The Southern Ocean Radiolarian (SO-RAD) dataset: a new compilation of modern radiolarian census data

Abstract

Abstract. Radiolarians (holoplanktonic protozoa) preserved in marine sediments are commonly used as palaeoclimate proxies for reconstructing past Southern Ocean environments. Generating reconstructions of past climate based on microfossil abundances, such as radiolarians, requires a spatially and environmentally comprehensive reference dataset of modern census counts. The Southern Ocean Radiolarian (SO-RAD) dataset includes census counts for 238 radiolarian taxa from 228 surface sediment samples located in the Atlantic, Indian, and southwest Pacific sectors of the Southern Ocean. This compilation is the largest radiolarian census dataset derived from surface sediment samples in the Southern Ocean. The SO-RAD dataset may be used as a reference dataset for palaeoceanographic reconstructions, or for studying modern radiolarian biogeography and species diversity. As well as describing the data collection and collation, we include recommendations and guidelines for cleaning and subsetting the data for users unfamiliar with the procedures typically used by the radiolarian community. The SO-RAD dataset is available to download from https://doi.org/10.1594/PANGAEA.929903 (Lawler et al., 2021).

Ecoregionalisation of the Southern Ocean Using Radiolarians

“…Regions within the SO are often referenced to in relation to the adjacent basin. There are three major geographical regions, the Atlantic Sector (65 • W to 20 • E), the Indian Sector (20-145 • E) and the Pacific Sector (145 • E to 65 • W) (Lawler et al, 2021). However, in this study, the Pacific is referred to as the Southwest Pacific (145 • E to 170 • W) due to the limited coverage of data in the Pacific sector within the SO-RAD (Lawler et al, 2021).…”

“…The Southern Ocean Radiolarian Dataset (SO-RAD) is a collection of 228 Holocene surface sediment samples from the Atlantic, Indian and Southwest Pacific Sectors of the SO (Figure 1; Lawler et al, 2021). Site locations range from the STZ to the AZ.…”

“…However, there has been insufficient species data to test this. In this paper we use a new radiolarian assemblage dataset (SORAD; Lawler et al, 2021) to determine radiolarian ecoregions in the Atlantic, Indian and southwest Pacific sectors of the SO and test the hypothesis that the SO exhibits zonal ecoregions.…”

“…Polycystine radiolarians are siliceous marine protists that occur as plankton in all the world's oceans typically living subsurface (100-500 m; Abelmann and Gowing, 1997;Rogers and De Deckker, 2007;Hernandez-Almeida et al, 2020). They are found throughout the SO and show a wide range of biodiversity (Lawler et al, 2021). They produce ornate siliceous skeletons ranging in size from below 40 µm to ∼2 mm (Boltovskoy, 2017).…”

“…In this paper, a new compilation of surface sediment radiolarian assemblages from across multiple SO sectors (SO-RAD; Lawler et al, 2021) is used to explore the ecoregions of the SO from the Subtropical Front (STF) to Antarctica based on species data. The 228 surface sediment samples include 238 radiolarian taxa, ranging in latitude from 10 • S to 80 • S and longitudinally from 50 • W to 190 • E (Figure 1).…”