Current projects within the CRP: HABs in Upwelling Systems
In 2006 the CRP committee reviewed the eight key research questions described in GEOHAB Core Research Project: HABs in Upwelling Systems and summarized ongoing and planned research in the four upwelling systems relevant to these eight key questions. The committee developed research projects related to six of the eight key questions, for which some research is already ongoing and could provide a core set of scientists for GEOHAB-related research. Descriptions of the research projects follow, including the motivation for the projects, likely participating regions, a project coordinator and participants (the intention is that this list will expand as more scientists worldwide link their research to these projects), project objectives, project approach and work plan, and expected project output.
Effects of nutrients on HAB population dynamics in upwelling systems.
Climate and HABs in upwelling systems.
Genetic comparisons of HABs in upwelling systems.
Coastal morphology and its influence on HABs in upwelling systems.
Seeding strategies within upwelling systems.
The role of across-shelf and alongshore currents in the transport of HABs in upwelling systems.
Project: Effetcs of nutrients on HAB population dynamics in upwelling systems
A defining attribute of upwelling systems is the periodic supply of nutrients from deeper waters that provides appreciable scope for phytoplankton growth and concomitant effects on higher trophic levels. Given the compelling evidence for a global increase in HABs, and their established negative impacts in coastal upwelling environments (Picher and Calder 2000, Smayda 2000), it is important to understand how this potential production is channeled into HABs as opposed to, or as a successional stage of, the more benign/beneficial blooms that generally characterize these regions. In this regard, there appears to be a dearth of information in coastal upwelling ecosystems relating specifically to the nutritional aspects of HABs compared to the more typical non-HAB, diatom-dominated assemblages.
Based on existing areas of research, these studies will be undertaken predominantly in the California Current, Benguela Current and Iberian Current systems. In the Benguela, the area of focus is the greater St Helena Bay region of the southern Benguela (33ºS), though opportunistic studies will be undertaken with blooms as and where they occur. The focus in the United States is central California, and the Washington State coastline. There may also be interested investigators in Oregon and southern California. In the case of the Iberian Current, the study area will be the Spanish Rías Baixas where existing data sets and ongoing research and monitoring programmes provide the opportunity for checking the variability of nutrient ratios and their influence on HABs.
Project Coordinator: T. Probyn [Marine & Coastal Management, Cape Town]
California Current – Coordinator: R. Kudela (UC Santa Cruz). Collaborators: W. Cochlan (San Francisco State University), J. Largier (UC Davis), K. Bruland (UC Santa Cruz), M. Wells (U. Maine), P. Strutton (Oregon State University), C. Trick (Canada)
Benguela Current – Coordinator: T. Probyn (M&CM, Cape Town). Collaborators: S. Seeyave, D. Purdie (NOC, Southampton), G. Pitcher (M&CM, Cape Town), S. Bernard, M. Lucas (U. Cape Town)
Iberian Current – X.A. Álvarez-Salgado (IIM-CSIC), C.G. Castro (IIM-CSIC), M.D. Doval (ITECMAR)
Quantify the importance of upwelled nutrients to HABs as the f-ratio (N-based).
Provide physiological understanding of HAB species’ nutrition (N, P, Si) and biological supply mechanisms (regeneration).
Determine the role of trace metals in HAB dynamics.
Identify how nutrient availability and speciation may affect cellular toxicity (N, P, Si, trace metals).
Provide input to HAB biogeochemical models.
Approach and Workplan
1] Macronutrients – This effort will focus on standard field-based, 15N tracer studies of new/regenerated production based on NO3, NH4 and urea (and other organic sources) utilization under different bloom scenarios. These studies should be supplemented with C productivity measurements. Use of size fractionation may provide important insight to the particular species under consideration and the general usefulness of a life-form approach to HAB nutrition. A combination of field measurements of N assimilation and toxin content (where relevant) could provide supporting information on N-speciation effects on cell toxin content. The “definitive” work in this regard would be addressed in culture studies, initially intended to focus on Alexandrium spp. and Pseudo-nitzschia spp. Nutrient addition bioassays (N, P, Si) with field samples, can be similarly employed for potential effects on cell toxin content. Measures of nutrient kinetics will allow parameterization of uptake, growth and toxin responses to concentration, light and temperature.
