192
E. D. 9. CORNER AND lLNTIiONY 0 . DAVIES
bottom in the organic material of the sinking plant cells, the phytoplankton-zooplankton-rcgenerated nutrient cycle waa the most important factor maintaining the turnover of nitrogen in Long Island
Sound.
Harris (1959) made the interesting observation that nutrient regeneration by zooplankton excretion is quite a rapid process and should
quickly lead to equilibrium in the nutrient-plant-animal cycle as the
nutrients are soon made available again for further phytoplankton
growth. By contrast, bacterially-induced regeneration is a much
slower process, von Brand et al. (1937) having shown in laboratory
experiments that between 8 and 20 days were necessary for the release
of 65-80% of the nitrogen in phytoplankton by bacteria. Moreover,
Johannes (1968) considers that only a small proportion of nutrient
regeneration is due directiy to bacteria : these organisms may, in fact,
compete with plant cells for dissolved nutrients.
These studies of partly enclosed sea areas have therefore emphasized
the importance of zooplankton in the marine food web. For apart from
providing a valuable source of food for higher trophic levels, these
animals, by grazing and excretion, rapidly re-circulate nutrients that
would otherwise be lost from the euphotic zone as sinking phytoplankton, thus ensuring that the period of primary production, on
which relies the rest of the food web, is extended well beyond the
phytoplankton bloom of early spring.
XI11 ACKNOWLEDGEMENTS
In preparing this review we received much helpful advice from
many of our colleagues, among whom we particularly wish to thank
Dr G. T. Boalch, Dr J. H. Wickstead and Dr S. M. Marshall, F.R.S.
We are also most grateful to Dr M. M. Mullin and Dr E. R. Brooks for
kindly allowing us t o refer to work that had not been published.
Our thanks are also due to the library staffs of the Plymouth Laboratory
and the Oceanographic Museum, Monaco, for their patience and valuable
help in obtaining numerous journals and translations of papers,
particularly those in Russian ; t o Miss Brigitte Eisenhutt and Miss
J. M. V. Irlam for typing the manuscript; and to Mr. G. A. W. Battin
and Mrs. P. A. Ashton for re-drawing many of the figures.
XIV REFERENCES
Adams, J. A. and Steelo, J. H. (1966). Shipboard experiments on the feeding of
Calanus jinmarchicua (Gunnerus). In ‘‘ Some Contemporary Studies in
Marine Science ” (H. Barnes, ed.), pp. 19-35. George Allen and Unwin,
London.
E. D. 9. CORNER AND lLNTIiONY 0 . DAVIES
bottom in the organic material of the sinking plant cells, the phytoplankton-zooplankton-rcgenerated nutrient cycle waa the most important factor maintaining the turnover of nitrogen in Long Island
Sound.
Harris (1959) made the interesting observation that nutrient regeneration by zooplankton excretion is quite a rapid process and should
quickly lead to equilibrium in the nutrient-plant-animal cycle as the
nutrients are soon made available again for further phytoplankton
growth. By contrast, bacterially-induced regeneration is a much
slower process, von Brand et al. (1937) having shown in laboratory
experiments that between 8 and 20 days were necessary for the release
of 65-80% of the nitrogen in phytoplankton by bacteria. Moreover,
Johannes (1968) considers that only a small proportion of nutrient
regeneration is due directiy to bacteria : these organisms may, in fact,
compete with plant cells for dissolved nutrients.
These studies of partly enclosed sea areas have therefore emphasized
the importance of zooplankton in the marine food web. For apart from
providing a valuable source of food for higher trophic levels, these
animals, by grazing and excretion, rapidly re-circulate nutrients that
would otherwise be lost from the euphotic zone as sinking phytoplankton, thus ensuring that the period of primary production, on
which relies the rest of the food web, is extended well beyond the
phytoplankton bloom of early spring.
XI11 ACKNOWLEDGEMENTS
In preparing this review we received much helpful advice from
many of our colleagues, among whom we particularly wish to thank
Dr G. T. Boalch, Dr J. H. Wickstead and Dr S. M. Marshall, F.R.S.
We are also most grateful to Dr M. M. Mullin and Dr E. R. Brooks for
kindly allowing us t o refer to work that had not been published.
Our thanks are also due to the library staffs of the Plymouth Laboratory
and the Oceanographic Museum, Monaco, for their patience and valuable
help in obtaining numerous journals and translations of papers,
particularly those in Russian ; t o Miss Brigitte Eisenhutt and Miss
J. M. V. Irlam for typing the manuscript; and to Mr. G. A. W. Battin
and Mrs. P. A. Ashton for re-drawing many of the figures.
XIV REFERENCES
Adams, J. A. and Steelo, J. H. (1966). Shipboard experiments on the feeding of
Calanus jinmarchicua (Gunnerus). In ‘‘ Some Contemporary Studies in
Marine Science ” (H. Barnes, ed.), pp. 19-35. George Allen and Unwin,
London.