Judul: Assessment Of Benthic Amphipod Grandidierella Bonnieroides Stephenson 1948 As A Test Organism For Metal Contaminated Sediment Bioassay
Abstrak: To date the evaluation of contaminated sediment using sediment toxicity testing approaches and bioavailable metal, which is a phase that is harmful to aquatic life, is the best approach. Sediment toxicity tests i.e. measuring directly biological effects of sediment contamination and account for additive, synergistic, and antagonistic effects between chemicals, relatively inexpensive and account for all routes of contaminant exposure to the test organism. Amphipod is the most sensitive taxa among benthic organisms that widely used in sediment bioassay. The procedures of using this amphipod as test species are well established in many countries, while in Indonesia, it has not established yet. The recent study aimed to determine benthic amphipod Grandidierella bonnieroides collected from Kramat Kebo estuary, Tangerang, Banten, as test organism for sediment bioassay through various sensitivity tests. These include sensitivity test to particle size and ammonia, cadmium, the salinity tolerance, and the response to field contaminated sediment. Cd, Pb, Cu and Zn content in sediment of Jakarta Bay were used to determine the response of the amphipod to field contaminated sediment. These tests were performed individually using different batch of amphipod collection. Amphipod used in all tests was 7 days laboratory cultured larvae production, and the size was 2.5-3.5 mm. Effect of sediment particle size on survival of benthic amphipod Grandidierella bonnieroides Stephensen 1948 was conducted in relation to the development of a standard test protocol for measuring sediment toxicity. The association of test species with sediment substrates is one of the essential factors in a sediment bioassay. The unfed amphipod was exposed to four different sediment substrates: sand (82% of particles were in the range of 63 μm-2 mm), muddy sand (57% of particle size in the range of 63 μm-2 mm and 43% of particle in the range of <63 μm), sieved mud (sieved through 63 μm pore size), and natural mud for 10 days. Survival of G. bonnieroides was well associated with all sediment types. Survival of the amphipod was significantly reduced (p< 0.05) in sand substrate compared with that in muddy sand and sieved sediments, suggested that survival of the amphipod was strongly related to finer sediment that contained more total organic matter as food source. The result showed that G. bonnieoides is suitable for the toxicity assessment of contaminated sediments with high proportion of mud. Ammonia toxicity was tested by using benthic amphipods Grandidierella bonnieroides to describe its role as a confounding factor in sediment quality assessment. High ammonia content in the pore water sediment can be potentially toxic to benthic biota that will interfere the results of sediment toxicity tests. The results showed that ammonia has a relatively low toxicity to amphipod and does not act as a confounding factor in sediment toxicity tests. This is because the content of ammonia in the sediment does not cause a significant impact on the 6 survival of amphipod if not exceeded its LC50 value (65.5 mg/L). Thus, the amphipod has potential as test organisms in sediment bioassay to assess contaminated sediment. Grandidierella bonnieroides was exposed to cadmium to determine its potential as test species for sediment
Keyword: amphipod, Grandidierella bonnieroides, sediment, bioassay, metals