Assessing the Performance and Application of Operational Lagrangian Transport HAB Forecasting Systems

Abstract

Availability of operational regional hydrodynamic models and near real time Harmful Algal Bloom (HAB) alerts from monitoring stations and remote sensing products have allowed the proliferation of short term advective HAB forecasts. However, their predictive ability in simulating HAB transport needs to be continuously evaluated in events of different HAB species to assess their applicability to different domains and the impacts of the choices made in model setup. Here we review the performance of three different modelling systems which were part of the PRIMROSE project against historical bloom events in different regions in the European Atlantic Area. The objectives are to understand their predictive ability and to demonstrate some aspects of Lagrangian model setup that are relevant to HAB early warning systems; in particular the use of advection-diffusion only models (without a biological component) and the effects of model configuration, especially model resolution. Hindcast and forecast simulations have been run in examples of high biomass blooms detected in satellite imagery; in the western English Channel, several events of potentially toxic species like Karenia mikimotoi and Prorocentrum cordatum (minimum) were simulated and in Western France a bloom of Mesodinium rubrum, prey of the toxic Dinophysis spp. Additionally, some simulations for studying the evolution of low biomass Dinophysis spp. blooms in Galicia-North Portugal were undertaken with models of different setup. Several metrics have been used to quantify the model performance and to compare the results of the different model configurations, showing that differences in hydrodynamical model configuration (initiation, resolution, forcing, and simulation domain) result in differences in the predicted transport of HABs. We find that advection only is a reasonable approximation but that it may do worse in an early (onset) phase than later on, and we find transport is generally increases with increasing resolution. Our results confirm that Lagrangian particle tracking tools can be integrated operationally in HAB early warning systems providing useful information on potential HAB evolution to users.

A demographic model to forecast Dinophysis acuminata harmful algal blooms

“…For this reason, the state-of-the-art in forecasting HABs use hydrodynamic simulations to force Lagrangian simulations of phytoplankton dispersion. Such are the cases of HABs forecasting in the North Atlantic, namely along the Iberian shelf, Bay of Biscay, British Isles and British Channel (Bedington et al, 2022;Hariri et al, 2022). Cell multiplication is the fundamental determinant of HABs during their earlier stages.…”

“…Cell multiplication is the fundamental determinant of HABs during their earlier stages. However, when populations have already achieved densities that are high and/or harmful, their transport and dispersion gain importance for the accuracy of the forecasts (Bedington et al, 2022). A significant portion of the lack of accuracy in our modelling efforts resulted from the lack of hydrodynamics in our model and this was exacerbated by a too wide census/projection interval.…”

Pelagic connectivity of European sea bass between spawning and nursery grounds

“…To mitigate this, a wide region was chosen for comparison around each estuary, rather than expecting to resolve recruitment into individual estuaries. However, future work should investigate the impact of higher resolution models (e.g., Graham et al, 2018), as improving resolution around the coast may be a significant factor in determining variability in particle trajectories (e.g., Dauhajre et al, 2019;Bedington et al, 2022). For example, supply to the Solent may be increased through improved resolution of flow around the region.…”

Red tides in the Galician rías: historical overview, ecological impact, and future monitoring strategies

“…and the potential advection of HAB populations. 103,108,118 In the case of red tides, numerical models can simulate the factors that can play a role in red tide development such as local oceanographic conditions associated with stratication due to warming or riverine input, nutrient dynamics, near bottom currents that might resuspend cysts and physical advection that can transport populations.…”