Projecting Future Climate Change-Mediated Impacts in Three Paralytic Shellfish Toxins-Producing Dinoflagellate Species

Abstract

Toxin-producing microalgae present a significant environmental risk for ecosystems and human societies when they reach concentrations that affect other aquatic organisms or human health. Harmful algal blooms (HAB) have been linked to mass wildlife die-offs and human food poisoning episodes, and climate change has the potential to alter the frequency, magnitude, and geographical extent of such events. Thus, a framework of species distribution models (SDMs), employing MaxEnt modeling, was used to project changes in habitat suitability and distribution of three key paralytic shellfish toxin (PST)-producing dinoflagellate species (i.e., Alexandrium catenella, A. minutum, and Gymnodinium catenatum), up to 2050 and 2100, across four representative concentration pathway scenarios (RCP-2.6, 4.5, 6.0, and 8.5; CMIP5). Despite slightly different responses at the regional level, the global habitat suitability has decreased for all the species, leading to an overall contraction in their tropical and sub-tropical ranges, while considerable expansions are projected in higher latitudes, particularly in the Northern Hemisphere, suggesting poleward distributional shifts. Such trends were exacerbated with increasing RCP severity. Yet, further research is required, with a greater assemblage of environmental predictors and improved occurrence datasets, to gain a more holistic understanding of the potential impacts of climate change on PST-producing species.

Impacts of Climate Change Impacts on the Biogeography of three Amnesic Shellfish Toxin-producing Diatom species

“…Concerning variable contribution, bathymetry was the most contributing variable for all species, with values between approximately 61% (P. fraudulenta) to approximately 82% (P. seriata). This trend has also been observed in SDMs with PST-producing dino agellates [54] and is to be expected when dealing with neritic species, and with occurrence data obtained mostly from coastal monitoring programs. At the same time, Pseudo-nitzschia blooms are known to be linked to upwelling regions [55,56].…”

“…Indeed, dino agellates in the Atlantic and Paci c oceans have been found to closely follow the rate of isotherm movement [10,[61][62][63], as the range of optimum environmental conditions shifts, effectively pressuring their ability to survive and adapt at lower latitudes and opening the possibility of HAB events in newer regions. Borges et al [54] also projected potential poleward shifts for PST-producing dino agellate species (i.e., Alexandrium minutum; A. catenella; and Gymnodinium catenatum), while other groups such as Cocolitophores [64] also exhibit the same distributional changes. Changes in temperature have also been shown to induce signi cant impacts in diatoms, with warming being linked to lower cell yield and promoted growth in Pseudo-nitzschia species [65], while extreme events such as heatwaves have also triggered pelagic HAB events [37].…”

“…This was performed using the function 'extract' from the package 'raster'. Afterwards, the spatial polygon objects were converted into data frame format and merged with the georeferenced depths, and the new data frames were subset to exclude depths greater than 200 m [5,54]. A second restriction clipping was employed to remove all points based on land.…”

“…To analyze potential changes in habitat suitability and species distribution across time and space, a serious of visual and quantitative post-analysis procedures were employed. These procedures are the same as in Borges et al [54], and the post-analysis scripts can be found in the Supplementary Material (See "Post_analysis" folder). First, to quantify the changes in the global latitudinal distribution for each species, the latitudinal centroids (i.e., the arithmetic mean latitude for the species-occupied cells) for each time and RCP scenario were plotted.…”

“…Not surprisingly, these models have already been employed to project potential marine climate changeinduced impacts in the distribution of phytoplankton [30], and speci cally of HAB species [5,53,54]. In this context, the objective of the present study was to evaluate the potential effects of future marine climate change on the distribution of three amnesic shell sh toxin (AST) producing Pseudo-nitzschia species: (i) P. australis; (ii) P. seriata; and (iii) P. fraudulenta.…”