Niche differentiation of Dinophysis acuta and D. acuminata in a stratified fjord

Abstract

Dinophysis acuta and D. acuminata are associated with lipophilic toxins in Southern Chile. Blooms of the two species coincided during summer 2019 in a highly stratified fjord system (Puyuhuapi, Chilean Patagonia). High vertical resolution measurements of physical parameters were carried out during 48 h sampling to i) explore physiological status (e.g., division rates, toxin content) and ii) illustrate the fine scale distribution of D. acuta and D. acuminata populations with a focus on water column structure and cooccurring plastid-bearing ciliates. The species-specific resources and regulators defining the realized niches (sensu Hutchinson) of the two species were identified. Differences in vertical distribution, daily vertical migration and in situ division rates (with record values, 0.76 d−1, in D. acuta), in response to the environmental conditions and potential prey availability, revealed their niche differences. The Outlying Mean Index (OMI) analysis showed that the realized niche of D. acuta (cell maximum 7 × 103 cells L−1 within the pycnocline) was characterized by sub-surface estuarine waters (salinity 23 -25), lower values of turbulence and PAR, and a narrow niche breath. In contrast, the realized niche of D. acuminata (cell maximum 6.8 × 103 cells L−1 just above the pycnocline) was characterized by fresher (salinity 17 -20) outflowing surface waters, with higher turbulence and light intensity and a wider niche breadth. Results from OMI and PERMANOVA analyses of co-occurring microplanktonic ciliates were compatible with the hypothesis of species such as those from genera Pseudotontonia and Strombidium constituting an alternative ciliate prey to Mesodinium. The D. acuta cell maximum was associated with DSP (OA and Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.DTX-1) toxins and pectenotoxins; that of D. acuminata only with pectenotoxins. Results presented here contribute to a better understanding of the environmental drivers of species-specific blooms of Dinophysis and management of their distinct effects in Southern Chile. Previous article Highlights► 48 h of high frequency physical data for co-occurring blooms of 2 Dinophysis species. ► D. acuta (exceptional µ) thin layer briefly disrupted by an increase in turbulence. ► Co-occurring D. acuminata and D. acuta blooms showed a clear niche differentiation. ► Niche analysis results compatible with putative ciliate prey other than Mesodinium. ► D. acuta maximum associated with DSP toxins (OA, DTX1), D. acuminata with PTX2 only.

Lipophilic Toxins in Chile: History, Producers and Impacts

“…In Aysén, D. acuminata is endemic and blooms of variable intensity and duration occur every year between spring and autumn. D. acuminata may co-occur with D. acuta, but their niches are vertically segregated [53]. In samples with an overwhelming dominance of D. acuminata (Figure 7D) in Puyuhuapi Fjord, LC-MS analyses revealed a cellular content of PTX2 alone.…”

“…Blanco et al [54] showed that during that event, D. acuminata was present most of the time along 350 km of the coast, with cell maxima of 600-900 cells L −1 in different bays. Samples for quantitative analyses were taken with a tube sampler from 0 to 15 m. This species frequently aggregates in narrow layers close to the surface [52,53,89] and differences between 1 and 2 orders of magnitude are easily observed between tube and bottle sample counts of Dinophysis [90]. It is thus highly probable that very high concentrations of D. acuminata occurred during that event.…”

Harmful Algal Blooms and their impacts on shellfish mariculture follow regionally distinct patterns of water circulation in the western English Channel during the 2018 heatwave

“…However, in this alternative example other factors also contributed to niche differentiation between these Dinophysis species; D. acuta was associated with higher salinity compared to D. acuminata (i.e. 23-25 psu compared to 17-20 psu), and with lower levels of turbulence and Photosynthetically Active Radiation (PAR) (Baldrich et al, 2021). At each of our coastal survey sites salinity remained within 33.5-35 psu throughput the water column, so the environmental niches at our sites were not comparable with those in Chile.…”

“…At each of our coastal survey sites salinity remained within 33.5-35 psu throughput the water column, so the environmental niches at our sites were not comparable with those in Chile. Discriminating niches for these species is important in shellfish waters, since D. acuta and D. acuminata may produce different profiles of DSP toxins (OA, DTX and PTX toxins) and profiles have been shown to vary between geographical regions (Reguera et al, 2014;Baldrich et al, 2021).…”

Latitudinal Variation in the Toxicity and Sexual Compatibility of <i>Alexandrium catenella</i> Strains From Southern Chile

“…These harmful algal blooms (HABs) mainly consist of diatoms (e.g., Pseudo-nitzschia spp.) [3], and dinoflagellates (e.g., Alexandrium catenella, Dinophysis acuta, D. acuminata, Protoceratium reticulatum, and Karenia selliformis) [1,[4][5][6]. The main causative organism of HABs is A. catenella and its negative repercussions on human health, ecosystems, fisheries, and aquaculture are well-documented [7,8].…”