[Response Behaviors of Heavy Metals at Tidal Currents Interface and Salinity Interface in the Estuary Area].

In China, trace metals (such as dissolved Cu, Zn, Pb, Cd, and Cr) are the routine mandatory monitoring indicators in existing Freshwater Quality Standard (FWQS, 2002) and Seawater Quality Standard (SWQS, 1997). Using Daliao River estuary as an example, we tried to research the general response patterns of these metals in estuarine system. Firstly, we determined the location of FSI (freshwater-seawater interface) and TCI (tidal currents interface), which were based on biological, chemical and geographic similarities by descriptive and quantitative methods, respectively. Secondly, two hypotheses were proposed to explain the difference based on distribution coefficient Kd along salinity and SS (suspended solids) gradient, these results revealed that the indicators for As, Cd and Cr may be prone to be affected by salinity, and the ones in the second pattern may be more sensitive to SS. Finally, we classified the response behaviors into two patterns based on the changing trends along the distance and magnitudes affected by the FSI and TCI: 1the obvious boundary break point from FSI for As, Cd and Cr; 2 the boundary zones from TCI for Zn, Cu, Pb and Ni. The partitioning behaviors showed similar changing trends at particle and sediment phases, especially for particle phase, depending on the concentration of SS along the salinity. The difference between general behaviors for the two patterns mainly existed at water phase. In general, this paper highlighted the need to consider the background difference of trace metals and identified the sensitive indicators controlled by different environment factors (such as salinity and SS) based on the native estuarine characteristics. Our work will assist the implementation of updating the current water quality standards in China.

[Assessing the benthic ecological status in Yangtze River Estuary using AMBI and M-AMBI].

Both AMBI and M-AMBI could effectively assess the benthic ecological status of estuaries and coastal systems with soft sediments, and show the response of benthic communities to human pressures and natural changes. To monitor the ecological status of Yangtze River Estuary, macroinvertebrate samples and environmental data were collected in April 2009. Results showed that the benthic habit of Yangtze River Estuary was disturbed to various degrees, especially in the watersheds of Hangzhou Bay, coastal areas of Zhoushan islands and in the inner part of Yangtze River Estuary, which was related to land resourced discharges, eutrophication and large amounts of coastal projects. No significant difference was found between the calculation results of AMBI and M-AMBI based on density and biomass, as indicated by one-way Analysis of Variance (ANOVA). Compared with AMBI, M-AMBI could be more effective to assess the ecological status of Yangtze River Estuary because M-AMBI matched the community structure and environmental variables better. Moreover, according to results of Pearson correlation and linear regression analysis, significant negative relationships were found between the eutrophication index both in the surface and bottom water layers and M-AMBI, but no significant relationship was found between the eutrophication index and AMBI. Therefore, M-AMBI could be more suitable in indicating the eutrophication stress of Yangtze River Estuary.

[Study on the changes of macrobenthos communities and their causes in Bohai Bay].

Based on the analysis of macrobenthos samples collected from Bohai Bay, China in 2011 and the data obtained from the nearly the same sampling area during last six years, as well as the hydrological conditions, nutrients and dissolved oxygen, the characteristics of the changes in macrobenthos communities and their response to environmental variables were derived. Results showed that the distribution of the values of species number, abundance, biomass, richness index and diversity index reflected a gradient from the coastline to the open sea with the higher values concentrated at the open sea in the north part of Haihe estuary. The macrobenthos communities showed an obvious fluctuation over last six years, composed of three nodes. The first time node was in 2005 and 2008, the total species number, abundance and biomass maintained relatively high; the second time node was in 2009 and 2010, the values of the above three indices were the lowest in the three time nodes due to the increasing anthropogenic disturbances and natural changes; the third time node was in 2011, the values of the above three indices were the highest since many effective environmental protection measures had been carried out, indicating that the macrobenthos communities were recovered to a certain degree. The integrated impacts from the physical, chemical and biological variables induced by natural changes and anthropogenic disturbances, such as over-fishing, coastal land reclamation and sewage discharge were the triggers for the changes of macrobenthos communities. Furthermore, the variation characteristics of macrobenthic communities and environmental factors were generally in accordance with each other.

[Comparison of trophic status analysis of the Daning River within the Three Gorges Reservoir before and after experimental impoundment].

We evaluated 4-year data set to assess the trophic state and limiting factors of the Three Gorges Reservoir (TGR) during the experimental impounding period (September 2005 to September 2007) and the normal operating period (September 2008 to September 2010). The results indicated that there had been appeared new characteristics in spatial and temporal distribution of trophic state indices after impoundment. The trophic state indices (TSI(TP)) showed increased trend after the TGR impoundment during the study area, but TSI(TN) and TSI(SD) had no significant changes after the TGR impoundment. The values of TSI(CHL) showed increased trend after the TGR impoundment in S1, and the values of TSI(CHL) did not show obvious changes in S2, S3 and S4 after the TGR impoundment. The values of TSI(TN), TSI(TP) and TSI(SD) show similar spatial variances with the highest value in S4, followed in a descending order by S3, S2 and S1. TSI(CHL) in the S2 and S3 were higher than that in S1 and S4. According to the characteristics of water level, the operational period of the TGR classified into following four stages: stage I (pre-November-April), stage II (May-July), stage III (July-September) and stage IV (September-November). The values of TSI(TN) and TSI(TP) in the Daning River and the TGR mainstream showed similar seasonal variances with the highest value in the stage II and III, followed in a descending order by stage I and IV. The values of TSI(CHL) varied substantially among the four stages, with the highest value in stage III, followed by stage II, IV and I. The trophic state indices differences were getting smaller between the four stages after the TGR impoundment. Using Carlson's two-dimensional approach, deviations of the TSI(S) indicated that factors other than phosphorous and nitrogen limited algal growth and that nonalgal particles affected light attenuation. These findings were further supported by the significant correlation among the values of TSI and hydrological factors.

