High variability and enhanced nocturnal oxygen uptake in coral reef sponges

Abstract

Sponges are animals that feed by filtering water through their perforated body. We examined the in situ diel dynamics of sponge metabolism by continuously measuring the oxygen concentrations in the water inhaled and exhaled by undisturbed sponges. A clear daily pattern of oxygen removal was evident for six of the seven species we studied with their nocturnal oxygen removal being almost double the diurnal values (+ 86 AE 57%). Oxygenic photosynthesis by the sponge's symbiotic or endolithic phototrophic microbes may explain some of the diel difference, but significant day-night differences were also observed in three sponge species for which no evidence of photosynthetic activity (tested with imaging pulse-amplitude-modulation Fluorometry) was found. Mean oxygen removal (AE 95% confidence interval for the mean) per species ranged from 1.7 AE 1 μmol O 2 per liter (hereafter: μmol O 2 L À1 ) for the low microbial abundance (LMA) sponge Callyspongia siphonella to 30.5 AE 10.5 μmol O 2 L À1 for the high microbial abundance HMA) sponge Theonella swinhoei with considerable variation in oxygen removal across all scales (minutes to hours, within and among specimens). Events of high oxygen removal (> 50 μmol L À1 ) were regularly observed for five of the seven species and were predominantly nocturnal, occasionally lasting several hours. The high variability in oxygen removal stresses the need for long-term in-situ measurements of benthic suspension feeders metabolism.

A comparison of mesophotic and shallow sponge holobionts resilience to predicted future temperature elevation

“…Oxygen concentration measurement in the aquarium surrounding water (DO Surr,t ) took place before each measurement of the sponge-oxygen removal. Oxygen concentration median values (for 10 min measurement) were then calculated for both, DO Surr,t and DO EX,t , and the DO removal per liter (DO 2 , µmol L -1 ) was calculated as follows (Moskovish et al, 2022) Changes in buoyant weight were measured using a digital scale (ViBRA AJ-320CE) following Osinga (1999).…”

Coral hosts provide more than shelter to boring bivalves

“…The bivalves in the live and stripped coral colonies were allowed to acclimate in the field for 1 month prior to the beginning of the measurements. The oxygen consumption of the bivalves (an indicator of metabolic activity) was quantified in situ, using optodes (FireSting-O2 system, PyroScience, Germany) and an automatic logger (Figure 1a, see Moskovich et al, 2023 for a detailed description of the methodology). The proportion of actively pumping L. simplex was quantified monthly using fluorescein dye released at the inhalant siphon opening of the boreholes (Figure 1b-d, see Video S1 for demonstration).…”