Fish assemblage structure in the hypoxic zone in the Changjiang (Yangtze River) estuary and its adjacent waters

Fish assemblage structure in the hypoxic zone in the Changjiang (Yangtze River) estuary and its adjacent waters were analyzed based on data from bottom trawl surveys conducted on the R/V Beidou in June, August and October 2006. Four fish assemblages were identified in each survey using two-way indicator species analysis (TWIA). High fish biomass was found in the northern part, central part and coastal waters of the survey area; in contrast, high fish diversity was found in the southern part of the survey area and the Changjiang estuary outer waters. Therefore, it is difficult to maintain high fishery production when high fish diversity is evenly distributed in the fish community. Fish became smaller and fish size spectra tended to be narrower because of fish species variations and differences in growth characteristics. Fish diversity increased, the age to maturity was reduced and some migrant species were not collected in the surveys. Fish with low economic value, small size, simple age structure and low tropic level were predominant in fish assemblages in the Changjiang estuary and its adjacent waters. The lowest hypoxic value decreased in the Changjiang estuary and its adjacent waters.     

Long-term changes in sedimentary diatom assemblages and their environmental implications in the Changjiang (Yangtze) River estuary,China

Long-term data on diatom assemblages in a sediment core （60 cm） obtained from the Changjiang （Yangtze） River estuary were analyzed in order to assess the environmental changes that took place in the approximately 38 years （as determined by 210pb measurements）, i.e., between 1974 and 2012, of sediment accumulation. From the sediment core, 62 diatom taxa and genera were identified. The diatom biomass in the core generally increased beginning in the mid-1990s （core depth： 35 cm）, accompanied by a shift in the dominant species from Podosira stelliger and two species of Cyclotella （C. stylorum and C. striata） to Paralia sulcata, three species of Thalassiosira （ T. eccentria, I＂. oestrupii, and T. excentrica）, Actinoptychus undulates, and Thalassionema nitzschioides. The changes in both species diversity and abundance suggested that since the 1980s the estuary has undergone extensive eutrophication. This conclusion was supported by the increased proportion of planktonic species, another indicator of high nutrients inputs, in the Changjiang River estuary.     

Spatiotemporal variation in community structure of marine benthic ciliates in the Yellow Sea during and after macroalgal and giant jellyfish blooms

The annual bloom of the green macroalgal Ulva prolifera from May through July since 2008 and another of giant jellyfish Nemopilema nomurai from June through September have been frequent events in the Yellow Sea. However, the patterns of benthic ciliate communities during and after the blooms are still not known. In combination with analyses of benthic environmental factors, we investigated the distribution and community composition of benthic ciliates in the Yellow Sea in July and November 2011. In July, ciliates had high standing crops and diversity in the northern Yellow Sea, and in the inshore area off the southern Shandong Peninsula, where large numbers of green macroalgae accumulated. In November, the abundance, biomass and diversity of ciliates were high in the sea areas off the Shandong Peninsula and Changjiang estuary, where a large quantity of jellyfish occurred in August. Neither the abundance nor the biomass had significant difference between seasons, or between different compartments of the Yellow Sea. The species number, and both Margalef and Shannon-Wiener indices of ciliates were all significantly higher in November than in July. In both seasons, prostomateans and karyorelicteans consistently constituted the first and second most important ciliate groups in biomass; and carnivorous ciliates constituted the primary feeding type in terms of biomass as well as species richness, followed by bacterivores, algivores and omnivores. Compared with that in June 2007 when no macroalgae occurred, the percentage of small-sized bacterivores (e.g. Metacystis spp., Euplotes spp. and scuticociliates) increased in July 2011. The proportion of carnivorous ciliates increased in November, and this increased dominance of carnivorous ciliates may be a response to the increase in predominance of heterotrophic nanoflagellates, which might in turn be ascribed to an effect of green macroalgal and giant jellyfish blooms in the Yellow Sea.     

