The Ecological Quality Evaluation Of Yellow River Estuary And Adjacent Waters Based On The Macrobenthos

Macrobenthos is widely used as indicator organism of estuarine environmentalquality status, it can take advantage of the changes between macrobenthos andenvironment relations to indicate the environmental quality of estuarine areas affectedby human activity. In May and August of2009and2010, water, sediments andmacrobenthos in Yellow River Estuary and adjacent sea were collected to research thephysico-chemical factors of depositional environment and water environment,distribution characteristics of macrobenthos, determing the extent of pollutionelements in Yellow River Estuary, and at the same time collecting the polluted factorswhich indicated the characteristic of ecological quality. Shannon-wiener diversityindex H’ and marine biotic index AMBI are used to evaluate the ecological quality ofthe region. AMBI is corrected by the selected indexes including NO₂-N, DO ofunderlying water, single factor pollution index of Hg and heavy metals potentialecological risk index RI in surface sediments. The evaluation index system based onthe macrobenthos in the ecological quality of the Yellow River Estuary wasestablished. The main conclusions are as follows:Distribution characteristics of the water environment factors of the Yellow RiverMouth coastal waters: COD, total inorganic nitrogen and DO content of the bottomwater in coastal area is higher than offshore waters. According to the evaluationresults of water environment quality, COD content of the bottom water are all in therange of seawater quality standards; Inorganic nitrogen exceed standard relativelyseriously, three cruises49%of stations are in range of standard Ⅰ, and13%of thestations are below the range of standard IV, with higher levels of NO₂-N concentration;the DO content of some of the stations are excessive, but are relatively light.Sedimentary environment features of Yellow River Estuary and adjacent sea: forthe grain size of surface sediments, a decreasing trend is found in general from theriver to the offshore direction, particle size of southern entrance stations is larger thanthe northern. For river and estuarine areas of the Yellow River mouth （salinity valuesless than24）, from the river to the entrance direction, elements contents show anincreasing trend. TOC, TN and TP content are in the range of safety level, Pb and As are main pollution factors in river and estuarine sediment, Hg and Cd are the mostimportant contribution factors of the ecological risk. For offshore region （salinityvalues greater than24）, sulfide, TOC and TN contents show the distributioncharacteristics of offshore stations higher than coastal stations, the TP content in theregion as a whole shows stable distribution and the heavy metals content all showdistribution characteristics of the coastal stations higher than offshore stations. TOCand TP are in the range of safety level, TN content is relatively serious. Pb is theprimary pollution factor in the offshore sediments, Hg and Cd are the most importantecological risk contribution factors.Macrobenthos distribution characteristics of Yellow River Estuary and adjacentsea: a total of11macrobenthos species are found in the river and estuarine areas andthe species number of most stations are0. Macrobenthos are dominated bypolychaetes, the number of species is increasing from the river to the mouth direction;abundance is also dominated by polychaetes, the distribution trend is consistent withthe species number; biomass is dominanted by molluscs. A total of137species ofmacrobenthos are collected in offshore areas, which belong to8ecological types,dominated by polychaetes and crustaceans; abundance is dominated by molluscs;biomass is dominated by echinoderms. The number of species, abundance andbiomass in offshore areas are significantly greater than river and estuarine areas. Lowvalue area of the number of species, abundance and biomass in coastal region locatein the stations near Yellow River mouth.According to the diversity index H’ evaluation results, in rivers and estuarineareas, the range of H’ is0.00⁰.92, all stations in rivers and estuarine areas are "verypoor". As strong regional hydrodynamic resulting in monotonous benthic community,diversity index H’ and AMBI index are not applicable to the evaluation of theecological quality of this region. In coastal region, the range of H’ is0.00⁴.22,32%of the stations in offshore areas are "good",34%of the stations are "general" andothers are "poor" or "very poor", and habitat quality as "poor" and "very poor"stations are located in the area near Yellow River mouth. The maximum of AMBI isfound near the mouth of estuary. The AMBI evaluation results show that, most of theoffshore area sites （94.59%） are excellent and above. In the coastal waters of theYellow River mouth area, the results of two evaluation indices are different. Generally,the evaluation results of the AMBI index is significantly better than the diversityindex H’, most evaluation results of the two indices present a difference of one level. Results show that the evaluation results of AMBI index is more in line with the actualsituation of the ecological quality of the region than H’. The relationship between thesalinity and ecological indicators in offshore areas was analyzed, apart from biomassand AMBI, it shows highly significant positive correlation between other ecologicalindicators and salinity, The impact of salinity on the diversity of macrobenthos isapparent.Using the environmental pollution indication factors NO₂-N, DO of underlyingwater, single factor pollution index of Hg and heavy metals potential ecological riskindex RI in surface sediments to correct the macrobenthos level in offshore area of theYellow River Estuary. With regard to not assigned species, determing the initial levelsaccording to the approximate species existing in the list of ecological groups and thencorrect the levels of macrobenthos combined with the indicate factors. As foridentified species, levels were corrected combined with the indicate factors directly.The correction of adjusted value of AMBI and bottom water NO₂-N, DO, singlefactor pollution index of Hg, heavy metals RI in surface sediments are improved,AMBI evaluation results are more consistent with the actual situation of theecological quality of the Yellow River Estuary and adjacent sea. Establishedevaluation index system of ecological quality based on the macrobenthos is moresuitable for the evaluation of the ecological quality of coastal waters in the YellowRiver Estuary.