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Rotifers were studied at two sites (Zhongda and Huangpu) in the tidal Guangzhou segment of the Pearl River in China, from April 2004 to March 2007. Fifty-six species were recorded. Rotifers were most abundant during late fall. Overall, densities ranged from 4 to 5975 ind. L–1, with mean densities of 1627 ± 233 ind. L–1 at Zhongda and 1051 ± 147 ind. L–1 at Huangpu. There was a positive correlation between rotifer density and chlorophyll a concentration at both sites. At Huangpu, rotifer abundance was significantly negatively correlated with salinity. Analysis of partial correlations suggested that the fluvial hydrodynamics and the physico-chemical characteristics of the river affected chlorophyll and the development of rotifer populations was determined by chlorophyll in the lower reaches of Pearl River. The results also show that rotifer density estimates are significantly affected by sampling method. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Surface sediments were collected from 10 locations to study the distribution of dinoflagellate resting cysts in Chinese coastal waters from July 2000 to May 2002. Sixty-one cyst morphotypes representing 14 genera of three orders were identified in this survey. Seventeen cyst types were recorded for the first time from Chinese coasts. Rich cyst assemblages were recorded in closed or semi-closed nearshore harbors. Scrippsiella trochoidea was the most dominant and common cyst type in this survey, especially in sediments from Daya Bay, Dapeng Bay and Shenzhen Bay. However, Protoperidinium cysts were the most diversified group, predominating in Changjiang River Estuary, Zhujiang River Estuary, Zhelin bay and the Nanao Island area. Cyst concentrations in the top 2 cm surface sediments varied from 258 to 25,037 cysts.g -1 dry weight sediment, and abundance was lower in Changjiang River Estuary and Zhujiang River Estuary. Cysts of two dinoflagellates capable of producing paralytic shellfish poisoning (PSP) - Alexandrium spp. and Gymnodinium catenatum - were detected almost in all locations. Furthermore, the ellipsoidal Alexandrium catenella and A. tamarense cyst complex was frequently observed in the surface sediment from Daya Bay, where high contents of PSP toxin and PSP episodes have been reported. Detailed descriptions and illustrations are provided of those cysts of newly recorded species, unidentified species, toxic species and dominant species.

SUMMARY Nine sediment cores of 8–26 cm in length were collected from two basins of Daya Bay, the South China Sea, by Tokyo University Fisheries Oceanography Laboratory core sampler in August 2001 to investigate the distribution of dinoflagellate resting cysts. In the present study, 51 different cyst morphotypes representing 22 genera were identified from 65 sediment samples. Among them, there were 21 autotrophic species and 30 heterotrophic ones. Cyst species richness in each sample varied from 12 to 29, while the values of Shannon-Weaver diversity index (H′) were between 0.15 and 4.13. There were an obvious increase in both species richness and values of H′in 2–6 cm sediments. Cyst concentrations varied from 154 to 113 483 cysts per gram dry weight sediment, and were much higher in upper sediments. Scrippsiella trochoidea was the most dominant cyst type, which took up over 90% of cyst assemblages in the upper sediments. The abrupt increase of S. trochoidea cysts in the surface sediments reflected the bloom of this species in Daya Bay in 2000. The results from cyst assemblages showed some trend of changes in water quality in this area, and indicated a typical type of pollution caused by cultural eutrophication, which started in the 1980s and greatly accelerated in the middle of 1990s. Cysts of Alexandrium, mainly those of Alexandrium catenella and Alexandrium tamarense complex, occurred frequently and abundantly in this area, with the highest concentration and relative frequency of 503 cysts per gram dry weight sediment and 22.3%, respectively. The high abundance of Alexandrium cysts provided rich ‘seed bed’ for Alexandrium blooms and was also an important source of paralytic shellfish poisoning toxins, especially in winter.