Application of a 3D Lagrangian model to explain the decline of a Dinophysis acuminata bloom in the Bay of Biscay

• Published in: Journal of marine systems Vol. 83; no. 3; pp. 242 - 252
• Main Authors: Velo-Suárez, L., Reguera, B., González-Gil, S., Lunven, M., Lazure, P., Nézan, E., Gentien, P.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-11-2010
• Subjects: Bay of Biscay; Biomass; Dinophysis acuminata; Dispersions; Harmful algal blooms; Lagrangian individual particle-tracking models; Marine; Maxima; Physical–biological interactions; Plumes; Rivers; Temperature gradient; Three dimensional; Transport; Dinophysis acuminata; Harmful algal blooms; Bay of Biscay; Physical–biological interactions; Lagrangian individual particle-tracking models
• ISSN: 0924-7963; 1879-1573
• DOI: 10.1016/j.jmarsys.2010.05.011

During July 2006, a cruise was carried out in the Northern Bay of Biscay (off Brittany, France) to study meso- and microscale patterns of phytoplankton distribution. Moderate concentrations (10
2–10
3
cells
L
−
1) of
Dinophysis acuminata were constrained to specific depths (upper layers above the pycnocline) at stations with lower surface salinity (34.5) and steep temperature gradients (18–13.5
°C between 4 and 7
m depth) within the Loire and Vilaine river plumes. On board incubations revealed a healthy
D. acuminata population at the biomass maxima with 89% of viable (FDA-treated) cells and moderate division rates (up to 0.10
d
−
1). Despite its good physiological condition, the population of
D. acuminata declined rapidly to undetectable levels during the second leg of the cruise.
A 3D Lagrangian Particle-Tracking Model (3D LPTM) was used to simulate the transport of
D. acuminata cells in the Loire and Vilaine river plumes from 15 June to 30 July. This 3D LPTM model was coupled to a MARS3D (Model for Applications at Regional Scale) model previously calibrated and validated for the region. Model results suggest that physical processes alone could explain the dispersion of the
D. acuminata population within the area. The application of a 3D-LPTM model shows how individual based model approaches are valuable to identify
Dinophysis spp. transport pathways and reproduce retention/dispersion patterns observed in the field.