The Important Role of Fish Histopathological Biomarkers In an Effort to Realize a Sustainable Bali Aquatic Ecosystem

Increasing industrialization along with increasing population also has an impact on the higher possible risk of decreasing water quality due to pollutants entering the aquatic environment. As is the case with the rivers and estuaries of Tukad Badung and Tukad Mati which are vulnerable to the presence of pollutants, this does not rule out the same for other aquatic ecosystems such as lakes and seas. Especially in Bali, the existence of aquatic ecosystems is very easy to find, especially marine ecosystems. So that more attention is needed regarding efforts to biomonitor aquatic ecosystems. Fish is one of the organisms that live scattered in various aquatic habitats, both fresh, brackish and marine waters. Therefore fish have the potential as a bioindicator. In addition, because fish have several requirements, including having an abundant amount and the ability to accumulate pollutants in their tissues, having a high sensitivity to environmental changes and wide tolerance to pressure in the aquatic environment. This shows that fish are good bioindicators in biological monitoring of aquatic ecosystems related to changes in water quality as a result of the presence of various types of pollutants, both organic and inorganic pollutants in waters such as phenols, pesticides, and heavy metals.

Various pollutants can enter the fish's body through the gills in the respiration mechanism and spread throughout the body. Furthermore, along with the blood flow, pollutants can reach the target organs, including the liver. In addition to playing an important role in the mechanism of respiration and osmoregulation, the gill organs are the initial place for pollutants to enter the fish's body which enter with the water, so that the gill organs allow continuous exposure to pollutants due to direct contact with the waters. Meanwhile, the liver is known to play a role in the metabolism and detoxification of toxic chemicals (toxicants). Pollutants that enter the bodies of aquatic organisms can accumulate in tissues and at certain concentrations can cause damage. This can result in pathological changes in the structure of the gills and liver in response to the effects of exposure to pollutants. Structural damage to organ tissue will of course also have an impact on damage and functional disorders of these organs. The higher the pollutant concentration will be able to cause greater damage to the tissue.

Histopathological changes in fish organs can be seen from histopathological examination. Histopathological changes in gills and liver are quite widely used in assessing the health of aquatic organisms, especially in fish due to exposure to acute effects in the short term and chronic effects in the longer term. Apart from gills and liver, histopathological examination can also be performed on other organs in fish such as intestines, kidneys and gonads. Histopathological changes that can be found in the gills include swelling (oedema), bleeding (hemorrhage), hyperplasia, lamella fusion, telangeactasis and also necrosis. Whereas in the liver, the histopathological changes found include swelling (oedema), bleeding (hemorrhage), vacuolar degeneration, congestion and necrosis.

The histopathological picture can provide signs or information about the impact of tissue damage on the fish body due to pollutant exposure at various levels of damage, including low, moderate and severe levels at the individual level. Therefore, histopathological features of organs in fish can be used as biomarkers as an organism's response to exposure to pollutants in the waters. Histopathological biomarkers are relatively easy to use in an effort to evaluate the long-term effects of exposure to environmental pollutants on aquatic organisms. Fish histopathology biomarkers are expected to be used as information as well as early detection related to exposure to toxic compounds that enter the bodies of individual aquatic organisms at the sub cellular level as an initial reaction before a more serious impact occurs and becomes a threat to the existence of aquatic ecosystems and human health. So that research opportunities related to histopathological examination of fish organs in a variety of aquatic ecosystems are needed in efforts to biomonitor the aquatic environment in order to achieve a sustainable balance of aquatic ecosystems in Bali