| The spatial and seasonal variation in numbers of bacteria and the community of the culturable heterotrophic bacteria in the surface seawater and sediment collected from costal Bohai Bay were investigated from July,2003 to May,2004 in four cruises. The bacterial indices included heterotrophic bacteria from 2216E plate counts (HBC), bacteria from acridine orange viable counts (AODC), bacteria from direct viable counts (DVC), coliform group, vibrio from TCBS plate counts and petroleum degrading bacteria(PDB). Moreover, the correlation between bacterial indices and other ecological factors were analyzed and the bacterial indices were applied to evaluate the quality of the studied area. Based on above results, a preliminary method was established to assess the quality of coastal areas.The main results were as follows: 1. Studies on bacteria in surface seawater and sediment 1.1 The spatial and temporal distribution of bacteria in surface seawaterThe highest population of HBC in surface seawater was recorded during summer, the second highest populations occurred in spring and the lowest were in winter with the exception of some stations with higher populations in autumn. Moreover, the higher density of HBC appeared in those stations near sewage drainage or near the shore.The abundance of AODC and DVC showed a similar trend that the populations were highest in autumn. Besides, The distribution of them were not as regular as that of HBC, but the lowest abundance did not appear in clean waters and the largest population did not appear in polluted waters.The number and detectable rate of coliform bacteria in spring was higher than that in winter. In addition, the distribution of bacteria was mostly determined by thedistance to the shore and the drainage and the station near the shore or drainage has larger populations.The abundance of vibrio was higher in spring and the station near the drainage and mariculture waters had the larger population.The distribution of PDB was positively correlated to the oil density. 1.2The fauna of HBC in surface seawaterThe Gram-negative bacteria accounted for 78.6% of 747 strains of HBC(20 genus) isolated from surface seawater and Pseudomonas, Photobacterium, Aeromonas and Vibrio were dominant genus. The proportions of Gram-positive bacteria were 15.5% and the dominant genus was Staphyloccus, Corytebacterium and Micrococcus.The dominant genus was roughly same in each season and alternated between Pseudomonas, Photobacterium and Aeromonas with the exception of summer. In addition, Pseudomonas and Photobacterium were dominant alternately in a majority of stations.The similarity of community composition of HBC between 10 stations was analyzed and the difference of environmental & geographic conditions could be expressed by the similarity. Furthermore, the similarity varied in different seasons. 1.3The spatial and temporal distribution of bacteria in sedimentThe distribution of HBC from sediment was similar to that in surface seawater, that is to say, the highest population of HBC in sediment appeared in summer, the second highest populations occurred in spring and the lowest were in winter. In addition, the lowest abundance did not appear in clean waters and the largest population did not appear in polluted waters. The abundance of HBC was related to the distance to the shore, drainage and aquacultural waters as well as the content of organic matter and type of sediment.The abundance of AODC and DVC showed a similar trend that the populations were highest in autumn bul lowest in winter and were not closely related to the distance to the shore and drainage due to the influence of the type of sediment and feeding activities. Besides, the abundance of AODC and DVC were evenly betweenthe stations and had no significant regularityThe abundance of coliform bacteria in spring was notably higher than that in winter and the density of coliform bacteria were higher in near-shore station and near-drainage station than in off-shore station and the station far away from drainage..The populations of vibrio distributed without a clear regularity except that the abundance in spring was remarkably heavier than that in winter.The distribution of PDB had not significant relation to the distance to the shore and the drainage. 1.4The fauna of HBC in sedimentSix hundred and one strains of HBC (20 genus) were isolated from the sediment and the Gram-negative bacteria counted up to 78.6% and Pseudomonas, Photobacterium, Aeromonas and Vibrio were dominant genus. The proportions of Gram-positive bacteria were 31.3%, which was much higher than that in surface seawater and the dominant genus were clostridium, Corytebacterium, Micrococcu and Streptomyces.The Gram-negative bacteria were in predominance in each season but the dominant genus differed in seasons. Pseudomonas was dominant in autumn, winter and spring while vibrio in summer.The similarity of community composition of HBC between 10 stations was analyzed and the results were similar to that in surface seawater. 