General Features of Dinoflagellate Material Collected by the "Anton Bruun"
165
Aden) were undertaken during the NE or post-NE monsoon period (December to April),
an attempt is made here to contrast the samples taken on these cruises with the remainder.
The reader is referred to RAMAGE (1969) for meteorology and WYRTKI (1973) for physical
oceanography. Here the following monthly monsoonal relations have been used:
December, January, February- NE monsoon; March, April- post NE monsoon; May,
June-early SW monsoon; July, August, September-full SW monsoon; October, November-post SW monsoon.
a) Southwest Monsoon, Intermonsoon/Southern Winter
Although this includes the material from Cruises II (106 -144), III (147 -160),
VI (328 - 349,355), VII (358 - 375) and VIII (396 - 420), these stations were not directly
situated in the regions of highest productivity associated with the SW monsoon in the
nothern Indian Ocean (Somali coast, south Arabian coast and the SW coast of India).
Nevertheless, all stations in the northern Indian Ocean, with the exception of cruise VI
(65°E meridian), seemed to show a peripheral influence in being generally rich in
dinoflagellates. Some stations showed high concentrations of coccolithophorids (157,
south of 32" S, and station 336 in the SW Monsoon Current). A dense bloom of the
blue-green alga Trichodesmium thiebautii (probably= T. erythraeum) occured at station
106 off the NW coast of India in May.
The 80 0 E meridian stations were occupied during the height of the SW monsoon
(July) and all stations north of 20 0 S were rich in dinoflagellates. Station 135 (20 0 S)
was interesting in having a group of species usually considered as deep-water species.
The poorest material of all the cruises was that of cruise VI (June, 65 a E), especially
south of 100 S.
Cruises VII and VIII were the only cruises undertaken in the Mozambique Channel
region. Appararently the season (late winter) is a relatively poor one for dinoflagellates.
Coastal stations were higher than central channel stations except those near Tulear on
the SW coast of Madagascar, which were poor. There was a decline from August to
September. The richest samples were from the vicinity of Durban and off Kenya (stations
418-420). Diatoms were plentiful off Durban, Nosy-Be (NW Madagascar) and Kenya.
Coccolithophorids appeared to be abundant at stations 374 and 417.
b) Northeast Monsoon/Southern Summer
Although only 2 of the cruises, I (Fig. 1, post NE monsoon) and V (stations 282 to
327, Fig. 2), are concerned with this period, they are represented by more samples (118)
than the total from the other cruises of the "Anton Bruun". The sampling of the Andaman
Sea-Bay of Bengal was more intensive than that of other regions, but cruise I was the
only cruise to cover this area and consequently seasonal comparison is not possible.
This is a pity, as the material from this cruise was in many respects the most interesting.
Large concentrations of the ph ago trophic species Noctiluca scintillans (= N. miliaris)
were present in the vicinity of the Gulf of Martaban and the Irrawaddy River delta in
the northern Andaman Sea, and in the NE Bay of Bengal close to the Burmese coast.
Throughout the entire Andaman Sea samples were rich in dinoflagellates and also to a
lesser extent over most of the Bay of Bengal. The only occurrence of a fresh-water species
in the material was also during cruise I with the presence of Peridinium achromaticum
at station 45 in water with a surface salinity of less than 20%0, presumably situated in a
narrow tongue of the Ganges River plume deflected eastwards by the cyclonic circulation
165
Aden) were undertaken during the NE or post-NE monsoon period (December to April),
an attempt is made here to contrast the samples taken on these cruises with the remainder.
The reader is referred to RAMAGE (1969) for meteorology and WYRTKI (1973) for physical
oceanography. Here the following monthly monsoonal relations have been used:
December, January, February- NE monsoon; March, April- post NE monsoon; May,
June-early SW monsoon; July, August, September-full SW monsoon; October, November-post SW monsoon.
a) Southwest Monsoon, Intermonsoon/Southern Winter
Although this includes the material from Cruises II (106 -144), III (147 -160),
VI (328 - 349,355), VII (358 - 375) and VIII (396 - 420), these stations were not directly
situated in the regions of highest productivity associated with the SW monsoon in the
nothern Indian Ocean (Somali coast, south Arabian coast and the SW coast of India).
Nevertheless, all stations in the northern Indian Ocean, with the exception of cruise VI
(65°E meridian), seemed to show a peripheral influence in being generally rich in
dinoflagellates. Some stations showed high concentrations of coccolithophorids (157,
south of 32" S, and station 336 in the SW Monsoon Current). A dense bloom of the
blue-green alga Trichodesmium thiebautii (probably= T. erythraeum) occured at station
106 off the NW coast of India in May.
The 80 0 E meridian stations were occupied during the height of the SW monsoon
(July) and all stations north of 20 0 S were rich in dinoflagellates. Station 135 (20 0 S)
was interesting in having a group of species usually considered as deep-water species.
The poorest material of all the cruises was that of cruise VI (June, 65 a E), especially
south of 100 S.
Cruises VII and VIII were the only cruises undertaken in the Mozambique Channel
region. Appararently the season (late winter) is a relatively poor one for dinoflagellates.
Coastal stations were higher than central channel stations except those near Tulear on
the SW coast of Madagascar, which were poor. There was a decline from August to
September. The richest samples were from the vicinity of Durban and off Kenya (stations
418-420). Diatoms were plentiful off Durban, Nosy-Be (NW Madagascar) and Kenya.
Coccolithophorids appeared to be abundant at stations 374 and 417.
b) Northeast Monsoon/Southern Summer
Although only 2 of the cruises, I (Fig. 1, post NE monsoon) and V (stations 282 to
327, Fig. 2), are concerned with this period, they are represented by more samples (118)
than the total from the other cruises of the "Anton Bruun". The sampling of the Andaman
Sea-Bay of Bengal was more intensive than that of other regions, but cruise I was the
only cruise to cover this area and consequently seasonal comparison is not possible.
This is a pity, as the material from this cruise was in many respects the most interesting.
Large concentrations of the ph ago trophic species Noctiluca scintillans (= N. miliaris)
were present in the vicinity of the Gulf of Martaban and the Irrawaddy River delta in
the northern Andaman Sea, and in the NE Bay of Bengal close to the Burmese coast.
Throughout the entire Andaman Sea samples were rich in dinoflagellates and also to a
lesser extent over most of the Bay of Bengal. The only occurrence of a fresh-water species
in the material was also during cruise I with the presence of Peridinium achromaticum
at station 45 in water with a surface salinity of less than 20%0, presumably situated in a
narrow tongue of the Ganges River plume deflected eastwards by the cyclonic circulation