Yibo Liao

Temporal and spatial variability of benthic macrofauna communities in the Yangtze River estuary and adjacent area

Four cruise surveys were carried out in summer, winter, spring, and autumn from 2006 to 2007 to evaluate the seasonal distribution of macrobenthos in the Yangtze River estuary and its adjacent waters. A total of 59 sites were sampled and divided into three areas (estuary, inshore, and offshore areas). In all, 335 taxa were collected with polychaetes and mollusks being the dominant groups. Two-way ANOVA revealed significant differences among the numbers of species, densities, and biomasses in the areas. However, several differences were found among seasons. SIMPER analysis showed that the dominant species of macrobenthos varied in different areas, and the inshore area was the most complex of the three. The abundance/biomass comparison (ABC) curve of macrobenthos in the inshore area showed apparent rises and falls, which are characteristic of disturbance to macrobenthos. Canonical correspondence analysis showed that echinoids were closely related to the presence of silicates and temperature, whereas polychaetes were closely related to depth and temperature.

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.

The ecological distributions of N, P utilizing bacteria and heterotrophic bacteria in the moderate hypoxia zone of the Changjiang Estuary

The distributions of N utilizing bacteria (denitrifying bacteria and ammonifying bacteria), P utilizing bacteria (organic phosphobacteria and inorganic phosphobacteria) and heterotrophic bacteria in the Changjiang Estuary, and the roles of main environmental factors in distributing bacteria, are explored with observations from two cruises in June and August 2006. Comparisons between the two important periods of initial hypoxia phase (June) and developed hypoxia phase (August) show differences in both bacterial distributions and the associated main environmental factors. First, the primary group of ammonifying bacteria has larger magnitude with spatial maximum value in the hypoxic stations related to sediment in August. The phosphobacterial abundance and detection rates in August are much lower than those in June, but the denitrifying bacterial abundance becomes greater in August. However, the difference of heterotrophic bacterial abundance between June and August is not obvious. Second, main environmental factors influencing bacteria vary from initial hypoxia phase to developed hypoxia phase. Two parameters (salinity and NO3−) in surface water and five environmental parameters (pH, salinity, PO43−, NO3− and temperature) in bottom water and surface sediment play major roles in the bacterial abundance in June, while different parameter combinations (salinity and PO4−) in surface water and different parameter combinations (DO, DOC, NO3−, PO43− and pH) in bottom water and surface sediment play major roles in August. Moreover, the bottom bacteria distributions in area south of 31°N are related to the position of the Taiwan Warm Current in June. The bacterial abundance and distribution may respond to the environmental change in the hypoxia processes of initial phase and developed phase. During the hypoxia processes, the whole structure of bacterial functional groups probably turns to different states, causing the recycling of nutrient regeneration and aggravating hypoxia regionally.

Benthic macrofaunal communities along an estuarine gradient in the Jiaojiang River estuary, China

Benthic macrofaunal communities along an estuarine gradient of a macrotidal estuary of the Jiaojiang River, China were analyzed to reveal spatial variations in those communities and their relationships with environmental variables. Benthic macrofauna were collected from 15 sampling stations in May and October 2010. Polychaetes and Mollusks are the dominant taxonomic groups. The species richness, density and Shannon diversity index generally tended to increase as one moved away from shore toward the outer stations of the estuary. Cluster analysis and multidimensional scaling ordinations indicated the presence of three distinct zones of macrofaunal communities in the estuary. Multivariate analyses showed a strong relationship exists between the macrofaunal communities and the environmental parameters in the Jiaojiang River estuary. Aside from salinity, dissolved inorganic nitrogen and soluble reactive phosphate contents were also the major factor affecting the structure of the macrofaunal communities. The results demonstrated the important effects of nutrient-load on the distributional patterns of benthic macrofaunal communities in nutrient-rich estuaries.