Implications for the mesopelagic microbial gardening hypothesis as determined by experimental fragmentation of Antarctic krill fecal pellets

Cavan, Emma L.; Kawaguchi, So; Boyd, Philip W.

doi:10.1002/ece3.7119

Cited by 9 publications

(9 citation statements)

References 75 publications

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“…9 ). Copepods have been observed to fragment FP 44 and it was recently shown experimentally that, depending on the FP composition, POC turnover rates can be significantly higher in fragmented compared to non-fragmented FP 45 . On a larger scale, Briggs et al 46 showed that fragmentation of sinking particles may explain 50% of the total carbon flux attenuation in the SO and North Atlantic.…”

Section: Discussionmentioning

confidence: 99%

Krill and salp faecal pellets contribute equally to the carbon flux at the Antarctic Peninsula

et al. 2021

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Krill and salps are important for carbon flux in the Southern Ocean, but the extent of their contribution and the consequences of shifts in dominance from krill to salps remain unclear. We present a direct comparison of the contribution of krill and salp faecal pellets (FP) to vertical carbon flux at the Antarctic Peninsula using a combination of sediment traps, FP production, carbon content, microbial degradation, and krill and salp abundances. Salps produce 4-fold more FP carbon than krill, but the FP from both species contribute equally to the carbon flux at 300 m, accounting for 75% of total carbon. Krill FP are exported to 72% to 300 m, while 80% of salp FP are retained in the mixed layer due to fragmentation. Thus, declining krill abundances could lead to decreased carbon flux, indicating that the Antarctic Peninsula could become a less efficient carbon sink for anthropogenic CO2 in future.

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Section: Discussionmentioning

confidence: 99%

Krill and salp faecal pellets contribute equally to the carbon flux at the Antarctic Peninsula

et al. 2021

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“…Further DOC may be released from phytoplankton cells via protozoan and zooplankton grazing, such as sloppy feeding, where 12%–50% of intercellular DOC is released into surrounding waters (Møller et al., 2003; Nagata et al., 2000). Antarctic krill release high but variable amounts of DOC (205 ± 77.7 mmol C m −2 d −1 , Ruiz‐Halpern et al., 2011) in their faecal pellets which may be colonized by bacteria following pellet fragmentation (Cavan et al., 2021). Krill may support heterotrophic bacteria and microbial remineralization of both carbon and dFe (Cavan et al., 2019).…”

Section: Discussionmentioning

confidence: 99%

Circumpolar Deep Water and Shelf Sediments Support Late Summer Microbial Iron Remineralization

Smith

Ratnarajah

Holmes

et al. 2021

Global Biogeochemical Cycles

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Despite widespread iron (Fe) limitation in the Southern Ocean, intense phytoplankton blooms are observed around productive coastal regions such as the Mertz Polynya (off George V Land and Adelie Land, East Antarctica; 140–155°E). Sources of Fe across coastal East Antarctica vary, with limited data available for late summer months. We investigated the sources of dissolved Fe (dFe; <0.2 μm) at 19 oceanographic stations in the Mertz Glacier Region (64–67°S; 138–154°E), between January and March of 2019. Concentrations of dFe ranged from below detection limit (0.03 nM) at the surface, to 0.34 nM above the base of the mixed layer (35 m), reaching 0.59 nM at depth (520 m). Using oceanographic features and trace element ratios (manganese and titanium), we identified Circumpolar Deep Water (CDW) and shelf sediment resuspension in modified CDW as contributors of dFe to the region over this period. Microbial Fe remineralization was evident where nutrient‐rich water met highly oxygenated waters over the continental shelf. Reduced Fe concentrations in the mixed layer and euphotic zones suggested rapid biological uptake prior to sampling. Despite proposals for pelagic Fe recycling by marine animals, preliminary investigations reveal no significant spatial relationship between animal presence and surface ocean Fe concentrations over the study area. Further research is required to identify seasonal changes to Fe supply in coastal areas which will strengthen our understanding of the Fe cycle and its influence on microbial and primary productivity in this globally significant region.

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“…The major consequence of sinking particle disaggregation is the enhancement of the development of associated microbial communities by providing more time for detritus into essential compounds conversion (van der Jagt et al 2020). In turn, these non-sinking nutritive materials could be efficiently harvested by zooplankton (Mayor et al 2014;Sanders et al 2016;Cavan et al 2021). Mayor et al (2014) speculate that fragmentation could be a deliberate behavior of zooplankton to promote harvestable production of microbial biomass from poor quality POC, terming this phenomenon "microbial gardening".…”

Section: Disaggregated Sinking Particlesmentioning

confidence: 99%

A focus on different types of organic matter particles and their significance in the open ocean carbon cycle

Baumas¹,

Bižić²

2024

Preprint

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Marine particles are key to the cycling of major elements on Earth and play an important role in the balance of nutrients in the ocean. Three main categories of marine particles link the different parts of the open ocean by shaping carbon distribution: (i) Sinking; (ii) Suspended, and (iii) Ascending. Atmospheric carbon captured by phytoplankton in the surface water, is partly sequestered by sinking particles to the bottom of the ocean, having an important role in controlling global climate. Suspended particles represent a major substrate of organic carbon for heterotrophic microorganisms, being more likely to get remineralized. Ascending particles, depending on their content, point of origin, and ascending velocity, may lead to carbon remineralization in the upper layers of the ocean in closer proximity to the atmosphere. Marine particles are hotspots of microbial activity and thus heavily colonized by microorganisms whose dynamics play an important role in organic matter degradation, aggregation and sinking, thus, directly influencing the biological carbon pump efficiency. Microbiomes of marine particles differ depending on particle size, source, and age. Nevertheless, these factors are generally overlooked, and particles are mostly studied as "bulk" without considering the high heterogeneity between individual particles. This hinders our understanding of the carbon budget in the ocean and thus future predictions of climate change. In this review we discuss characteristics of known particle-types and associated sampling methods. We further identify gaps in knowledge and highlight the need to better understand the single particles ecosystem to improve upscaling rates to the global scale.

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Implications for the mesopelagic microbial gardening hypothesis as determined by experimental fragmentation of Antarctic krill fecal pellets

Abstract: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Cited by 9 publications

References 75 publications

Krill and salp faecal pellets contribute equally to the carbon flux at the Antarctic Peninsula

Krill and salp faecal pellets contribute equally to the carbon flux at the Antarctic Peninsula

Circumpolar Deep Water and Shelf Sediments Support Late Summer Microbial Iron Remineralization

A focus on different types of organic matter particles and their significance in the open ocean carbon cycle

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