used to benefit the restoration of river waters by creating habitats that encourage colonization macrozoobenthos. Macrozoobenthos community even become a source of energy for the fishery in the river ecosystem.