2] Trace metals – For some organisms, such as Pseudo-nitzschia, trace metals, particularly Fe and Cu, are thought to be critical factors in determining toxicity. These effects will be addressed similar to the macronutrient studies, including the use of laboratory studies to examine, for example, growth and transport kinetics. Field incubations can be carried out with metal additions or, alternatively, with chelators such as DFB (an Fe-binding compound). Non-invasive methods, such as variable fluorescence, may also be useful for rapidly assessing micronutrient status in relation to environmental conditions.
3] In addition to the incubation-based approaches mentioned above, routine measurements of nutrient concentrations (macro and micro) and ratios, coupled with detailed taxonomic studies and toxin content, could provide valuable insight to the controlling effects of nutrients on key HAB processes. Such measurements would address both particulate and dissolved concentrations as is deemed important.
These studies will make use of ongoing field studies and cruises as well as dedicated research cruises. Exchange of cultures from the different regions would be highly beneficial for comparative laboratory studies.
Improved understanding of HAB nutrient dynamics in upwelling systems, relating both to the different phases of bloom development and decline, and to cellular toxicity.
Realistic parameterization of biogeochemical models for the regions under study.
Informed advice to managers regarding, for example, consumer safety and potential HAB threats to the marine ecosystem.
Post-graduate student training.
Project: Climate and HABs in upwelling systems
Changes in upwelling intensity provide one of the substantiated lines of evidence for warming climatic trends (Bakun 1994), although the specific regional responses are still being established (e.g., Diffenbaugh et al. 2004). Several research groups have documented a correlation between HAB events (frequency and magnitude) and changing climate indicators. For example, HAB events are believed to be occurring more frequently during El Niño/Southern Oscillation (ENSO) events in the Humboldt Current system when low abundance of diatoms coincides with increasing numbers of new species (primarily dinoflagellates, including some toxigenic species) resulting in serious problems to the anchovy fishery (Rojas de Mendiola 1981, Rojas de Mendiolo et al. 1985), while ENSO events have also been correlated with toxic HAB events in Mexico (Ochoa 2003). There is a need to compare interannual variability of HABs among upwelling systems as well as at different latitudes within a system. The study of regions in different hemispheres will allow comparisons to be made on the effects of the seasonal timing of arrival of climatic signals on HABs. For example, the ENSO signal arrives in the summer in one hemisphere, but in the winter in the other hemisphere; similarly, each basin has unique climatic signals, such as the Pacific Decadal Oscillation (PDO) in the Pacific versus the North Atlantic Oscillation (NAO) in the Atlantic.
Influences of climate require well-documented time series of a sufficient duration to characterize the underlying mechanisms. Research needed to establish linkages between HABs and climate change includes data-mining efforts for short-term time series (examination of time series and satellite data, e.g. Sacau-Cuadrado et al. 2003), as well as projects involved in micro-paleontology (dating and characterizing sediment cores) for longer time series, and finally development of hindcast and forecasting models to help apply the knowledge gained to our understanding of HAB dynamics.
However, comprehensive, complete, long-term HAB datasets and corresponding environmental data are rarely available. Many HAB data are collected by managers only when necessary for the protection of public health, resulting in incomplete time series or inconsistent datasets. Effective time-series analysis requires very large data sets; an appropriate data policy conducive to data sharing will need to be established(i.e., individual investigators will be willing to share data knowing that it will only be used for meta-analysis).Furthermore, care will need to be taken to differentiate climatic effects from other long-term changes such as urbanization and land-use practices, fresh-water diversion, etc.
Iberian, Californian, Benguela, Canary, Humboldt
Project Coordinator: V. Trainer (NOAA, USA)
Iberian: T. Moita (IPIMAR), A. Rocha (U. Aveiro), Y. Pazos (CCMM, Spain), L. Valdez (Spain, RADIALES project), A. Amorim (U. Lisbon).
