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Successful and sustainable oyster reef restoration relies on suitable substrate material that is both readily available and encourages long-term recruitment and growth of oysters. China is increasing oyster reef restoration, however, little information is available to guide sustainable practices under local conditions and on ecologically relevant time scales. This study examines the effects of four substrate materials (oyster shell, clam shell, limestone, and clay brick) on community demographics for the Kumamoto oyster (Crassostrea sikamea) and associated macrofauna over a 3-y period in Xiangshan Bay, China. During the first 2 y, oyster and clam shell had similarly high recruitment and abundance of live oysters when compared with limestone and clay bricks. All substrate types, however, ended up with similar oyster abundances and size distributions after 3 y. Similar trends existed with regard to structural complexity (weight and volume) of substrate and any differences at the onset of the experi...

The Suminoe oyster Crassostrea ariakensis and the Kumamoto oyster Crassostrea sikamea coexist and are habitat-forming ecosystem engineers in the Yangtze River estuary and its adjacent coasts. To date, little quantitative information is available on the intertidal zonation patterns of these two oysters within their native range or on the related mechanisms generating these spatial patterns. This study first carried out field surveys and laboratory experiments to explore the vertical zonation patterns of the two oysters in the intertidal habitats of northern Hangzhou Bay, assess the roles of abiotic (aerial exposure stress) and biotic (larval distribution, recruitment, and competition) factors in regulating vertical zonation and understand their driving mechanisms. At the study site, C. sikamea dominated the higher intertidal zone (approximately 6.7 h and 56% emersion/12 h tidal cycle), whereas C. ariakensis occupied the three deeper intertidal zones (mid, mid-low, and low intertidal). Mean aerial exposures of 56% and 42% represented the optimal growth zones and the lower limits of C. sikamea, respectively. The growth boundary of the two oysters was located in the intertidal zone that was exposed 42% of the time. The area with the highest C. ariakensis densities (the optimal growth zone) was the mid-low intertidal (mean: 3.0 h and 25% emersion/tidal cycle). In a laboratory 72-h aerial exposure experiment, the percentage of water loss was significantly greater for C. ariakensis than for C. sikamea after 24 h (P 0.05). Twenty-two individuals among the 30 oyster recruits (73%) in the high intertidal region were identified as C. sikamea, and six recruits (20%) were identified as C. ariakensis. All 36 recruits (100%) in the low intertidal region were identified as C. ariakensis. It was concluded that the differential larval distribution, settlement, and post-settlement mortality along the intertidal elevation gradients served as a mechanism for vertical zonation of these two oyster species.

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 o...

Oysters and the reefs they build are being recognized and restored increasingly for the broad suite of ecosystem services they can provide. However, surprisingly little effort has been devoted to documenting the outcomes of such restoration or creation projects through time, or to comparing projects from different regions. In this study, we examined the oyster (Crassostrea ariakensis) and benthic macrofaunal development on a created intertidal oyster (Crassostrea ariakensis) reef along a salinity and exposure (vertical position on reef) gradient 5 y after creation in the Yangtze River estuary, China. Three years after reef creation, sustainable oyster populations were established successfully and market-size oysters accounted for more than 24% of the total reef cover, with mean abundances ranging from 95–225 adult oysters/m2. Associated community metrics (species richness, abundance. and biomass) of benthic macrofauna showed generally increasing trends with reef development during the 5-y period;...

Correlation of heavy metals in the tissues of typical organisms (i.e., fishes and crabs) and those in their living environments (i.e., surface water, bottom water, and sediment) in Yangtze River Estuary has been qualitatively and quantitatively analyzed. Metal levels followed the trend: sediments > Eriocheir sinensis > Eriocheir leptognathus > benthic fish > pelagic fish > bottom water > surface water. Tissues in fishes and crabs of different species and sizes had diverse metal bioaccumulation characteristics, which was significantly affected by environment factors and their living habits. Metal levels in legs of crabs, and heads and skins of fishes showed significant correlations with those in their living environments. Collichthys lucidus is an effective bioindicator for assessing metal levels in water. No significant health risk was identified by the estimated daily intake and target hazard quotients analyses.

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 (δ13C and δ15N) 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 δ13C 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.

