DETECTION OF AN ANATOXIN-A(S)-LIKE ANTICHOLINESTERASE IN NATURAL BLOOMS AND CULTURES OF CYANOBACTERIA BLUE-GREEN ALGAE FROM DANISH LAKES AND IN THE STOMACH CONTENTS OF POISONED BIRDS/

Ten natural bloom samples of cyanobacteria from the Danish lakes Knud so (5), Ravn so (4), and Salten Langso (1) collected during 1993-1995 were assayed for toxicity by mouse bioassay, for acetylcholinesterase inhibiting activity by a colorimetric method, and for microcystins by enzyme-linked immunosorbent assay. In the mouse bioassay, seven sample s were neurotoxic, two were non-toxic and one gave a protracted toxic response, One of the non-toxic and the single protracted toxic sample both contained anticholinesterase activity equivalent to 4 mu g anatox in-a(s) g(-1). The neurotoxic samples contained equivalents to 20-3300 mu g anatoxin-a(s) g(-1). The highest anticholinesterase activities ( equivalent to 2300 and 3300 mu g anatoxin-a(s) g(-1), respectively) we re found in samples collected from Lake Knud so in connection with bir d-kills in 1993 and 1994. Small amounts of microcystins (0.1-0.9 mu g g(-1)) were detected in all samples but one. All Lake Knud so and Lake Ravn so samples were dominated by Anabaena lemmermannii, and the Lake Salten Langso sample by several species of Anabaena. Gel filtration p rofiles indicated similarity between the toxic component from the Lake Knud so 1994 bloom with registered bird-kills and anatoxin-a(s) isola ted from Anabaena flos-aquae NRC-525-17. Anti-cholinesterase-producing cultures of A. lemmermannii were isolated from the Lake Knud so 1993 bloom. These laboratory cultures produced anatoxin-a(s) equivalents of 29-743 mu g g(-1). Other cultures of A. lemmermannii isolated from La ke Knud so and Lake Ravn se were hepatotoxic or non-toxic. Dead birds collected from Lake Knud so during the neurotoxic 1993 Anabaena bloom possibly died from cyanobacterial toxicosis. The stomach contents cont ained colonies and single trichomes of Anabaena: and anticholinesteras e activities equivalent to 2.1-89.7 mu g anatoxin-a(s) kg(-1) body wei ght and microcystins(53-95 ng kg(-1)) were also detected. (C) 1997 Els evier Science Ltd.