Seasonal changes in phytoplankton biomass and dominant species in the Changjiang River Estuary and adjacent seas: General trends based on field survey data 1959–2009

The characteristics of seasonal variation in phytoplankton biomass and dominant species in the Changjiang River Estuary and adjacent seas were discussed based on field investigation data from 1959 to 2009. The field data from 1981 to 2004 showed that the Chlorophyll-a concentration in surface seawater was between 0.4 and 8.5 μg dm-3. The seasonal changes generally presented a bimodal trend, with the biomass peaks occurring in May and August, and Chlorophyll-a concentration was the lowest in winter. Seasonal biomass changes were mainly controlled by temperature and nutrient levels. From the end of autumn to the next early spring, phytoplankton biomass was mainly influenced by temperature, and in other seasons, nutrient level(including the nutrient supply from the terrestrial runoffs) was the major influence factor. Field investigation data from 1959 to 2009 demonstrated that diatoms were the main phytoplankton in this area, and Skeletonema costatum, Pseudo-nitzschia pungens, Coscinodiscus oculus-iridis, Thalassinoema nitzschioides, Paralia sulcata, Chaetoceros lorenzianus, Chaetoceros curvisetus, and Prorocentrum donghaiense Lu were common dominant species. The seasonal variations in major dominant phytoplankton species presented the following trends: 1) Skeletonema(mainly S. costatum) was dominant throughout the year; and 2) seasonal succession trends were Coscinodiscus(spring) →Chaetoceros(summer and autumn) → Coscinodiscus(winter). The annual dominance of S. costatum was attributed to its environmental eurytopicity and long standing time in surface waters. The seasonal succession of Coscinodiscus and Chaetoceros was associated with the seasonal variation in water stability and nutrient level in this area. On the other hand, long-term field data also indicated obvious interannual variation of phytoplankton biomass and community structure in the Changjiang River Estuary and adjacent seas: average annual phytoplankton biomass and dinoflagellate proportion both presented increased trends during the 1950 s-2000 s.     

Seasonal variability of phytoplankton community structure in relation to different nitrogen-phosphorus ratios in the southern coastal waters of Zhejiang, China

With the rapid development of economy and increase of population in the drainage areas, the nutrient loading has increased dramatically in the Changjiang estuary and adjacent coastal waters. To properly assess the impact of nutrient enrichment on phytoplankton community, seasonal microcosm experiments were conducted during August 2010–July 2011 in the coastal waters of Zhejiang Province. The results of the present study indicated that the chl a concentration, cell abundance, diversity indices, species composition and community succession of the phytoplankton varied significantly with different N/P ratios and seasons. Higher growth was observed in the 64:1 (spring), 32:1 (summer), 16:1 (autumn) and 128:1, 256:1 (winter) treatments, respectively. The values of Shannon-Wiener index (H′) and Pielou evenness index (J) were lower in the 8:1 and 16:1 treatments in autumn test, while H′ value was higher in the 128:1 and 8:1 treatments in winter test. A definite community succession order from diatoms to dinoflagellates was observed in the autumn and winter tests, while the diatoms dominated the community throughout the culture in the spring and summer tests.     

Interdecadal variability in ecosystem health of Changjiang(Yangtze) River estuary using estuarine biotic integrity index

Ichthyoplankton samples were collected from Changjiang(Yangtze) River estuary in May 2016.Species composition was studied by DNA barcoding and morphological identification.To make better use of the estuarine biotic integrity index(EBI) to assess the ecosystem health of the Changjiang River estuary over the past 30 years,we collected the data of a spring ichthyoplankton survey in the estuary from 1986 to 2016.The EBI was calculated using 12 evaluation metrics,namely,the number of total ichthyoplankton species,estuarine spawning species,estuarine nursery species,estuarine resident species,benthic species,pelagic species,and intolerant species,and the percentages of tolerant species,omnivores,insectivores,carnivores,and natural hybrid species.EBI was calculated in spring in four periods(1986,1999,2007,and 2016) by assigning points of 1,3 or 5,giving values of 50,38,36,and 32,respectively,corresponding to "Good", "Fair-Poor", "Fair-Poor",and "Poor" EBI levels,respectively.Changes in species composition were the primary reason for the significant decreases in EBI between 1986 and 1999,and for the large differences between 1986 and 2007 and between 2007 and 2016.The changes in species composition were influenced by declines in ichthyoplankton species,pollution sensitive species,estuarine nursery species and estuarine sedentary species,and an increase in pollution re sistant species.An analysis of EBI interdecadal variability showed that the health status of the Changjiang River estuary ecosystem over the last 3 0 years first declined and then stabilized at a lower level.This result further settled the argument for urgent protection and restoration of the Changjiang River estuary.     

