Changes of Lake Engure Sedimentation Conditions Reflected by Paleovegetation Records

摘要

Shallow Lake Engure is lake of lagoonal origin, formed in the result of sea water level changes during the several Baltic Sea development stages. Lake sediment, especially their superficial layer investigation from core No. 11 by biological composition, Loss-on ignition, palaeobotanical methods and ~(210)Pb dating indicate that lake is sensitive to anthropogenic influence. Sediment biological, plant macroremain and pollen analysis clearly indicate intensification of Lake Engure eutrophication and overgrowing processes after the Mersrags Canal excavation and building. Presence of plant macroremains of Fennel Pondweed (Potamogeton pectinatus) and Horned Pondweed (Zannichellia palustris) point on conditions with sea water inflow in te lake. Appearance of these plant remains and presence of brackish diatoms (Mastogloia elliptica, M. smithii, Diploneis didyma etc.) is more frequent from the depth of 20 cm, which is dated by ~(210)Pb method (160.3 years) and is in good correlation with the Mersrags Canal excavation date.