Chapter

Bacterial Standing Stock and Consumption Of Organic Carbon in The Benthic Boundary Layer of The Abyssal North Atlantic

07/2011; DOI:10.1007/978-94-011-2452-2_1 pp.1-10

ABSTRACT In order to assess the effects of seasonal deposition of detrital organic matter in the abyssal Northeast Atlantic, annual
changes in bacterial biomass and remineralization of 14C-labelled cultured algae (Synechococcus sp.) were investigated. Sediment bacterial biomass increased seasonally in response to sedimentation of organic matter. This
seasonal increase was caused by bacterial growth at the expense of the sedimented organic matter. Most of the total integrated
bacterial biomass from surface waters to deepsea sediments is contained in the sediments, while bacterial activity in these
sediments is lower than suggested by the high biomass concentrations. The complex organic matter of the added algal material
was remineralized by sediment bacteria under simulated deep-sea conditions at rates of 0.6% to 2.3% d-1 during the initial rapid degradation phase of approximately 400 hrs. These rates are only slightly lower than those found
in shallow water sediments. Under in situ pressure, more of the organic matter was consumed than at 1 atm.

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  • Article: Foraminiferal Assemblages as Palaeoenvironmental Bioindicators in Late Jurassic Epicontinental Platforms: Relation with Trophic Conditions
    Matías Reolid, Jenö Nagy, Francisco J. Rodríguez-Tovar, Federico Olóriz
    [show abstract] [hide abstract]
    ABSTRACT: Foraminiferal assemblages from the neritic environment reveal the palaeoecological impact of nutrient types in relation to shore distance and sedimentary setting. Comparatively proximal siliciclastic settings from the Boreal Domain (Brora section, Eastern Scotland) were dominated by inner-shelf primary production in the water column or in sea bottom, while in relatively seawards mixed carbonate-siliciclastic settings from the Western Tethys (Prebetic, Southern Spain), nutrients mainly derived from the inner-shelf source. In both settings, benthic foraminiferal assemblages increased in diversity and proportion of epifauna from eutrophic to oligotrophic conditions. The proximal setting example (Brora Brick Clay Mb.) corresponds to Callovian offshore shelf deposits with a high primary productivity, bottom accumulation of organic matter, and a reduced sedimentation rate for siliciclastics. Eutrophic conditions favoured some infaunal foraminifera. Lately, inner shelf to shoreface transition areas (Fascally Siltstone Mb.), show higher sedimentation rates and turbidity, reducing euphotic-zone range depths and primary production, and then deposits with a lower organic matter content (high-mesotrophic conditions). This determined less agglutinated infaunal foraminifera content and increasing calcitic and aragonitic epifauna, and calcitic opportunists (i.e., Lenticulina). The comparatively distal setting of the Oxfordian example (Prebetic) corresponds to: (i) outer-shelf areas with lower nutrient input (relative oligotrophy) and organic matter accumulation on comparatively firmer substrates (lumpy lithofacies group) showing dominance of calcitic epifaunal foraminifera, and (ii) mid-shelf areas with a higher sedimentation rate and nutrient influx (low-mesotrophic conditions) favouring potentially deep infaunal foraminifers in comparatively unconsolidated and nutrient-rich substrates controlled by instable redox boundary (marl-limestone rhythmite lithofacies).
    Acta Palaeontologica Polonica 01/2010; · 1.49 Impact Factor
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Keywords

1 atm
 
14C-labelled cultured algae
 
abyssal Northeast Atlantic
 
bacterial activity
 
bacterial biomass
 
bacterial growth
 
complex organic matter
 
deepsea sediments
 
detrital organic matter
 
initial rapid degradation phase
 
organic matter
 
rates
 
seasonal increase
 
sediment bacteria
 
Sediment bacterial biomass
 
sedimentation
 
sedimented organic matter
 
shallow water sediments
 
situ pressure
 
surface waters