156
F. J. R. TAYLOR:
Parahistioneis, Histioneis (Fig. 4e) and Citharistes (Fig. 4g) in which the blue-green algal
cells were termed "phaeosomes" by early authors. According to NORRIS (1967), who has
cultured 2 of the blue-green partners (the isolation having been achieved on cruises I and II
of the "Anton Bruun"), some or all of the bodies formerly considered to be chloroplasts
(chromatophores) within some genera such as Amphisolenia may also be endosymbiotic
blue-greens. From the point of view of the ecologist, it is the total effect of the consortium
on the food web which is important. Consequently it becomes an academic question as to
the precise nature of the carbon fixer in cases like this, just as in the case of nitrogen
fixation associated with patches of Trichodesmium. A most interesting possibility is
that the blue-green partners of dinophysoid dinoflagellates are nitrogen fixers as well as
carbon fixers. Such an attribute would presumably be of great value in the Indian Ocean
where nitrogen-depleted conditions seem to be much more frequent than phosphorus
depletion in terms of photosynthetic requirements.
In view of the apparently widespread nature of endocyanosis (endocellular blue-green
symbionts) in tropical dinoflagellates, it is important that this be studied in much greater
detail to determine if such consortia are "functional autotrophs" and significant as
primary producers. In this connection KHMELEVA (1967) believes that radiolaria/
zooxanthella consortia are more highly productive in the Red Sea than the phytoplankton.
In summary, many dinoflagellates can participate in primary production as auxotrophic (vitamin-requiring) autotrophs. An undetermined fraction of these may also ingest
other cells, thus acting as primary consumers as well as primary producers (myxotrophs).
Nonphotosynthetic dinoflagellates, also numerous, may function as grazers or feeders on
particulate or even dissolved organic matter. Finally, those forming consortia with bluegreen algal cells may be shown in the future to be "functional autotrophs" and thus
primary producers.
Many of the photosynthetic dinoflagellates are apparently able to tolerate remarkably
low inorganic nutrient levels, a factor which might explain their relative success in
oligotrophic tropical oceanic waters. While this may be theroretically attributed to a
greater efficiency in nutrient uptake, perhaps related to their motility (such as a more
efficient "flushing" of their uptake surfaces), the observation of QASIM (1973) that the
photosynthetic rate of a species of Ceratium was depressed by an increase of nitrate in
culture relative to diatoms, suggests that a difference in metabolism may also be involved
in some tropical species.
II. The "Anton Bruun" Material
1. Species Composition
This contribution is based on the floristic analysis of the dinoflagellates from 213
samples of microplankton. They were collected routinely during the International Indian
Ocean Expedition (HOE) by the RV "Anton Bruun" on 9 cruises (designated A, I-VIII)
in the northern and western regions of the Indian Ocean during 1963 and 1964 (Figs. 1,2).
All samples were collected by vertical net tows from 200 m to the surface and preserved
with formalin.
Over 300 species, including many varieties and forms, from more than 40 genera, were
identified and illustrated. It was for this reason that a fully illustrated report is being
prepared in the hope that the range of material covered will make it useful in identifying
F. J. R. TAYLOR:
Parahistioneis, Histioneis (Fig. 4e) and Citharistes (Fig. 4g) in which the blue-green algal
cells were termed "phaeosomes" by early authors. According to NORRIS (1967), who has
cultured 2 of the blue-green partners (the isolation having been achieved on cruises I and II
of the "Anton Bruun"), some or all of the bodies formerly considered to be chloroplasts
(chromatophores) within some genera such as Amphisolenia may also be endosymbiotic
blue-greens. From the point of view of the ecologist, it is the total effect of the consortium
on the food web which is important. Consequently it becomes an academic question as to
the precise nature of the carbon fixer in cases like this, just as in the case of nitrogen
fixation associated with patches of Trichodesmium. A most interesting possibility is
that the blue-green partners of dinophysoid dinoflagellates are nitrogen fixers as well as
carbon fixers. Such an attribute would presumably be of great value in the Indian Ocean
where nitrogen-depleted conditions seem to be much more frequent than phosphorus
depletion in terms of photosynthetic requirements.
In view of the apparently widespread nature of endocyanosis (endocellular blue-green
symbionts) in tropical dinoflagellates, it is important that this be studied in much greater
detail to determine if such consortia are "functional autotrophs" and significant as
primary producers. In this connection KHMELEVA (1967) believes that radiolaria/
zooxanthella consortia are more highly productive in the Red Sea than the phytoplankton.
In summary, many dinoflagellates can participate in primary production as auxotrophic (vitamin-requiring) autotrophs. An undetermined fraction of these may also ingest
other cells, thus acting as primary consumers as well as primary producers (myxotrophs).
Nonphotosynthetic dinoflagellates, also numerous, may function as grazers or feeders on
particulate or even dissolved organic matter. Finally, those forming consortia with bluegreen algal cells may be shown in the future to be "functional autotrophs" and thus
primary producers.
Many of the photosynthetic dinoflagellates are apparently able to tolerate remarkably
low inorganic nutrient levels, a factor which might explain their relative success in
oligotrophic tropical oceanic waters. While this may be theroretically attributed to a
greater efficiency in nutrient uptake, perhaps related to their motility (such as a more
efficient "flushing" of their uptake surfaces), the observation of QASIM (1973) that the
photosynthetic rate of a species of Ceratium was depressed by an increase of nitrate in
culture relative to diatoms, suggests that a difference in metabolism may also be involved
in some tropical species.
II. The "Anton Bruun" Material
1. Species Composition
This contribution is based on the floristic analysis of the dinoflagellates from 213
samples of microplankton. They were collected routinely during the International Indian
Ocean Expedition (HOE) by the RV "Anton Bruun" on 9 cruises (designated A, I-VIII)
in the northern and western regions of the Indian Ocean during 1963 and 1964 (Figs. 1,2).
All samples were collected by vertical net tows from 200 m to the surface and preserved
with formalin.
Over 300 species, including many varieties and forms, from more than 40 genera, were
identified and illustrated. It was for this reason that a fully illustrated report is being
prepared in the hope that the range of material covered will make it useful in identifying