Planktic foraminiferal production stimulated by chlorophyll redistribution and entrainment of nutrients

• Published in: Deep-sea research. Part I, Oceanographic research papers Vol. 48; no. 3; pp. 721 - 740
• Main Authors: Schiebel, Ralf, Waniek, Joanna, Bork, Matthias, Hemleben, Christoph
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-03-2001; Elsevier; Pergamon Press Inc
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Atlantic Ocean, North; Biochemistry; Biological and medical sciences; BIOTRANS; Chlorophyll; Chlorophylls; Earth sciences; Earth, ocean, space; Eastern North Atlantic; Exact sciences and technology; External geophysics; Foraminifera; Fundamental and applied biological sciences. Psychology; Geochemistry; Globigerina bulloides; Globigerinella siphonifera; Globigerinoides ruber; Globigerinoides sacculifer; JGOFS 47°N, 20°W; Marine; Marine biology; Micropaleontology; Mineralogy; Neogloboquadrina incompta; Oceanography; Orbulina universa; Paleontology; Physical and chemical properties of sea water; Physics of the oceans; Planktic foraminifers; Plankton; Population dynamics; Pteropoda; Sea water ecosystems; Seasons; Silicates; Synecology; Turbulent entrainment; Water geochemistry; North Atlantic; Northeast Atlantic; Western Europe; ANE, North Atlantic; JGOFS 47°N, 20°W; Eastern North Atlantic; Turbulent entrainment; BIOTRANS; Population dynamics; Micropaleontology; Seasons; Chlorophylls; Planktic foraminifers; sea water; foraminifers; time variations; Europe; Atlantic Ocean; planktonic taxa; chlorophyll; nitrates; spatial distribution; nutrients; surface water; foraminifera; modern; hydrochemistry; spatial variations; Invertebrata; Protista; seasonal variations
• ISSN: 0967-0637; 1879-0119
• DOI: 10.1016/S0967-0637(00)00065-0

During September and October 1996 planktic foraminifers and pteropods were sampled from the upper 2500
m of the water column in the BIOTRANS area (47°N, 20°W), eastern North Atlantic, as part of the JGOFS program. Hydrography, chlorophyll fluorescence, and nutrient content were recorded at high spatial and temporal resolution providing detailed information about the transition time between summer and fall. At the beginning of the cruise a shallow pycnocline was present and oligotrophic conditions prevailed. Over the course of the cruise, the mixed layer depth increased and surface water temperature decreased by 1.5°C. Both chlorophyll-
a dispersed in the upper 50
m by vertical mixing and chlorophyll-
a concentrations at the sea surface increased. The nitracline shoaled and nutrient enriched waters were entrained into the mixed layer. Planktic foraminifers and pteropods closely reflected the changes in the hydrography by increased growth rates and changes in species composition. Three main groups of planktic foraminiferal species were recognized: (1) a temperate and low-productivity group dominated by
Neogloboquadrina incompta characterized the shallow mixed layer depths. (2) A temperate and high-productivity group dominated by
Globigerina bulloides characterized the period with wind-induced dispersal of chlorophyll-
a and entrainment of nutrient-enriched waters. (3) A warm water group containing
Globigerinoides sacculifer,
Orbulina universa,
Globigerinoides ruber (white), and
Globigerinella siphonifera was most common during the first days of sampling. Synchronous with the hydrographic change from summer to fall, planktic foraminiferal and pteropod growth was stimulated by redistribution of chlorophyll-
a and entrainment of nutrient-enriched waters into the mixed layer. In addition, the seasonal change in the eastern North Atlantic resulted in a transition of the epipelagic faunal composition and an increased calcareous particle flux, which could be used to trace seasonality in fossil assemblages and allow for better paleoceanographic interpretation of the boreal Atlantic.