Assessment of heavy metal pollution in Laizhou Bay(China)using the ecological risk index and the integrated biomarker response of the goby Acanthogobius ommaturus

We used the Integrated Biological Responses version 2(IBRv2)method to evaluate the biological eff ects of heavy metals in the sediments in Laizhou Bay,China on the benthic goby Acanthogobius ommaturus.In December 2018,gobies and sediments were collected from 15 stations.We measured the activities of defense enzymes and the contents of malondialdehyde(MDA)and metallothionein(MT)in the goby liver as well as the levels of heavy metals in the sediments and goby muscle tissue.Most of the heavy metal concentrations in sediment at each station were below the Class I criteria set by Chinese Standards for Marine Sediment Quality,and the Håkanson ecological risk index suggested low risk for the heavy metals.We found that A.ommaturus could eff ectively accumulate mercury,cadmium,arsenic,and zinc and that the contents of MT and MDA and the activities of glutathione peroxidase and glutathione reductase were suitable biomarkers of heavy metal pollution in this species.The IBRv2 method integrated these four biomarkers and discriminated stations according to heavy metal pollution.Higher IBRv2 values suggested more adverse eff ects in gobies,corroborating more serious heavy metal contamination.The stations with high IBRv2 values and high contents of heavy metals were mainly distributed in the west and northeast parts of the bay.These results show that the IBRv2 approach is a feasible strategy for assessing heavy metal pollution through biological response and biological status and that it can be implemented for environmental monitoring in Laizhou Bay.

Discordant patterns of genetic variation between mitochondrial and microsatellite markers in Acanthogobius ommaturus across the coastal areas of China

Acanthogobius ommaturus, which belongs to the family Gobiidae, is a euryhaline and demersal fish that is widely distributed in the coastal areas, harbors, and estuaries of China, D. P. R. Korea and Japan. In this study, the genetic diversity and genetic structure of five geographical populations of A. ommaturus was assessed using the mitochondrial hypervariable region gene and microsatellite markers. The results of the two genetic markers indicated that the A. ommaturus populations had a high level of genetic diversity. The mitochondrial marker detected weak genetic differentiation among populations, and the Neighbor-Joining tree showed that there was no obvious pedigree branches and geographic structure as well. However, population of Zhoushan showed significant genetic differentiation with other populations by microsatellite markers. The population of A.ommaturus has not experienced bottleneck effect recently. We speculated that the Pleistocene climate change and juvenile fish dispersal played an important role in the population differentiation of A. ommaturus.

Profile and development of microsatellite primers for Acanthogobius ommaturus based on high-throughput sequencing technology

Acanthogobius ommaturus,a fish species of the Family Gobiidae,is a marine commercial fish perched on the bottom of seawater.In this study,Illumina high-throughput sequencing technology was applied to obtain the candidate microsatellite markers of A.ommaturus.A total of 4746 microsatellite-rich fragments were found,of which 4542 microsatellites are with primer fragments,containing 971 dinucleotide sequences,2643 trinucleotide sequences,569 tetranucleotide sequences,406 pentanucleotide sequences,and 212 hexanucleotide sequences.Based on the results of high-throughput sequencing,a total of 141 pairs of the microsatellite primers were designed and screened.And then 24 polymorphic primers were finally obtained by polyacrylamide gel electrophoresis.In total,271 alleles were detected in the 24 pairs of primers.The number of alleles for different primers ranged from 5 to 19.The average number of effective alleles(Na)was 11.292;the average observed heterozygosity(Ho)of the 24 pairs of primers was 0.665,the average expected heterozygosity(He)was 0.880,and the average polymorphic information content was 0.846.All sites were highly polymorphic(PIC>0.50).