Project background

 

Marine aquaculture

 

 

The continued increase of the world population demands a similar increase in the production of food protein and carbohydrates.

 

The need for an increase in the food production calls for intensified exploitation of marine living resources, either through commercial fishing of wild stocks, or, more likely, through large scale aquaculture of fish, shellfish and algae in coastal areas.

It is estimated that our use of aquaculture facilities will increase ten fold by the year 2050.

 

The Impact of harmful algal blooms

 

In the marine environment, microalgae can often grow rapidly or be concentrated by physical factors to attain extremely high concentrations such that they discolor the water and may toxify shellfish.

 

Although algal "blooms" can be a common occurrence in aquatic habitats, they can also impart serious detrimental effects to the environment and to public health when they are associated with toxicity for human and/or sea products.

Before national fisheries can proceed with any intensified exploitation of the coastal marine waters for food production, the extent of harmful algal blooms (HABs), in time and space, must be reduced or monitored more effectively.

 

The occurrence of HABs has been known since antiquity, but during recent years these events have become an increasing problem in coastal marine waters, and particularly along European coasts. This phenomena is increasing not only in terms of the frequency of their occurrence but also in the severity of their economic impact. It has been suggested that this is basically the result of eutrophication of coastal areas (Smayda, 1990) and/or the spreading of more or less endemic species because of increased commercial exchanges. However, this increase could also be the result of a better detection of these blooms in many different countries for health and economic reasons (Hallegraeff, 1993).

 

Monitoring of blooms

 

Monitoring for HABs is a requirement of EU directive 91/492/CEE and most European countries have monitoring programs to ban shellfish harvesting during harmful algal bloom events or when shellfish reach a specified level of toxicity that is potentially harmful to humans.

 

 

Toxic algal species

 

 Alexandrium catanella 

The microalgal species causing harmful algal blooms (HABs) are relatively few in number (200) in comparison to the total biodiversity of microalgal species believed to exist (>10,0000), and they are distributed among all major taxonomic algal groups: diatoms, dinoflagellates, haptophytes, and cyanobacteria (blue-green algae) and are found on a global scale.

 

Planktonic toxic blooms can cause neurotoxic shellfish poisoning (NSP), paralytic shellfish poisoning (PSP), amnesic shellfish poisoning (ASP), ciguatera fish poisoning (CFP) or diarrhetic shellfish poisoning (DSP). New species of harmful algae are continuously detected, and more worrisome new toxins being found and chemically characterized. Currently, PSP is the most widespread shellfish poisoning occurring all over the world, followed by DSP. These two toxic syndromes are of particular importance on European coasts. The other poisonings, ASP and NSP, have more restricted geographical occurrences, although there are now new reports of ASP from Scotland. CFP is only localized in tropical waters.

 

 

Application of molecular tools

 

Molecular biological tools have greatly enhanced our ability to identify toxic algae species/strains rapidly and with higher sensitivity and to estimate distribution of species in time and space. DNA and RNA probes, cell-surface antibodies and other molecular and biochemical techniques have come into more widespread use for identification of a limited number of harmful algal species. These techniques can be used collectively to verify and cross-corroborate identifications made using classical procedures. Although rRNA and antibody probes are available for some toxic algae, a platform that allows for a routine automated application of these probes to identify HAB species in field and laboratory studies is not yet available (Tyrrell et al. 1997).

The goals of DETAL

  The collection and cultivation of harmful algae belonging to the genera Alexandrium (dinoflagellate, PSP), Pseudonitzschia (diatom, ASP) and Prymnesium (haptophyte, fish kills).

  The development of a fluorescent technique using specific antibodies and rRNA-targeted oligonucleotide probes for the detection of the algae.

Optimisation of the fluorescent detection method for analysis by a solid phase cytometer (SPC) to allow enumeration of the target algae in the marine environment.

  Transfer of the technology to the harmful algae monitoring networks.