Abstract:Zooplankton fecal pellets have long been thought to be a dominant component of the sedimentary flux in marine and freshwater ecosystems, but that view is changing. The last 2 decades have seen publication of > 500 studies using sediment traps, which reveal that zooplankton fecal pellets often constitute only a minor or variable proportion of the sedimentary flux. Substantial proportions of this flux are from organic aggregates ('marine snow') of various origins, including phytoplankton blooms, which sediment d… Show more
“…3). The cylindrical faecal pellets were probably derived from copepods and euphausiids, and the ovoid faecal pellets may originate from small copepods or larvaceans (Gonzalez, 1992;Turner, 2002;Wilson et al, 2008;Wexels Riser et al, 2008).…”
Section: Composition Of Particlesmentioning
confidence: 99%
“…Bishop, 1989;Buesseler, 1991;Newton, 1995, 1999;Buesseler and Boyd, 2009). Of particular interest is determining the conditions under which phytoplankton can be directly exported via physical flocculation and sinking, without passing through higher trophic levels that engender respiration losses of POC (Michaels and Silver, 1988;Alldredge and Jackson, 1995;Turner, 2002).…”
a b s t r a c tThe SAZ-Sense project examined ecosystem controls on Southern Ocean carbon export during austral summer (January-February 2007) at three locations: P1 in the low biomass Subantarctic Zone (SAZ) west of Tasmania, P3 in a region of elevated biomass in the SAZ east of Tasmania fuelled by enhanced iron supply, and P2 in High-Nutrient/Low Chlorophyll (HNLC) Polar Frontal Zone (PFZ) waters south of P1 and P3. Sinking particles were collected using (i) a cylindrical time-series (PPS3/3) trap for bulk geochemical fluxes, (ii) indented rotating sphere (IRS) traps operated as in-situ settling columns to determine the flux distribution across sinking-rate fractions, and (iii) cylindrical traps filled with polyacrylamide gels to obtain intact particles for image analysis.Particulate organic carbon (POC) flux at 150 m (PPS3/3 trap) was highest at P1, lower at P2, and lowest at P3 (3.3 71.8, 2.1 7 0.9, and 0.9 70.4 mmol m À 2 d À 1 , respectively). Biogenic silica (BSi) flux was very low in the SAZ (0.2 7 0.2 and 0.02 7 0.005 mmol m À 2 d À 1 at P1 and P3, respectively) and much higher in the PFZ (2.3 7 0.5 mmol m À 2 d À 1 at P2). Hence, the high biomass site P3 did not exhibit a correspondingly high flux of either POC or BSi. Separation of sinking-rate fractions with the IRS traps (at 170 and 320 m depth) was only successful at the PFZ site P2, where a relatively uniform distribution of flux was observed with $ 1/3 of the POC sinking faster than 100 m d À 1 and 1/3 sinking slower than 10 m d À 1 .Analysis of thousands of particles collected with the gel traps (at 140, 190, 240, and 290 m depth) enabled us to identify 5 different categories: fluff-aggregates (low-density porous or amorphous aggregates), faecal-aggregates (denser aggregates composed of different types of particles), cylindrical and ovoid faecal pellets, and isolated phyto-cells (chains and single cells). Faecal-aggregates dominated the flux at all sites, and were larger in size at P1 in comparison to P3. The PFZ site P2 differed strongly from both SAZ sites in having a much higher abundance of diatoms and relatively small-sized faecalaggregates. Overall, the particle images suggest that grazing was an important influence on vertical export at all three sites, with differences in the extents of large aggregate formation and direct diatom export further influencing the differences among the sites.
“…3). The cylindrical faecal pellets were probably derived from copepods and euphausiids, and the ovoid faecal pellets may originate from small copepods or larvaceans (Gonzalez, 1992;Turner, 2002;Wilson et al, 2008;Wexels Riser et al, 2008).…”
Section: Composition Of Particlesmentioning
confidence: 99%
“…Bishop, 1989;Buesseler, 1991;Newton, 1995, 1999;Buesseler and Boyd, 2009). Of particular interest is determining the conditions under which phytoplankton can be directly exported via physical flocculation and sinking, without passing through higher trophic levels that engender respiration losses of POC (Michaels and Silver, 1988;Alldredge and Jackson, 1995;Turner, 2002).…”
a b s t r a c tThe SAZ-Sense project examined ecosystem controls on Southern Ocean carbon export during austral summer (January-February 2007) at three locations: P1 in the low biomass Subantarctic Zone (SAZ) west of Tasmania, P3 in a region of elevated biomass in the SAZ east of Tasmania fuelled by enhanced iron supply, and P2 in High-Nutrient/Low Chlorophyll (HNLC) Polar Frontal Zone (PFZ) waters south of P1 and P3. Sinking particles were collected using (i) a cylindrical time-series (PPS3/3) trap for bulk geochemical fluxes, (ii) indented rotating sphere (IRS) traps operated as in-situ settling columns to determine the flux distribution across sinking-rate fractions, and (iii) cylindrical traps filled with polyacrylamide gels to obtain intact particles for image analysis.Particulate organic carbon (POC) flux at 150 m (PPS3/3 trap) was highest at P1, lower at P2, and lowest at P3 (3.3 71.8, 2.1 7 0.9, and 0.9 70.4 mmol m À 2 d À 1 , respectively). Biogenic silica (BSi) flux was very low in the SAZ (0.2 7 0.2 and 0.02 7 0.005 mmol m À 2 d À 1 at P1 and P3, respectively) and much higher in the PFZ (2.3 7 0.5 mmol m À 2 d À 1 at P2). Hence, the high biomass site P3 did not exhibit a correspondingly high flux of either POC or BSi. Separation of sinking-rate fractions with the IRS traps (at 170 and 320 m depth) was only successful at the PFZ site P2, where a relatively uniform distribution of flux was observed with $ 1/3 of the POC sinking faster than 100 m d À 1 and 1/3 sinking slower than 10 m d À 1 .Analysis of thousands of particles collected with the gel traps (at 140, 190, 240, and 290 m depth) enabled us to identify 5 different categories: fluff-aggregates (low-density porous or amorphous aggregates), faecal-aggregates (denser aggregates composed of different types of particles), cylindrical and ovoid faecal pellets, and isolated phyto-cells (chains and single cells). Faecal-aggregates dominated the flux at all sites, and were larger in size at P1 in comparison to P3. The PFZ site P2 differed strongly from both SAZ sites in having a much higher abundance of diatoms and relatively small-sized faecalaggregates. Overall, the particle images suggest that grazing was an important influence on vertical export at all three sites, with differences in the extents of large aggregate formation and direct diatom export further influencing the differences among the sites.
