Three major mesoplanktonic communities resolved by in situ imaging in the upper 500 m of the global ocean

Abstract

AimThe distribution of mesoplankton communities has been poorly studied at global scale, especially from in situ instruments. This study aims to (1) describe the global distribution of mesoplankton communities in relation to their environment and (2) assess the ability of various environmental‐based ocean regionalizations to explain the distribution of these communities.LocationGlobal ocean, 0–500 m depth.Time Period2008–2019.Major Taxa StudiedTwenty‐eight groups of large mesoplanktonic and macroplanktonic organisms, covering Metazoa, Rhizaria and Cyanobacteria.MethodsFrom a global data set of 2500 vertical profiles making use of the Underwater Vision Profiler 5 (UVP5), an in situ imaging instrument, we studied the global distribution of large (>600 μm) mesoplanktonic organisms. Among the 6.8 million imaged objects, 330,000 were large zooplanktonic organisms and phytoplankton colonies, the rest consisting of marine snow particles. Multivariate ordination (PCA) and clustering were used to describe patterns in community composition, while comparison with existing regionalizations was performed with regression methods (RDA).ResultsWithin the observed size range, epipelagic plankton communities were Trichodesmium‐enriched in the intertropical Atlantic, Copepoda‐enriched at high latitudes and in upwelling areas, and Rhizaria‐enriched in oligotrophic areas. In the mesopelagic layer, Copepoda‐enriched communities were also found at high latitudes and in the Atlantic Ocean, while Rhizaria‐enriched communities prevailed in the Peruvian upwelling system and a few mixed communities were found elsewhere. The comparison between the distribution of these communities and a set of existing regionalizations of the ocean suggested that the structure of plankton communities described above is mostly driven by basin‐level environmental conditions.Main ConclusionsIn both layers, three types of plankton communities emerged and seemed to be mostly driven by regional environmental conditions. This work sheds light on the role not only of metazoans, but also of unexpected large protists and cyanobacteria in structuring large mesoplankton communities.

Key link between iron and the size structure of three main mesoplanktonic groups (Crustaceans, Rhizarians, and colonial N2-fixers) in the Global Ocean

“…The first two groups represent 45% and 15% of the total image diversity in UVP datasets, while the latter correspond to 81% of the overall scanner images (Figure 1B). This result is consistent with a recent study highlighting the main communities of mesoplankton in the epipelagic layer based on UVP profiles solely ( 43 ). In this study, we used UVP profiles to characterize the occurrences of colonial N 2 -fixers and Rhizarians which are both strongly undersampled when collected with plankton nets due to mesh exclusion or destruction ( 39 ).…”

“…Sea surface temperature (SST) ranked first for colonial N 2 -fixers and Rhizarians, and fourth for Crustaceans, thus representing one of the main factors explaining the global patterns in mesoplankton size distribution. This finding is consistent with the global analysis of UVP ( 43 ) and scanned nets collected during the Tara Oceans global expedition ( 32 ), as well as a meta-analysis of phytoplankton ( 50 ), mixotrophic Rhizarians (e.g. Collodaria, Acantharia and Foraminifera) ( 30 ), and copepod ( 33 ) biogeography.…”

“…Colonial N 2 -fixers present the highest percentage of empty records, with 64% of the bins without occurrences, while empty bins represented only one third and one tenth of the dataset for Rhizarians and Crustaceans respectively (Figure 2B). Modeled abundances, derived from the predicted NBSS parameters (slope, intercept, size range), showed very contrasting biogeography across the three main mesoplankton groups, with a good agreement between observations and predictions (Figure 2C) corresponding to the different habitats discussed in Panaïotis et al (43). Likewise, we found that colonial N 2 -fixers were restricted to the subtropical latitudes, that Rhizarians were mostly present in the subtropics although they were also relatively abundant at higher latitudes and in the Californian upwelling system, and that Crustaceans were generally ubiquitous, with the highest abundances observed in productive ecosystems (e.g.…”

“…Here, we present a global compilation of direct size estimates in the 200-20,000 µm size range, defined as mesoplankton by Sieburth et al ( 42 ), associated with three groups that dominate community abundances in the upper ocean ( 43 ): Colonial N2-fixers, Rhizarians, and Crustaceans. We depict the spectral biogeography of Colonial N2-fixers and Rhizarians using a range of Underwater Vision Profilers (UVP), since these organisms can only be monitored by non-intrusive imaging systems, and net collected samples imaged with benchtop scanners for Crustaceans.…”

Rhizaria in the oligotrophic ocean exhibit clear temporal and vertical variability

“…Cruises were conducted at approximately monthly intervals. Rhizaria individuals were sampled using the Underwater Vision Profiler 5 [UVP5; Picheral et al (2010)], a tool which is well established to accurately quantify large Rhizaria (Barth and Stone, 2022; Biard et al, 2016; Biard and Ohman, 2020; Drago et al, 2022; Llopis Monferrer et al, 2022; Panaïotis et al, 2023; Stukel et al, 2019; Stukel et al, 2018). The UVP5 was mounted to the sampling rosette and collected data autonomously on routine casts, from which only the downcast data are utilized.…”