# Characteristics of a Dinophysis cf acuminata Population from a Tidewater Glacier Lagoon in a Temperate Latitude: Applications to Dinophysis Studies

## TL;DR

This paper studies a unique population of Dinophysis acuminata in a tidewater glacier lagoon in Chile, highlighting its role in shellfish poisoning and its adaptation to a rare ecosystem.

## Contribution

The study presents a novel PTX2-containing Dinophysis cf acuminata population in a unique tidewater glacier lagoon environment.

## Key findings

- Dinophysis acuminata was the only species observed in the lagoon's cold, brackish waters.
- Cell densities varied seasonally, reaching up to 2800 cells per liter in summer.
- Genetic analysis confirmed the species' relation to European and North American strains and identified Mesodinium rubrum as the plastid source.

## Abstract

Dinophysis acuminata, the main agent of diarrhetic shellfish poisoning (DSP) worldwide, shows a high variability in morphology and toxin content between strains from contrasting habitats. Most frequent uncertainties in morphological discrimination are within the “D. acuminata complex”, but confusion with other species (e.g., D. norvegica, D. fortii) also occurs. Here we describe a unique PTX2-containing population of Dinophysis cf acuminata observed during opportunistic samplings in San Rafael Lagoon (Chilean Patagonia), the only tidewater glacier lagoon remaining in the glacier with the world’s lowest latitude. Dinophysis acuminata was the only Dinophysis species observed during three seasonal surveys in the well-mixed cold (4–7° C) and brackish (salinity 14–15) waters of the lagoon. Cell densities ranged from 500 cells L−1 (winter) to 2800 cells L−1 (summer). Partial sequences of their ITS rDNA aligned them with D. acuminata strains from Europe and North America, and sequences of their stolen plastids 23S rDNA confirmed ciliates of the Mesodinium rubrum + major complex as their prey and plastid source. All these reasons make this lagoon a highly sensitive area and natural laboratory for climate change-related topics and Dinophysis issues related to (i) the effect of long-term exposure of marine fauna to pectenotoxins and (ii) the adaptations of D. cf acuminata to persist in a unique ecosystem with austral water characteristics located in a warm temperate latitude light regime. Results here add knowledge to the biogeography and habitat ranges of D. acuminata and the problems faced to monitor and provide early warning of its distribution.