CANIGO: Canary Islands Azores Region - Particle Flux and Paleocanography in the eastern boundary current

• Research unit: EU RFP
• Project number: 95.0355

Key words (English)

North Atlantic Eastern boundary current; paleoceanography; flux; coccolithophores; morphometrics; gephyrocapsa

Alternative project number (English)

EU project number: MAS3-CT96-0060

Research programs (English)

EU-programme: 4. Frame Research Programme - 3.2 Marine sciences and technologies

Short description (English)

See abstract

Partners and International Organizations (English)

Instituto ESPA,Ol De Oceanografia

Abstract (English)

The main goal of CANIGO is to understand the marine system in the Canary-Azores-Gibraltar region and its links with the Alboran Sea through comprehensive interdisciplinary basin scale studies. Within CANIGO the ETH working group mainly contribute to subproject 3 'Particle Flux and Paleoceanography in the Eastern Boundary Current'. Towards our goals within subproject three sea water filtration as well as sediment sampling were completed during R/V Meteor cruise 42. The subsequent analyses of filter samples collected along the E-W fertility gradient near the mooring stations EBC2, ESTOC and LP1 revealed a strong gradient in total coccolithophore cell densities from the open ocean location LP1(~ 40'000 cells/l ) to the near-shore location EBC2 (~ 120'000 cells/l) during winter as well as during late summer (~ 18'000 cells/l to ~ 45'000 cells/l). Maximum cell densities usually occurred in the upper photic zone above the deep chlorophyll maximum which was located between 50 m and 125 m water depth. Only four coccolithophore species dominated all assemblages analysed so far. The most abundant species was Gephyrocapsa ericsonii which dominated the upper photic zone at the nearshore station. Umbellosphaera tenuis dominated only during late summer from 0m to 50m water depth at LP1 and ESTOC. Florisphaera profunda was the third most abundant species during all analysed seasons below the deep chlorophyll maximum. Emiliania huxleyi was only found to dominate from 50m to 100m during winter timein the open ocean. Bulk mass accumulation rates along the E-W transect decrease from a high of 5-9 g cm--2 ka-1 nearshore, to 1-2 g cm-2 ka-1 in the deeper oceanic domain for both the Holocene and the Last Glacial Maximum (LGM). While in the oceanic setting (~LP1, ~ESTOC) the accumulation rates of various components are comparable in the Holocene and LGM, they change considerably in the nearshore site. Both bulk and fine fraction (<38 mm) carbonate accumulation increased slightly during the LGM in the neritic domain. Non-carbonate fine fraction accumulation was significantly reduced during the LGM at the nearshore site, whereas it remained constant at the other locations. In the Holocene, the accumulation of coccoliths decreases from a high of 132*109 coccoliths cm-2 ka-1 nearshore (~EBC2) to 34*109 coccoliths cm-2 ka-1 at the outermost oceanic site (LP1). During the LGM, however, accumulation of coccoliths was strongly reduced in the neritic realm (45*109 coccoliths cm-2 ka-1 ), but remained comparable to Holocene values in the oceanic domain (31*109 coccoliths cm-2 ka-1).There is evidence for enhanced biogenic carbonate dissolution and fragmentation during the LGM, but it is unlikely that the strong collapse of coccolith accumulation rates in the neritic domain can be explained by preservational processes alone. We propose that the likely process is biogenic carbonate supply (i.e. productivity), for which we currently seek independent evidence.

References in databases (English)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 95.0355