Abundance and distribution of potentially toxic phytoplankton in aquaculture sites along the Peruvian coast

The presence of harmful microalgae in aquaculture sites represents a risk for production and human health, so surveillance of these species is relevant for early warning of harmful algal blooms. Here we examine the monitoring results of potentially toxic phytoplankton in Peruvian coastal sites associated with the cultivation of Argopecten purpuratus and natural banks of other mollusks. We evaluated the density, frequency, temporal and spatial distribution of these species, as well as blooms occurred from 2011 to 2019. Results showed that the most abundant species was Heterosigma akashiwo, and the most frequent ones were Pseudo-nitzschia delicatisima and seriata complexes. The majority of blooms were caused by H. akashiwo (21 events) and Dinophysis acuminata (19 events). Canonical correspondence analysis revealed the preference of dinoflagellates to warmer sea surface temperatures and more stable conditions (indicated by low wind velocities) than Pseudo-nitzschia species. Generalized additive models (GAMs) indicated that wind velocities > 3.7 m s⁻¹ and El Niño conditions favor Pseudo-nitzschia species while warm temperatures (> 20 °C), weaker winds (< 3.7 m s⁻¹), and cold periods associated with La Niña promoted higher densities of D. acuminata complex. A recent increasing trend in the density of D. acuminata was observed. This information is useful to understand the dynamics of potentially toxic species in upwelling regions.