Application of polychaete in ecological environment evaluation of laizhou bay

Abstract

Polychaete, often linked in the past to the concept of opportunistic species able to proliferate after an increase the quantity of organic matter, have played an especially important role in impacted soft-bottom habitats. They frequently used as a biological indicator of environmental disturbance. The polychaete at 20 sampling sites in Laizhou were investigated by taxonomy and subjected to study the composition of dominant species, biodiversity pattern and spatial distribution in 2011. Spearman correlations of trace metals, natural sediment characteristics and polychaete community were also analyzed. Our results show that Lumbrineris heteropoda and Capitella capitata were dominant polychaete species in spring, and Index of Relative Importance (IRI) value were 5489 and 2008 respectively. The dominant polychaete switched to be Cirratulus cirratus in summer, and IRI value became 3960. The opportunity polychaete accounted for 37. 5% in dominant polychaete species of Laizhou Bay. The averages Shannon-Wiener indices were lower at the stations of S01, S05, S08, S13, S14, S15, S18, S19 and S20, and relatively higher at the stations of S04, S06, S07, S11, S16 and S17. The hierarchical clustering, un-weighted pair group method with arithmetic mean (UPGMA), and non-metric multidimensional scaling (NMDS) approaches were used to analyze the pattern of community compositions. Two polychaete community assemblages were found in Laizhou Bay in our study. Sampling stations of S19 and S20 formed an independent cluster, and the other stations constituted the group II. Abundance biomass comparison (ABC) calves and W-statistic were used to analyze the disturbed states. In undisturbed states, the community was supposed to be dominated by k-selected species (slow-growing, large, late maturing), the biomass curve lied above the abundance curve, and the W-statistic value was positive. With increasing disturbance, the system was increasing dominated by r-selected species (fast-growing, small, opportunistic), the biomass curve would lie below the abundance curve, and the Statistic value was negative. Both ABC and statistic values were generated by PRIMER software (Plymouth Routines in Multivariate Ecological Research). Intersection was found between the abundance curves and the biomass curves in Laizhou Bay, indicating current polychaete communities were moderately disturbed. The BOPA index, appropriate for surveys the temporal changes of macrobenthic systems at high frequencies, can be used to assign estuarine and coastal communities ng into five statuses of ecological quality. The BOPA index showed that two stations (S15 and S16) had moderate ecological status in spring, and one site was heavily polluted in summer. Therefore, such trend revealed by the ABC plot and BOPA index suggests that Laizhou Bay was in an ecology unhealthy condition. The sediment was sorted into medium sand, fine sand, fine silt and clay. Textural pattern such as fine silt, silty sand and sandy silt were observed in Laizhou Bay with various levels of mixing of the three textural grades of sand, silt and clay. Analysis of the correlations between the polychaete community and environmental variablesfor all the stations yielded high values of the rank correlation coefficient (p) for the best-correlated variable combination (>0. 8), suggesting that physical and chemical characteristics of the sediments played a significant role in affecting the polychaete community structure in Laizhou Bay. Individual analysis of correlation showed the higher values of ρs and differences in the best-correlated variable combinations in different seasons. The BIO-ENV analyses indicated that the grain size fractions (medium sand and fine sand) were the major environmental variables influencing the polychaete community patterns. Nevertheless, other unmeasured, physical, chemical and biological factors and their interactions may also have been involved in affecting the macrobenthic patterns. Therefore, components of dominant species, biodiversity pattern, spatial distribution and correlation of trace metals, natural sediment characteristics and polychaete community were important to evaluate the quality of ecological environment in Laizhou Bay, and could provide the basic scientific information for environmental pollution control and marine ecological protection.