Dinophysis acuminata or Dinophysis acuta: What Makes the Difference in Highly Stratified Fjords?

Abstract

Dinophysis acuminata and D. acuta, which follows it seasonally, are the main producers of lipophilic toxins in temperate coastal waters, including Southern Chile. Strains of the two species differ in their toxin profiles and impacts on shellfish resources. D. acuta is considered the major cause of diarrhetic shellfish poisoning (DSP) outbreaks in Southern Chile, but there is uncertainty about the toxicity of D. acuminata, and little information on microscale oceanographic conditions promoting their blooms. During the austral summer of 2020, intensive sampling was carried out in two northern Patagonian fjords, Puyuhuapi (PUY) and Pitipalena (PIT), sharing D. acuminata dominance and D. acuta near detection levels. Dinophysistoxin 1 (DTX 1) and pectenotoxin 2 (PTX 2) were present in all net tow samples but OA was not detected. Although differing in hydrodynamics and sampling dates, D. acuminata shared behavioural traits in the two fjords: cell maxima (>103 cells L−1) in the interface (S ~ 21) between the estuarine freshwater (EFW)) and saline water (ESW) layers; and phased-cell division (µ = 0.3–0.4 d−1) peaking after dawn, and abundance of ciliate prey. Niche analysis (Outlying Mean Index, OMI) of D. acuta with a high marginality and much lower tolerance than D. acuminata indicated an unfavourable physical environment for D. acuta (bloom failure). Comparison of toxin profiles and Dinophysis niches in three contrasting years in PUY—2020 (D. acuminata bloom), 2018 (exceptional bloom of D. acuta), and 2019 (bloom co-occurrence of the two species)—shed light on the vertical gradients which promote each species. The presence of FW (S < 11) and thermal inversion may be used to provide short-term forecasts of no risk of D. acuta blooms and OA occurrence, but D. acuminata associated with DTX 1 pose a risk of DSP events in North Patagonian fjords.

An Unprecedented Bloom of Oceanic Dinoflagellates (Karenia spp.) Inside a Fjord within a Highly Dynamic Multifrontal Ecosystem in Chilean Patagonia

“…By the end of summer 2020, a moderate-density population of Karenia spp. (>10 5 cells L −1 ) was fortuitously detected in samples from Pitipalena Fjord collected during a 24 h study focused on Dinophysis [ 56 ]. Here, for the first time in Chile, the microscale distribution of Karenia spp.…”

“…Here, the natural barrier seems to be the isohaline of 21, i.e., the presence of EFW. In an earlier study, we concluded that the presence of EFW was a salinity barrier preventing the development of D. acuta in the northern Patagonian fjords [ 56 ]. During the present survey, D. acuta only appeared, briefly, when the warmer and saltier water (ESW) was at the surface.…”

“…The main river flowing into the fjord, the Palena River (average river discharge 800 m 3 s −1 ), is located at the very mouth of the fjord [ 52 , 53 ]. This distinct feature affects the site-specific hydrodynamics of Pitipalena Fjord, including water residence time (~200 days) [ 54 , 55 ], and the advection and retention of phytoplankton populations, including HABs [ 56 ].…”

Toxic Algal Bloom Recurrence in the Era of Global Change: Lessons from the Chilean Patagonian Fjords

“…The potential impacts of climate variability on the multi-decadal fluctuations in the composition and abundance of different functional groups, and on their respective trophic levels, have been the focus of attention in recent decades, due to the threat of climate change and global warming [ 36 ]. The effects will be exacerbated in highly heterogeneous systems such as the Patagonian fjords, where multiple niches promote the development or aggregation of different species, including microalgae [ 37 , 38 ]. Long-term variations in some phytoplanktonic species have been associated with anomalous oceanographic events that occur periodically over decadal time scales [ 39 ].…”

“…australis (2 × 10 6 cells L −1 ), and resulted in intense brown patches in waters close to the head of the fjord, as well as the death of juvenile hake. Given the niche differences of these HAB species [ 37 , 38 ], while the event was highly anomalous, the potential for its recurrence, and the consequences thereof, cannot be ignored.…”