Changes Of Phytoplankton And Harmful Algae In Jiulongjiang Estuary

Estuarine ecosystems are attacting more and more concerns in recent years. An estuary is a partially enclosed body of water along the coast where freshwater from rivers and streams meet and mix with salt water from the ocean, and this water provides diverse and valuable services to human beings. The major characteristics of estuarine ecosystem include: 1) estuarine waters lies within tidal area; 2) more and more human disturbances occur in this area; 3) the filtration process in this area creates cleaner and clearer water, which benefits both people and marine life; 4) this area is easily and strongly affected by changes in salinity and chemical parameters etc.; 5) estuarine environment is among the most productive on earth, and the productivity and variety of estuarine habitats foster a wonderful abundance and diversity of wildlife; 6) this area provides ideal areas for migratory animals to rest and refuel during their long journeys; and 7) estuary provides shelter waters as protected places for many species of fish and wildlife to spawn. So, estuarine ecosystem is vital to human beings but vulnerable, and it is necessary to understand this ecosystem's structure and function, which will help to support our decision in protection measures.Nowadays, more and more human activities occurred along the river and around the estuary, and nutrients were overloaded in estuarine area, resulting severe eutrophication. The consequrences of eutrophication include: 1) red tide, especially harmful algal blooming (HAB), causing food safety and human health problems; 2) hypoxia, resulting losses in fishery and mariculture; 3) changes in phytoplankton community, leading to changes in the whole ecosystem through food web. At the same time, as the primary producers, phytoplankton plays vital roles in the balance of ecosystem's nutrients, and community composition and biomass respond sensitively to complex environmental parameter changes. Now, it is widely acceptable that phytoplankton abundance and diversity can be used as the indicators for water quality and eutrophication.Therefore, this research aimed to study the phytoplankton community and harmful agal species in estuarine area, and assess the effects from environmental parameter changes. Based on these, protection and management measures were proposed.Seawater samples were collected from 18 sites in Jiulongjiang Estuary, Xiamen, Fujian Province, China in May, August and Novebmer, 2009. Phytoplankton pigment analyses were conducted for samples collected in August and November, 2009 by high-performance liquid chromatography (HPLC), in order to explore the phytoplankton community composition. We have also launched a more detailed study about changes of HAB species in May, August and November of 2009 by real-time fluorescent quantitatie polymerase chain reaction technology (RFQ-PCR). Results were as follows:1. Results of high performance liquid chromatography (HPLC):(1) Pigment analyses: the main featured pigments of Jiulongjiang estuary were peridinin (PERI), fucoxanthin (FUCO), alloxanthin (ALLO) and zeaxanthin (ZEA). The content of FUCO was the highest but distributed unevenly. The distribution of PERI is discontinuous. The content of PERI was below detection limit in most sites, but concentration was generally high when above detection limit(the maximum of detected was 0.43μg/L). The spatial distribution patterns of the pigment varied distinctively with different seasons, and seasonal pigment concentration changes were also found in each sampling site.(2) Phytoplankton community structure of Jiulongjiang Estuary: the predominantphytoplankton in Jiulongjiang Estuary was bacillariophyceae, then chryptophyceae. Dinophyceae and cyanophyceae were very few. Phytoplankton species diversity of Jiulongjiang Estuary was low and varied in different stites. The phytoplankton species composition in near-river waters was different from that in away-from-river waters and Xiamen west water.2. Results of real-time fluorescent quantitatie polymerase chain reaction (RFQ-PCR):HAB species with toxin production, Gymnodinium mikimotoi was detected with the maximum density of 23845 cell/l in Jiulongjiang estuary waters, and therefore more attention should be paid to this species including monitoring efforts. Cymnodinium sanguineum and Phaeocystis globosa were not enough to form a red tide event in Jiulongjiang estuary as found in this study.Conclusively, the phytoplankton and red tide algae results indicated that Jiulongjiang Estuarine ecosystem was under healthy state, and more attention should paid to nutrient loading either from river or the area around the estuary.