a a a m m m mm b bfd How to know the freshwater benthic algae Maria Kahlert

freshwater benthic algae Check first: Color: –Bluegreen: bluegreen algae –Green: green algae –Yellowish-Brown: brown algae Diatoms Chrysophytes Brown algae –Red: red algae Be aware of exceptions!!!

freshwater benthic algae Exceptions in color: Bluegreen red alga: Chroodactylon Green ‘brown’ alga: Vaucheria Green ‘brown’ alga: diatoms in bad shape Red green alga: Haematococcus

freshwater benthic algae Check also: Absence/presence of cell organelles: –Absence: bluegreen algae = cyanoBACTERIA –Presence: all other algae Presence of siliceous cell wall (distinctly shaped ‘glass house’): diatoms

freshwater benthic algae Check next: Bluegreen algae –Organization of thallus: Coccoid Filamentous –No branches –False branches –True branches –Presence/absence and place of heterocysts (N 2 fixation) (only for the filamentous forms) –Length of cell

freshwater benthic algae Check next: Green algae –Organization of thallus: Coccoid –Single cell/colonies/coenobia Filamentous –Not branched/branched –Chloroplast morphology: Cup-shaped Parietal (like a tapestry, middle of cell is vacuole) Axial (in the middle of cell)

freshwater benthic algae Check next: ‘Brown’ algae – Diatoms –Identification of living diatoms only grossly, must be prepared (see separate information) raphe (slit in cell wall) no raphe pennate centric

freshwater benthic algae Check next: ‘Brown’ algae –Chrysophytes and ‘real’ brown algae Very few in freshwater, very different: Hydrurus (golden) Ophiocytium (green) Tribonema (golden) Vaucheria (green) Pleurocladia (brown) Hildenbrandia (brown)

freshwater benthic algae Check next: Red algae –Very few in freshwater Heribaudiella Chroodactylon Audouinella Batrachospermum

freshwater benthic algae Some algal terms Cell organelles – cell content with a membrane inside the cell Siliceous cell wall – cell wall outside cell in diatoms, made from glass Heterocysts – special cells in bluegreens fixating N 2 Thallus – body of alga Coccoid – ball formed thallus Filamentous – hair formed thallus Coenobia- cell cannot divide mitotically, after meiosis, the mother cells dies and relieves a certain number of identically shaped daughter cells, a finished colony