The role of phototrophic sulfur bacteria as food for meiobenthic harpacticoid copepods inhabiting eutrophic coastal lagoons
✍ Scribed by L. P. Souza-Santos; J. Castel; P. J. P. Santos
- Publisher
- Springer
- Year
- 1996
- Tongue
- English
- Weight
- 784 KB
- Volume
- 329
- Category
- Article
- ISSN
- 1573-5141
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✦ Synopsis
Laboratory experiments were undertaken using Amonardia normani and Schizopera cf compacta, two meiobenthic harpacticoid copepods commonly found in coastal lagoons . The first experiments were designed to determine if the phototrophic sulfur bacteria Chromatium gracile can be ingested by these copepods and at what concentrations . Egestion rate was used as an index of feeding rate. The response of the egestion rate, expressed in numbers of faecal pellets produced by copepod per day, as a function of bacterial concentration followed the functional model . A . normani attained constant feeding rates from the bacterial concentration of 1 x 107 cells ml -1 (5 jig C ml -1 ) onwards, S. cf. compacta attained constant feeding rates from 2 .6 x 107 cells ml -1 (13 pg C ml -1 ) onwards. The faecal pellet volume changed significantly (p<0 .05) between food concentrations for A . normani but not for S. cf. compacta (p>0.05) . In order to investigate the effect of the phototrophic bacterial diet on the population dynamics of A . normani three groups of nauplii were maintained at 2 x 107 cells ml -1 and observed every day. The mortality of these nauplii was very high compared to those maintained on a diatom diet (Nitzschia constricta) ; only in one of the groups did some copepodites develop but no adults were ever observed. Adults fed on bacteria did not have different (p>0.05) survival rates compared to those fed on diatoms, nevertheless, the number of nauplii produced was significantly less (p<0 .05) on the bacterial diet. These results lead us to suggest that although the phototrophic sulfur bacteria (Chromatium gracile) can be ingested by both copepod species it cannot sustain the full development of the A. normani population . Thus, a bloom of phototrophic sulfur bacteria does not seem to be a favourable situation for opportunistic benthic copepods to colonize eutrophic coastal lagoons after a dystrophic crisis .