Abstract
Suspension feeding is a key ecological strategy in modern oceans that provides a link between pelagic and benthic systems. Establishing when suspension feeding first became widespread is thus a crucial research area in ecology and evolution, with implications for understanding the origins of the modern marine biosphere. Here, we use three-dimensional modelling and computational fluid dynamics to establish the feeding mode of the enigmatic Ediacaran pentaradial eukaryote Arkarua. Through comparisons with two Cambrian echinoderms, Cambraster and Stromatocystites, we show that flow patterns around Arkarua strongly support its interpretation as a passive suspension feeder. Arkarua is added to the growing number of Ediacaran benthic suspension feeders, suggesting that the energy link between pelagic and benthic ecosystems was likely expanding in the White Sea assemblage (~ 558–550 Ma). The advent of widespread suspension feeding could therefore have played an important role in the subsequent waves of ecological innovation and escalation that culminated with the Cambrian explosion.
Highlights
Suspension feeding is a key ecological strategy in modern oceans that provides a link between pelagic and benthic systems
Osmotrophy relies on a high surface area-to-volume (SA):V ratio to enhance the uptake of dissolved organic matter through o smosis[22,34], but the values obtained for models of Arkarua (2.10 and 2.48 mm–1), Cambraster (1.22 mm–1) and Stromatocystites (0.61 mm–1) are much lower than extant osmotrophic megabacteria, which range from 8–20,000 mm–1
Our results reveal that low velocity flow and, at higher inlet velocities, reversed flow was concentrated over specific parts of the models, i.e. the central depression and associated grooves
Summary
Suspension feeding is a key ecological strategy in modern oceans that provides a link between pelagic and benthic systems. Benthic suspension feeders are responsible for removing suspended organic particles from the water column, thereby reducing primary production and increasing the retention time for suspended particles on the seafloor This provides a link between the pelagic and benthic realms and exerts a powerful control over rates and patterns of energy t ransport[10,11,12]. We use a virtual modelling approach called computational fluid dynamics (CFD) to visualize water flow around putative feeding structures for models of Arkarua, and compare the resulting flow patterns to those produced by models of Cambraster and Stromatocystites. Using these data, we test the hypothesis that Arkarua was a benthic suspension feeder. The results allow us to build a more complete picture of White Sea assemblage palaeoecology, shedding light on the importance of suspension feeding in the Ediacaran
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