“…Sinking rates ( ) of organic material from PP and SP were adopted from Turner (2002) SP carcasses are assumed equivalent to detritus entangled in sinking marine snow and respired as such (Iversen and Ploug, 2010;Tang and Elliott, 2013). We assumed a consumption rate similar to that of sinking faecal pellets ( _ , from Eq.…”
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Citation (APA):Cosme, N. M. D., Koski, M., & Hauschild, M. Z. (2015). Exposure factors for marine eutrophication impacts assessment based on a mechanistic biological model. Ecological Modelling, 317, 50-63. DOI: 10.1016/j.ecolmodel.2015.09.005 Cosme et al. / Ecological Modelling 317 (2015
AbstractEmissions of nitrogen (N) from anthropogenic sources enrich marine waters and promote planktonic growth. This newly synthesised organic carbon is eventually exported to benthic waters where aerobic respiration by heterotrophic bacteria results in the consumption of dissolved oxygen (DO). This pathway is typical of marine eutrophication. A model is proposed to mechanistically estimate the response of coastal marine ecosystems to N inputs. It addresses the biological processes of nutrient-limited primary production (PP), metazoan consumption, and bacterial degradation, in four distinct sinking routes from primary (cell aggregates) and secondary producers (faecal pellets, carcasses, and active vertical transport). Carbon export production (P E ) and ecosystems eXposure Factors (XF), which represents a nitrogen-to-oxygen 'conversion' potential, were estimated at a spatial resolution of 66 large marine ecosystem (LME), five climate zones, and site-generic. The XFs obtained range from 0.45 (Central Arctic Ocean) to 15.9 kgO 2 ·kgN -1 (Baltic Sea). While LME resolution is recommended, aggregated P E or XF per climate zone can be adopted, but not global aggregation due to high variability. The XF is essential to estimate a marine eutrophication impacts indicator in Life Cycle Impact Assessment (LCIA) of anthropogenic-N emissions. Every relevant process was modelled and the uncertainty of the driving parameters considered low suggesting valid applicability in characterisation modelling in LCIA.
“…Numerous field studies (> 500) using sediment traps have revealed that zooplankton fecal pellets often constitute a minor portion of the sedimentary flux, much less than what would be expected from the zooplankton abundances and expected fecal pellet production rates (González & Smetacek 1994, Turner 2002. A reduced vertical flux is often attributed to recycling and repackaging of the fecal pellets by coprophagous (ingestion of pellets) copepods (Smetacek 1980, Bathmann et al 1987, González & Smetacek 1994, González et al 1994a, Lane et al 1994, Urban-Rich et al 1999.…”
Section: Introductionmentioning
confidence: 99%
“…A reduced vertical flux is often attributed to recycling and repackaging of the fecal pellets by coprophagous (ingestion of pellets) copepods (Smetacek 1980, Bathmann et al 1987, González & Smetacek 1994, González et al 1994a, Lane et al 1994, Urban-Rich et al 1999. Also, coprorhexy (fragmentation of pellets) and coprochaly (loosening of pellets) may increase the residence time of fecal material in the water column (Lampitt et al 1990, Noji et al 1991) and make it subject to enhanced microbial degradation (Turner 2002), thus accelerating recycling of fecal pellet material in the water column.…”
Decades of sediment trap studies have revealed that zooplankton fecal pellets constitute a much smaller fraction of the sedimentary flux than expected from the abundance of copepods and their anticipated production rates of fecal pellets. The explanation for this is thought to be coprophagy (ingestion) of fecal pellets by copepods. We examined fecal pellet clearance rate of Acartia tonsa and Temora longicornis and feeding behaviour of A. tonsa. Pellet clearance rates in A. tonsa and T. longicornis females were similar but low on their own pellets (11 to 22 ml female -1 d -1 ). Our own data together with observations compiled from the literature revealed that copepod fecal pellet clearance rates decrease with increasing relative pellet size and that all species can be described by a common relationship. In A. tonsa, the presence of alternative phytoplankton food increased pellet clearance rate. Direct observations revealed that this was accomplished through the modulating effect of phytoplankton on the feeding behaviour. In the absence of phytoplankton, A. tonsa is nonmotile but perceives sinking fecal pellets at distance. However, only a small fraction of the pellets that came within detection distance elicited an attack. In the presence of phytoplankton food, A. tonsa switched to suspension feeding, and all fecal pellets entrained in the feeding current were encountered. Independent of the feeding mode, fecal pellets were mainly degraded by fragmentation during rejection and only a small fraction was actually ingested (5%). The main impact of A. tonsa on the vertical flux of fecal pellets is therefore through coprorhexy (fragmentation) turning fecal pellets into smaller, slower-sinking particles.
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