Health Assessment Of Benthic Habitat Based On The Biotic Index In Laizhou Bay And Its Adjacent Waters

The macrobenthos are extremely sensitive to response to environmentalchanges, which could effectively indicate the health status of its habitat. Based onthe data obtained from May and August,2009, August,2010, May and August2011,this paper focuses on the macroinvertebrates in Laizhou Bay and its adjacent waters,analyzes the species composition and distribution characteristics of macrobenthos,and applies the Shannon-wiener diversity index and A Marine Biotic Index(AMBI)to evaluate the health condition of benthic habitat. Through the results comparison oftwo indices in different areas and the sensitivity analysis combined withenvironmental factors (salinity, dissolved oxygen), the applicability of two indices isdiscussed. The main conclusions are as follows:The distribution characteristics of macrobenthos species are as follows: a totalof214species of macrobenthos are identified in the study area, includingPolychaetes (77species), Crustaceans (67species), Mollusks (54species), andothers Oligochaeta, Platyhelminthes, Coelenterate, Nemertinea, Echinoderms,Brachiopoda (sum to16species).175macrobenthos species are collected in theLaizhou Bay waters with salinity greater than25;12macrobenthos species arecollected in the the Yellow River estuary with salinity less than25, with62.5%of thestations collected no any macrobenthos;93macrobenthos species are collected in theXiaoqing River estuary with salinity less than25, with a predominance ofpolychaetes in each region.The distribution characteristics of macrobenthos abundance are as follows: theaverage abundance of Laizhou Bay area with salinity greater than25is484.54ind./m2, with the abundance predominance of mollusks, followed by polychaetes andcrustaceans, which the proportions are57.85%,27.00%,13.57%, respectively; theaverage abundance of macrobenthos abundance in Yellow River estuary with salinityless than25is31.73ind./m2, which is the lowest; the average value of XiaoqingRiver estuary with salinity less than25is1672.23ind./m2, far higher than the centralarea of Laizhou Bay and the Yellow River estuary. The abundance of polychaete hasthe bigger advantage in Yellow River estuary and Xiaoqing River estuary whosesalinity is less than25. The macrobenthos abundance in May is significantly higher than August.The distribution characteristics of macrobenthos biomass are consistent with theabundance, with its value in summer higher than spring. The average biomass ofLaizhou Bay area with salinity greater than25is5.53g/m2; Yellow River estuarywith salinity less than25has the lowest biomass average value,0.38g/m2; theaverage value of Xiaoqing River estuary with salinity less than25is158.45g/m2,much higher than the values in Laizhou Bay waters and Yellow River estuary.Mollusks is in dominant biomass in the above three areas, with the proportion of45.59%,51.99%, and91.40%, respectively.The diversity index H’ values are ranged from0to4.23, which are higher inspring than summer and lower near the Yellow River estuary and Xiaoqing Riverestuary. Richness index(d) values range from0to3.00, and that of evenness index(J)range from0to1.00, which both have a significant positive correlation with thediversity index H’. The average H’ value in Laizhou Bay waters with salinity greaterthan25is2.36, and the station number with H’≥2accounting for67.63%, the habitatquality status(EcoQs) are High or Good,10.79%of the stations H’<1coming to Pooror Bad. Average value of diversity index H’ in Yellow River estuary with salinity lessthan25is0.17, with90%stations H’<1, their EcoQs as Poor or Bad. That ofXiaoqing River estuary with salinity less than25is1.71, with43.48%stations H’≥2,the EcoQs are High or Good,21.64%of the stations H’<1, EcoQ as Poor or Bad.After classifying the macrobenthos’ ecological grades and analyzing theassessment results of AMBI, the percentage of EGI and EGII species is72%inLaizhou Bay waters with salinity greater than25, only7.43%of EGIV and EGVspecies, and AMBI average value is1.70,95.68%of stations AMBI≤3.3, indicatingthe normal benthic community, no or minor disturbance in stations and high or goodhabitat quality status; in Yellow River estuary with salinity less than25,62.5%of thestations collect not any benthos, indicating stations subjected to serious disturbanceand bad habitat quality status, and the collected species are mainly EGII and EGIIIspecies with high or good habitat quality; in Xiaoqing River estuary with salinityless than25, the percentage of EGI and EGII species is62.36%, EGIII species for23.66%, and the AMBI average value is2.69, and69.57%of stations AMBI≤3.3,indicates that the benthic community is normal, where the stations are subjected toslight disturbance and High or Good habitat quality condition, and15.22%of the serious stations disturbance and Poor and Bad habitat quality.Compared with the results of the two biotic indices, there are two situationshaving the larger differences: firstly, when the species number is less than or equal to3, the evaluation results of the AMBI index showing the poor reliability, this indexmay be too high to evaluate the EcoQ level; secondly, with uniform abundance,while a higher proportion of the poor ecological level exists, the diversity index H’may too high to evaluate the EcoQ level. Correlation analyses between the two bioticindices and environmental factors (bottom water salinity, DO) reflect that both H’and AMBI index have the obvious correlation with salinity, and the AMBI indexalso shows a significant negative correlation with the bottom water DO, which ismore sensitive to environmental change.Based on the discussions of evaluation results between H’ and AMBI index andthe correlation analyses between them and environmental factors, the conclusion areas follows: in Laizhou Bay waters with salinity greater than25, with rich species inmost stations and uniform abundance of each species, AMBI index could betterreflect the situation of disturbed benthic community and the EcoQ level; in YellowRiver estuary with salinity less than25, the numbers of species in stations do notexceed3, using diversity index H’ to evaluate its habitat condition is more suitable;in Xiaoqing River estuary with salinity less than25, when species number is nomore than3, the diversity index H’ should be used, otherwise the AMBI index shouldbe applied to evaluate the habitat condition. And the evaluation results show that:among five cruises,81.43%of the stations the EcoQ level is High, Good andModerate, so the overall level of its benthic habitat is in Moderate in Laizhou Bayand adjacent waters.