| 英文摘要 |
The survival of aquatic organisms were threatened by contaminated sediments seriously, and the pollutants became highly risk to entire aquatic ecosystem and human health after transferred by food chain through bioconcentration and biomagnification process. Using benthic invertebrate bioassay to evaluate sediment toxicity was broadly discussed internationally, both USA and EU also had developed different testing methods, but these methods were constructed under their environmental conditions, or the organisms were locally restricted in use. In here, the developing of standard bioassay methods to evaluate sediment toxicity by native species is an urgent demand, finding out suitable and sensitive surrogate species is a key requirement to make sure the standard methods can be execute.
Benthic invertebrate direct contact with sediments, individuals can quick and significant response to the poison of pollutants, they not only can be a bioindicator for sediment pollutions also be good target animals for sediment toxicity bioassays. After searching the references and archives related to sediment biotoxicity, the most common test organism for bioassays were annelids, arthropods and mollusks. For the purpose of searching native species to be the testing targets, two seasonal aquatic ecological investigation was accomplished, surveyed area include light polluted water bodies located in Taiwan and off-shore islands. The investigation contents included habitat types, environmental factors (water body and sediment) and biota (fish and benthic animals). There were 105 species of fishes and 447 taxa of benthic invertebrates were found, the distribution of species depend on geographical district and habitat difference (sediment, tidal effects etc.).
According to ecological investigation results and reviewing reference to screen out the useable dominant species to be a surrogate species for bioassay, 8 species were selected and raised successfully in laboratory. The laboratory culture procedure was well documented and primary life history study was done. The eight candidate species are Cipangopaludina chinensis (Griffith et Pidgeon, 1865), Perinereis mictodonta (Marenzeller, 1879), Grandidierella sp., Ptilohyale sp., Asellus sp., Chlamydotheca arcuate (Sars, 1901), Stenocypris major (Baird, 1859) and Kiefferulus longilobus (Kieffer, 1916). After toxicity tolerance pilot study, we found only five of them were good candidates, and the test of optimal experimental condition and sensitivity to Cu poison was completed. The continue test of other three species were not conducted because of Grandidierella sp. was too fragile to handle, the life cycle of Asellus sp. was too long and the Cu poison tolerance of Perinereis mictodonta was too high.
Diptera midge Kiefferulus longilobus larvae live in sediment, 3rd instar was testing target, optimal living temperature was 25℃, salinity tolerance range 0-37psu, Cu spiked water 96 hr LC50 was 1.28 (mg/L), and Cu spiked sediment 10 days LC50 was 19.25 (mg/kg). This species has high sensitivity to Cu poison and easy to culture in laboratory, it can be applied for sediments from freshwater body and estuarine region. Marine amphipod Ptilohyale sp. thrive on sediment surface, individuals with 2.5-3.5mm was testing target, optimal living temperature was 25℃, salinity tolerance range 15-37psu, Cu spiked water 96 hr LC50 was 0.729 (mg/L), and Cu spiked sediment 10 days LC50 was 55.1 (mg/kg). This species has low sensitivity to Cu poison and easy to culture in laboratory, it can be applied for sediments from estuarine region. Freshwater ostracod Chlamydotheca arcuate thrive on sediment surface and sometime hiding in sediment, adult individuals was testing target, optimal living temperature was 25℃, Cu spiked water 96 hr LC50 was 0.635 (mg/L), and Cu spiked sediment 10 days LC50 was 44.29 (mg/kg). This species has median sensitivity to Cu poison and easy to culture in laboratory, it can be applied for sediments from freshwater body. Freshwater ostracod Stenocypris major thrive on sediment surface and sometime hiding in sediment, adult individuals was testing target, optimal living temperature was 25℃, Cu spiked water 96 hr LC50 was 0.464 (mg/L), and Cu spiked sediment 10 days LC50 was 29.97 (mg/kg). This species has high sensitivity to Cu poison and easy to culture in laboratory, it can be applied for sediments from freshwater body. Freshwater field snail Cipangopaludina chinensis thrive on sediment surface and sometime hiding in sediment, individuals with 7±2mm body length was testing target, optimal living temperature was 25℃, Cu spiked water 96 hr LC50 was 0.407 (mg/L), and Cu spiked sediment 10 days LC50 was 29.59 (mg/kg). This species has high sensitivity to Cu poison and easy to culture in laboratory, it can be applied for sediments from freshwater body and can tolerate fine particulate clay sediment.
Based on systematic requirements, ideal candidates for whole sediment bioassay will be : 1). Experimental system must be simple and easy to operate; 2). Low coast and reliable; 3). Methods can be standardized; 4). Experimental methods with appropriate sensitivity; 5). Experimental result with appropriate discrimination power; 6). Apparent ecological relationship and test methods can link to wild reality; 7). Futuristic developing potential and easy link to management standards.
For the purpose to improve the whole sediment bioassay experimental guide line, more study cycles still need to be run in the future. The studies include 1) Target specie expose to different pollutants to evaluate biotoxic sensitivity; 2). Interactive effects of Nonpollution stressors on Diptera midge K. longilobus and ostracods; 3). Refining experimental conditions of freshwater field snail C. chinensis and study of pollutant concentration mechanism for future applications; 4). Construct study methods for chronic toxicity of different pollutants on Diptera midge K. longilobus ; 5). Target species expose to low concentration pollutants to study semilethal effects, expose time lasting over different generation, evaluate risky of living based on individual growth, behavior, abnormality and breeding potential etc; 6). Construct a method to get resting eggs of ostracods in quick way, using hatchling of resting egg to run whole sediment bioassay. In advance, develop an experimental kit and standardized testing methods for users, they can get study material easily.
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