[Applications of diatom in river health assessment: a review].

Diatom, as a kind of autotrophic photosynthetic eukaryotic algae, is an important primary producer in aquatic ecosystem, and can reflect the average status of water environment. As the bio-indicators of the environment, Nitzschia communis, Navicula minuscula, and Gomphonema parvulum can indicate the eutrophication of waters, whereas Gomphonema angustum, Epithemia adnata, and Diatoma moniliformis can indicate the oligotrophication of waters. Cyclotella bodanica, Neidium affine, and Eunotia exigua are all the eosinophilic species that can indicate waters acidity, Aminutissimum nodusa can indicate water's Cu concentration, and Synedra ulna can indicate the Zn concentration in waters. Some other diatoms can also indicate water' s contamination. This paper reviewed the research progress on the applications of diatom and diatom indices in river health assessment, pointed out the related existing problems, and put forward some future research directions, e. g., further perfect the classification and identification of diatoms, broadly carry out the researches of diatom indices upon different areas and conditions, pay more attention to the screening of diatom bio-integrality indices, and establish a benchmark which suits for the assessment of water quality.

[Temporal and spatial distribution of red tide in Yangtze River Estuary and adjacent waters].

The events of red tide were collected in Yangtze River Estuary and adjacent waters from 1972 to 2009. Based on geographic information system (GIS) analysis on the temporal and spatial distribution of red tide, the distribution map was generated accordingly. The results show: (1) There are three red tide-prone areas, which are outside the Yangtze River estuary and the eastern of Sheshan, Huaniaoshan-Shengshan-Gouqi, Zhoushan and the eastern of Zhujiajian. The red tide occurred 174 times in total, in which there were 25 times covered the area was larger than 1 000 km2. After 2000, the frequency of red tide were significantly increasing; (2) The frequent occurrence of red tide was in May (51% of total occurrence) and June (20% of total occurrence); (3) In all of the red tide plankton, the dominant species were Prorocentrum danghaiense, Skeletonema costatum, Prorocentrum dantatum, Nactiluca scientillans. The red tides caused by these species were 38, 35, 15, 10 times separately.

[Distribution characteristics of the typical persistent organic pollutants (POPs) in Suaeda heteroptera].

The Suaeda heteroptera are widely distributed in intertidal zone, in order to investigate its function in preventing the transfer of the contaminants from land to sea, the levels and the distribution characteristics of organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), decabromodiphenyl ether (BDE209), and polychlorinated biphenyls (PCBs) in Suaeda heteroptera and their associated soils were studied with GC-MS. The results indicated that the levels of these pollutants in Suaeda heteroptera were in the following order: sigma PAHs > OCPs > BDE209 > sigma PCBs (96-1 506 ng/g, 14-577 ng/g, 1.8-33 ng/g, and 399-2 161 pg/g, respectively). The levels of OCPs, PAHs, and PCBs in sediments from Yingkou intertidal zone were higher than that from Donying intertidal zone, however, these pollutants in Suaeda heteroptera leaves were approximately equal, respectively. The distribution of OCPs in Suaeda heteroptera appeared in the following order: stem > root > leaf, and the distribution of PAHs and PCBs in Suaeda heteroptera from Dongying intertidal zone were different from Yingkou intertidal zone, due to the difference of the organic matter content in sediments. The level of BDE209 in sediment from Dongying intertidal zone (19.7 ng/g) was higher than that from Yingkou intertidal zone (2.36 ng/g), and appeared different distribution in Suaeda heteroptera from the two intertidal zones.

[Estuary health assessment using a benthic-index of biotic integrity in Yangtze Estuary and its adjacent waters].

A benthic index of biotic integrity (B-IBI) was developed for application in estuaries health assessment of the Yangtze Estuary and its adjacent waters. Benthic macro-invertebrate samples were collected from 41 stream sites (13 non-degraded stations and 28 degraded stations) in the Yangtze Estuary and its adjacent waters in July, 2005. The analyses of the range of index value distribution, Pearson correlation and judgment ability were performed on fourteen candidate metrics. Six biological metrics were selected for the establishment of B-IBI, which were Shannon-Wiener index, the species number, total density, total biomass, Carapace Animals density percentage and Echinoderms density percentage. B-IBI was obtained by sum up all these indices after which were transformed into a uniform score by using the ratio scoring method. Base on 50 percentile of B-IBI value in reference sites, the criteria of health ranking was determined. The proposed criteria of benthic-index of biotic integrity were as follows: B-IBI > 2.48 was regarded as health, 1.86-2.48 sub-health, 1.24-1.86 fair, 0.62-1.24 poor, and B-IBI < 0.62 very poor. Assessing with these criteria, the results showed that among the 41 sites in Yangtze Estuary and its adjacent waters, 7 sites were health, 2 sites were sub-health, 8 sites were fair, 8 sites were poor and 16 sites were very poor. An independent data set sampled in June of 2006 was used to validate the index, the results indicated that final combined index correctly classified 89% of stations in the validation data set.