Factors regulating the recruitment of cyanobacterial and eukaryotic phytoplankton from littoral and profundal sediments

Abstract

Many phytoplankton species produce resting cysts, forming 'seed banks' on lake sediments until they germinate and provide inocula (recruitment) for future pelagic populations. We have addressed the question of whether the littoral or the profundal zone provides the inoculum for planktonic populations in a eutrophic and dimictic lake (Lake Erken, Sweden). Our hypotheses were that high temperature, light, and sediment mixing would enhance recruitment. Also, we hypothesized that recruitment from littoral sediments would be greater than from profundal sediments. In situ recruitment traps were utilized to compare littoral and profundal recruitment, while laboratory experiments were performed to analyze which factors were most important. Seven common taxa were investigated: Asterionella formosa (Bacillariophyceae), Ceratium hirundinella (Dinophyceae), Microcystis botrys, M. wesenbergii, Anabaena sp., A. solitaria, and A. lemmermannii (Cyanobacteria). Our main findings were that light and sediment mixing were the most important factors in triggering and enhancing recruitment in the laboratory. Temperature and sediment origin (littoral/profundal) had a significant effect on recruitment only for A. lemmermannii and C. hirundinella, respectively. The field experiments showed that recruitment at the littoral site was much higher than at the profundal site, where little or no recruitment occurred. Together, these results strongly suggest that littoral sediments in temperate lakes provide inocula for most phytoplankton populations, likely due to favorable light conditions and high sediment mixing.

Water Management Strategies Against Toxic Microcystis Blooms In The Dutch Delta

“…During winter, benthic Microcystis cells remain viable and are gradually transported to the deepest parts of the lake. A fraction of this overwintering benthic population eventually recruits to the water column (Preston et al 1980, Trimbee and Harris 1984, Hansson et al 1994), most likely due to resuspension (Ståhl-Delbanco and Hansson 2002, Rengefors et al 2004, Verspagen et al 2005. Our results show that both recruitment from this benthic population and the overwintering pelagic population contribute to the development of dense Microcystis blooms during the next summer.…”

“…Recruitment of Microcystis from the benthic populations to the pelagic population depends mostly on sediment resuspension and light availability (Ståhl-Delbanco and Hansson 2002, Rengefors et al 2004). Since light availability at the sediments is very low in Lake Volkerak, we assume that its effect is negligible.…”

Microbial communities reflect temporal changes in cyanobacterial composition in a shallow ephemeral freshwater lake

“…Recruitment of bloom-forming cyanobacteria from littoral zones (Kononen et al, 1996) has been demonstrated to be significantly enhanced by high water temperatures and disturbance of these sediments (Rengefors et al, 2004). Although littoral recruitment cannot be ruled out, the shallow ephemeral nature of the lake suggests that mixing is not critical for the recruitment of cyanobacteria from the sediment.…”

An overview of diversity, occurrence, genetics and toxin production of bloom-forming Dolichospermum (Anabaena) species

“…First, the shallowness of the littoral zone facilitates akinete germination, as the adequate light and temperature requirements for germination are more readily met for shallow rather than deep sediments (Stå hl-Delbanco and Hansson, 2002). Second, wind-generated turbulence can easily bring the akinetes into the water column in the shallow zone, thus making them accessible to available light and nutrients (Rengefors et al, 2004). Third, sediments obtained from shallow waters can have higher nutrient concentrations than those sourced from deep water, thereby promoting cyanobacterial growth and recruitment.…”