Bioaccumulation And Trophic Transfer Of Antibiotics In A Food Web From Coastal Area Of Laizhou Bay

Antibiotics are a group of drugs that have antibacterial activity,and widely used in human medicine,animal husbandry,and aquaculture.Antibiotics are heavily used but limitedly bioavailable,and thus can continuedly enter coastal ecosystems through terrestrial inputs and wastewater discharge from mariculture.Due to their pseudo-persistence,the marine organisms will receive chronical and continuous exposure to antibiotics throughout the life cycle.Antibiotics have been detected in aquatic organisms at various trophic levels(TL),in which their bioaccumulation factors(BAF)are reported to be as high as 105 L/kg.Furthermore,some antibiotics seem to have comparable trophic magnification potentials.However,the bioaccumulation patterns and trophic transfer of antibiotics in a coastal marine food web remain unclear.Therefore,in this thesis,19 frequently detected antibiotics were selected,including 9 sulfonamides(SA),5 fluoroquinolones(FQ),4 macrolides(ML),and trimethoprim(TMP).The bioaccumulation pattern,tissue distribution,trophic transfer and dietary health risks of these antibiotics were investigated in 19 natural marine species from Laizhou Bay,North China.The main research contents and results are as follows:(1)Bioaccumulation patterns and tissue distribution of antibiotics were investigated in the marine organisms.Five pelagic fish,five benthic fish,and nine invertebrates were collected in the coastal areas of Laizhou Bay without aquaculture,and 19 antibiotics were analyzed by LC-MS/MS in gills,muscles,kidneys,and livers of these species.The results showed that all the antibiotics were detected and the total concentrations of antibiotics ranged from 57 to 1370 ng/g wet weight(ww).The bioaccumulation patterns of antibiotics in these organisms were influenced by their living modes and feeding modes.The invertebrates accumulated more antibiotics than the fish,whereas the benthic fish accumulated more antibiotics than the pelagic fish(p<0.05).The total concentrations of antibiotics in the species with different feeding modes followed the order filter-feeding>carnivorous>planktonic-feeding>omnivorous(p<0.05).The tissue distribution patterns of different groups of antibiotics were different.In details,for ∑MLs,it followed the order livers>gills ≥muscles ≥ kidneys,and for ∑SAs,TMP,and ∑FQs,it followed the same orders muscles>gills ≥ livers ≥ kidneys.(2)By using physiologically based toxicokinetic(PBTK)models,the tissue concentrations of sulfamethoxazole,trimethoprim,ofloxacin,and erythromycin were predicated in the sea perch(Lateolabrax maculates)and silvery pomfret(Pampus argenteus).The tissue concentrations of erythromycin in these fish were well predicated and all of them were within a factor of 10 of the corresponding measured values.Furthermore,the concentration orders of erythromycin predicated in different compartments were livers>gills>kidneys>intestines>richly perfused tissues>adipose>muscles.They were in good agreement with the tissue tissue distribution patterns of erythromycin observed in these fish,indicating that the partitioning of erythromycin in fish tissues follows the passive diffusion.The liver/blood partition coefficients were the highest,and this was why erythromycin primarily accumulated in fish liver according to the passive diffusion meachanism.The concentrations of sulfamethoxazole,trimethoprim,and ofloxacin in the gills and livers were well predicated within a factor of 10 of the corresponding measured concentrations,whereas their concentrations in the muscles and kidneys were underestimated by one to four orders of magnitude,suggesting the prediction ability was poor for these antibiotics with relatively weak hydrophobicity,and PBTK modelling failed in explaining their tissue distribution patterns.(3)Trophic transfer of these antibiotics was investigated in a food web from the coastal areas of Laizhou Bay,and dietary health risks associated with intake of seafoods from Laizhou Bay were assessed.The stable isotope carbon/nitrogen ratios were determined in the muscles,and TLs and relative carbon sources of each species were calculated.A coastal food web from Laizhou Bay across three TLs(2.00-4.10)was characterized,consisting of eight fish species and nine invertebrates.The mullet(Liza haematocheilus)and eelgoby(Odontamblyopus rubicundus)were not included because they have other dietary sources.Combined the antibiotic concentrations in the muscles and the TLs,the trophic transfer of antibiotics in the food web were investigated and the trophic magnification factors(TMF)were calculated.The logarithmic concentrations of 5 SAs(sulfamethoxazole,sulfachlorpyridazine,sulfadimidine,sulfadiazine,and sulfamonomethoxine)and TMP significantly increased with TLs increasing(p<0.05),and their TMF values were 1.4-3.9,indicating that they biomagnified in the food web.The logarithmic concentrations of enoxacin,ofloxacin,enrofloxacin,azithromycin,and erythromycin significantly decreased with TLs increasing(p<0.05),and their TMF values were 0.4-0.7,indicating that they were biodiluted.However,the trophic transfer of the other eight antibiotics were not observed.The hazard quotients(HQs)and cumulative hazard indices(HIs)for Chinese residents associated with dietary intake of seafoods from Laizhou Bay were less than 0.1.suggesting low health risks.The antibiotic concentrations in human urines were much lower than the minimum inhibitory concentrations(MIC)of Escherichia coli after daily intake of seafoods from Laizhou Bay,suggesting that exposure to such antibiotic concentrations did not result in enrichment for the resistant mutants of E.coli in the adults.