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R. FENAUX: Appendicularia from the Indian Ocean, the Red Sea and the Persian Gulf
The area can be divided into some subareas which are characterized by the predominance of 1 or 2 species, or groups of species. It appears that the boundaries of the subareas
coincide, in the main, with the boundaries of some water bodies represented in the
"Summary of Oceanographic Conditions in the Indian Ocean" published by the U.S. Navy
Hydrographic Office in 1960. The cruises of the "Discovery" and the "Anton Bruun"
present one special interest. The first cruise was made during SW monsoon and the
second 3 months later, between the monsoons but both along the Arabian coast. During
the "Discovery" cruise 2 subareas were distinct: the western part characterized by the
predominance of M. huxleyi and the eastern part by O. longicauda; during the "Anton
Bruun" cruise, those differences disappeared.
Quantitatively there is no significant difference in subareas or distances from the
shore and there is no relation between the quantity of appendicularians and the total
plankton biomass or the phytoplankton from the upper layer. The size and state of
maturity were recorded in representative samples for some species and considerations
on geographical distribution with the maturity are given.
The early knowledge of this group was mainly based on systematic work. Subsequent
studies gave information on geographical distribution. Finally, geographical distribution
has been correlated with the distribution of water currents and water masses. The study
of seasonal variations is now beginning for some areas.
I think we now know the major part of the species of the Indian Ocean and it seems
they are the same ones to be found in all the temperate or tropical oceans, except for
M. huxleyi. This species is an Indo-Pacific form and it would be interesting to know
exactly what its status is in the Cape Town area, where the waters of the Indian and
Atlantic Oceans converge.
There are many regions which were not so well known before the HOE but which
are better known at present, e.g. the Arabian Sea and the Bay of Bengal. Certain other
regions, the hydrography of which is peculiar, such as the Agulhas Bank and the Somali
coast, have also been investigated. Finally, interesting observations were made on the
latitudinal variations in the central part of the Indian Ocean.
Thus it cannot be denied that here, as in many fields, the HOE has been very benefical.
However, for the appendicularians as for other fragile planktonic groups, the very bad
state of preservation of many of the samples of the IOBC collection is to be regretted.
Further disappointment arises from the fact that the number of cruises, their situations
and the periods in which they took place, led one to hope that it would be possible to
carry out a comprehensive study which would incorporate both space and time. The few
collections which were or are in a state fit to be examined have given and will give only
partial results, and they cannot be reconciled in space or time. Finally, mention should
be made of the fact that the design of the standard net was for vertical hauls from 200 m
to the surface, without intermediate closing; this precluded from the start the possibility
of a study of bathymetric variations being carried out.
R. FENAUX: Appendicularia from the Indian Ocean, the Red Sea and the Persian Gulf
The area can be divided into some subareas which are characterized by the predominance of 1 or 2 species, or groups of species. It appears that the boundaries of the subareas
coincide, in the main, with the boundaries of some water bodies represented in the
"Summary of Oceanographic Conditions in the Indian Ocean" published by the U.S. Navy
Hydrographic Office in 1960. The cruises of the "Discovery" and the "Anton Bruun"
present one special interest. The first cruise was made during SW monsoon and the
second 3 months later, between the monsoons but both along the Arabian coast. During
the "Discovery" cruise 2 subareas were distinct: the western part characterized by the
predominance of M. huxleyi and the eastern part by O. longicauda; during the "Anton
Bruun" cruise, those differences disappeared.
Quantitatively there is no significant difference in subareas or distances from the
shore and there is no relation between the quantity of appendicularians and the total
plankton biomass or the phytoplankton from the upper layer. The size and state of
maturity were recorded in representative samples for some species and considerations
on geographical distribution with the maturity are given.
The early knowledge of this group was mainly based on systematic work. Subsequent
studies gave information on geographical distribution. Finally, geographical distribution
has been correlated with the distribution of water currents and water masses. The study
of seasonal variations is now beginning for some areas.
I think we now know the major part of the species of the Indian Ocean and it seems
they are the same ones to be found in all the temperate or tropical oceans, except for
M. huxleyi. This species is an Indo-Pacific form and it would be interesting to know
exactly what its status is in the Cape Town area, where the waters of the Indian and
Atlantic Oceans converge.
There are many regions which were not so well known before the HOE but which
are better known at present, e.g. the Arabian Sea and the Bay of Bengal. Certain other
regions, the hydrography of which is peculiar, such as the Agulhas Bank and the Somali
coast, have also been investigated. Finally, interesting observations were made on the
latitudinal variations in the central part of the Indian Ocean.
Thus it cannot be denied that here, as in many fields, the HOE has been very benefical.
However, for the appendicularians as for other fragile planktonic groups, the very bad
state of preservation of many of the samples of the IOBC collection is to be regretted.
Further disappointment arises from the fact that the number of cruises, their situations
and the periods in which they took place, led one to hope that it would be possible to
carry out a comprehensive study which would incorporate both space and time. The few
collections which were or are in a state fit to be examined have given and will give only
partial results, and they cannot be reconciled in space or time. Finally, mention should
be made of the fact that the design of the standard net was for vertical hauls from 200 m
to the surface, without intermediate closing; this precluded from the start the possibility
of a study of bathymetric variations being carried out.