Harmful phytoplankton diversity and dynamics in an upwelling region (Sagres, SW Portugal) revealed by ribosomal RNA microarray combined with microscopy

Abstract

The study region in Sagres, SW Portugal, is subject to natural eutrophication of coastal waters by winddriven upwelling, which stimulates high primary productivity facilitating the recent economic expansion of bivalve aquaculture in the region. However, this economic activity is threatened by harmful algal blooms (HAB) caused by Pseudo-nitzschia spp., Dinophysis spp. and other HAB dinoflagellates, all of which can produce toxins, that can induce Amnesic Shellfish Poisoning (ASP), Diarrhetic Shellfish Poisoning (DSP) and Paralytic Shellfish Poisoning (PSP). This study couples traditional microscopy with 18S/28S rRNA microarray to improve the detection of HAB species and investigates the relation between HAB and the specific oceanographic conditions in the region. Good agreement was obtained between microscopy and microarray data for diatoms of genus Pseudo-nitzschia and dinoflagellates Dinophysis spp., Gymnodinium catenatum and raphidophyte Heterosigma akashiwo, with less effective results for Prorocentrum. Microarray provided detection of flagellates Prymnesium spp., Pseudochattonella spp., Chloromorum toxicum and the important HAB dinoflagellates of the genera Alexandrium and Azadinium, with the latter being the first recorded from the study region. Seasonality and upwelling induced by northerly winds were found to be the driving forces of HAB development, with Pseudo-nitzschia spp. causing the risk of ASP during spring and summer upwelling 2 season, and dinoflagellates causing the risk of DSP and PSP during upwelling relaxation, mainly in summer and autumn. The findings were in agreement with the results from toxicity monitoring of shellfish by the Portuguese Institute for Sea and Atmosphere (IPMA, 2014(IPMA, -2016 and confirm the suitability of the RNA microarray method for HAB detection and aquaculture management applications.

Variability patterns and phenology of harmful phytoplankton blooms off southern Portugal: Looking for region-specific environmental drivers and predictors

“…Available information on HABs enabled the development of group-specific predictive models for northwestern Iberia (Palma et al, 2010;Moita et al, 2016;Díaz et al, 2016;Ruiz-Villarreal et al, 2016;Palenzuela et al, 2019;Alaéz et al, 2021). By contrast, knowledge of planktonic HABs over the south and southwest Portuguese coasts is still limited (Moita, 2001), mostly covering the westernmost sector of the south coast (Loureiro et al, 2005(Loureiro et al, , 2011Danchenko et al, 2019;Santos et al, 2021), or specific HAB events (Mateus et al, 2013;Pinto et al, 2016;Caballero et al, 2020). Beyond a mechanistic Lagrangian model previously used for predicting HABs along the southwest and south Portuguese coasts, during a limited period (Silva et al, 2016), no group-specific predictive models for HABs are currently available for the complex coastal domains off southern Portugal.…”

Dinoflagellate Assemblages in the West Iberian Upwelling Region (Sagres, Portugal) During 1994–2001

“…Type I (Gymnodiniods) by Smayda and Reynolds (2001) could not be compared with the results of this study because only larger armored dinoflagellates were collected. However, in the data obtained at the same location during 2010-2016 (Goela et al, 2014;Danchenko et al, 2019) Gymnodinioid species were frequently present during summer upwelling season, often concurrently with diatom blooms.…”

“…This may possibly promote more intensive phytoplankton blooms in spring related with upwelling events outsides of the main upwelling season. Such blooms are initially dominated by diatoms and flagellates in the study area (Loureiro et al, 2005;Goela et al, 2014), but at the later stages of succession dinoflagellates may be promoted, including HAB species e.g., as observed in spring 2016, when diatom bloom was followed by the appearance of HAB dinoflagellates (Danchenko et al, 2019).…”

“…The corresponding winter dinoflagellate community in this study contained species of the "Tripos" Group 1 and some rare species in low proportions. Spring and early summer at study site were characterized (Loureiro et al, 2005(Loureiro et al, , 2011Goela et al, 2014Goela et al, , 2015Danchenko et al, 2019) by the proliferation of blooms, mainly composed of diatoms belonging to genera Chaetoceros, Guinardia, Pseudo-nitzschia and marked by an increase in Chl a. These spring blooms could be initiated by the upwelling-driven increase in nutrients, increasing photoperiod and SST (Loureiro et al, 2005(Loureiro et al, , 2011Goela et al, 2014).…”

“…The study of the cysts of dinoflagellates Gymnodinium catenatum and Lingulodinium polyedra in the coastal sediments (Amorim et al, 2002) suggests regular development of these toxic species along the S and SW coasts of Portugal that are affected by upwelling, including the Sagres area. Recent studies at Sagres (Loureiro et al, 2005(Loureiro et al, , 2011Goela et al, 2014Goela et al, , 2015Danchenko et al, 2019;Santos et al, 2020) reported phytoplankton blooms dominated by diatoms and demonstrated a frequent presence of harmful phytoplankton species, including dinoflagellates of genera Dinophysis, Prorocentrum, Lingulodinium, Gymnodinium, Karlodinium, Azadinium and their relation with seasonal upwelling.…”