2.Studies on the correlation between bacteria indices and other ecological factors (biological factors and unbiological factors) 2.1 Surface seawater2.1.1 The correlation between the number of different bacteria in surface seawater There was significantly positive correlation between the value of HBC,AODC andDVC and between HBC and coliform group, but the value of these kinds of bacteria were not closely correlated with the concentration of the vibrio and PDB.2.1.2 The correlation of bacteria between different seasons in surface seawater There was a correlation of bacteria between different seasons in some degree andthe values of bacteria in autumn, winter and spring were closely correlated with each other.2.1.3 The correlation between the number of different bacteria and the chemical & physical factors in surface seawaterThe value of HBC was closely positively correlated with nitrites, inorganic phosphorus, TOC and TN but significantly reversely correlated with the value of pH; the value of AODC was closely positively correlated with nitrites, ammonia and inorganic phosphorus but reversely correlated with the value of pH, active silicon and diaphaneity; the value of DVC was closely positively correlated with water temperature, nitrites and inorganic phosphorus but significantly reversely correlated with the value of pH, diaphaneity and Pb2+; the value of coliform group was closely positively correlated with nitrites and nitrates but reversely correlated with the value of PH and salinity; the value of vibrio was closely positively correlated with ammonia and chlorophyll but not correlated with other factors; the value of vibrio was closely positively correlated with the concentration of oil but not correlated with other factors.2.1.4 The correlation between bacteria and biological factors in surface seawaterThe values of these kinds of bacteria were not closely correlated with the density of zooplankton, phytoplankton and chlorophyll with the exception that the value of vibrio was significantly correlated with the concentration of chlorophyll. This result was different from many researcher's. 2. 2Sediment 2.2.1Tthe correlation between the number of different bacteria in sedimentThe value of HBC was positively correlated with coliform group, but was not closely correlated with other bacteria. So did the value of AODC and DVC. 2.2.2 The correlation of bacteria between different seasons in sedimentThere was close correlation of bacteria between different seasons and any season was significantly positively correlated with the following season or the season before. 2.2.3The correlation between the number of different bacteria and the chemical & physical factors in seawaterThe value of HBC was positively correlated with TOC and TN but other bacteria were not closely correlated with the chemical & physical factors. 2.2.4 The correlation between bacteria and zoobenthic in sedimentThe values of these kinds of bacteria were not closely correlated with the density of zoobenthic with the exception that the value of vibrio was significantly correlated with the density of zoobenthic. 2.3The relationship between the bacteria in surface seawater and that in sedimentA majority of the bacteria in sediment was not closely correlated with the bacteria in surface seawater, but the coliform group in sediment was positively correlated with the value of HBC, AODC, DVC in sediment and coliform group in surface seawater. 3.The application of bacterial indices on the evaluation of quality of coastal environment3.1 The evaluation results of the quality of investigated stations by using the biological indices3.1.1 According to the evaluation results of HBC, the organic matter pollution of the studied waters was moderate-polluted and the results indicated that the water quality was seriously polluted in the station A3 and A4, moderate-polluted in the station A5, A14 and A20; slightly-polluted in the station A9, A10, A15 and A21 and clean in the station All.3.1.2 According to the evaluation results of coliform group, the sanitary quality of the studied waters was moderate-polluted and the results indicated that the water quality was seriously polluted in the station A3, A4 and A5 and slightly-polluted in the station A11 and A21.3.1.3 According to the evaluation results of vibrio, the water quality of the station A3, A4 and A5 near the drainage was seriously polluted by vibrio and did not meet the requirement for aquacultural use.3.1.4 According to the evaluation results of PDB, the PDB was detectable in all the investigated stations. The results indicated that the studied waters was polluted by oil matter, but the pollution was not as heavy as other seriously polluted waters.3.1.5 As to the sediment, according to the evaluation results of coliform group, the sanitary quality of the station A3 and A4 was seriously polluted and in spring the sediment of many stations was polluted by coliform group and could not meet the requirement for aquacultural use. 3.2The better indices for evaluation of costal environmentThe indices chosen for this investigation, HBC, coliform group, the ratio of HBC to AODC and DVC, vibrio and PDB was suitable for the assessment of the water quality of coastal environment, so that they can be used for monitoring and evaluating the deterioration of costal habitat. The index of coliform group in sediment was closely correlated with the fecal pollution, but the related data was too little to make an accurate conclusion.4. Preliminary establishment of the method of evaluating marine habitat deterioration of coastal areasThe method of assessing the quality of coastal areas by using bacterial indices was established initially to monitor and evaluate the deterioration of water quality at the level of bacterial production, the value of different bacteria, bacteria fauna, enzyme produced by bacteria and molecular method. Besides, this method can be applied on the assessment of sediment quality .At the same time, some physiological groups of bacteria, such as coliform group(or fecal coliform bacteria), PDB, some bacteria indicating anaerobic conditions, heavy metal-tolerant bacteria and pollutant degrading bacteria and so on was advised to be chosen to assess the fecal pollution, anaerobic conditions and other pollutant directly.
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