York River Destratification: An Estuary-Subestuary Interaction

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

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.

Gender differences and reproducibility in exploratory eye movements of normal subjects

Exploratory eye movements were recorded using an eye-mark recorder in 48 normal subjects (24 male and 24 female). Gender differences were examined regarding four eye movement parameters such as the mean gazing time, the total number of gazing points, and the mean eye scanning length and the total eye scanning length. The mean gazing time of women was significantly longer than that of men, and the total number of gazing points of women was significantly less than that of men. The mean eye-scanning length of men and women did not differ. The total eye scanning length of men was significantly longer than that of women. Reproducibility between sessions of the four eye movement parameters above was expressed as Pearson correlation coefficients (r) in 24 healthy adults before and after a month interval, yielding respective coefficients of 0.65, 0.42, 0.56 and 0.61. These results suggested that differences in exploratory eye movements between men and women may reflect differences in the characteristics of visual information processing and also confirmed the reproducibility of exploratory eye movement parameters.