Field studies

Three regions important for aquaculture are identified for field studies. These are the Rias of Galicia (NW Spain), the estuarine plume zones of the Atlantic coast of France, and the bays of southwestern Ireland. All regions are very important shellfish production areas, yet all have a history of harvest closures resulting from contamination with DSP toxins. Oceanographically, all regions are well understood, and all have the logistic support of weekly reports, based on intensive samplings undertaken by the local or national monitoring programmes.

The Rias Baixas are chosen as the main experimental site, due to the predictability of the occurrence of Dinophysis populations there. Knowledge of time-windows when infestations of harmful populations of Dinophysis occur ensures a minimal risk element to the project. High-density thin layers of Dinophysis are known to arise annually in the vicinity of the bays of southwestern Ireland and the estuarine plume zones of the Atlantic coast of France. Thin layer studies will also be carried out in these locations, but a second focus here will be the application of results attained from them into physical models. High quality physical (3D) models exist for the Atlantic shelf area of France (MARS 3D) and for the northern Celtic Sea (Cefas A1225) at the second shelf site (SW Ireland).

Fieldwork organisation

The proposed fieldwork activities build on preliminary research carried out in joint studies in the Ria de Vigo, Ría de Pontevedra and adjacent shelf (NW Spain), in August 2003. In this instance, it was quickly established that a bloom of Dinophysis caudata was occurring as a thin layer at the pycnocline. The population exhibited signs of mixotrophic behaviour at certain depths, with small vacuolae of the same size and fluorescing with the same colour as surrounding picoplanktonic microorganisms containing phycoerythrin (Reguera, Gentien, unpublished data). The schedule of joint activities is as follows:

June 2005: 12 day study in Rias Baixas. Objective: to describe and study the biological relationships pertinent to thin layers. To study the behaviour of key species within these layers. To test trophic relationships within the layers. To study the effect of vertical turbulence on the maintenance of thin layers.

August 2005: 12 day study, southwestern Ireland. Objective: to observe features relevant to the occurrence of thin layers of Dinophysis. To measure horizontal diffusion within thin layers through dye studies. To test the use of models to predict occurrence of HAB (Dinophysis) events along the Irish coast.

July 2006: 21 day study Loire plume. Objective: to observe relationships between physical structures (small gyres, degrees of thermohaline stratification) and thin layers. To utilise models to establish how the features are dispersed/advected on to the coast. This will be coupled with time series data from monitoring locations along the coastline.

June 2006: 12 day study in Rias Baixas. Objective: to describe and study the biological relationships pertinent to thin layers. To study the behaviour of key species within these layers. To elucidate biochemical interactions within populations containing Dinophysis.