Abstract
A digital, four-channel thermistor flowmeter integrated with time-lapse cameras was developed as an experimental tool for measuring pumping rates in marine sponges, particularly those with small excurrent openings (oscula). Combining flowmeters with time-lapse imagery yielded valuable insights into the contractile behaviour of oscula in Cliona orientalis. Osculum cross-sectional area (OSA) was positively correlated to measured excurrent speeds (ES), indicating that sponge pumping and osculum contraction are coordinated behaviours. Both OSA and ES were positively correlated to pumping rate (Q). Diel trends in pumping activity and osculum contraction were also observed, with sponges increasing their pumping activity to peak at midday and decreasing pumping and contracting oscula at night. Short-term elevation of the suspended sediment concentration (SSC) within the seawater initially decreased pumping rates by up to 90%, ultimately resulting in closure of the oscula and cessation of pumping.
Highlights
Marine sponges (Porifera), and their associated microbial symbionts, perform many ecologically important functions including: creating and bioeroding substrate, coupling bentho-pelagic biogeochemical fluxes, forming intricate associations with other organisms (Bell, 2008; Maldonado, Ribes & Van Duyl, 2012), and converting dissolved organic matter to particulate organic matter for use in oligotrophic food webs (De Goeij et al, 2013; Maldonado, 2016)
In order to elucidate the relationship between sponge oscula opening/closing behaviour and pumping rate, we examined the common, Indo-pacific bioeroding sponge Cliona orientalis (Thiele, 1900)
In this study we report the first specific volume pumping rates for C. orientalis
Summary
Marine sponges (Porifera), and their associated microbial symbionts, perform many ecologically important functions including: creating and bioeroding substrate, coupling bentho-pelagic biogeochemical fluxes (e.g., carbon, nitrogen, silicon, and phosphorus cycling), forming intricate associations with other organisms (Bell, 2008; Maldonado, Ribes & Van Duyl, 2012), and converting dissolved organic matter to particulate organic matter for use in oligotrophic food webs (De Goeij et al, 2013; Maldonado, 2016). Water is pumped through small incurrent pores (ostia) to a system of channels leading to chambers full of choanocytes before flowing out via larger excurrent openings (oscula) (Bergquist, 1978). They depend on this water circulation for most of their essential physiological processes, i.e., food capture, waste elimination, gas exchange and reproduction (Bergquist, 1978). Sponges filter large volumes of water, with retention efficiencies between 75 and 99% for particles and biota of various sizes (Reiswig, 1971; Reiswig, 1975; Pile et al, 1997). Sponge populations can filter the equivalent volume of the overlaying water column in
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