Remote sensing, in situ monitoring and planktonic toxin vectors of harmful algal events in the optically complex waters of the Galician rias (NW Spain) Memoria presentada por Evangelos Spyrakos: Licenciado en Ciencias del Mar (University of Aegean, Greece, 2005) MSc en Integrated Coastal Zone Management (University of Aegean, Greece, 2007) MSc en Física Aplicada (Universidad de Vigo, España, 2009) para optar al grado de Doctor por la Universidad de Vigo Dirigida por: Dr. Jesús M. Torres Palenzuela: Laboratorio de Teledetección y SIG Física Aplicada Universidad de Vigo Dra. África González Fernández: Área de Inmunologia Universidad de Vigo Dr. Cástor Guisande: Departamento de Ecologia y Biologia animal Universidad de Vigo & FAO Roma Vigo, October 2011 El Dr. Jesús M. Torres Palenzuela, profesor titular del departamento de Física Aplicada de la Faultad de Ciencias de la Universidad de Vigo, la Dra África González Fernández, Directora del Centro de Investigaciones Biomédicas y Catedrática de Inmunología de la Universidad de Vigo y el Dr. Cástor Guisande González, Catedrático de Ecología de la Universidad de Vigo, INFORMAN: Que la presente memoria, titulada ¨Remote sensing, in situ monitoring and planktonic toxin vectors of harmful algal events in the optically complex waters of the Galician rias (NW Spain)¨, presentada por D. Evangelos Spyrakos para optar al grado de Doctor por la Universidad de Vigo, ha sido realizada bajo su dirección y reúne los requisitos necesarios para ser defendida ante el tribunal calificador. Por tanto, autorizan su presentación ante el Consejo de Departamento y la Comisión de Doctorado. Y para que conste a los efectos oportunos, firman en la presente certificación En Vigo a 25 de Octubre 2011 Dr. Jesús M. Torres Palenzuela Dra. África González Fernández Dr. Cástor Guisande González This PhD project was supported by European Commission's Marie Curie Actions through a grant within the project 20501 ECOsystem approach to Sustainable Management of the Marine Environment and its living Resources (ECOSUMMER). MERIS data were obtained through EUROPEAN SPACE AGENCY/ENVISAT project AO-623. A part of the chlorophyll data base was provided by the Technological Institute for the Control of the Marine Environment of Galicia. Content Summary ............................................................................................................................... iii Summary in spanish .............................................................................................................. vi Graphical abstract ................................................................................................................ ix List of tables ........................................................................................................................... xi List of figures ....................................................................................................................... xiii List of abbreviations ............................................................................................................ xv Acknowledgments .............................................................................................................. xvii Dissemination of and development from work performed for this thesis ...................... xix Thesis outline .......................................................................................................................... 1 CHAPTER I ▐ 5 Overall introduction 9 1.1 Satellite remote sensing of coastal optically complex waters 12 1.2 ELISA for DA detection 14 1.3 Harmful algae interactions with marine planktonic grazers 15 1.4 Study area: Galician rias 17 1.5 Motivations and thesis objectives 21 1.6 References CHAPTER II ▐ Development of regionally specific chlorophyll a algorithms of optically complex 29 waters for MERIS full resolution data Abstract 31 2.1 Introduction 32 2.2 Material and methods 34 2.3 Results 44 2.4 Discussion 52 2.5 References 57 CHAPTER III ▐ Application of a regionally specific 63 chlorophyll a algorithm for MERIS full resolution data during an upwelling cycle 65 Abstract 66 3.1 Introduction 68 3.2 Material and methods 74 3.3 Results & Discussion 88 3.4 References CHAPTER IV ▐ Remote sensing, in situ monitoring and environmental perspectives of toxic Pseudo- 95 nitzschia events in the surface waters of two Galician rias Abstract 97 4.1 Introduction 98 i 4.2 Material and methods 100 4.3 Results 106 4.4 Discussion 116 4.5 References 122 CHAPTER V ▐ Ingestion rates of the heterotrophic dinoflagellate Noctiluca scintillans fed on the 129 toxic dinoflagellate Alexandrium minutum (Halim) 131 Abstract 132 5.1 Introduction 133 5.2 Material and methods 137 5.3 Results 141 5.4 Discussion 144 5.5 References CHAPTER VI ▐ Modelling PST transfer and accumulation in 149 two planktonic grazers Abstract 151 6.1 Introduction 152 6.2 Methods 154 6.3 Results 163 6.4 Discussion 171 6.5 References 174 CHAPTER VII 181 General discussion & further considerations 183 7.1 Development of regional specific chla algorithms from MERIS FR data for optically complex waters 184 7.2 Remote sensing chla mapping during an upwelling cycle 186 7.3 Harmful Pseudo-nitzschia spp. events in the surface waters of two Galician rias 187 7.4 Planktonic grazing on a PST-producer dinoflagellate 188 7.5 General discussion to all chapters 189 7.6 References Conclusions ........................................................................................................................ 191 Annex I ............................................................................................................................... 