Open Access

Potential bioassay of natural seawaters and influence of certain trace elements on the growth of phytoplankton organisms

  • A. A. Aleem1, 2
Helgoländer wissenschaftliche Meeresuntersuchungen20:BF01609902


1. Natural sea water collected at different months from the English Channel at Plymouth and from the Celtic Sea were enriched with N, P, Fe and bioassayed with unialgal cultures of the pelagic diatomChaetoceros didymus, a reddish flagellate “A” andPhaeodactylum tricornutum.

2. The first two organisms together with the green algaStichococcus sp. (cf.S. cylindricus Butcher) were isolated from the Plymouth plankton and subcultured in artificial sea water, and thePhaeodactylum cornutum was supplied from the strain culture of the Plymouth Laboratory. The relative growth constant ofChaetoceros didymus was taken as an index to classify the different waters according to their suitability for the growth of this diatom. These waters could then be classified in the following order: (a) Celtic sea water of March, (b) Plymouth water of February, (c) Celtic sea water of May, (d) Plymouth water of July, (e) Celtic sea water of July and (f) Plymouth water of March.

3. Mixing of “good” and “bad” waters improved the qualities of the bad water, but growth again declined after 10–15 days.

4. Artificial sea water with soil extract approximates the qualities of “good” natural sea water.

5. Properties of the “bad” or “sterile” waters could be improved by additions of Cu, particularly when this metal in the natural water was impoverished.

6. Celtic Sea waters of May, July and (to a lesser extent) of March, induced auxospore formation inChaetoceros didymus. This capacity was inhibited by additions of traces of Cu.

7. Li causes elongation of cells in bothChaetoceros didymus andStichococcus sp. The morphological effects of this element on phytoplankton cells require further studies.

8.Phaeodactylum tricornutum and flagellate “A” gave similar results to those ofChaetoceros didymus with regard to the bioassayed waters employed.

9.Phaeodactylum tricornutum andStichococcus sp. appear to be sensitive to traces of Cu, while the latter species, together with flagellate “A”, can tolerate high concentrations of Li.

10. Evidence has also been obtained that the ageing of sea water could improve its qualities.