California: V. Trainer, B. Peterson (NOAA), N. Mantua, B. Hickey, R. Horner (U. Washington), R. Kudela (UCSC), F. Schwing (NOAA, ARD), F. Chavez (MBARI), P Strutton (OSU), E. Venrick (Scripps), G. Gaxiolla (Mexico), John Hunter, SWFSC, P. Strutton (Oregon State University), M. Wood (University Oregon) and Tim Baumgartner, CICESE/Scripps.
Humboldt: S. Sánchez (IMARPE, Peru).
Benguela: B. Dale (U. Oslo, Norway).
In addition, several international research projects with climate aspects are underway, providing opportunities for collaboration with the above-mentioned GEOHAB collaborators. These projects and programs include GLOBEC, IMBER, CLIVAR, LOICZ, IMAGES, CPPS, ERFEN.
The GEOHAB Core Research Project on Eutrophication has also identified climate change and HABs as one of their areas of focus. We anticipate working closely with this group.
1] To investigate potential correlations between “long-term” HAB monitoring data (shellfish toxicity, toxigenic species, continuous plankton recordings) and local environmental data (e.g., nutrients, wind, temperature) as well as regional and global climate indicators (ENSO, PDO, NAO).
Approach and Workplan
Biological data for addressing climate impacts on HABs within each region should include the following: phytoplankton species distribution (with a focus on HAB species), shellfish toxin levels, numbers of shellfish closures, and sediment cores that provide information on the history of HAB species through their presence in the sediments either as vegetative or cyst stages. Meteorological (wind speed and direction, temperature), physical (ocean current direction and speed, temperature, salinity, river flow), and chemical (nutrients, oxygen levels) records that can be correlated with biological datasets should all be collected and quality controlled. Although satellite data are only available for the past two to three decades, these should be included to determine trends in temperature and biomass over larger spatial regions.
Regions will collaborate to determine best methods for data analysis and comparison, including statistical analysis, modeling, and development of forecasting capabilities. Important to this work will be agreements on data sharing and quality control of data.
An understanding of which environmental conditions are conducive to HAB occurrences and whether the same environmental variables are important to the initiation of HABs in comparable upwelling systems and at different sites within an upwelling system.
Determination of whether environmental and climate indicators can be used to determine which HAB events are due to anthropogenic factors (such as increased nutrient inputs) or climate change (such as ENSO).
The synthesis of predictive models that can forecast the years in which HAB events might be most severe. This will provide advice to managers who could respond, for example, by increasing their monitoring effort during these years.
Identification of endemic organisms versus those that appear suddenly in a time series, owing, for example, to human-mediated transport.
Project: Genetic comparisons of HABs in upwelling systems
This project will address the role of genetic predisposition versus environmental conditions in toxin production in different upwelling systems within a given genus or species. It is well known that toxigenic HAB species exhibit variability in toxin production, both at the species and genus level, within a given upwelling system. Multiple environmental factors have been shown to influence HAB toxicity and ecology and it is possible that the entire range of observed spatial and cell-specific variability in toxin production is a response to subtle environmental cues. However, variability in genotypes is a common feature of phytoplankton. These genotypic differences are responsible for markedly different phenotypic expression in response to environmental cues within the same putative species. Therefore, the variability in toxin production is likely caused by a combination of genotype and environmental conditions. A genetic comparison of HAB organisms among regions is useful for differentiating between genetics and environment. Although there are several genetic comparisons that could be identified, here we focus on four potential targets that are found in all regions: Pseudo-nitzschia spp., Protoceratium reticulatum, Lingulodinium polyedrum, and Alexandrium catenella.
