Text S7. Diatom analysis
Diatom is a widely used proxy of variations in water quality, including
levels of salinity in coastal and estuarine environments (Zong et al.,
2013). A total of 67 sediment samples were analyzed; 12 from KhqS, 20
from KHQ-14, and 35 from XS-1603. Diatoms were identified under oil
immersion at 1000x using an OLYMPUS BX-51 microscope. Only samples that
yielded in excess of 300 diatom valves were included; numbers of diatom
valves in the vast majority of samples from XS-1603 fell well below this
standard. As a result, no detailed analysis of diatoms from XS-1603 is
presented here, although statistically significant counts were obtained
for five samples from above -2.0 m OD in the core. In the current
research, diatom species are classified into one of six habitat
groupings: marine plankton, marine epiphytes, marine/brackish epipelon,
brackish plankton, freshwater plankton and freshwater benthos/epiphytes.
Zonation of diatom assemblages is carried out with CONISS module in
Tilia. The diatom fragments (<1/2 valve) which cannot be
identified as one valve were counted.
Diatoms indicative of freshwater conditions, such as Aulacoseira
Canadensis (Hustedt) Simonsen, Aulacoseira granulata (Ehrenberg)
Simonsen, are common species in disturb river and estuary.Cyclotella distinguenda Hustedt and Cyclotella
meneghiniana Kützing are often found in freshwater river and lake.Actinocyclus ehrenbergii Ralfs, Actinoptychus undulates(Bailey) Ralfs and Coscinodiscus spp. (mainly Coscinodiscus
radatius , Coscinodiscus subtilis ), Melosira sulcata(Ehrenberg) Kützing are the most common of the marine taxa present,
while Diploneis smithii (Brébisson) Cleve, Cyclotella
stylorum Brightwell and Cyclotella striata Grunow in Cleve &
Grunow are abundant brackish-water indicators.