The effects of invasive cordgrass Spartina alterniflora on burrowing crab communities in the salt marshes of the Yangtze River Estuary, China, were studied. Crab abundance, distribution and diets were compared in native Phragmites australis and invasive S. alterniflora stands. Spartina- invaded stands had 42% higher crab density than did native P. australis stands, largely because 2 dominant grapsoid crabs, Helice tientsinensis and Chiromantes dehaani, thrived in S. alterniflora stands. Sediment grain size, water content and vegetation stem height were the main factors corre- lated with crab distributions. Crab diet analyses revealed that crab stomach fullness was similar in stands of different plant species, indicating that in Spartina-invaded stands crabs can find compati- ble food quantity as in native plant stands. Both H. tientsinensis and C. dehaani from S. alterniflora stands had significantly higher δ 13 C values than those from P. australis stands, suggesting that the crabs consumed S. alterniflora in the invasive marshes. This non-selective feeding may be driving the success of H. tientsinensis and C. dehaani in invasive Spartina stands.

To test whether invasive Spartina alterniflora marshes were functionally equivalent to native Scirpus mariqueter marshes, the present study used bottomless lift nets (20 m2) during 12 high-tide events from August to October 2008 to compare nekton densities and biomass between the two marsh types in the Dongtan wetland. A total of eight species of fish, two species of shrimp, and three species of crab were collected. So-iny mullet Chelon haematocheilus, keeled mullet Liza carinata, Asian freshwater goby Acanthogobius ommaturus, and ridge-tail prawn Exopalaemon carinicauda dominated samples from the two marsh types and accounted for over 90% of the total catch. There were significantly greater densities and biomass (p 0.05) between the two marsh types were observed for densities and biomass of any species or total nekton in September and October 2008. Non-metric multidimensional scaling ordination did not show clear separation of samples between the two marsh types (r = 0.071, p = 0.159). Furthermore, there were no habitat-specific differences (p > 0.05) in the size distributions of the three numerically dominant species (C. haematocheilus, L. carinata, and A. ommaturus). We concluded that S. alterniflora marshes were utilized by nekton in a fashion similar to their utilization of native S. mariqueter marshes under similar physical conditions.

Stable isotope values, δ13C and δ15N, were determined for four primary producers and 19 dominant consumers in a small artificial lagoon located in Hangzhou Bay. Based on these results the major pathways for energy flow and trophic structure of the artificial lagoon ecosystem were characterized. The mean δ13C values for the 19 consumers ranged from −22.99‰ to −14.24‰. Apart from so-iny mullet Liza haematocheila, the other 18 consumers had intermediate δ13C values between those of epibenthic microalgae and particulate organic matter (POM). The results of a multiple source linear mixing model (IsoSource model) indicated that 50% or more of the organic carbon in the tissues of most consumers was derived from epibenthic microalgae. This indicated that these primary producers were the main food source fueling the lagoon food web. The mean δ15N values for the 19 consumers varied between 4.93‰ and 12.97‰ and indicated four trophic levels in the lagoon. Four macroinvertebrates and zooplankton represented the primary consumers, whilst the other 14 consumers occupied the secondary and tertiary consumer levels. The 19 consumers were divided into three trophic guilds (detritivores/suspension feeders, omnivores and carnivores).

Spatial and temporal distributions of nutrients (N and P) and heavy metals (Cu, Zn, Pb and Cd) in the intertidal sediments at Dongtan wetland of the Changjiang River (Yangtze River) Estuary were examined by laying one transect running seaward to landward during January, April, June, August and October of 2005. Total nitrogen (TN) and heavy metal concentrations in the intertidal sediment showed an increasing trend from open bare flat to the high marsh, with the maximum concentrations in the high marsh and the minimum values in open bare flat. In contrast, sediment total phosphorus (TP) concentrations changed little among sampling sites. One-way ANOVA found that there were significantly temporal variations of nutrients and heavy metals concentrations in the intertidal sediment (P < 0.05). The concentrations of heavy metals generally showed an increasing trend from January to October. As compared with other large estuaries, heavy metal contamination in the intertidal sediment of the Changjiang River Estuary was relatively low.

Fish communities in a (third-order) intertidal creek in Dongtan marsh in the Changjiang (Yangtze) River estuary were investigated seasonally for one year. A total of 1 996 fish specimens (10 967.8 g) comprising 26 species and 15 families were collected. Abundances of fish communities in the intertidal salt marsh creek were primarily dominated by Boleophthalmus pectinirostris (19.8%), Collichthys lucidus (18.6%), Periophthalmus magnuspinnatus (18.2%), Liza haematocheilus (17.9%), and secondarily by Mugilogobius abei (8.5%), L. carinatus (7.2%), Odontamblyopus lacepedii (4.3%), and Acanthogobius ommaturus (3.9%); another 18 species were present only occasionally. Non-MDS ordination and SIMPER analysis indicated that there were two fish communities in the intertidal salt marsh creek. In spring, the communities were dominated by B. pectinirostris, P. magnuspinnatus, C. lucidus and M. abei; in summer, autumn, and winter by L. haematocheilus, L. carinatus, A. ommaturus and O. lacepedii. Some species showed strong habitat selection; L. carinatus and P. magnuspinnatus were distributed mainly in the upper and middle creek, while B. pectinirostris, M. abei and O. lacepedii inhabited the middle and lower creek. The study indicated that the salt marshes of the Changjiang River estuary are an important nursery and feeding habitat for many fishes and should be protected.