Participating Regions: Benguela, California Current System, Iberian Peninsula
Project Coordinator: R. Kudela, University of California Santa Cruz (USA)
Benguela: C. Marangoni, G. Pitcher, T. Probyn
California Current System: V. Armbrust, L. Busse, P. Franks, B. Jenkins, R. Kudela, P. Miller, G. Rocap, C. Scholin, G. Smith, P. Strutton, V. Trainer, M. Wood
Iberian Peninsula: A. Amorim, S. Fraga, T. Moita, B. Paz
Molecular characterization (e.g. sequence analysis for application of RNA/DNA molecular probes) for harmful algal species in each region
Based on (1), determine whether HAB-producing organisms are genetically distinct for the comparable regions
Utilize differences in cell toxin quota of a given species in separate upwelling regions to allow characterization of genes and biochemical pathways important for toxin synthesis
Approach and Workplan
To address these questions, a combination of comparative field and laboratory approaches is required:
- A critical baseline component for genetic comparison would be accurate characterization of the organisms by traditional taxonomic methods in coordination with the genetic work, to ensure that molecular databases are compatible with traditional identification methods.
- For the molecular work, a first step would be to assemble a collection of isolates from the three regions for each HAB species of interest for evaluation of physiological and genetic variability under controlled (laboratory) conditions. At minimum, the following laboratory work is envisioned:i) Isolation and culture of representative organisms; ii) Molecular phylogeny (ITS sequences, etc); iii) Characterization of growth rates, maximum cell density; iv) toxicity in relation to:light, temperature, macronutrients; and v) genetic expression using, e.g., targeted probes from previous studies*
- Field studies. Guided by the results and questions from laboratory studies, molecular genetic approaches should be applied to field data to: i) Test molecular probes (for species identification and/or biochemical pathways) on natural field assemblages - this will provide information on cross-reactivity and specificity; ii) Correlate genetic signatures to environmental factors - methods such as RFLP or micro-satellite analysis can be used to differentiate genetically distinct sub-populations within a species* - comparative studies may help to identify environmental factors that consistently trigger genes of interest
Vectors (e.g., shellfish, planktivorous fish) for HAB toxins should also be examined for differences in toxin retention, since regional variability in HAB events may be less related to the genetic/environmental characteristics of the algae, and more a function of the vectors (e.g., different species of shellfish will exhibit widely different toxicity)
* Developing new molecular information (e.g., subtraction libraries, RFLPs, etc.) is costly, and would require substantial project support. Application of existing molecular probes is considerably less expensive, and could serve as the basis for future funding.
Ideally, molecular techniques for toxic algae would focus on the detection of genes that are “turned on” during toxin production, not merely on cell or toxin detection alone (Plumley 1997). New molecular techniques such as subtractive hybridization permits the identification of genes that are differentially expressed in organisms grown under different conditions, for example, those that induce toxin production and those that do not induce toxin synthesis. If genetically related organisms can be identified which produce toxin in one region but not another, it is much more likely that “toxin genes” or pathways can be identified. Output from this project would generate the following:
- Species-specific rDNA probes for each region (ideally “global” probes)
- Regional cross-reactivity and sensitivity assays for rDNA probes
- Phylogenetic map of variability between regions
- Ideally, toxic and non-toxic strains would be identified
- For toxic/non-toxic strains, gene expression libraries would be obtained
- Correlation of molecular data to specific regional environmental conditions
- Probes for toxin genes or pathways allowing ID of most threatening strains may ultimately be developed, with direct application to monitoring/forecasting programs
Project: Coastal morphology and its influence on HABs in upwelling systems
Alongshore variability of coastal upwelling is mainly controlled by the interaction of the wind-forced shelf flow with coastline and bottom topography, resulting in the amplification and/or reduction of upwelling-downwelling processes (Figueiras et al. in press). Consequent spatial variability in upper mixed layer characteristics and shelf flow related to coastline discontinuities, such as pronounced capes, coastal embayments or Rias (in northwestern Iberia), often favours HAB development by enhancing vertical stratification and by forming regions of retention. Comparative research within these regions will serve to assist in identifying the underlying physical processes responsible for the higher incidence of HABs within these regions.
