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structures, consisting mainly of CaC03 with small and variable proportions of other substances
such as MgC0 3 • Carbon export from ecosystems with such organisms is thus in stoichiometric
imbalance relative to nitrogen, i.e. each atom of nitrogen derived from allochthonous nutrients
effectively causes, under steady state conditions, the export of more atoms of carbon than
predicted from the Redfield ratio.
Many dinoflagellates are enclosed in a theca, usually consisting mainly of cellulose (Loeblich,
1970), but sometimes of other carbohydrates (e.g. a non-cellulosic polyglucan in the case of
Peridinium cinctum; Nevo and Sharon, 1969). A thick cell wall contributes to increasing the
carbon content of thecate dinoflagellates (Gonyaulacales and most Peridiniales are armoured
with several thick plates). Wynne et ai. (1982), for instance, found a C/N ratio of 13.9 for
Peridinium cinctum under bloom conditions in Lake Kinneret, Israel. Similarly, Haug et ai.
(1973) reported that, during the annual phytoplankton annual cycle in Trondheimsfjord,
Norway, insoluble carbohydrate accounted for 32-52 % of the organic matter in those samples
rich in dinoflagellates whereas the figure was usually < 10% when dinoflagellates were
scarce, and they ascribed the difference to dinoflagellate thecal carbon.
Plankton with calcareous tests include photosynthetic cells (mainly coccolithophores),
protozoans (foraminifers) and metazoans (mainly thecosomatous pteropods). Unfortunately,
no maps of global carbonate productivity have been established (Bishop, 1989). However,
according to Lisitzin (1972, as quoted by Bishop, 1989), coccolith and foraminiferal
productivity is maximal between 50 0 N and 50 0 S, in general coincidence with waters with a
temperature above 10°C; the highest concentrations of suspended particulate carbonate are
found in surface waters in two mid-latitude belts, i.e. near the Antarctic Convergence
(40-60 0 S) in the southern hemisphere and near the polar front in the northern hemisphere, and
along the continental margins. In the North and tropical Atlantic Ocean, Honjo (1980) and
Takahashi and Be (1984) report average sinking velocities between 65 and 2500 m d- 1 for
foraminiferal and pteropod tests, with a value> 5000 m d- 1 for the larger pteropod shells (ca.
10 mm); coccoliths, in that case, were mainly carried in faecal pellets, and thus had a
sedimentological behaviour similar to large particles. Calcareous tests may therefore be very
efficient in exporting biogenic carbon to depth.
structures, consisting mainly of CaC03 with small and variable proportions of other substances
such as MgC0 3 • Carbon export from ecosystems with such organisms is thus in stoichiometric
imbalance relative to nitrogen, i.e. each atom of nitrogen derived from allochthonous nutrients
effectively causes, under steady state conditions, the export of more atoms of carbon than
predicted from the Redfield ratio.
Many dinoflagellates are enclosed in a theca, usually consisting mainly of cellulose (Loeblich,
1970), but sometimes of other carbohydrates (e.g. a non-cellulosic polyglucan in the case of
Peridinium cinctum; Nevo and Sharon, 1969). A thick cell wall contributes to increasing the
carbon content of thecate dinoflagellates (Gonyaulacales and most Peridiniales are armoured
with several thick plates). Wynne et ai. (1982), for instance, found a C/N ratio of 13.9 for
Peridinium cinctum under bloom conditions in Lake Kinneret, Israel. Similarly, Haug et ai.
(1973) reported that, during the annual phytoplankton annual cycle in Trondheimsfjord,
Norway, insoluble carbohydrate accounted for 32-52 % of the organic matter in those samples
rich in dinoflagellates whereas the figure was usually < 10% when dinoflagellates were
scarce, and they ascribed the difference to dinoflagellate thecal carbon.
Plankton with calcareous tests include photosynthetic cells (mainly coccolithophores),
protozoans (foraminifers) and metazoans (mainly thecosomatous pteropods). Unfortunately,
no maps of global carbonate productivity have been established (Bishop, 1989). However,
according to Lisitzin (1972, as quoted by Bishop, 1989), coccolith and foraminiferal
productivity is maximal between 50 0 N and 50 0 S, in general coincidence with waters with a
temperature above 10°C; the highest concentrations of suspended particulate carbonate are
found in surface waters in two mid-latitude belts, i.e. near the Antarctic Convergence
(40-60 0 S) in the southern hemisphere and near the polar front in the northern hemisphere, and
along the continental margins. In the North and tropical Atlantic Ocean, Honjo (1980) and
Takahashi and Be (1984) report average sinking velocities between 65 and 2500 m d- 1 for
foraminiferal and pteropod tests, with a value> 5000 m d- 1 for the larger pteropod shells (ca.
10 mm); coccoliths, in that case, were mainly carried in faecal pellets, and thus had a
sedimentological behaviour similar to large particles. Calcareous tests may therefore be very
efficient in exporting biogenic carbon to depth.