In terms of spatial distribution, the phytoplankton pigment ratios
and community composition (which was strongly influenced by environmental
conditions) showed patterns similar to the T–S properties
(Figs. 6 and 7). In coastal areas of the YS the concentrations of N, P
and Si compounds are high, reflecting the effects of the Changjiang
effluent plume, surface runoff from the west and east coasts, and circulation
in the YS (Liu et al., 2003). However, because of the unique basin
topography and strong tidal currents, the YSCWM is fringed by typical
tidal mixing fronts, which separate the cold, stratified water at the offshore
side from the warm, well-mixed, shallow water on the other
side (Qiao et al., 2006). Thus, significantly lower nutrient and Chl a concentrations
are observed on the surface of the YSCWM area than in the
surrounding water in summer (Fu et al., 2009). In the present study,
much evidence was presented of the YSCWM area behaving differently
from the rest of the sampled region, especially with regard to phytoplankton
community structure (Figs. 2–8).