ECOLOGICAL OBSERVATIONS ON THE PLANKTONIC CYANOPHYTE GLEOTRICHIA ECHINULATA1

Abstract

Gleotrichia echinulata was planktonic in Green Lake (Seattle, Washington) during summer, making its initial appearance between May and early July and disappearing during September. It apparently spent 8 to 10 months of the year on the bottom where colonies developed from spores deposited by the preceding year’s bloom. The depth of spore deposition may be important in determining the success of spore maturation, and solar radiation may be a primary factor in inducing the annual return of this alga to the plankton. The maximum growth rate in 1886 was about 0.124 colony doublings per day. The vertical distribution of the colonies was controlled primarily by wind‐induced currents. The colonies had no measurable effect on light penetration even at a maximum density of over 400 colonies per liter. Laboratory studies indicated that G. echinulata can fix nitrogen. Only one herbivore in Green Lake, Lindia euchromatica, is known to feed on this species.

Light-dependent germination and subsequent proliferation of N2-fixing cyanobacteria in a large shallow lake

“…Since akinetes are long-lived and also may act as a longterm survival mechanism for a species (Livingstone and Jaworski, 1980), the surface layer of sediment can be seen as an akinete stock of all N 2 -fixing species that have differentiated into akinetes during the previous years. At favourable growth conditions, their germination provides a source of inoculum for subsequent populations (Roelofs and Oglesby, 1970;Reynolds, 1972;Gorzo´, 1987;Karlsson-Elfgren et al, 2004;Kim et al, 2005;Faithfull and Burns, 2006). These resting propagules may also influence the succession of different species in the plankton community (McQuoid and Hobson, 1995;Rengefors and Anderson, 1998) and explain the dominance of some species (Hansson et al, 1994;Head et al, 1998Head et al, , 1999.…”

Factors regulating recruitment from the sediment to the water column in the bloom‐forming cyanobacterium Gloeotrichia echinulata

“…Baker, 1999). The switch between the benthic and pelagic life stage in G. echinulata is preceded by germination of the akinetes, followed by a period of growth on the sediment (Roelofs & Oglesby, 1970;Barbiero, 1993) before gas vesicles are formed and the new colonies migrate up into the water. Recruitment of akineteforming cyanobacteria from the sediment into the water column can be active or passive.…”

Epiphytic cyanobacterium Gloeotrichia pisum as an indicator of nitrogen depletion

“…The affinity of cyanobacteria to warm (>15°C) water temperatures is well documented (Konopka & Brock 1978, Robarts & Zohary 1987. of low DIN and the first occurrence of G. pisum, consistent with the 25 to 36 d lag required for germination and pelagic recruitment of G. echinulata (Roelofs & Oglesby 1970, Carey et al 2008. This coincidence suggests that the development time of G. pisum may be similar to that of the better studied planktonic taxon.…”

“…We studied the epiphytic cyanobacterium Gloeotrichia pisum, which forms spherical colonies embedded in a gelatinous matrix that is attached to submerged aquatic vegetation (Granetti 1969, Aziz & Whitton 1988. G. pisum is morphologically similar to the better-studied G. echinulata, which is a taxon that exhibits a planktonic phase after its initial development in shallow littoral sediments (Roelofs & Oglesby 1970, Carey et al 2008 ) and total dissolved phosphorus (< 20 µg P l -1 G. pisum in the St. Lawrence River coincided with latesummer depletion of DIN in an area located downstream of a dense wetland through which water percolated slowly (Vis et al 2008). These observations led us to hypothesize that the occurrence of this species could reflect the overall hydrological and chemical conditions prevailing during the entire growing season, thus integrating seasonal variations in water chemistry in rivers and reservoirs, where water quality changes quickly with discharge (Chêtelat & Pick 2001, Hudon & Carignan 2008.…”