Ecology of amorphous aggregations (marine snow) in the Northern Adriatic Sea. II. Microbial density and activity in marine snow and its implication to overall pelagic processes

Herndl, G. J.

doi:10.3354/meps048265

Cited by 100 publications

(61 citation statements)

References 27 publications

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“…Because episodic inputs do not affect oxygen consumption values as much as long-term processes (25), particles with an actively respiring community need to remain stationary for a significant amount of time to leave an imprint on oxygen values in the water column. Although a general relationship exists between particle size and sinking rates, there are also numerous examples where Stoke's Law does not strictly apply and even where centimeter-to meter-size particles are neutrally buoyant (26,27). If a large portion of deep-sea particles were neutrally buoyant or slowly sinking (12), they would not appear in sediment traps or impact thorium disequilibrium profiles (28).…”

Section: Resultsmentioning

confidence: 99%

“…In addition, the size range of particles between ∼50 and 500 μm may represent a significant amount of particulate matter and biomass; however, it was not accounted for with either of our methods. In the upper water column, situations in which macroscopic particles such as marine snow dominate overall water column metabolism are rare (26). In most cases, freely suspended microbes dominate water-column respiration, and water volume-based sampling methods are justifiable.…”

Section: Resultsmentioning

confidence: 99%

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Role of macroscopic particles in deep-sea oxygen consumption

Bochdansky

Aken²,

Herndl³

2010

Proc. Natl. Acad. Sci. U.S.A.

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Macroscopic particles (>500 μm), including marine snow, large migrating zooplankton, and their fast-sinking fecal pellets, represent primary vehicles of organic carbon flux from the surface to the deep sea. In contrast, freely suspended microscopic particles such as bacteria and protists do not sink, and they contribute the largest portion of metabolism in the upper ocean. In bathy-and abyssopelagic layers of the ocean (2,000-6,000 m), however, microscopic particles may not dominate oxygen consumption. In a section across the tropical Atlantic, we show that macroscopic particle peaks occurred frequently in the deep sea, whereas microscopic particles were barely detectable. In 10 of 17 deep-sea profiles (>2,000 m depth), macroscopic particle abundances were more strongly crosscorrelated with oxygen deficits than microscopic particles, suggesting that biomass bound to large particles dominates overall deepsea metabolism.ecology | video analysis | marine snow | Atlantic ocean P articles have to be of a size visible to the unaided eye before they appreciably contribute to the vertical flux in the ocean (1-3). These particles-dubbed marine snow because they resemble snowflakes in the backscatter of dive lights (4, 5)-are best enumerated by photographic means. However, microscopic and colloidal particles, a large portion of which are freely suspended bacteria and protists (6), are better quantified using optical backscatter (7). Using both techniques in tandem, we can contrast the relative distribution of microscopic and macroscopic particles in the ocean. Most video profiles in the past have been taken to a maximum depth of 1,500 m (8-10), and very few profiles exist to 4,000 m (11, 12). Thus, the data presented here, with a maximum deployment depth of 6,000 m, represent the most comprehensive basin-scale video analyses of deep-sea particles to date. To what extent and at which depth these imaged particles contribute to vertical flux remains unknown; however, a link to oxygen deficits may reflect their significance as hotspots of microbial metabolic activity. Results and DiscussionThe Archimedes III research expedition on the research vessel Pelagia was conducted from December 17, 2007 to January 16, 2008; it followed a cruise track from Fortaleza, Brazil, along the equator to the Sierra Leone Basin and then, headed northwest toward the Cape Verde Islands. The video profiles reported here were collected over a transect of ∼4,000 km (Fig. 1). The Romanche Fracture Zone, the location of the greatest depth in the Mid-Atlantic Ridge, was sampled at a higher resolution than the western and eastern basins of the tropical Atlantic (Fig. 1). Microscopic particle abundance as assessed by optical backscatter generally decreased with depth, except for a pronounced peak in the oxygen minimum zone (250-500 m). Macroscopic particle numbers (>500 μm) as detected by video analysis usually decreased below the oxygen minimum zone to 2,000 m, but then, they frequently increased, forming peaks of high particle numbers ( Figs. 1 and 2). ...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Role of macroscopic particles in deep-sea oxygen consumption

Bochdansky

Aken²,

Herndl³

2010

Proc. Natl. Acad. Sci. U.S.A.