Phytoplankton assemblage structure shaped by key environmental variables in the Pearl River Estuary,South China

Spatial distribution and temporal dynamics of phytoplankton community and their relationships with environmental factors were studied in the Pearl River Estuary (PRE), South China, in three seasons. Salinity was considered as the key environmental variable controlling horizontal distributions of phytoplankton community composition. A transition from dominance of freshwater diatoms (Aulacoseira granulata and A. granulata v. angustissima) to estuarine species (Skeletonema costatum and Pseudonitzschia delicatissima) was observed in the high flow season (summer) along the estuary gradient; in the low flow season (spring), the inner estuary was relatively homogeneous and some typical estuarine species could be found near the river mouth. In the normal flow season (autumn), a potentially toxic bluegreen species, Microcystis spp. was predominant in the middle reaches of the estuary, which should be seeded from upstream and transported downstream by river discharges. Phytoplankton abundance was negatively correlated with suspended solid content and nutrient concentration in the PRE, suggesting that turbidity and nutrient availability were the crucial factors regulating the algal biomass. Phytoplankton abundance in the outer estuary was enhanced by increasing irradiance and continued to be enhanced until phosphorus-limitation.     

Response of rotifer community to environmental changes in five shallow lakes in the middle reach of Changjiang River,China

We evaluated the response of a rotifer community to environmental changes in five shallow lakes in the middle reach of the Changjiang （Yangtze） River in summer and autumn 2010. These five lakes differed in trophic status and rotifer community structure. Twenty-nine rotifer species were collected, of which Keratella cochlearis, Polyarthra dolichoptera, and Trichocerca elongate were dominant. The mean density, Shannon-Wiener diversity, and equitability among the five lakes differed significantly （P〈0.05）. The mean rotifer density was positively correlated with trophic state. The diversity was higher in lakes with high macrophyte coverage. The composition of rotifer species was closely associated with the trophic gradient. Five environmental variables, Secchi depth, conductivity, TN, NHa-N, and TP, significantly affected the composition of rotifer species. Keratella quadrata, Brachionus calyciflorus, and B. forficula were more common in eutrophic conditions. Our results suggest that eutrophication has a significant influence on the rotifer community structure and highlight the potential for using rotifer community structure as an indicator of trophic status in subtropical lakes.     

Impact factors on distribution and characteristics of natural plant community in reclamation zones of Changjiang River estuary

To identify impact factors on the distribution and characters of natural plants community in reclamation area, with survey data from 67 plant quadrats in July 2009, soil properties data from 216 sampling points in April 2009, and TM (30 m) data in 2006, the composition and characteristics of natural plants community in different time of the Fengxian area in the Changjiang (Yangtze) River estuary were analyzed with two-way indicator species analysis (TWINSPAN), multivariate analysis of variance (MANOVA), detrended canonical correspondence analysis (DCCA) and canonical correspondence analysis (CCA). The results show that: 1) The plant communities in the reclaimed area are mainly mesophytes and helophytic-mesophytic transitional communities, showing a gradient distribution trend with the change in reclamation years. Species richness (MA), species diversity (H) and above-ground biomass also increase with the increase of reclamation years. Nevertheless, they appear to decline slightly in the middle and late reclamation period (> 30 years). 2) With the rise in land use levels, the changes in species richness and species diversity tend to increase at first and then decrease; species dominance (D), however, tends to decline; and above-ground biomass increases slightly. 3) The distribution of the plant community is mainly influenced by the following factors: land use levels (R = 0.55, p < 0.05), soil moisture (R = 0.53, p < 0.05), soil salinity (R = 0.43, p < 0.05) and reclamation time (R = 0.40, p < 0.05).     

SPECIES COMPOSITION, HORIZONTAL DISTRIBUTION AND SEASONAL SUCCESSION OF PHYTOPLANKTON IN THE CHANNEL FROM DONGTING LAKE TO THE CHANGJIANG RIVER, CHINA

The species composition, horizontal distribution and seasonal succession of the phyto-plankton at five sampling stations in the channel between Dongting Lake and the Changjiang River, China were studied from May 1995 to December 1997. A total of 416 taxa were observed; diatoms comprised the most diverse taxonomic group representing 58.2 % of the total species. The β-mezotrophic indicators were 92 taxa or 22 % of the total, the a-mezotrophic or α, β-eutrophic indicators decreased distinctly to 20 taxa or 4.8 % of the total. The species number and composition of various phyla were approximately similar at Stations 1, 2, 3 and 4, but at Station 5 the number of species was the minimum and the ratio of diatoms to total phytoplankton in the number of species was the highest. In seasonal succession of the phytoplank-ton species, the number was the highest in May and June, lower in December, January, March and July in the channel. The dominant species were different in different months. The ratio of diatoms species number to blue green algae and green algae species number diminished gradually from winter to summer and autumn, and then increased gradually from autumn to winter and early spring in the annual cycle. Margalef, Simpson and Shannon—Weaver diversity indices changed in different months, their values were higher in winter, lower in summer. Nygaard‘s diatoms quotients were lower in winter, then in spring and autumn, higher in summer. These results indicated that the water quality was the best in winter, better in spring and autumn than in summer. The relationship between the structure of the phytoplankton communi-ty and the water environmental quality was discussed.     

