Comparison of pelagic and nepheloid layer marine snow: implications for carbon cycling

Ransom, Barbara; Shea, Kevin F; Burkett, P. J.; Bennett, Richard H.; Baerwald, Roy J.

doi:10.1016/s0025-3227(98)00052-8

Cited by 65 publications

(31 citation statements)

References 38 publications

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“…Foraminifera larger than 125 µm can be assumed to fall vertically through the water column and are not easily redistributed (Fok-Pun & Komar, 1983). In contrast, organic matter may be incorporated into nepheloid aggregates once it reaches the dynamic and high shear nepheloid layer depths, where frequent resuspension leads to offshore transport and dispersion (Ransom et al, 1998).…”

Section: Core-top Radiocarbon Agesmentioning

confidence: 99%

See 1 more Smart Citation

Rapid lateral particle transport in the Argentine Basin: Molecular 14C and 230Thxs evidence

Mollenhauer

McManus

Benthien

et al. 2006

Deep Sea Research Part I: Oceanographic Research Papers

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Recent studies have revealed that lateral transport and focusing of particles strongly influences the depositional patterns of organic matter in marine sediments. Transport can occur in the water column prior to initial deposition or following sediment re-suspension. In both cases, fine-grained particles and organic-rich aggregates are more susceptible to lateral transport than coarse-grained particles (e.g. foraminiferal tests) because of the slower sinking velocities of the former. This may lead to spatial and, in the case of redistribution of resuspended sediments, temporal decoupling of organic matter from coarser sediment constituents. Prior studies from the Argentine Basin have yielded evidence that suspended particles are displaced significant distances (100 -1000 km) northward and downslope by strong surface and/or bottom currents. These transport processes result in anomalously cold alkenone-derived sea surface temperature (SST) estimates (up to 6°C colder than measured SST) and in the presence of frustules of Antarctic diatom species in surface sediments from Thxs-based focusing factors of 1.4 to 3.2 at sites where alkenone-based SST estimates were 4 -6 °C colder than measured values. In contrast, alkenone radiocarbon data suggest coeval deposition of marine biomarkers and planktic foraminifera, as alkenones in core-tops were younger than, or similar in age to, foraminifera. We therefore infer that the transport processes leading to the lateral displacement of these sediment components are rapid, and hence probably occur in the upper water column (< 1500 m).

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Section: Core-top Radiocarbon Agesmentioning

confidence: 99%

“…on the shelf) followed by selective re-suspension of organic matter-rich aggregates (e.g. Ransom et al, 1998;Thomsen & Gust, 2000;Mollenhauer et al, 2003Mollenhauer et al, , 2005 could result in significant age offsets between the individual sediment fractions.…”

Section: Potential Transport Mechanismsmentioning

confidence: 99%

Rapid lateral particle transport in the Argentine Basin: Molecular 14C and 230Thxs evidence

Mollenhauer

McManus

Benthien

et al. 2006

Deep Sea Research Part I: Oceanographic Research Papers

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“…In natural aqueous environments examples of floc formation include the transport and deposition of particulate matter in estuaries (Manning and Dyer, 1999), the assemblage of marine particles (e.g. plankton, organic matter, faecal material and minerals) into large aggregates known as marine snow (Ransom et al, 1998) and the colloidal aggregates that are present in most natural surface waters (Gregory, 1997). However, industrial processes that require the separation of solids from liquids may be enhanced by an artificially induced floc formation stage.…”

Section: Introductionmentioning

confidence: 99%

Measuring Floc Structural Characteristics

Jarvis

Jefferson

Parsons

2005

Rev Environ Sci Biotechnol

104

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“…It is present only during the summer and has some of the characteristics of a ''nepheloid benthic or bottom layer,'' i.e., high porosity (Ͼ97% of water) and large quantities of unconsolidated organic matter and phytoplankton. Ransom et al (1998) reported the presence of a ''nepheloid layer'' with the prevalence of clay organic-rich aggregates, which are suggested to be formed by the deposition of pelagic marine snow. In fact, the flocculent layer on the sediments of Concepción Bay could be the result of the aggregation and coagulation of large quantities of both living and dead phytoplankton that sink to the bottom.…”

