420 Reviews the difference in the plankton of the two areas is mainly

420
Reviews
the difference in the plankton of the two areas is mainly to be seen in the
summer. The influence of seasonal changes in direction of prevalent winds,
with resultant movement of surface water, and the effect of the effluents
upon the transparency of the water are described in some detail. It is shown
that the vertical distribution of the phytoplankton in summer is different in
the two areas. In the outer more than 50 % of the plankton was in the
upper 10 m.; in the inner, only 1 % was found below ]0m. (data from
table on p. 31).
The influence of the Oslo sewage on the general biological conditions
is well illustrated by Fig. 9 on p. 42. In this, the differences between the
highest and lowest records of oxygen percentages in the upper 10 m. are
shown. The greatest (130) was found at the station in Oslo Harbour; the
smallest (16) at Ferder, the furthest station in the outer area. Finally, the
authors deal with the effect of the sewage on the composition of the phytoplankton and recognize poly-, meso-, and oligo-saprobic elements.
This area is still under investigation (vide pp. 35 and 41) and it is to be
expected that some of the points brought to light in the present paper will
be considered again. Strictly quantitative plankton studies of this kind
involve an enormous expenditure of time and energy on the part of the
biologist. Parallel chemical analyses, in comparison, can be carried out so
quickly and their value is so great, when the time eventually comes to
interpret the biological material, that the day has surely arrived when
extensive plankton work should not be undertaken without the fullest support
from the chemist.
A C G
J. H e n s c h e l . "Vertikale Wanderungen und unperiodische Schwankungen
des Copepodenplanktons im Fehmarnbelt, Juni/Juli 1936." Kieler
Meeresforsch, Bd. Ill, H. 1, S. 99—113, 7 Abb. Kiel, 1939.
As a further contribution to the knowledge of vertical distribution in
the plankton, Dr. H e n s c h e l has collected a number of 2-litre samples
of the Copepoda at the Fehmarnbelt Lightvessel over a period of eighteen
days in the summer. Contrary to the more usual conditions for such work,
there is here a marked stratification due to the presence of fresher surface
water from the Baltic and salter deep water from the Skagerak. Typically
the boundary lies at 15—20 metres and shows rapid changes for both salinity
and temperature, although oxygen values show little relation to the boundary
and the light decreases steadily towards the bottom after falling rapidly
at first.
Altogether 1491 adult copepods were collected. Acartia bifilosa formed
55'5 % of the total and was most abundant at 10 m., extending to the
surface. Pseudocalanui elongatus, forming 15'4 °/0, was the second and was
most abundant at 20 m., extending from 15 to 25 m. Other significant forms
were Temora longicornis (maximum at 10 m. and extending from 5—15 m.),
Centropages hamatus (maximum at 15 m. and extending from 5—15 m.),
Oithona similis (maximum at 15 m. and extending from 10—15 m.), and
Acartia longiremis (maximum at 25 m. and extending from 15—25 m.). In
addition a few individuals of Eurytemora hirundo and Paracalanus parvus
were found, mainly between the surface and 15 m. depth.
Reviewing the evidence from his own and other data, H e n s c h e l
suggests that Acartia bifilosa and Eurytemora were both carried by the
Baltic flow, whilst Pseudocalanus and Acartia longiremis were brought from
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421
the Skagerak. Although Centropages, Temora and Oithona are also North
Sea and Skagerak forms, their general distribution about the lower edge
of the upper layer (i.e., in intermediate salinities), together with the generally
restricted distributions of the others, lead him to consider the possible
migrations of the copepods into optimum physiological zones. He suggests
that the particularly limited distribution of Oithona may be due to its
lesser salinity tolerance, whilst the distribution of Acartia longiremis may
be related to the lower temperatures of the bottom water as well as to its
higher salinity, since it may also be found nearer the surface in the wintertime.
Although the numbers are relatively very small, there is evidence in
Acartia bifilosa of a distinct diurnal movement, from the 10 m. depth in
the daytime to the surface waters at night. Further analysis shows that in
general the males had a more limited and deeper distribution during the day
whilst the females were more restricted and rather higher during the night.
Such diurnal variations were disturbed by the non-periodic changes due to
the varying directions and speeds of the two currents, but analysis of these
and the associated salinity changes provided further evidence of the Baltic
origin of Acartia bifilosa and of the salinity effect upon its vertical
distribution.
Such work, attempting to show the inter-relationships of different'
factors, is important in solving the problems of vertical distribution. It
would be interesting to see it repeated under rather different conditions, e.g.,
as H e n s c h e l has suggested, in Bornholmbecken, where the relations
between the temperature and the salinity boundaries are different. In
conditions of greater complexity, it might also be desirable to take larger
samples than has been the case here.
C. E. Lucas.
R. Bassindale. "The Intertidal Fauna of the Mersey Estuary." Journ.
Mar. Biol. Assoc, Vol. XXIII, No. 1, pp. 83—98, 1 plate. Cambridge, 1938.
Der Verfasser berichtet hier iiber seine faunistischen Untersuchungen in der
Gezeitenregion des Unterlaufs der Mersey, von oberhalb Runcorn Gap
(Gezeitengrenze) bis ins offene Meer. Diese Strecke ist gekennzeichnet durch
das Vorhandensein ausgedehnter, bei Ebbe trocken fallender Schlick- und
Sandbanke, deren Fauna im Sommer 1933 eingehend erforscht wurde; sie
zerfallt in zwei Abschnitte; einen oberen, der seewarts bis zum Rock Light
reicht, und einen unteren, Liverpool Bay.
Die Bodenfauna des oberen Abschnittes hat einen ausgesprochen mesohalinen Charakter, artenarm aber individuenreich. Bemerkenswert ist das iiberall
hauf ige Vorkommen von Nereis diversicolor, das Vorherrschen auf weicherem
Boden von Clitellio arenarius und das stellenweise sehr zahlreiche Auftreten
von Pygospio elegans. Die beiden Polychaten finden sich, zusammen mit
Corophium volutator, ebenfalls haufig im oberen Abschnitt, auch im unteren
Teil des Astuars, allerdings nur wo der Alt, ein kleiner Fluss, miindet; also
ebenfalls in brackischem Wasser. Obrigens ist die Fauna hier rein marin und
sehr artenreich. Die schlickigen und aus einer Mischung von Sand und
Schlick bestehenden Banke sind dicht besiedelt; die aus reinem Sand bestehenden sind arm, mitunter ganz steril.
Angaben iiber den aktuellen Salzgehalt an den iiber hundert Stationen