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Front. Mar. Sci. | doi: 10.3389/fmars.2017.00373

Assessing the Potential of Sponges (Porifera) as Indicators of Ocean Dissolved Si Concentrations

  • 1Department of Geology, Lund University, Sweden
  • 2Earth Surface Geochemistry, GFZ German Research Centre for Geosciences, Germany
  • 3Geoscience, Swedish Museum of Natural History, Sweden

We explore the distribution of sponges along dissolved silica (dSi) concentration gradients to test whether sponge assemblages are related to dSi and to assess the validity of fossil sponges as a palaeoecological tool for inferring dSi concentrations of the past oceans. We extracted sponge records from the publically available Global Biodiversity Information Facility (GBIF) database and linked these records with ocean physiochemical data to evaluate if there is any correspondence between dSi concentrations of the waters sponges inhabit and their distribution. Over 320,000 records of Porifera were available, of which 62,360 met strict quality control criteria. Our analyses was limited to the taxonomic levels of family, order and class. Because dSi concentration is correlated with depth in the modern ocean, we also explored sponge taxa distributions as a function of depth. We observe that while some sponge taxa appear to have dSi preferences (e.g. class Hexactinellida occurs mostly at high dSi), the overall distribution of sponge orders and families along dSi gradients is not sufficiently differentiated to unambiguously relate dSi concentrations to sponge taxa assemblages. We also observe that sponge taxa tend to be similarly distributed along a depth gradient. In other words, both dSi and/or another variable that depth is a surrogate for, may play a role in controlling sponge spatial distribution and the challenge is to distinguish between the two. We conclude that inferences about palaeo-dSi concentrations drawn from the abundance of sponges in the stratigraphic records must be treated cautiously as these animals are adapted to a great range of dSi conditions and likely other underlying variables that are related to depth. Our analysis provides a quantification of the dSi ranges of common sponge taxa, expands on previous knowledge related to their bathymetry preferences and suggest that sponge taxa assemblages are not related to particular dSi conditions.

Keywords: Sponge assemblages, palaeoecological indicators, spatial distribution, dissolved silica gradient, Depth gradient, SI cycle

Received: 12 Apr 2017; Accepted: 07 Nov 2017.

Edited by:

Brivaela Moriceau, Centre national de la recherche scientifique (CNRS), France

Reviewed by:

Sönke Hohn, Leibniz Centre for Tropical Marine Research (LG), Germany
Paco Cardenas, Uppsala University, Sweden  

Copyright: © 2017 Alvarez, Frings, Clymans, Fontorbe and Conley. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Belinda Alvarez, Lund University, Department of Geology, Sölvegatan 12, Lund, SE-223 62, Sweden, belinda.alvarez@geol.lu.se