Considerable overlap is found in the HAB species of interest in upwelling systems. Alexandium catenella is responsible for PSP in both the California Current System and Benguela, whereas Gymnodinium catenatum causes PSP off the Iberian Peninsula. PSP has been recorded in the Humboldt but the causative organism has yet to be identified. A number of species of Dinophysis (e.g., D. acuminata) are common to all regions and are in most cases associated with DSP. Yessotoxins appear common and are produced by either Protoceratium reticulatum or Lingulodinium polyedrum. Other red tide-forming dinoflagellates are associated with anoxia in the Benguela and Humboldt currents. ASP is a concern in most regions, particularly in the California Current System, and the diatom Pseudo-nitzschia australis, typically responsible for ASP, is common to all regions. Blooms of the raphidophyte Heterosigma akashiwo are also of concern to most regions. The development of high biomass blooms of the above species are often associated with coastline discontinuities which result in alongshore variability giving rise to areas of convergence or retention. Initial studies will focus on the following embayments:
California Current System – Monterey Bay 37oN, Bodega Bay 38oN, Willapa Bay 46oN
Iberian Upwelling System – Lisbon Bay 38oN, Rias 42o
Benguela Upwelling System – St Helena Bay 33oS
Humbolt Current System – Paracas Bay 14oS
Project Coordinator: G. Pitcher (Marine & Coastal Management, Cape Town)
California Current System: N. Banas, S. Bograd, J. Goldberg, B. Hickey, R. Kudela, J. Largier, J. Ryan, P. Strutton, M. Wood
Iberian Upwelling System: A. Amorim, P. Oliveira, J. de Silva, A. Peliz, M. Santos, T. Moita, V. Brotas (Lisbon Bay) X. Álvarez-Salgado, D. Barton, F. Figueiras, S. Fraga, Y. Pazos, B. Reguera, C. Castro, P. Montero, M. Villareal, R. Torres, S. Groom, J. Allen [Rias]
Benguela Upwelling System: S. Bernard, N. Burls, A. Fawcett, P. Penven, G. Pitcher, T. Probyn, C. Whittle
Humboldt Current System: L. Carbajo, E. Delgado, R. Flores, S. Sánchez, J. Tam
To establish the importance of coastline morphology and bathymetry in:
1] creating local upper mixed layer conditions favourable for the selection and development of HABs and;
2] determining bay circulation patterns favouring bloom development through retention.
Approach and workplan
Circulation patterns for each study area need to be determined in an effort to identify bloom transport mechanisms and regions of convergence and retention important in the development of blooms. For this purpose, measures of ocean currents and the construction of hydrodynamic models incorporating data from meteorological stations, and themistor and current meter moorings are important. Phytoplankton distributions need to be linked to spatial variations in upper mixed layer characteristics and to circulation patterns, primarily through ship-based measurements, but may be supplemented by near-shore monitoring programmes. Attempts may be made to track bloom development and transport by means of mooring systems, drogue deployments, AUV surveys and satellite observations, and hydrodynamic models should be used to support observations.
- Identification of similar or contrasting patterns of local modulation of the upwelling process in response to time-varying wind forcing and spatially variable coastal morphology and bathymetry, important in establishing areas of higher bloom incidence.
- Determination of common processes driving spatial and temporal changes in the upper mixed layer characteristics, responsible for changes in the community composition, incorporating those species responsible for harmful blooms.
Establishment of common circulation patterns, driven by similar processes, important to the introduction, concentration, retention or dissipation of blooms.
Advancement of predictive skills of HABs based on understanding the physical forces underlying these areas.
