Náttúrufræðingurinn - 2004, Page 18

Náttúrufræðingurinn
10. mynd. Ungi maðurinn á myndinni tínir krækling i f'ótuna sína þrátt fyrir
kalsaveður, enda kominn vetur. Einna öruggast er líklega að tína krækling síðla vetrar
og snemma vors. - A young man collecting blue mussels in winter. Late winter and
early spring seem to be the safest seasons for mussel collecting. Ljósm./Photo: Karl
Gunnarsson.
þó ekki mælt. P. pseudodelicatissima
hefur áður fundist í talsverðum
mæli hér við land, meðal annars við
Vestfirði.10 Þar var blóminn til staðar
í nokkrar vikur án þess að ASP-
eitrun mældist í skelfiski á svæðinu.
Rannsóknir á öðrum hafsvæðum
hafa leitt í ljós að tegundin myndar
ekki alltaf eitur.29 Hins vegar hefur
ASP-eitrun mælst í kræklingi víða í
Norður-Atlantshafi eftir blóma
Pseudo-nitzschia-tegunda. Það er því
full ástæða til að vera á varðbergi og
mæla ASP í skelfiski ef vart verður
við mikinn þéttleika af Pseudo-
nitzschia.
Niðurlag
Niðurstöður rannsóknarinnar í
Hvalfirði árið 1997 sýna að þegar
eiturþörungar voru til staðar var
kræklingurinn fljótur að safna upp
eitri, en það tók hann hins vegar
langan tíma að hreinsa sig af því
aftur. Skelfiskeitrunar getur því gætt
mun lengur en aðalvaxtartími skoru-
þörunganna varir. Neysla skelfisks
úr Hvalfirði var varhugaverð frá því
blómi Dinophysis norvegica varð í júlí
og fram á vetur (10. mynd).
SUMMARY
Phytoplankton and shellfish
poisoning in Hvalfjörður,
Southwestem Iceland
During the year 1997 phytoplankton
succession was followed in Hvaifjördur,
southwestern Iceland (Fig. 2). Several
species known to cause shellfish poisoning
were found during the study. This paper de-
scribes the results with respect to the toxic
algae found. Samples were collected ap-
proximately once every week at two
stations in the inner part of Hvalfjörður.
Phytoplankton species were determined
and counted in quantitative samples and
net samples were used for identification of
species. Mussels, Mytilus edulis, were collect-
ed simultaneously for DSP-toxidty tests.
Eight potentially toxic species were
found and some of them were present the
whole year (Table 1). The diatom Pseudo-
nitzschia pseudodelicatissima, known to
cause amnesic shellfish poisoning (ASP),
occurred in large numbers in July; howev-
er, the blooming was unlikely to have poi-
soned shellfish in the area, mainly because
of its short duration (Figs. 7 and 9). On the
other hand, the dinoflagellate Dinophysis
norvegica, known to cause diarrhetic shell-
fish poisoning (DSP), bloomed for a more
extended period from July till September
(Figs. 6 and 8). After September, D. norveg-
ica was present only in low numbers. Tox-
icity tests on the mussels revealed high lev-
els of DSP during the period from July
until the sampling ended in November
(Table 2). This shows that DSP in the mus-
sels can be attained quickly and retained
long after the algae causing it declines in
number.
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