Concentration and distributions of fatty acids in algae, submerged plants and terrestrial plants from the northeastern Tibetan Plateau

We systematically investigated the concentration and distributions of saturated fatty acids (FAs) in 66 submerged plants (including 48 Potamogeton, 7 Myriophyllum and 11 Ruppia), 59 algae (including 26 Chara, 20 Cladophora and 13 Spirogyra) and 32 terrigenous plants from 18 lakes on the northeastern Tibetan Plateau. The results indicate that C-14-C-32 FAs in algae, submerged plants and terrigenous plants were dominated mainly by C-16 and C-20-C-32. FAs in algae and submerged plants were predominantly C-24, but also contained a relatively high abundance of C-26. The submerged plants had high C-26-C-32 concentration, with average values of 216 lg/g for Potamogeton, 52 lg/g for Myriophyllum and 134 lg/g for Ruppia, close to those of terrigenous plants (avg. 161 lg/g). Algae exhibited low C-26-C-32 FA concentration, with mean values of 7 lg/g for Chara, 8 lg/g for Cladophora and 18 lg/g for Spirogyra. The C-26-C-32 FAs in algae and submerged plants accounted for a large proportion of C-20-C-32, yielding average ratios (C-26-C-32 vs. C-20-C-32) of 33, 35, 31, 15, 19 and 23% for Potamogeton, Myriophyllum, Ruppia, Chara, Cladophora and Spirogyra, respectively. Therefore, the contribution of submerged plant C-26-C-32 FAs to lake sediments should be considered due to their high concentration, whereas the influence of algae was minor. Meanwhile, by comparing the values of average chain length (ACL), alga/terrigenous ratio (ATR) and submerged/terrestrial ratio (STR), we found that ACL14-32 and ATR could be used to distinguish algal FAs from those of other plants and that STR could be used to differentiate FA sources from submerged and terrestrial plants. Thus, we suggest that using specific chain lengths to determine source inputs is not adequate when applying sedimentary FAs for paleoclimatic reconstruction, while ACL 14-32, ATR and STR may aid in determining FA sources in sedimentary records. (C) 2017 Elsevier Ltd. All rights reserved