Project: Seeding strategies within upwelling systems
The identification of seed or over-wintering populations and the establishment of seeding strategies are important in understanding the development of HABs in upwelling systems, which are recurrent but not always predictable. To better understand and model HABs, species-specific life-history transitions, which may determine the initiation or termination of a bloom, must be considered as an important source of variance. In upwelling systems, advective processes are important in determining species-specific over-wintering and seeding strategies. For example, the encystment and excystment of dinoflagellates is often used to explain seasonal patterns; however, very few studies have been conducted in the field. In areas where these studies have been performed results indicate that closely related species differ markedly in their adaptive strategies despite their similarity in life-history transitions and habitat (e.g. Montresor et al. 1998). Dale and Amorim (2000) suggested three different seedbed strategies for HAB dinoflagellates: (1) those species without resting cysts, (2) those species heavily dependent on seedbeds, and (3) those species that produce large numbers of cysts but are seemingly independent of seedbeds. Thes strategies should be investigated for different dinoflagellate species within and between upwelling systems. Diatom populations such as Pseudo-nitzschia are often associated with thin layers both in the water column and near bottom (e.g. Rines et al. 2002). Cells under these low light conditions are found to be viable, indicating that Pseudo-nitzschia may be present as “shade flora” in stratified water masses, which may function as seedbeds under favorable conditions. Other physical settings, including mesoscale eddies and frontal systems, have also been found to favour the accumulation of Pseudo-nitzschia populations. The existence of a Pseudo-nitzschia resting stage has been suggested, but no clear seeding strategy has been established.
Understanding and comparing species-specific seeding strategies in different upwelling systems will be useful in the development of models aimed at forecasting blooms and their impacts in coastal regions. A collaborative approach using standardized methods will benefit attempts to establish the sites of seedbeds and to determine the seeding strategies for HAB species in upwelling systems.
Participating regions: California Current System, Benguela, Iberian coast
Project Coordinator: A. Amorim (U. Lisbon, Portugal)
Iberian: A. Amorim (U. Lisbon), B. Dale /U. Oslo), T.Moita (IPIMAR), I.Bravo (IEO), F.G. Figueiras (IIM-CSIC)
Benguela: L. Joyce and G. Pitcher (M&CM)
California Current System: M. Vernet (Scripps I.O.), R. Horner (U. Washington), M. Silver (U. California, Santa Cruz), P. Strutton (Oregon State University), M. Wood (University Oregon)
To identify seed populations of particular HAB species in relation to oceanographic features important to their development.
To describe sedimentary processes determining the location and accumulation of seedbeds (e.g. dinoflagellate cyst beds).
To describe the seeding and overwintering strategies of particular HAB species.
To determine the role of environmental parameters in species-specific seeding strategies (e.g., in establishing cyst dormancy, germination, growth, and the periodicity of blooms).
To determine whether strategies of seeding between upwelling regions are similar.
Approach and Workplan
Comparative field and laboratory approaches are required:
Mapping of cyst beds. Surveys of bottom sediment should be conducted to map cyst populations. Hydrological features related to cyst beds should also be determined, focusing on areas with a history of HAB events.
Establishing the distribution of HABs during non-bloom periods. Overwintering populations occurring in frontal systems, within pycnoclines, nitraclines, within near-bottom layers, etc., should be identified and the viability of cells should be established. Simulated upwelling of these populations can also be used to examine viability and growth.
Studying excystment and encystment. Time series of cyst germination will be based on collection of surface sediment samples (cysts may be collected by vacuum harvesting of sediment floc and others devices) and laboratory experiments. Dormancy periods of each target species should also be established through laboratory experiments. Encystment within the field may be established by means of sediment trap deployments. Corresponding environmental data will be collected to determine those factors influencing encystment and excystment.
- To describe the most probable areas and periods for bloom initiation for inclusion in species-specific models (G. catenatum, Alexandrium spp., Pseudo-nitzschia spp.).
- To determine whether the same factors control cyst deposition and excystment in different upwelling regions.
- To identify overwintering and non-bloom period strategies for organisms that do not produce cysts.
Project: The role of across-shelf and along-shore currents in the transport of HABs in upwelling systems
Upwelling systems are essentially heterogeneous, with mesoscale structures such as eddies, fronts, filaments and river plumes interacting with alongshore and across-shelf currents. These currents are among the most important physical features of upwelling systems and frequently interact to influence HABs in upwelling regions (e.g. Fraga et al. 1988, Pitcher et al. 1998, Trainer et al. 2002). Along-shore currents are able to transport blooms from their sites of initiation while on-shore transport, associated with downwelling, often favours bloom accumulation in coastal waters where they impact fisheries and tourism. Offshore transport resulting from upwelling promotes HAB dispersion from coastal systems. Understanding the relative contribution of alongshore and across-shelf flow to the transport of harmful algae to and from the coast will be important in the development of accurate physical-biological models. Comparison among systems will reinforce observations and help to refine models.
