Silicon utilization by sponges: an assessment of seasonal changes

Abstract

Awareness that sponges are relevant silicic acid (DSi) users is growing; however, understanding how their DSi consumption kinetics perform is still limited. We investigated the effects that seasonal changes in a temperate ecosystem (Bay of Brest, France) have on the DSi consumption of 2 dominant sponge species: Hymeniacidon perlevis and Tethya citrina. The results indicated that while both species increased their rate of DSi utilization with DSi availability following saturable Michaelis-Menten kinetics, only the kinetics of T. citrina shifted seasonally. This species consumed DSi at a higher rate in autumn than in summer. Surprisingly, the increase in DSi utilization did not involve an increase in net affinity for DSi but rather augmentation of both the half-saturation concentration and the maximum velocity of transport characterizing the kinetics. By quantifying the biomass of the 2 sponge species in the bay and the monthly availability of DSi over an annual cycle, a yearly DSi consumption of 2.50 ± 3.21 × 10 6 mol Si was calculated for their populations. The oversight of the seasonal kinetic change would introduce inaccuracies of 10% into the global DSi consumption budget of the bay. Because the seasonal kinetic differences increased enormously with increasing DSi availability, the relevance of the kinetic shift into the budgets could increase to > 30% for sponge assemblages other than those in the bay whenever they are characterized by higher DSi availability, as is typically occurring at high latitudes and in the deep sea.

In situ determination of Si, N, and P utilization by the demosponge Tethya citrina: A benthic-chamber approach

“…When the consumption rates determined in situ in the assayed individuals were compared with the rates predicted by the models elaborated elsewhere through laboratory incubations of T . citrina [27], their values closely matched (Fig 3). The consumption rate of all incubated individuals fell consistently within the 95% confidence interval of the laboratory kinetic model for DSi consumption in T .…”

“…We preferentially used sponge volume for normalization because it facilitates future comparisons without the need of using destructive sampling on the sponge communities. The normalized rates of DSi consumption obtained from the in situ incubations were compared with the consumption rates predicted from two kinetic models previously developed by us through laboratory incubations [27]. The two models used for the comparison incorporate the variability in the DSi consumption kinetics in T .…”

“…Here we have assayed the demosponge Tethya citrina by taking the incubation chambers to the natural habitat rather than taking the sponges to the laboratory. We have compared subsequently the in situ experimental results with those previously obtained for this same species in laboratory incubations [27]. Thus, this study provides a first test for "laboratory" versus "field" determinations of DSi utilization rates in a shallow-water sponge.…”

Phosphorites, glass ramps and carbonate factories: The evolution of an epicontinental sea and a late Palaeozoic upwelling system (Phosphoria Rock Complex)

“…Dissolved silica (silicic acid; DSi) availability in the oceans is an important limiting parameter in modern siliceous sponge growth and is elevated in many modern sponge‐dominated habitats (Maldonado et al., ; Conway et al., ; Hogg et al., ; López‐Acosta et al., ,b). As a result, elevated DSi might favour (or be required for?)…”

“…Diatoms have played a large part in the DSi deficiency since the Cretaceous. As such, Palaeozoic oceans likely had higher DSi, which might have created conditions more favourable for siliceous sponges (Maldonado et al., ; Racki & Cordey, ; Planavsky et al., ; López‐Acosta et al., 2018a). However, DSi alone cannot explain the uneven distribution of pre‐Cretaceous glass ramps (Ritterbush, ), nor does it provide a mechanism to explain the limited temporal extent of the Tosi.…”