12th International Conference on Harmful Algae

INTERNATIONAL SOCIETY FOR THE STUDY OF HARMFUL ALGAE12 th <strong>International</strong> <strong>Conference</strong> on Harmful Algae, Copenhagen, Denmark, 4-8 September 2006PO.05-46Protease inhibition assay as atool to test the toxicity ofcyanobacterial toxinsSession: PO.05: Toxin analysisKirsten S Christoffersen 1 , U. Friberg-Jensen 1 , G. Mulderij 1 , T. Rohrlack 21 University of Copenhagen, HILLERØD,Denmark2 Norwegian Institute for Water Research,OSLO, NorwayBioactive compounds fromcyanobacteria can affect other biotaand the adverse effects on e.g.Daphnia survival and feeding haveoften been used as a firstapproximation of toxicity. Recently,it has been reported that toxins suchas microcystin and microviridin canhave strong protease inhibitoryeffects on e.g., trypsin,chymotrypsin and elastase. Thisstudy made in vitro test of mixedsolutions of extractedcyanobacterial metabolites fromcultures and lake scums as well aspurified peptides on daphnidproteases. Trypsin-like proteaseswere extracted from Daphniamagna. The effects of metabolitesfrom cultured strains Microcystisand Planktothrix and from mixedlake bloom material were tested onthe daphnid trypsin-like enzymeactivity using a photometricaldetection. The majority of theextracts tested were inhibitors ofdaphnid trypsin-like enzymes aswell as on the pork trypsin used forcomparison. In conclusion, proteaseinhibitors which occur in manylaboratory strains and fieldpopulations of Microcystis,Planktothrix, and other genera ofcyanobacteria may induce severeprotease inhibition in Daphnia.Thus, protease inhibitors are apotential threat to organisms thatdeliberately or accidentally take upcyanobacterial cells. The associatedphysiological implications caninclude incomplete proteindigestion, molting problems,reduced feeding, growth andreproduction as well as death.PO.04-10Effects of the toxic dinoflagellateAlexandrium minutum, grownunder different N/P ratios, on thecopepod Acartia tonsaSession: PO.04 – Food chainsE.D. Christou 1 , I. Maneiro 2 , I Varkitzi 1 ,S. Zervoudaki 1 , K. Pagou 11 HCMR, ATHENS, Greece2 Facultad de Ciencias del Mar,Universidad, VIGO, SpainAn experimental study was carriedout to test the effects ofAlexandrium minutum, cultured atthree different N/P ratios (5, 16 and80), on the copepod grazer Acartiatonsa. The ingestion rate, eggproduction and hatching success,as well as the toxin content intissues, eggs and pellets of thecopepods were checked at differentconcentrations of food, which alsooncluded a constant concentrationof the non-toxic dinoflagellateProrocentrum micans. Cell toxicityof the A. minutum varied among thedifferent N/P treatments, but itremained constant during eachexperiment. Copepods ingestedboth toxic and non-toxic food at alltreatments and concentrations.There was a positive correlationbetween A. minutum concentrationand ingestion by copepods.Production of eggs andpellets appeared to be affected byfood toxicity, while increasing toxiningestion reduced hatching successas well as increased toxin levels intissues and pellets. Our resultsindicate that A. minutum toxicity152