195 Annex II............................................................................................................................... 211 ii Summary Transient increases of phytoplankton abundance, referred to as blooms, are a common and recurrent phenomenon in many coastal areas around the world including the upwelling estuarine systems of the Galician rias (embayments in North-West Spain). Harmful algal events due to toxic phytoplankton species and/or high-biomass blooms pose an increasing threat to aquaculture and fishing industries, ecosystem health and diversity and have possible implications to human health and activities. A multidisciplinary approach was followed in this PhD thesis in order to detect and study harmful algal events and their driving forces in the waters of the Galician rias and explore the possible toxin planktonic vectors and the fate of the toxins in the marine system. A set of neural network-based chlorophyll a (chla) algorithms for Medium Resolution Imaging Spectrometer (MERIS) full resolution (FR) data using in situ data sets and fuzzy clustering techniques was developed specifically for the optically complex waters (defined as Case 2 waters) of the Galician rias. Three clusters were determined, which represent the different structures found in the data base. Three different neural networks (NNs) were developed: one including the whole data set, and two others using only data points belonging to one of the clusters. The fitting results were fairly good and proved the capability of the tools to predict chla concentrations in the study area. The best prediction was given by the NN trained with high-quality data using the most abundant cluster data set. The NNs developed in this study detected accurately the peaks of chla, in both training and validation sets, outperforming the algorithms that are routinely used for MERIS data in Case 2 waters. As a continuation, this thesis takes advantage of these regionally specific algorithms and the characteristics of MERIS in order to deliver more accurate and detailed chla maps of optically complex coastal waters during an upwelling cycle and harmful algal events. The main changes in chla concentration and distribution were clearly captured in the images. There was a significant variation in the timing and the extent of the maximum chla areas. The maps confirmed that the spatial structure of the phytoplankton distribution in the rias Baixas is complex and it is affected by the surface currents and winds on the adjacent continental shelf. Relatively high biomass “patches” were mapped in detail inside the rias. During the sampling campaigns (2007-2009) that were carried out in the study area, toxigenic events due to Pseudo-nitzshia spp. and high abundances of the harmful dinoflagellate red Noctiluca scintillans were recorded. iii A combined analysis of satellite imagery data, measurements of biotic and abiotic parameters and mixed effects modelling was used to study Pseudo-nitzschia blooms in the surface waters of two of the rias. Domoic acid (DA) concentrations from natural Pseudo- nitzshia populations in the Galician rias were for the first time, to our knowledge, measured in the study area (below detection limits-2.5 μg L-1). Two DA outbreaks were recorded in the area. P. australis was the dominant Pseudo-nitzschia species during the blooms. The application of a regional algorithm in combination with the characteristics of MERIS FR allowed for accurate mapping of chla and the detection of small, high in chla and Pseudo- nitzschia spp. “patches” in the rias. The optimal model for the Pseudo-nitzschia spp. abundance and DA concentration suggested the significant effect of some macronutrients as well as other abiotic and biotic parameters, approximating in that way the potential environmental causes and effects of the harmful Pseudo-nitzschia spp. blooms in the area. In the case of N. scintillans, speciments of this species were collected from the rias and were established in laboratory cultures. This species was fed with the toxic (Paralytic Shellfish Poisoning or PSP) dinoflagellate Alexandrium minutum in order to evaluate its ingestion and clearance rates and test for toxin accumulated in the individuals. N. scintillans actively fed on A. minutum showing no satiated feeding. No detectable amounts of toxins in the individuals revealed from the High Performance Liquid Chromatography (HPLC) toxin analysis. In order to calculate detoxification rates of N. scintillans a new experiment this time performed using a different strain and species of Alexandrium, A. catenatum which was characterised by higher levels of toxin content. N. scintillans showed relatively high detoxification rates (-0.17 pg toxin ind-1 h-1). Using the results of these two experiments in combination to previously published data, dynamic models were developed in order to study the PST transfer and accumulation in two planktonic organisms, namely the copepod Acartia clausi and and the heterotrophic dinoflagellate N. scintillans. This thesis shows the capability of NN models to predict chlorophyll concentrations on the Galician coast from MERIS images following the widespread understanding of the need for regionally specific models. According to the recorded in situ data, the model presented here is an improvement on other previously used techniques, and made it possible to obtain reliable chlorophyll maps using almost every image. These maps were used to study the evolution of local oceanographic processes, which in turn were related to the development of algal blooms in the area. The present study allows more detailed examination of the chla distribution and detection of high biomass areas in the Galician rias and the adjacent area and should be an integral part of the monitoring programs. Moreover, the results of this study deduce that toxic events due to DA should be an iv