Metalimnetic cyanobacteria in hard‐water lakes: Buoyancy regulation and physiological state

Abstract

During summer stratification, Crooked and Little Crooked Lakes, Indiana, contained phytoplankton dominated by populations ofAphanizomenonj7o.vaquae that stratified in the metalimnion where photon irradiance was 6% of that at the surface. The gas vacuolate Aphanizomenon filaments from Little Crooked Lake lost buoyancy when exposed to irradiances > 100 pmol photons m-2 s-l. If 2 PM KH,PO, was added to the water samples, however, exposure to irradiances >200 pmol photons m -2 s-l was necessary to obtain buoyancy losses. Phosphate also affected the recovery of buoyancy by sinking filaments. Filaments that had lost buoyancy due to incubation in the light recovered it when incubated for 5 h in the dark. Addition of phosphate increased the rate of buoyancy recovery by 50%. The metalimnetic populations had stratified in a zone of relatively low irradiance and inorganic nutrient concentration. The physiological state of the populations was evaluated by determining the kinetic characteristics for phosphate, nitrate, and ammonia uptake and the cellular contents of surplus phosphate and chlorophyll a. On the basis of the premise that cells limited by a particular element will express a high uptake potential for that element, the metalimnetic populations showed characteristics of organisms not limited by the availability of light, phosphorus, or nitrogen.

Potential factors leading to the formation of cyanobacterial scums in a mesotrophic softwater lake in Ontario, Canada

“…leading to cultural eutrophication between 1860 and1900 (A.M. Paterson, unpubl.). While the naturally elevated phosphorus concentrations can support cyanobacterial dominance and influence cyanobacteria buoyancy control (Konopka 1989), we believe it is less important for the transition from bloom to scum. Differences in dominant cyanobacteria species among the 3 years may be linked to differences in their niches.…”

Artificial mixing to control cyanobacterial blooms: a review

“…However, many cyanobacteria possess buoyancy regulation mechanisms, which allow them to actively control their vertical position in the water column. Examples include Anabaena (Oliver and Walsby 1988), Microcystis (Kromkamp and Mur 1984;Ibelings et al 1991;Visser et al 1996b), Aphanizomenon (Konopka 1989) and Oscillatoria (Walsby et al 1983). Extensive reviews of the factors affecting buoyancy regulation are given by Reynolds (1987), Oliver (1994) and Walsby (1994).…”

Design, Construction, and Application of an Inexpensive, High-Resolution Water Sampler

“…To provide additional evidence for the accurate, high-resolution performance of this sampler, we measured Chl a concentrations at each depth sampled in a temperate freshwater lake, Little Crooked Lake, Indiana. Little Crooked Lake is a relatively shallow (maximum depth, 15 m) hard water marl lake with significant biogenic and abiogenic turbidity; light intensity at a depth of 3 m is less than 10% of surface irradiance and the lake supports a metalimnetic cyanobacterial bloom during summer stratification [15]. Limnological studies of this lake and the adjoining Crooked Lake were published over 30 years ago.…”