Bioaccumulation And Transferation Of Microcystins-LR In Daphnia Magna And Macrobrachium Rosenbergii

Microcystins can bioaccumulate and transfer along the food chain. Studies onvarious aquatic organisms have demonstrated that MC can bioaccumulate inzooplankton, bivalves, crustaceans and fish, and even in some aquatic vertebrates suchas turtles, ducks and water birds. Microcystins produced by Microcystis aeruginosa alsoposes potential threats to human health. The thesis systematically reported MC-LRbioaccumulation in Daphnia magna and Macrobrachium rosenbergii. It was confirmedthat MC-LR can be transferred along the food chain. MC-LR content is usually verylow in organism sample, and there are a lot of interfering substances. Thus, the studywas to establish a detection method of microcystins in organisms, and through effectiveenrichment, separation and purification process to achieve high sensitivity and highspecificity analysis, to provide a scientific basis for the prawn healthy farming and foodsafety management. The main research results were as follows:1. A detection method of MC-LR in organisms was established by using Ultraperformance liquid chromatography-mass spectrometry （UPLC）. MC-LR content wasdetected in Microcystis aeruginosa, Daphnia magna and Macrobrachium rosenbergiisamples. It can also apply to study microcystins bioaccumulation and transfer inorganisms, metabolic detoxification as well as the safety of aquatic products. Thelinearity of the method was assessed at MC-LR concentration ranging from1to250ng/mL. A pretreatment method of aquatic samples by using solid-phase extraction （SPE）was set up. It was reliable to test MC-LR content in aquatic samples. The LOD andLOQ in this method were0.0075μg/g and0.01575μg/g, respectively. SatisfactoryMC-LR recoveries ranging from98.4%to103.4%were obtained by using the proposedmethod. The precision was satisfactory since the RSD of the mean recovery was lessthan13%.2. The average MC-LR content in Daphnia magna was （1.12±0.12） μg g^-1 during24h of exposure to Microcystis aeruginosa. The two peaks of MC-LR content were（2.42±0.25） μg g^-1 and （2.72±0.09） μg g^-1 at10h and16h, respectively. The MC-LR content in Daphnia magna showed no significant difference （P>0.05） initially （before6h）. It was significantly increased （P <0.01） from8h to10h, and then it extremelysignificantly reduced （P <0.01）. However, it was extremely significantly increased （P<0.01） after12h and reached the second peak at16h, and then extremely significantlyreduced （P <0.01） until the end of the test.3. Prawns （Macrobrachium rosenbergii） were exposed to Microcystis aeruginosafor24h, MC-LR failed to be detected in the muscle samples. MC-LR is detected at8h inblood samples, the content was （0.15±0.004） μg g^-1, the others were not detected.MC-LR content at2,8,16and24h in gills were （2.16±0.19）,（6.08±0.59）,（3.57±0.44） and （0.89±0.08） μg g^-1, respectively; MC-LR content at2,8,16and24h inhepatopancreas were0.02,（0.06±0.01）,（0.19±0.03） and （0.20±0.04） μg g^-1;MC-LR content at2,8,16and24h in digestive tract were （0.35±0.02）,（0.77±0.07）,（0.69±0.08） and （0.56±0.02） μg g^-1. MC-LR content is not increased with time, thecontent of each tissue bioaccumulation: gill> digestive tract> hepatopancreas.4. Prawns （Macrobrachium rosenbergii） were fed with toxic Daphnia magna,MC-LR content at8h in gill, hepatopancreas and digestive tract were （0.05±0.005）,（0.04±0.02） and （0.05±0.01） μg g^-1; MC-LR content at16h in the hepatopancreasand digestive tract were （0.05±0.01） and （0.14±0.01） μg g^-1; MC-LR content at24hin blood, hepatopancreas and digestive tract were （0.02±0.005）（0.10±0.02） and （0.40±0.04） μg g^-1. MC-LR was not detected in prawns muscle samples, MC-LR content inhepatopancreas and digestive tract increased with time, and digestive tract accumulatedmore MC-LR.5. Microcystis aeruginosa, Daphnia magna and Macrobrachium rosenbergiiconstituted a simple aquatic food chain. MC-LR could not be detected in the musclesamples during the24h test, MC-LR was detected in blood samples at2h, the contentwas （0.03±0.005） μg g^-1, the others were not detected. MC-LR content at2,8,16and24h in gills were （0.37±0.04）,（1.59±0.09）,（1.66±0.18） and （1.11±0.12） μg g^-1;MC-LR content at2,8,16and24h in hepatopancreas were （0.17±0.02）,（0.18±0.01）,（0.40±0.04） and （0.49±0.04） μg g^-1; MC-LR content at2,8,16and24h in digestivetract were （0.62±0.16）,（1.34±0.08）,（2.19±0.30） and （1.29±0.11） μg g^-1. MC-LRcontent is not increased with time, the content of each tissue accumulation: the digestivetract> gill> hepatopancreas.6. The distribution of MC-LR in prawn （Macrobrachium rosenbergii） tissues was different. Prawns exposed to Microcystis aeruginosa trial （A）,2h: gills （85%）>digestive tract （14%）> hepatopancreas （1%）;8h: gills （86%）> digestive tract （11%）>blood （2%）> hepatopancreas （1%）;16h: gills （80%）> digestive tract （16%）>hepatopancreas （4%）;24h: gills （54%）>digestive tract （34%）> hepatopancreas （12%）.Prawns fed with freeze-dried toxic Daphnia magna test （B）,8h: gills （36%）=digestivetract （36%）> hepatopancreas （28%）;16h: digestive tract （74%）> hepatopancreas （26%）;24h: digestive tract （77%）> hepatopancreas （19%）> blood （4%）. Prawns and a plenty ofDaphnia magna were common exposed to Microcystis aeruginosa trial （C）,2h:digestive tract （53%）> gill （32%）> hepatopancreas （15%）;8h: gills （51%）> digestivetract （43%）> the hepatopancreas （6%）;16h:digestive tract （52%）> gill （39%）> thehepatopancreas （9%）;24h: digestive tract （44%）> gills （38%）> hepatopancreas（17%）>blood （1%）.