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“…The relationship is specific for each individual bloom, but no general overall relationship between TEP and chl. a can be derived (Herndl, 1988;Berman & VinerMozzini, 2001), as too many other processes are interfering. During growth of a bloom, the concentration of TEP (µg Xeq.…”

Section: Release Of Tep or Tep-precursorsmentioning

confidence: 99%

Transparent exopolymer particles (TEP) in aquatic environments

Passow

2002

Progress in Oceanography

959

951

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Since the development of methods to quantify transparent exopolymer particles (TEP) 1993, it has been shown that these gel-particles are not only ubiquitous and abundant, but also play a significant role in the biogeochemical cycling of elements and the structuring of food webs. TEP may be quantified either microscopically or colorimetrically. Although data based on measurements using one or other of these methods are not directly comparable, the results are consistent. TEP abundances in fresh and marine waters are in the same range as those of phytoplankton, with peak values occurring during phytoplankton blooms. TEP are very sticky particles that exhibit the characteristics of gels, and consist predominantly of acidic polysaccharides. In marine systems the majority of TEP are formed abiotically from dissolved precursors, which are released by phytoplankton that are either actively growing or are senescent. TEP are also generated during the sloughing of cell surface mucus and the disintegration of colonial matrices. The impact of exopolymers in the creation of microhabitats and in the cycling of trace compounds varies with the state in which the polymers occur, either as particles or as solute slimes. As particles, TEP provide surfaces for the colonization by bacteria and transfer by adsorption, trace solute substances into the particulate pool. As dissolved polymers they are mixed with the water and can neither be filtered nor aggregated. Because of their high abundances, large size and high stickiness, TEP enhance or even facilitate the aggregation of solid, non-sticky particles. They have been found to form the matrices of all marine aggregates investigated to date. By aggregating solid particles, TEP promote the sedimentation of particles, and, because their carbon content is high, their direct contribution to fluxes of carbon into deep water is significant. The direct sedimentation of TEP may represent a mechanism for the selective sequestration of carbon in deep water, because the C:N ratios of TEP lie well above the Redfield ratio. The turnover time of TEP as a result of bacterial degradation appears to range from hours to months, depending on the chemical composition and age of TEP. TEP may also be utilized not only by filter feeders (some protozoans and appendicularian) but TEP-rich microaggregates, consisting of pico-and nano-plankton are also readily grazed by euphausiids, thus permitting the uptake of particles that would otherwise be too small to be grazed directly by euphausiids. This short-circuits food chains and links the microbial food-web to the classical food-web. It is suggested that this expansion of the concept of food webs, linking the microbial loop with an aggregation web will provide a more complete description of particle dynamics. 

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“…EFs observed in this study compare with literature reporting enrichment of microorganisms in marine snow. For aquatic protozoans, EFs range from 1 for monads from the Northern Adriatic Sea (Herndl 1988), to , 10 4 for ciliates Fig. 5.…”

Section: Water Typementioning

confidence: 99%

Association of Toxoplasma gondii oocysts with fresh, estuarine, and marine macroaggregates

Shapiro

Silver

Largier

et al. 2012

Limnology & Oceanography

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The protozoan parasite Toxoplasma gondii infects a large proportion of threatened California sea otters (Enhydra lutris nereis), and is an important waterborne pathogen in humans. Contamination of coastal waters with T. gondii is thought to occur through delivery of environmentally resistant oocysts to nearshore regions via overland runoff. The objectives of this study were to evaluate whether T. gondii oocysts and surrogate microspheres attach to aggregates ($ 0.5 mm), and whether the magnitude of aggregation depends on water type, specifically salinity. Laboratory aggregation studies were conducted by adding T. gondii oocysts and surrogate microspheres to riverine, estuarine, and marine waters, and quantifying the proportion of oocysts and surrogates in aggregate-rich and aggregate-free water fractions. Attachment of oocysts and surrogates to aggregates occurred in all water types, but was greater in estuarine and marine waters, with concentrations of T. gondii in aggregates enriched 3-4 orders of magnitude. Aquatic aggregates may, thus, significantly influence waterborne transport of terrestrially derived pathogens, both through enhanced settling and subsequent concentration in the benthos, as well as by facilitating ingestion by invertebrate vectors that can transmit pathogens to susceptible hosts, including sea otters and humans.

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Ecology of amorphous aggregations (marine snow) in the Northern Adriatic Sea. II. Microbial density and activity in marine snow and its implication to overall pelagic processes

Cited by 100 publications

References 27 publications

Role of macroscopic particles in deep-sea oxygen consumption

Role of macroscopic particles in deep-sea oxygen consumption

Transparent exopolymer particles (TEP) in aquatic environments

Association of Toxoplasma gondii oocysts with fresh, estuarine, and marine macroaggregates

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