| dc.description.abstract | 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
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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 toxicity assays in Indonesia. Cadmium is a widespread pollutant in the environment and also commonly used as reference toxicant in toxicity testing. The study revealed that sensitivity varied within the species with the LC50 values ranged between 0.35 mg/L and 0.88 mg/L. Amphipods responded to polluted environmental that made it suitable test species for toxicological testing including sediment bioassay.
Sensitivity of benthic amphipod Grandidierella bonnieroides to salinity was tested to describe their potential as test organism in sediment assessment studies. Salinity plays an important role in physiological aspect of many aquatic organisms. Amphipod was tested to different salinity (20, 25, 30 and 35 ppt) for ten days and the salinity of 30 ppt as a control. Results of the study showed that the tolerable salinity was 25 and 30 ppt. LC50 value could not be calculated for the amphipod since the mortality was less than 50% in all salinity tested. The finding suggested that the amphipod was able to inhabit a wide range of salinity, though phyisological effects may occured at salinity lower and higher than the background level. This indicated that the amphipod could be proposed as test organism for sediment bioassay.
The sediments collected from the river mouth of Ancol and Sunter, Jakarta Bay were tested using amphipod Grandidierella bonnieroides to determine the capability of this amphipod to response to the contaminated sediments. Cd, Pb, Cu and Zn were analyzed for the geochemical component of sediment, namely easily reducible (ER), reducible (RED), organic (ORG) and residual (RES). The results showed that most of metals were in four geochemical fractions. These four metals from Jakarta Bay sediments were derived from anthropogenic activities (non-lithogenic fraction/RES) and were on the labile phase (ER+RED, bioavailable), means that they can easily bind with other toxic compounds and regarded as a dangerous phase for biota. Cadmium was a dangerous metal for benthic organisms with percentage of labile phase higher than other metals. The highest toxic response was found in sediments closed to Ancol and Sunter rivers, and decreased towards the sea. Metals that strongly associated with the survival of the amphipod were Cd, Pb and Cu in four sediment geochemical fractions.
In general conclusion, this species fulfills most of the criteria required for suitable sediment toxicity tests. It may be an alternative or complementary test species for ecotoxicological studies in Indonesian marine ecosystems. The use of metal speciation in the sediment quality assessment is highly recommended to obtain the better understading of the effects on benthic organisms. | id |
