Growth performance of Alexandrium catenella from the Chilean fjords under different environmental drivers: plasticity as a response to a highly variable environment

Abstract

Alexandrium catenella, the main species associated with harmful algal blooms, has progressively increased its distribution through one of the most extensive and highly variable fjord systems in the world. In order to understand this successful expansion, we evaluated the effects of different salinities, light intensity, temperatures, nitrogen (N) forms and nitrogen/phosphate (N:P) ratio levels on the growth performance, using clones isolated from different locations across its wide geographic distribution. Results showed that the growth responses were plastic and, in some cases, different reaction norms among clones were observed. Despite plasticity, the optimal growth of A. catenella (i.e. highest growth rate and highest maximal cells density) was reached within a narrow thermal range (12–15°C), while salinity (20–30 PSU) and light intensity (20–120 μmol m−2 s−1) ranges were wider. These results are partially consistent with the highest cell densities recorded in the field. Furthermore, optimal growth was reached using reduced forms of nitrogen (i.e. urea and NH4+) and in unbalanced N:P ratios (18:1 and 30:1). These characteristics likely allow A. catenella to grow in highly variable environmental conditions and might partly explain the recent expansion of this species.

Predicting the Effects of Climate Change on the Occurrence of the Toxic Dinoflagellate Alexandrium catenella Along Canada’s East Coast

“…The model fit our samples accurately (AUC = 0.88). Our GAMM predicts A. catenella bloom occurrences to be most likely when SSS is 15-28 and SST is 9-19 • C (optima at 23 and 14 • C, respectively), which is consistent with several laboratory and field studies showing that optimal growth rates and/or high abundances of this species are measured within this environmental window (Etheridge and Roesler, 2005;Condie et al, 2019;Paredes-Mella et al, 2020). Our results compare to past observations made by Weise et al (2002) in the EGSL near Sept-Îles, who showed that the highest A. catenella concentrations occurred when SSS was 20-26 and SST was ≥12 • C. In July 1998, during a red tide event in the LSLE, A. catenella in situ growth rates were highest when SSS was ≤24.5 and SST was ≥10 • C (Fauchot et al, 2005).…”

Blooms of Alexandrium catenella in Coastal Waters of Chilean Patagonia: Is Subantarctic Surface Water Involved?

“…Moreover, the higher abundances of A. catenella were more associated with depths of 5 m and greater, in contrast to the elevated abundances of S. costatum associated with estuarine water (EW) at depths of 5 m and shallower (Figure 5). Using a larger data set, a similar response has been shown for field populations of A. catenella in the Magellan region (Paredes-Mella et al, 2020). An association with higher temperatures was evident in the Aysén and Los Lagos regions (Paredes-Mella et al, 2020), but it is notable that the elevated abundances of A. catenella were still associated with the temperature and salinity characteristic of oceanic waters at these latitudes (Sievers and Silva, 2008).…”

“…Cultures of A. catenella isolated from Patagonian waters and maintained under controlled conditions have also shown complex relationships between temperature/salinity, growth rate and cell yields (Uribe et al, 2010;Aguilera-Belmonte et al, 2013;Avila et al, 2015). The optimal growth of Chilean strains of A. catenella (i.e., highest growth rate and highest maximal cell density) was reached within a narrow thermal range (12-15 • C), while optimal growth salinity (20-30) showed a broader range (Paredes-Mella et al, 2020). Lower temperatures of ∼10 • C have been shown to increase the excystment and shorten the dormancy of resting cysts (Mardones et al, 2016a) and to increase the toxin content of A. catenella (Aguilera-Belmonte et al, 2013;Navarro et al, 2006).…”

“…Lower temperatures of ∼10 • C have been shown to increase the excystment and shorten the dormancy of resting cysts (Mardones et al, 2016a) and to increase the toxin content of A. catenella (Aguilera-Belmonte et al, 2013;Navarro et al, 2006). The response of A. catenella to temperature and salinity changes shows a considerable plasticity that appears to be partially dependent on individual strains (Paredes-Mella et al, 2020).…”

“…However, vertical gradients of DIN and DIP resulting from variations in relative inputs of SASW and freshwater could have some impact on toxicity. Optimum growth of A. catenella in cultures has been shown to occur at unbalanced (elevated) N:P ratios (Paredes-Mella et al, 2020), however, these experiments were conducted by varying P concentrations at very high saturating concentrations of N.…”