Synergistic effects of nutrients and light favor Nostocales over non-heterocystous cyanobacteria

Abstract

Blooms of Nostocales (Cyanobacteria) are thought to be invading subtropical and temperate water bodies. According to nutrient stoichiometry and physiological differences between cyanobacterial groups, the replacement of non-heterocystous species by Nostocales is favored when dissolved inorganic nitrogen decreases. However, some studies have shown different trends. We used laboratory bioassays to evaluate the concomitant effects of light and nutrient enrichment on phytoplankton assemblages dominated by non-heterocystous filamentous cyanobacteria. Three nutrient conditions (no addition, addition of phosphate, and addition of nitrate and phosphate) and two light intensities (40 and 80 lmol photon m -2 s -1 ) were assayed. Nostocales replaced or co-dominated with non-heterocystous species in all treatments by the end of the study. The shift in community composition towards Nostocales dominance led to an increase in species richness, which suggests that species with different eco-physiological traits may have differential impacts on diversity. The highest saxitoxin concentrations were measured in no addition treatments, which could link production to nutritional stress. Nostocales featured high phenotypic plasticity in terms of changes in average trichome Handling editor: Boping Han

Drivers and ecological consequences of dominance in periurban phytoplankton communities using networks approaches

“…This was well reflected in the number of nodes composing the networks. (Aguilera et al, 2017a;Dokulil and Teubner, 2000;Litchman, 2003). Similarly, observations of reduced number of taxa in microbial communities dominated by Cyanobacteria are legions (Bagatini et al, 2014;Filstrup et al, 2014;Holland and Kinnear, 2013;Louati et al, 2015;Toporowska and Pawlik-Skowrońska, 2014;C.…”

“…nitrogen fixation, specific CO 2 fixation, buoyancy). Another hypothesis might be related to the effect of competition/exclusion mechanisms on community composition (Aguilera et al, 2017a;Dokulil and Teubner, 2000;Litchman, 2003). For instance, Cyanobacteria are more efficient than other groups for light-harvesting in low-light conditions generated by high biomass (Litchman, 2003;Schwaderer et al, 2011) and are able to release a wide variety of allelochemical compounds (Dias et al, 2017;Holland and Kinnear, 2013;Leflaive and Ten-Hage, 2007).…”

Regulation of phosphate uptake reveals cyanobacterial bloom resilience to shifting N:P ratios

“…Although we did not analyse the zooplankton community in our study, previous evidence has shown that zooplankton (mainly small‐sized) does not exert top‐down control on phytoplankton in Lago Rodó (Lacerot, Kruk, Lürling, & Scheffer, ; Scasso et al., ). Filamentous cyanobacterial blooms are common in well‐mixed waters with different light intensity conditions (Aguilera et al., ; Havens, James, East, & Smith, ; Paerl et al., ). For instance, while some species such as Cylindrospermopsis raciborskii , a species phylogenetically related to R. mediterranea (Aguilera, Berrendero, Kaštovský, Echenique, & Salerno, in press; Moustaka‐Gouni, Kormas, Vardaka, Katsiapi, & Gkelis, ), succeed under high‐ Z eu / Z mix conditions (values ≥1) (Bonilla et al., ), P. agardhii blooms in highly turbid water columns ( Z eu / Z mix < 1; Bonilla et al., ) (Scheffer et al., ).…”

“…Under such P-deficiency, it is expected that cyanobacteria may become vulnerable to population collapse (Catherine et al, 2008). This critical situation becomes even more severe when N colimits growth with P, as it has been evidenced in several laboratory and mesocosm studies (e.g., Aguilera et al, 2017;Davis, Bullerjahn, Tuttle, Mckay, & Watson, 2015;Paerl et al, 2014Paerl et al, , 2016. However, N-and P-limitation may also be temporally segregated.…”

Recent insights into physiological responses to nutrients by the cylindrospermopsin producing cyanobacterium, Cylindrospermopsis raciborskii

“…Comparison of field studies of this species has given conflicting results regarding the importance of nutrients in promoting blooms. In the case of phosphorus, field and bioassay studies have shown both positive and negative correlations between phosphorus concentrations and C. raciborskii cell densities (Bonilla et al, 2012;Kokociński and Soininen, 2012;Muhid et al, 2013;Soares et al, 2013;Aguilera et al 2017). Chislock et al (2014) also showed that C. raciborskii can dominate under a range of phosphorus levels: Posselt et al (2009) also found this but only when nitrogen levels were not elevated.…”