Participating regions: California Current, Benguela, Iberian, Humboldt
Project coordinator: F.G. Figueiras (IIM-CSIC, Spain)
California Current: B. Hickey (U. of Washington), M. Foreman (Institute of Ocean Sciences, Sydney, Brithish Columbia, Canada), A. MacFadyen, F.Chavez (MBARI), J. Ryan (MBARI), R. Kudela (UCSC), L. Washburn (UCSB), P. Franks (Scripps), P. Strutton (Oregon State University), V. Trainer (NOAA Fisheries), M. Wood (University Oregon)
Benguela: S. Bernard (U. Cape Town), A. Fawcett (U. Cape Town), P. Penven (U. Cape Town), G. Pitcher (M&CM), T. Probyn (M&CM), C. Whittle (U. Cape Town)
Iberian: D. Barton (IIM-CSIC), X. Alvarez-Salgado (IIM-CSIC), F.G. Figueiras (IIM-CSIC), G. Rosón (U. Vigo), B. Reguera (IEO-Vigo), T. Moita (IPIMAR), P. Relvas (U. Algarve), J. Silva (IH), J. Vitorino (IH), R. Neves (IST), P. Oliveira (IPIMAR), A. Peliz (U Aveiro), P. Chambell (IST)
Humboldt: L. Pizarro (IMARPE), C. Grados (IMARPE), S. Sanchez (IMARPE)
Main objective: To determine the relative importance of alongshore and across-shelf transport within the 4 regional upwelling systems in the initiation, accumulation, and transport of harmful algae to coastal environments.
- To describe similarities/differences in the wind regimes and consequent current patterns, including short-term wind events and seasonal wind patterns, paying particular attention to transitional periods and the interaction with coastal morphology and bathymetry (canyons, banks, shelf-break, width of the shelf).
- To compare: seasonal and short-term circulation patterns, from local to mesoscale, and mesoscale physical structures relevant to HABs (upwelling and convergence fronts, eddies, buoyancy plumes, pycnoclines).
To develop empirical relationships (models) between winds and transport (upwelling-downwelling, across-shelf and alongshore currents, counter currents).
To identify similarities/differences in: Variability, including latitudinal differences, in HAB assemblages and their relationship to the physical-chemical environment (empirical or probabilistic relationships).
To establish the extent to which the dynamics of HABs are influenced by the physical transport of HAB populations versus the modification of environmental conditions via transport mechanisms.
Approach and workplan
Two phases are identified:
First Phase (comparative analysis of historical and ongoing records)
Wind regimes: analyze wind records from different locations within each system.
Circulation patterns: analyze current records, buoy deployments with meteorological and physical-biological sensors, drifters, models, and remote-sensing facilities.
Databases: compile historical data obtained from mesoscale and short-term cruises and monitoring programmes to determine the hydrographic fields and the temporal and spatial distributions of phytoplankton, with an emphasis on HABs.
Second phase (depending on the outputs of the first phase)
To design multidisciplinary large and mesoscale field observations during the HAB season (spring to autumn) to identify areas of higher HAB prevalence.
To plan multidisciplinary cruises of short duration to specifically address the transport of HABs. For example, a series of across-shelf transects could be occupied alongshore during a HAB event to document transport processes.
Genetic identification of populations may assist in determining if populations or conditions propagate alongshore.
1] To determine the relative importance of alongshore and across-shelf and poleward vs. equatorward processes in the accumulation, transport and dispersion of HABs and/or toxicity in the four eastern boundary upwelling regions.
2] To model and forecast the appearance of HABs (toxicity) in coastal environments.