Náttúrufræðingurinn - 1984, Blaðsíða 33

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SUMMARY
Some observations on the
seasonal variations in tempera-
ture, salinity and zooplankton
in Hvammsfjörður, West
Iceland
by
Ólafur S. Ástþórsson
and
Unnsteinn Stefánsson*
Marine Research Institute
P. O. Box 390, Reykjavík, lceland
*and University of Iceland.
The paper reports on preliminary stud-
ies of the seasonal variations in tempera-
ture, salinity and zooplankton in the shall-
ows of the fjord Hvammsfjörður, West
Iceland (Fig. 1).
The temperature reached a maximum of
11°—12°C during August while the lowest
temperatures of -1.5° to -1.8°C were
recorded in December—January (Fig. 2).
Throughout the months November-
March the water temperature was gen-
erally below - 1.5°C. The salinity
remained relatively uniform during most
part of the year (32%„-33%o) except in
April when it dropped down to 25%o-
26^o. These low salinity values in spring
are likely to be due to the melting of
sea-ice and freshwater run-off which both
reach their peak during that time of year.
Copepods were the zooplankton group
observed in greatest numbers in the
push-net samples (49% of the total num-
bers of animals in the samples). Peaks in
the number of copepods were observed in
May and June—July while relatively few
animals were observed in the plankton
during the latter part of the year (Fig. 5).
Amphipods were the group second in
numbers in the samples (19% of the total).
The amphipod species most important was
Calliopius laevisculum. As was the case
with the copepods it was observed in
greatest numbers in May and June-July
(Fig. 5). Larvae of cirripeds, decapods and
polychaetes were only observed between
May-July, but not during the latter part
of the year (Fig. 5). Zooplankton samples
taken on a section along Hvammsfjörður
consisted on the average of copepods
(92%) and Cladocera (8%) at the six stat-
ions.
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