Seasonal Partitioning of Primary Production and Biomass between Phytoplankton and Metaphyton in a Shallow Lake Agmon, Hula Valley (Israel)

摘要

Agmon is a small, shallow man-made lake (area: 1.1 km style="font-family:Verdana;">2 style="font-family:Verdana;">; mean depth style="font-family:Verdana;">0.45 style="font-family:Verdana;"> m), excavated in the peat soils of the Hula Valley in northern Israel, that was filled with water in A style="font-family:Verdana;">ugust style="font-family:Verdana;"> 1994. We followed the seasonal variations in phytoplankton and metaphyton biomass, primary production and related environmental conditions style="font-family:Verdana;">between style="font-family:Verdana;"> December 1995 style="font-family:Verdana;">and style="font-family:Verdana;"> July 1997. Water temperature ranged style="font-family:Verdana;">between style="font-family:Verdana;"> 9.5 style="white-space:nowrap;">°C - style="font-family:;" "=""> style="font-family:Verdana;">30.8 style="white-space:nowrap;">°C style="font-family:Verdana;">; style="font-family:Verdana;"> pH ranged style="font-family:Verdana;">between style="font-family:Verdana;"> 7.2 style="font-family:;" "=""> style="font-family:Verdana;">- style="font-family:;" "=""> style="font-family:;" "=""> style="font-family:Verdana;">8.6. The algae in Lake Agmon were characterized by seasonal alterations between summer-fall phytoplankton blooms and spring proliferation of benthic algal mats, with a winter clear-water phase. Chlorophyll style="font-family:Verdana;">a style="font-family:Verdana;"> content in the water, as a measure of planktonic algal biomass, was low in winter (1.75 style="font-family:Verdana;">- style="font-family:Verdana;"> 5 style="font-family:;" "=""> style="font-family:;" "=""> style="font-family:Verdana;">μg style="white-space:nowrap;">·L style="font-family:Verdana;">-1 style="font-family:Verdana;">) and high in summer (>100 style="font-family:;" "=""> style="font-family:;" "=""> style="font-family:Verdana;">μg style="white-space:nowrap;">·L style="font-family:Verdana;">-1 style="font-family:Verdana;">), when planktonic cyanobacteria ( style="font-family:Verdana;">Microcystis style="font-family:Verdana;">spp.) bloomed. Metaphyton biomass varied style="font-family:Verdana;">between style="font-family:Verdana;"> 3.5 style="font-family:Verdana;">and style="font-family:;" "=""> style="font-family:Verdana;"> 970 g style="white-space:nowrap;">·dry style="white-space:nowrap;">·wt style="white-space:nowrap;">·m style="font-family:Verdana;">-2 style="font-family:Verdana;">, with chlorophyll style="font-family:Verdana;">a style="font-family:Verdana;">content ranging from 5 style="font-family:;" "=""> style="font-family:Verdana;">- style="font-family:;" "=""> style="font-family:;" "=""> style="font-family:Verdana;">701 mg style="white-space:nowrap;">·m style="font-family:Verdana;">-2 style="font-family:Verdana;">. The dominant benthic algal genera were style="font-family:Verdana;">Spirogyra style="font-family:Verdana;"> and style="font-family:Verdana;">Oedogonium style="font-family:Verdana;"> in 1996 and style="font-family:Verdana;">Cladophora style="font-family:Verdana;"> in 1997.