title: Characteristics of Phytoplankton Biomass, Primary Production and Community Structure in the Modaomen Channel, Pearl River Estuary, with Special Reference to the Influence of Saltwater Intrusion during Neap and Spring Tides.
abstract: In recent decades, increasing frequency and intensity of saltwater intrusion in the Modaomen Channel has threatened the freshwater supply in the surrounding cities of the Pearl River Estuary, and ulteriorly changed the environmental conditions of the estuarine waters. Phytoplankton biomass, primary production (PP) and species composition, as well as hydrological and chemical parameters were examined along a downstream transect in the Modaomen Channel during neap tide (NT) and spring tide (ST), when a strong saltwater intrusion event occurred in late September, 2011. A total of 46 species phytoplankton were identified, including Bacillariophyta (25 species), Dinoflagellate (14 species), Chlorophyta (4 species), Cyanophyta (2 species) and Euglenozoa (1 species). The dominant species were shifted from freshwater diatoms (e.g., Melosira granulata and Melosira granulata var. angustissima) in the upper reaches to saline water diatoms (e.g., Skeletonema costatum and Coscinodiscus sp.) in the river mouth. Generally, phytoplankton density, biomass (chl-a) and PP decreased from the upper to lower reaches along the channel, and were significantly higher in NT than those of ST. There was a shift from large-sized phytoplankton (>20 μm) in the upper reaches to relative small-sized cells (5-20 μm) in the lower reaches. Compared to NT, low discharge and flow velocity, coupled with strong easterly winds during ST specially aggravated saltwater intrusion further to the upstream (~50 km from the estuary). The intruded saltwater diluted nutrients, N/P ratios, chl-a, and phytoplankton abundances, and thereby led to a decline in PP during ST.
authors.affiliation: Key Laboratory of Tropical Marine Bio-resources and Ecology, and Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.|Tropical Marine Biological Research Station in Hainan, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Sanya, China.
authors.forename: Weihua
authors.identifier: http://orcid.org/0000-0002-1056-7612
authors.initials: W
authors.lastname: Zhou
authors.affiliation: South China Business College, Guangdong University of Foreign Studies, Guangzhou, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Gao
authors.affiliation: Key Laboratory of Tropical Marine Bio-resources and Ecology, and Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.|Tropical Marine Biological Research Station in Hainan, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Sanya, China.|University of Chinese Academy of Sciences, Beijing, China.
authors.forename: Jianzu
authors.initials: J
authors.lastname: Liao
authors.affiliation: South China Sea Environment Monitoring Center, State Oceanic Administration, Guangzhou, China.
authors.forename: Ronggui
authors.initials: R
authors.lastname: Shi
authors.affiliation: Key Laboratory of Tropical Marine Bio-resources and Ecology, and Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.|Tropical Marine Biological Research Station in Hainan, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Sanya, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Li
authors.affiliation: Key Laboratory of Tropical Marine Bio-resources and Ecology, and Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.|Tropical Marine Biological Research Station in Hainan, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Sanya, China.|University of Chinese Academy of Sciences, Beijing, China.
authors.forename: Yajuan
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Key Laboratory of Tropical Marine Bio-resources and Ecology, and Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.
authors.forename: Aimin
authors.initials: A
authors.lastname: Long
mesh_terms: D018533:Biomass; D002681:China; D000460:Chlorophyta / Q000254:growth & development; D000458:Cyanobacteria; D017377:Diatoms / Q000254:growth & development; D004141:Dinoflagellida / Q000254:growth & development; D005618:Fresh Water; D010839:Phytoplankton / Q000254:growth & development*; D045483:Rivers; D012621:Seasons; D012623:Seawater; D014881:Water Supply