Section: Discussionmentioning

confidence: 99%

Massive developments of microbial mats following phytoplankton blooms in a naturally eutrophic bay: Implications for nitrogen cycling

Graco

Farı́as

Molina

et al. 2001

Limnology & Oceanography

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Benthic nitrogen processes have received substantial attention because the release of nutrients from sediments can contribute to the requirements of pelagic primary production; their study can also give an estimation of the importance of the sediment as a source or a sink of nutrients. Concepción Bay is located in central Chile and is the largest (167.4 km 2 ) and most enclosed embayment on the Chilean coastline. The bay is characterized by a strong hydrographic variability produced by the spring/summer seasonal upwelling of Equatorial subsurface waters (ESSW), rich in nutrients (ϳ25 M NO 3 Ϫ ) and poor in oxygen (Ͻ44.6 M). The area was studied in order to understand the consequences of phytodetrital deposition and oxygen deficiency on the environment and benthic communities. The study was carried out by sampling at a single station (28-m depth) in the inner part of the bay during winter (June 1998) and spring/summertime (November 1998 and January and March 1999). It was focused on measurements of benthic nitrogen fluxes, sulfate reduction, and denitrification rates before and after a phytoplankton bloom. Additionally, samples from the flocculent layer and from a semipurified bacterial mat were incubated under controlled oxygen conditions to determine NH 4 ϩ production. NH 4 ϩ exchange showed a clear seasonal pattern, with influxes during the winter (Ϫ7.6 Ϯ 4.9 mmol m Ϫ2 d Ϫ1) and high effluxes during the summer (36.6 and 20.8 mmol m Ϫ2 d Ϫ1 ) when the accumulation of fresh organic matter (evidenced as chlorophyll a) produced a flocculent layer over the sediments. Besides natural hypoxia of the bottom water associated with ESSW, the large input of organic matter resulted in anoxia within the sediment, as a consequence of respiration processes, and an enhancement in sulfate reduction rates (up to 200 mmol m Ϫ2 d Ϫ1 ). The flocculent layer then provided a favorable environment for the extensive development of Beggiatoa spp. mats. Overall, during the sampling period, NO 3 Ϫ was consumed at an average rate of 1.33 mmol m Ϫ2 d Ϫ1. In the summer, denitrification appeared to be partially inhibited by the very negative redox conditions and could explain only 24% of the NO 3 Ϫ uptake by the sediment. The balance may be due to NO 3 Ϫ incorporation into Beggiatoa spp. Short incubations with these bacteria suggest that they are able to produce NH 4 ϩ by dissimilatory NO reduction, taking advantage of their ability to store NO 3 Ϫ , though its Ϫ 3 uptake was not observed in these experiments. The NH 4 ϩ flux obtained using Beggiatoa spp. mat cultures was 5 mmol m Ϫ2 d Ϫ1 , which accounts for 17% of the total NH 4 ϩ efflux during the summer period (January and March). The ecological implications of a large input of organic matter, evidenced by the presence of a flocculent benthic layer and Beggiatoa spp., are discussed in relation to their contribution, during the upwelling season, toward the long-term eutrophication of Concepción Bay.High rates of primary production in the world oceans take place in coastal areas. Th...

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Comparison of pelagic and nepheloid layer marine snow: implications for carbon cycling

Cited by 65 publications

References 38 publications

Rapid lateral particle transport in the Argentine Basin: Molecular 14C and 230Thxs evidence

Rapid lateral particle transport in the Argentine Basin: Molecular 14C and 230Thxs evidence

Measuring Floc Structural Characteristics

Massive developments of microbial mats following phytoplankton blooms in a naturally eutrophic bay: Implications for nitrogen cycling

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