An intertidal oyster reef (∼260 ha) 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 ± 241 ind./m 2 ) and biomass (3175 ± 532 g/m 2 ) 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 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.

Tidal marshes provide nursery habitats for many commercial nektonic species; thus, determining trophic linkages between tidal marshes and aquatic consumers is important for sustain- ing fishery production in estuarine ecosystems. We examined stable isotopes (δ 13 C, δ 15 N) in 4 com- mercial nekton species (Chelon haematocheilus, Synechogobius ommaturus, Lateolabrax maculatus and Exopalaemon carinicauda) in the tidal marshes of the Yangtze River estuary, China. We esti- mated the frequency and range of potential contribution (0 to 100%) from different food sources (benthic microalgae, suspended particulate organic matter, the invasive C4 plant Spartina alterniflora and native C3 plants Phragmites australis and Scirpus mariqueter) to the nektonic consumers, and then pooled the contributions for primary producers with similar isotope values (giving 3 groups: microalgae, invasive C4 plant and native C3 plants). Marsh vascular plants and microalgae were at the base of the food web supporting these nektonic species. For C. haematocheilus and S. ommatu- rus, vascular plants constituted a larger fraction of their carbon source than microalgae. S. alterniflora contributed more than 50% of their total organic carbon and was more important than the native C3 plants. For L. maculatus and E. carinicauda, intermediate δ 13 C values precluded definitive assign- ment of a major carbon source. We have shown that tidal marshes provide important food sources for some dominant estuarine nektonic species, and that the exotic plant S. alterniflora has been incorpo- rated into aquatic food webs of the Yangtze River estuary.

We examined the variation in aboveground biomass accumulation and tissue concentrations of nitrogen (N), phosphorus (P), copper (Cu), zinc (Zn) and lead (Pb) in Phragmites australis (common reed), Spartina alterniflora (salt cordgrass), and Scirpus mariqueter throughout the growing season (April-October 2005), in order to determine the differences in net element accumulation and distribution between the three salt marsh macrophytes in the Yangtze River estuary, China. The aboveground biomass was significantly greater in the plots of S. alterniflora than in the plots of P. australis and S. mariqueter throughout the growing season (P

Eutrophication is a global problem, and the key of its controlling is to manipulate the structure of aquatic ecosystem, to recover the function of natural, healthy and stable aquatic ecosystem, and to improve the biological purification capability of eutrophic water body. Aquatic higher plant and vegetation is the most important primary producer in aquatic ecosystem, because of its large individual, long life cycle, and strong capability of absorbing nutrients. Maintaining and restoring a certain amount of aquatic plant could restrain the growth of phytoplankton, improve the biodiversity of aquatic ecosystem, and stabilize its structure. Aquatic animal plays an important role in material and energy cycles of aquatic ecosystem. Zooplankton and benthos can graze phytoplankton directly, so as to controll the number of phytoplankton. It is possible to improve the number of zooplankton by changing the structure of fish population, which might control the serious reproduction of phytoplankton, and achieve the goal of controlling eutrophication. The research of biological purification is still at its initial stage in China. In future, the following two aspects of researches should be enforced: the key technology of biological purification of aquatic higher plant and vegetation; the new model of breed aquatics. These technologies will have a important significance to controlling eutrophication and in sustainable utilization of water body.

Chao, M.; Shi, Y.; Quan, W.; Shen, X.; An, C.; Yuan, Q., and Huang, H., 2012. Distribution of benthic macroinvertebrates in relation to environmental variables across the Yangtze River Estuary, China. This article reports on a study of the spatial and seasonal distribution of benthic macroinvertebrates and reveals the correlation between benthic macroinvertebrate community and environmental variables in the Yangtze River Estuary, China. A total of 75 species from seven phyla were identified during sample collection in May, August, and November of 2010 and February of 2011; among which, Annelida and Mollusca were found to be the predominant phyla. No significant difference in the community parameters (species, abundance, biomass, Shannon-Winner index, distinctness) of benthic macroinvertebrates was observed among survey trips. In contrast, an increasing tendency of abundance and biomass from river channels to the east waters was observed, and the differences between different geographic zones or c...