Macrobenthic community in the Xiaoqing River Estuary in Laizhou Bay, China

The macrobenthic community of the Xiaoqing River Estuary and the adjacent sea waters was investigated in May and November 2008, August 2009, and May and September 2010, respectively. A total of 95 species of macrobenthos were identified in the five cruises and most of them were polychaetes (46.39%), mollusks (28.86%) and crustaceans (20.62%). The Shannon-Wiener index of macrobenthos was lower than 2 in 67% sites. Along the stream channel, estuary and the coastal waters, the species of polychaetes reduced gradually, while the abundance increased at first and then decreased. The abundance was the biggest at regions with salinity of 5–20 in the estuary. The species and abundance of mollusks and crustaceans increased gradually. As for seasonal distribution, the species, abundance and biomass were higher in spring and lower in summer and autumn. Contemporaneously compared with Laizhou Bay and Yellow River Estuary, the species of macrobenthos appeared in the Xiaoqing River Estuary were much less, while the percentage of polychaetes was higher. Abundance and biomass were higher in Xiaoqing River estuary, then consequently followed by Laizhou Bay and Yellow River Estuary. The dominant species in Xiaoqing River Estuary was polychaete, and Layzhou Bay mollusk. The community structure characteristics of macrobenthos in the Xiaoqing River Estuary revealed a significant pollution status in this region.     

Seasonal Changes in Phytoplankton Biomass and Dominant Species in the Changjiang River Estuary and Adjacent Seas：General Trends Based on Field Survey Data 1959-2009

The characteristics of seasonal variation in phytoplankton biomass and dominant species in the Changjiang River Estuary and adjacent seas were discussed based on field investigation data from 1959 to 2009. The field data from 1981 to 2004 showed that the Chlorophyll-a concentration in surface seawater was between 0.4 and 8.5 ktg dm-3. The seasonal changes generally presented a bimodal trend, with the biomass peaks occurring in May and August, and Chlorophyll-a concentration was the lowest in winter. Seasonal biomass changes were mainly controlled by temperature and nutrient levels. From the end of autumn to the next early spring, phytoplankton biomass was mainly influenced by temperature, and in other seasons, nutrient level （including the nutrient supply from the terrestrial runoffs） was the major influence factor. Field investigation data from 1959 to 2009 demonstrated that dia- toms were the main phytoplankton in this area, and Skeletonerna costatum, Pseudo-nitzschia pungens, Coscinodiscus oculus-iridis, Thalassinoema nitzschioides, Paralia sulcata, Chaetoceros lorenzianus, Chaetoceros curvisetus, and Prorocentrum donghaiense Lu were common dominant species. The seasonal variations in major dominant phytoplankton species presented the following trends： 1） Skeletonema （mainly S. costatum） was dominant throughout the year; and 2） seasonal succession trends were Coscinodiscus （spring） →Chaetoceros （summer and autumn） → Coscinodiscus （winter）. The annual dominance of S. costatum was attributed to its environmental eurytopicity and long standing time in surface waters. The seasonal succession of Coscinodiscus and Chaetoceros was associated with the seasonal variation in water stability and nutrient level in this area. On the other hand, long-term field data also indicated obvious interannual variation of phytoplankton biomass and community structure in the Changjiang River Estuary and adjacent seas： average annual phytoplankton biomass and dinoflagellate proportion both presented inc     

Primary fish survey in the Huanghe River estuary

The survey in the Huanghe River estuary indicated that the 85 fish species found there comprised three faunal elements: warm-water species (29.4%), warm-temperate species (55.3%) and cold-temperate species (15.3%). The seasonal changes of fish species, density and biomass are obvious. The total biomass is highest (7 699t) in August and lowest (489 t) in January.Setipinna taty has mean density of 9 278 indiv/km², and is the most important species constituting 25.5% of the total weight of fish caught.Trichiurus haumela was a dominant species in the 1950s, but no one was caught in this survey. There were obvious changes of the dominant fish species during the recent three decades. The demersal fish biomass has dropped greatly to only 1/10 in over 50 years since 1930. Contribution No. 2210 from the Institute of Oceanology, Academia Sinica.     

