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Chao, M.; Shi, Y.; Quan, W., and Shen, X., 2015. Distribution of macrocrustaceans in relation to abiotic and biotic variables across the Yangtze River Estuary, China In this article, we report on a study of the spatial and seasonal distribution of macrocrustaceans and reveal the correlation between macrocrustacean community and environmental variables in the Yangtze River Estuary, China. A total of 44 species belonging to 21 families were identified during sample collection in May, August, and November 2010 and February 2011. Species richness of four survey trips showed significant differences among seasons and zones. The most frequent species identified were Neoeriocheir leptognathus (M.J. Rathbun, 1913) in February and May; Palaemon gravieri (Yu, 1930) in August; and Exopalaemon annandalei (Kemp, 1917) in November. The mean macrocrustacean abundance in May 2010, August 2010, November 2010, and February 2011 was 24.94, 19.82, 29.46, and 17.14 individuals/1000 m2, respectively. The distribution of macrocrustaceans demonstrated a significant variation among seasons and zones based on PERMANOVA analysis. In terms of the value of species dominance, P. gravieri was the most dominant species throughout the study period, which composed 27.4% of the total specimens obtained. The distribution of macrocrustacean abundance in relation to biotic and abiotic variables was studied by multivariate analysis of macrocrustaceans using cluster and canonical correspondence analyses. These results demonstrated three typical classifications of communities and a significant relationship between macrocrustaceans and environmental variables. Salinity was the determining factor for spatial distribution of species and temperature for species occurrence on the entire estuarine scale. Additionally, biotic variables such as abundance of Polychaeta, abundance of primary production, and abundance of estuarine resident fishes also found significant variables that correlated with the abundance of macrocrustaceans in the Yangtze River Estuary. The study on relationship between macrocrustaceans and environmental variables provided baseline information for future ecological risk assessment in the Yangtze River estuary. [ABSTRACT FROM AUTHOR]

The annual variability of ichthyoplankton in the Yangtze River estuary, located at the junction of the East China Sea and the Yellow Sea, on the continental shelf at the western rim of the Pacific Ocean, was studied using vertical tows at twenty stations from August 2002 to August 2009. Basic oceanographic parameters such as temperature and salinity were also measured to evaluate their relationship to the abundance of ichthyoplankton. The eggs or larvae of a total of 34 fish species were present in the samples. Only 8 species were found to occur during every year. Engraulis japonicus and Stolephorus commersonii eggs, as well as Coilia mystus and Stolephorus commersonii larvae, were highly abundant during this period. Additionally, water storage in the Three Gorges Reservoir, which began in June 2003, had significant effects on the abundance of estuarine species, as well as on the composition and diversity of ichthyoplankton; this became evident when these values were compared to the findings from 2002. The number of species (species richness) and abundance of each species varied among the stations relative to the salinity in the estuary during the study period. [ABSTRACT FROM AUTHOR]

Oysters can create reefs that provide habitat for associated species resulting in elevated resident abundances, lower mortality rates, and increased growth and survivorship compared to other estuarine habitats. However, there is a need to quantify trophic relationships and transfer at created oyster reefs to provide a better understanding of their potential in creating suitable nekton habitat. Stable isotope analyses (δC and δN) were conducted to examine the organic matter sources and potential energy flow pathways at a created intertidal oyster ( Crassostrea ariakensis; hereinafter, oyster) reef and adjacent salt marsh in the Yangtze River estuary, China. The δC values of most reef-associated species (22 of 37) were intermediate between those of suspended particle organic matter (POM) and benthic microalgae (BMI), indicating that both POM and BMI are the major organic matter sources at the created oyster reef. The sessile and motile macrofauna colonizing the reef make up the main prey of transient nekton (e.g., spotted sea bass, Asian paddle crab, and green mud crab), thus suggesting that the associated community was most important in supporting higher trophic levels as opposed to the direct dietary subsidy of oysters. The created oyster reef consistently supported higher trophic levels than the adjacent salt marsh habitat due to the dominance of secondary consumers. These results indicate that through the provision of habitat for associated species, created oyster reefs provide suitable habitat and support a higher average trophic level than adjacent salt marsh in the Yangtze River estuary. [ABSTRACT FROM AUTHOR]

Abstract: An intertidal oyster reef (∼260ha) was created by planting hatchery-reared seed oysters (Crassostrea rivularis) on an artificial concrete modular reef in the Deepwater Navigation Channel Regulation Project of the Yangtze River estuary. We examined the development of reef communities (oyster, barnacle and motile epibenthic macrofauna), characterized nekton use and assessed the habitat value of the constructed reef. The C. rivularis oyster population showed a rapid exponential increase with time and reached maximum density (3410±241ind./m2) and biomass (3175±532g/m2) after one year of restoration. The barnacle Balanus albicostatus was the most abundant sessile macrofauna and had a significantly greater density in the high intertidal zone than in the low intertidal zone (P <0.05). The reef also supported diverse motile epibenthic macrofauna (11 mollusks, 11 crustaceans, 4 annelids and 2 fishes), and the reef-associated communities were numerically dominated by Neanthes japonica, Perinereis aibuhitensis, Nerita yoldi and Littorinopsis intermedia. A total of 50 nekton species (31 fishes, 9 shrimps and 10 crabs) utilized the constructed intertidal oyster reef, and grass shrimp Palaemon spp. dominated the nekton communities in term of abundance. Since the constructed intertidal oyster reef supports a variety of reef communities and abundant nektons, it should be recognized as an important and protective fish habitat in the Yangtze River estuary. [Copyright &y& Elsevier]