Historical changes of phytoplankton community in Fuxian and Dianchi
lakes recorded by alkyl diols and sterol biomarkers
Abstract
We investigated historical changes in temperature and phytoplankton in
Fuxian Lake (FX) and Dianchi Lake (DC), two plateau lakes in Southwest
China. We detected sterols and alkyl diols as algal biomarkers
(Dinoflagellates, Diatoms, Eustigmatophytes, Cyanobacteria, and
Chlorophyta) in the sediment cores by using GC-MS. We characterized
sedimentary organic matter (SOM) via C-13 isotope and C/N ratio, and
Rock-Eval analysis to obtain total organic carbon (TOC), S2, the
hydrogen index (HI), refractory carbon (RC), and nutrient status such as
total phosphorus (TP) and total nitrogen (TN) in the sediment cores. The
results showed that the sedimentation rates measured by
210Pb dating ranged from 0.02 to 0.30 g
cm-2 yr-1 and 0.07 g
cm-2 yr-1 in FX and DC,
respectively. The Bayesian isotope mixing model indicated that organic
matter from plankton was the main contributor of organic matter in FX
and DC and, its contents was gradually increasing . Primary productivity
derived from the S2 and HI parameters showed an increasing trend in FX
and DC. Cyanobacteria and Chlorophyta were the two dominant phyla in the
two lakes. Algal growth was controlled primarily by temperature and
nutrient availability. Principal component analysis (PCA) and multiple
linear regression analysis showed that the major factors controlling the
historical change in phytoplankton growth were TN and temperature in FX
and DC.