Zooplankton Distribution in Coastal Water off Gopalpur,North-Western Bay of Bengal

An interannual study on zooplankton abundance, biomass, and species composition was carried out during different seasons in two local coastal water types off Gopalpur, north-western Bay of Bengal. Although, Type-1 was observed with higher zooplankton abundance in comparison to Type-2, pattern of variation followed similar seasonal trends in both water types during individual years. Well pronounced seasonality was observed in zooplankton distribution. Zooplankton community was composed of 217 holoplankton and 22 meroplankton. The holoplankton community was predominated by copepod in terms of species diversity and abundance followed by hydrozoa, tintinnida, malacostraca, gastropoda, chaetognatha and chordata. The meroplankton were represented by larval forms viz. bivalve veliger, brachyuran zoea larvae, caridean larvae, copepod nauplii, fish egg and gastropod veliger. Dominance of copepod species viz. Acrocalanus longicornis, Paracalanus aculeatus and Paracalanus parvus were observed frequently in both water types. The species richness was higher in Type-1 in comparison to Type-2 during both the years. Salinity regimes and availability of phytoplankton prey influenced the distribution and species composition of zooplankton assemblage.     

Spatial and seasonal pattern of macrozoobenthic assemblages and the congruence in water quality bioassessment using different taxa in artificial Mingzhu Lake in Shanghai

The spatial and seasonal pattern of macrozoobenthic structure and its relationship with environmental factors were studied from July 2006 to April 2008 in Mingzhu Lake, Chongming Island, Shanghai at the Changjiang River mouth. The congruences in water quality bioassessment based on diversity and biotic indices and using different taxonomic categories were also explored to find the best assessment method of water quality for the lake. All major structural characteristics of macrozoobenthic community, including species composition, abundance, biomass and four biomass-based diversity indices (Shannon’s diversity, Simpson’s diversity, Pielou’s evenness and Simpson’s evenness index) fluctuated significantly in season but in space. The above four abundance-based diversity indices plus abundance-based Margalef’s richness index did not display significant spatial variations; and significant seasonal differences were found in three indices only. Water temperature was the key environmental factor responsible for macrozoobenthic spatio-temporal distribution patterns. Water quality assessed by Shannon’s index (H _a′) and biological pollution index (BPI) rather than the other four biotic indices were consistent with those by trophic state index (TSI). Results from chironomids and oligochaetes did not always agree to those from the whole community when H _a′ or Hilsenhoff biotic index was applied to bioassessment. Therefore, combining multiple indices and avoiding a single taxonomic category to assess water quality are strongly recommended and in Mingzhu Lake using a mixture of H _a′ and BPI will ensure the most effective investigation of water quality. Our results also show that the main structural characteristics of macrozoobenthic communities in the small lake may display consistent spatial patterns.     

Zooplankton spatial and diurnal variations in the Changjiang River estuary before operation of the Three Gorges Dam

Estuarine plankton communities can serve as indicators of ecosystem modification in response to anthropogenic influences. The main objectives of this study were to describe the spatial distribution and diurnal variability in zooplankton abundance and biomass over almost entire salinity gradient of the Changjiang (Yangtze) River estuary and to provide a background reference for future studies. To accomplish this, data were collected from 29 stations in the estuary from May 19 to 26, 2003, including two anchor stations. The spatial and diurnal variations in zooplankton characteristics, i.e. abundance, biomass, and gross taxonomic composition, were examined. Generally, both the abundance and biomass gradually increased seaward and presented distinct spatial variations. In addition, the spatial data revealed a significant correlation between abundance and biomass; however, there was no significant correlation between abundance and biomass for the diurnal data. Although the zooplankton composition indicated distinct spatial differences in terms of dominant groups, copepods accounted for >50% of the total zooplankton abundance in most regions and times. Three zooplankton assemblages were recognized through hierarchical cluster analysis. These assemblages existed along the salinity gradient from fresh water to seawater, and their positions coincided with those of the three principal water masses in the estuary. The assemblages were classified as: (1) true estuarine, (2) estuarine and marine, and (3) euryhaline marine, which were characterized by the copepods Sinocalanus dorrii, Labidocera euchaeta, and Calanus sinicus, respectively. Both spatial and diurnal data indicated that there was no significant correlation between zooplankton abundance/biomass and depth-integrated phytoplankton abundance.     

