Observations on attachment strategies of periphytic diatoms in changing lotic systems (Ottawa, Canada)
Wang, Qian; Hamilton, Paul B.; Kang, Fuxing
The scanning electron microscope (SEM) was used to image the adhesive structures secreted by Achnanthidium, Cocconeis, Cymbella, and Cyclotella taxa as they colonize surfaces, under natural lotic conditions. Results revealed that long filaments, short fibrillar filaments attached by densely branched stalks, and biofilms, changed form under different environmental and microhabitat conditions. With the increase in river velocity, the lengths of stalks produced by Achnanthidium taxa were short and denser; biofilms over Cocconeis taxa were secreted in order to maintain their position in faster flows. The observations of Cyclotella meneghiniana showed that this taxon can produce fibrillar attachments to rocks and associated substrates, in contrast to the planktonic Cyclotella taxa which lack attachment structures. The riverine benthic community along with the associated tychoplanktonic species represents a dynamically changing microhabitat based on adaptive mechanisms to changing environmental conditions, especially current flow.