Spatial differences in benthic activity in the Aegean Sea
Duineveld, G.; Van der Weele, J.; Berghuis, E.; Witbaard, R.; Tselepides, A. (2000). Spatial differences in benthic activity in the Aegean Sea, in: Balopoulos, E.T. et al. International conference - Oceanography of the eastern Mediterranean and Black Sea: Similarities and differences of two interconnected basins, Zappeion international conference Centre, Athens, Greece, 23 to 26 February 1999. Research in Enclosed Seas Series, 8: pp. 263
In: Balopoulos, E.T. et al. (2000). International conference - Oceanography of the eastern Mediterranean and Black Sea: Similarities and differences of two interconnected basins, Zappeion international conference Centre, Athens, Greece, 23 to 26 February 1999. Research in Enclosed Seas Series, 8. European Commission: Brussel. ISBN 92-828-9019-8. 494 pp., meer
In: Research in Enclosed Seas Series. Office for Official Publications of the European Communities: Luxemburg, meer
|
| Beschikbaar in | Auteurs |
|
Documenttype: Congresbijdrage
|
| Auteurs | | Top |
- Duineveld, G., meer
- Van der Weele, J.
- Berghuis, E.
|
|
|
| Abstract |
Previous studies on the distribution of benthic biomass in the Aegean Sea indicated a significant difference between the carbon input into the northern basins and the southern basin (Cretan Sea) with the latter one being the most oligotrophic. This difference is supposedly related to the presence of continental riverine and Black Sea water input in the north. During two MATER cruises, ie. in September '97 and March '98, we made in-situ measurements on the oxyger consumption of the sediment (SCOC) as an approximation for the mineralisation (and supply) of labile organic carbon in the sediment. The availability of carbon in the different sediments was furthermore assessed through shipboard incubations of cores in which flux es of oxygen, nutrients and CO2 were measured under in-situ temperatures. These measurements were accompanied by a study on the distribution and composition of phytoplankton pigments in the water column, short term sediment trap and sediment in order to trace deposition of fresh algal carbon.The in-situ SCOC measurements revealed a consistently higher mineralisation in the northern basins in both cruises Expressed in carbon equivalents, the lowest mineralisation rate in the south was 3 mg C m-1d-1, while the maximum value in the north was 30 mg C m-1d-1, a tenfold difference. The minimum value in the south is in agreement with earlier measurements carried out in tbe CINCS program. In spite of clear differences in algal biomass in the water column between tbe two cruises, no significant temporal difference could be found in SCOC. Additional results fron shipboard SCOC measurements and porewater oxygen profiling supported the difference in in-situ rates between the two areas. The sediment concentration and near bottom flux es of chlorophyll-a collected in a Technicap PPS3 sediment trap on the bottom lander were distinctly higher in the northern basins as compared to the southern Cretan Sea. SEM image of trap material indicate that mainly larger algae (diatoms, silico-flagellates) reach the deeper part of the basins Marker pigments of Cyanobacteria and Prochlorophytes which are present up to relatively high concentrations in the photic zone do not appear in trap samples, thus indicating that the benthic community can not profit from this production. All data analyzed so far demonstrate that the basins in the northern Aegean have a relatively higher flux of labile POC, a higher rate of benthic mineralisation and a correspondingly higher biomass of infauna. These results conform to the general concept of a deep sea sediment community driven by the rain of fresh POC to the sea floor. Video recordings of predators approaching bait attached on the benthic lander, however, suggest that mobile scavengers may not entirely fit in this scheme. The abundance and rapid approach to bait of the scavengers in the southern Aegean as compared to their apparent scarcity in the northern basins, suggest that there perhaps exists an alternative route for food for the southern scavengers, one that does not incorporate the relatively poor sediment community. |
|