Records of bulk organic matter and plant pigments in sediment of the “red-tide zone” adjacent to the Changjiang River estuary

Cultural eutrophication caused by nutrient over-enrichment in coastal waters will lead to a cascading set of ecosystem changes and deleterious ecological consequences,such as harmful algal blooms(HABs) and hypoxia.During the past two decades since the late 1990s,recurrent large-scale HABs(red tides)and an extensive hypoxic zone have been reported in the coastal waters adjacent to the Changjiang River estuary.To retrieve the history of eutrophication and its associated ecosystem changes,a sediment core was collected from the "red-tide zone" adjacent to the Changjiang River estuary.The core was dated using the~(210)Pb radioisotope and examined for multiple proxies,including organic carbon(OC),total nitrogen(TN),stable isotopes of C and N,and plant pigments.An apparent up-core increase of OC content was observed after the 1970s,accompanied by a rapid increase of TN.The concurrent enrichment of δ~(13)C and increase of the C/N ratio suggested the accumulation of organic matter derived from marine primary production during this stage.The accumulation of OC after the 1970 s well reflected the significant increase of primary production in the red-tide zone and probably the intensification of hypoxia as well.Plant pigments,including chlorophyll a,p-carotene,and diatoxanthin,showed similar patterns of variation to OC throughout the core,which further confirmed the important contribution of microalgae,particularly diatoms,to the deposited organic matter.Based on the variant profiles of the pigments representative of different microalgal groups,the potential changes of the phytoplankton community since the 1970s were discussed.     

Temporal and spatial variations of bacterial community compositions in two estuaries of Chaohu Lake

The distinctive estuary hydrodynamics and nutrient input make the estuary ecosystem play a key role in lake ecosystems. The Nanfei River and Zhaohe River are two main inlets of Chaohu Lake, Anhui, East China. We selected estuaries of the two rivers as representative areas to study temporal and spatial changes of bacterial communities. In August (summer) and November (autumn) 2016 and February (winter) and May (spring) 2017, 16 water and sediment samples were collected from the estuaries. Physicochemical characteristics indicate significant differences in the nutritional status and eutrophication index of the estuaries due mainly to organic input. Examination of the number of operational taxonomic units, the diversity index, the community composition, and redundancy analysis revealed the following. First, the existence of varying degrees of seasonal differences in the distribution of almost all bacteria. In addition, the species diversity in the sediment samples was higher than that in the water samples, and the dominant species differed also among these samples. Second, a large number of unknown genera were detected, especially in the sediment samples, such as unclassified Xanthomonadales incertae sedis, unclassified Anaerolineaceae, and unclassified Alcaligenaceae. Last, TP, TN, and TOC were the main influential factors that affected the bacterial community structure.     

Temporal and spatial variations in the distribution of macroalgal communities along the Yantai coast,China

To explore the impact of environmental variables on macroalgal communities, their temporal and spatial distributions were examined along the Yantai coast, China between April 2010 and March 2011. Macroalgae sampling was conducted monthly at four sites along the coast： Jiahe River estuary, Zhifu Island, Fisherman＇s Wharf, and Yangma Island. The species composition and abundance, and their relationship with environmental variables were assessed. Along the Yantai coast, 35 macroalgae species were identified, including 24 Rhodophyta spp., 7 Chlorophyta, and 4 Phaeophyta spp. Highest species numbers were recorded in the summer at all sampling sites, except in the Jiahe River estuary. Macroalgae biomass was the greatest in the summer. Year-round, the highest species number and dry biomass recorded at Fisherman＇s Wharf and Yangma Island was attributed to the substrate type. In summer, Ulva pertusa Kjellman was the dominant species identified along the Yantai coast, which indicates a risk ofmacroalgae blooms. Our results show that seawater temperature and nutrients appear to significantly affect the temporal and spatial patterns of macroalgal abundance along the Yantai coast. The effects of environmental variables on the macroalgae on the Yantai coast need further study.     

PRIMARY FISH SURVEY IK THE HUANGHE RIVER ESTUARY

The survey in the, Huanghe River estuary indicated that the 85 fish species found there comprised three faunal elements: warm-water species (29.4%), warm-temperate species (55.3%) and cpld-temperate species. (15.3%). The seasonal changes of fish species, density and bipmass are obvious. The total biomass is highest (7699t) in August and lowest(489 t) in January. Setipinna taty has mean density of 9278 indiv/km2, and is the most important species constituting 25.5% of the total weight of fish caught. Trichiurus haumela was a dominant species in the 1950s, but no one was caught in this survey. There were obvious changes of the dominant fish species during the recent three decades. The demersal fish biomass has dropped greatly to only 1/10 in over 50 years since 1930.