Water Sampling for the Presence of Toxin Producing Algae

Regulation (EC) 854/2004 specifies the requirements for the monitoring of toxin producing phytoplankton within shellfish production waters. Water samples from classified shellfish production areas are tested for the presence of toxin producing phytoplankton on a fortnightly basis throughout the year.

Trigger Levels for PSP/DSP/ASP and VSP

There is a lack of scientific understanding of the factors determining toxin production in phytoplankton and the uptake of toxins in different molluscan species. It has not been possible, therefore, to demonstrate a direct correlation between numbers of toxic phytoplankton present in a water sample and the concentration of toxins in shellfish. Additionally the phytoplankton producing azaspiracid poisoning is as yet unknown.

The use of phytoplankton cell counts alone is, therefore, not a useful method for determining or predicting toxicity in shellfish. The method is however, useful as an “early warning” to indicate potential occurrence of toxins, direct the type of analysis required and supplement the results of toxin analysis of shellfish.

Analysis is carried out according to Agri Food and Biosciences Institute (AFBI) (Mareco1010) as defined by National Reference Laboratory (NRL) method version 4 – identification and enumeration of potentially toxic Phytoplankton. The test of uncertainty of measurement = +/- 20%.

Exceedance of a ‘trigger level’ will initiate additional shellfish tissue sampling. FSA in NI publish all water sampling results. These can be found www.food.gov.uk website at: http://www.food.gov.uk/enforcement/monitoring/shellfish/nibiotoxin/

Alert Level Phytoplankton concentrations

Biotoxin Phytoplankton Alert

PSP Alexandrium Greater than 0 cells/litre of Alexandrium (Saxitoxin)

DSP Dinophysis Greater than or equal to 100 cells/litre of Dinophysis, and by historical data. (Okadaic Acid)

ASP Pseudo-nitzschia Greater than or equal to 150,000 cells/litre of Pseudo-nitzschia, and/or historical data (Domoic Acid) Table of Toxin Producing Phytoplankton Trigger Levels

ALGAE TOXICITY TRIGGER LEVEL

Alexandrium spp. PSP Presence

Dinophysis acuminata DSP 100 cells l-1

Dinophysis acuta DSP 100 cells l-1

Dinophysis norvegica DSP 100 cells l-1

Dinophysis rotundata DSP 100 cells l-1

Dinophysis spp. DSP 100 cells l-1

Prorocentrum lima DSP 100 cells l-1

P. cordatum DSP 100 cells l-1

Gonyaulax grindleyi, DSP 100 cells l-1

Lingulodinium polyedrum DSP 100 cells l-1

Pseudo-nitzschia spp. ASP 150,000 cells l-1

Karenia mikimotoi, ASP 150,000 cells l-1

Noctiluca scintillans ASP 150,000 cells l-1

Phaeocystis spp ASP 150,000 cells l-1