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

Abstract

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.

Tagging of water masses with covariance of trace metals and prokaryotic taxa in the Southern Ocean

“…Results), suggesting that factors that are dependent and independent of size fraction both influence the observed biogeographical patterns. Particles are known to host distinct communities and the nature of the particles can shape the associated prokaryotic assemblages (Baumas and Bizic 2023). Sinking particles were suggested to act as vectors for microbes across the water column (Mestre et al 2018), an idea that is supported by the about 2-fold lower number of indicator species for a given water mass for the particle-attached (121) as compared to the free-living ( 213) communities (Fig.…”

Composition of the sinking particle flux in a hot spot of dinitrogen fixation revealed through polyacrylamide gel traps

“…Capturing their diversity and determining who constitute and drive the flux in a given region is therefore challenging. Sediment traps allow to collect particles and to assess the relationship between PP, particle export and attenuation in the mesopelagic zone (Buesseler and Boyd, 2009;Baker et al, 2020;Baumas and Bizic, 2023). Polyacrylamide gels mounted on sediment traps enable the composition of the sinking flux to be estimated by collecting and preserving and preservation of their morphological characteristics during deposition in the gel (Jannasch et al, 1980;Lundsgaard, 1995;Waite et al, 2000).…”

A novel method to sample individual marine snow particles for downstream molecular analyses

“…Sinking particles vary in age and origins (phytoplankton cells, fecal pellets, or aggregated detritus) (Simon et al 2002; Le Moigne 2019), sinking speeds (Alldredge and Silver 1988; Armstrong et al 2002; Trull et al 2008; Turner 2015), density, porosity, and fractal dimension (Guidi et al 2008; Laurenceau‐Cornec et al 2019). Sinking particles constitute unique small ecosystems in continuous interactions with diverse associated microbial communities (Simon et al 2002; Grossart et al 2006; Bizic‐Ionescu et al 2018; Baumas and Bizic 2023). In order to predict changes in POC sequestration under future climate scenarios it is crucial to have an exhaustive understanding of the processes attenuating POC fluxes such as microbial degradation.…”

“…However, due to the fragile structure of sinking particles, and their scarcity in the small volumes of sampled water, these methods are inadequate to representatively sample gravitational sinking particles (Alldredge and Silver 1988; Planquette and Sherrell 2012; Puigcorbé et al 2020; Baumas et al 2021). To target sinking particles and associated microbial communities, alternative approaches such as the marine snow catcher (e.g., Duret et al 2019; Baumas et al 2021) or sediment traps (Baumas and Bizic 2023 and references within) have been used. Yet, most of these studies still use a filtration step.…”