Research

Introduction

Research in the field of toxic planktonic microalgae has been ongoing for around twenty years. So, there is a large amount of available knowledge. This is not so with regard to the field of benthic toxic microalgae, because their habitat is much less frequently investigated as they have mainly created problems in tropical/subtropical areas and in area not surveyed by research institutions.

Relevant studies are sparse and mainly deal with Gambierdiscus species that produce toxins which are accumulated through the trophic web in herbivorous fish, causing a syndrome named ciguatera, which is completely different from the effects deriving from Ostreopsis blooms. In temperate areas, research on Ostreopsis blooms and toxins are limited to a few studies carried on in New Zealand, where there has not yet been any recorded toxic incident.

In the study of Harmful Benthic Algal Blooms (HBABs) two distinct aspects should be distinguished. One concerns the underlying mechanisms causing the blooms which, due to the great toxicity of the species, represent a potential danger for human health and marine ecosystem throughout the trophic web. The other is the direct impact on human health of the toxins in the seawater and aerosol. As a matter of fact, this peculiar kind of impact is not necessarily associated with large blooms, as marine animal death or human intoxications have occurred when blooms have been relatively small.

Strategy

The unique and complex nature of the problems associated with Ostreopsis blooms and the urgent need to provide information that can support appropriate protection and mitigation actions, requires the participation of many research groups. As Italy is not the only victim of Ostreopsis blooms collaborations are being formulated with colleagues from other countries within the Mediterranean area. 

The discrete occurrence of Ostreopsis blooms in coastal waters of Italy is unusual, as hydrological and ecological differences are likely to exist among these different places. The comparison of Ostreopsis occurrences based on toxicity, morphology, genetic and ecology features in different places and conditions is needed, in order to understand the environmental factors that promote these blooms. Ecological studies linking environmental and biomass (Ostreopsis and community) data, will be used to clarify the spatial and temporal patterns of Ostreopsis distribution and other benthic dinoflagellates. In addition to the sampling sites that will be selected based on their hydrodynamic, geomorphologic and biological characteristics, appropriate samples collected by coastal operators (coastal guards, scuba divers, etc.) will also be analysed. Collaboration is planned with local agencies devoted to environmental protection activities.

Environmental data will be collected, including meteorological, hydrographical and biological data to determine the causal factors of bloom development and the associated negative impacts. This study will provide the tools for the development of short-term models. A close collaboration with modellers is planned from the onset of the project, to ensure the collection of all the data and information needed for the models.

The macrophytes on which Ostreopsis grows will be sampled and preferred substrates assessed. Due to the extreme toxicity of Ostreopsis and to the lack of information on the possible toxin pathways along the trophic web, sampling will include benthic fauna (molluscs, crustaceans and fishes) to determine if they are victims or vectors of the toxins. Identification of vectors of toxins is important in the risk assessment for human health through seafood consumption.

In addition to field studies, laboratory research will be conducted using material collected during the sampling activity and algal cultures established from this material. These studies will include the description of the life cycle and physiological characteristics of Ostreopsis that can favour its massive growth. The exopolymeric matrix (mucilage) that is produced during the blooms will be chemically characterised, and the levels of production of mucilage and biofilms during the microalgal growth will be monitored in special flow-lane incubators, to assess the role of exopolymeric substances in the adhesion, cohesion and detachment phases. The role of bacteria in these processes and in the production of toxins will be addressed. Toxin production during different phases of the life-cycle will be analysed. Grazing experiments will evaluate possible effects on planktonic and benthic communities, including fish.

The species responsible for the benthic blooms will be characterised from the morphological and genetic point of view, coupling optical and electronic microscopy with molecular techniques. In addition to taxonomic confirmation, the latter methodologies will aim at addressing the intraspecific variability and relating it to the environmental conditions, toxin production and biogeography. In the long run, genomic research would be useful to clarify the mechanisms underlying the production of palytoxin-like and other compounds under different environmental conditions.

The program aims to define the chemical and toxicological characteristics of the toxins produced by Ostreopsis, which to date are only broadly defined as ‘palytoxin-like’ compounds. We don’t know as of yet whether these palytoxin-like compounds are exclusively responsible for the symptoms that follow exposure to seawater and aerosols or some other unknown compounds are involved. From a practical point of view, methods to detect the toxins in seawater, aerosol and marine organisms should be urgently developed, to allow for extensive analyses during the high risk phases of blooms.

A very important aspect of the present program is an optimal plan for communication between science and society at all steps of development of the research activities. This implies a close exchange and collaboration among different groups of interest that are involved in the study, monitoring, management and exploitation of the coastal areas. New information and dissemination systems need to be set in place along with extensive training and education activities at all levels and through adaptation of results to the needs of different categories of users.

Questions

The research project will address the following questions:

• which species cause HBABs? How do morphological, genetic, physiological, and toxicological characters of these species vary?
  
• have Ostreopsis spp. always been present in the Mediterranean? Rather, have the species been introduced from tropical areas via natural or human mediated transport? Are these species currently becoming more extensive?
  
  
• which populations co-occur in Ostreopsis spp. blooms? Which are the colonised macrophytes (macroalgae and or phanerogames) and the invertebrates and vertebrates which graze on benthic microalgae and/or on the colonised macrophytes?
  
  
• what is the temporal development of the blooms as to their formation, peak and decline?
  
  
• what is the spatial and seasonal variability of microalgal communities that include Ostreopsis spp. and other harmful benthic species?
  
  
• which are the local phenomena and specific anthropic factors that affect their development?
  
  
• which environmental conditions and edaphic factors promote the formation and decline of the HBABs?
  
  
• which Ostreopsis spp. life stages are able to accumulate in sediments and affect bloom dynamics?
  
  
• what is the structural and ecological role of the mucilaginous matrix that is produced during massive Ostreopsis spp. blooms?
  
  
• which toxins are produced?
  
  
• is the production of toxins affected by the environment?
  
  
• which stages of the life cycle produce and release toxins?
  
  
• what is their fate in the seawater, aerosol and in the trophic levels of the food web?