Spicule records of Ephydatia fluviatilis as a proxy for hydrological and environmental changes in the shallow Lake Trasimeno (Umbria, Italy)

Abstract

This research shows the results of an analysis of siliceous spicules found in sediment cores collected in Lake Trasimeno (Umbria, Italy), a shallow lake that experienced an important water level lowering during the last century. A morphological analysis of sedimentary sponge records revealed that the spicules accumulated in the lake sediments over the last 150 years are attributable to Ephydatia fluviatilis, the only sponge species found in the lake in recent years. The stratigraphic analysis of the cores showed that the abundance and size of the sponge spicules (megascleres) have remarkably decreased, suggesting that a significant depletion of the sponge fauna occurred, particularly during the first half of the twentieth century. A correlation analysis has identified morpho-hydrological and related variables (the theoretical fraction of lake surface subjected to resuspension and the amount of total suspended solids) as the most significant factors explaining the change in density of sponge spicules. Two ecological explanations of the sponge decline are proposed, based on the sensitivity of the sponge both to the availability of suitable hard substrata for colonization, and to the amount of wind-resuspended solids. One-ended sigmoid response curves were obtained by regression and corresponding transfer functions were derived, which allow the mean water depth of the lake and total suspended solids to be inferred from spicule density records. The results support the use of sponge spicules as a paleohydrological and paleoecological proxy, application of which appears particularly promising for shallow-water systems.

Utilizing sponge spicules in taxonomic, ecological and environmental reconstructions: a review

“…Such studies require spicule-rich sediment portions ( Volkmer-Ribeiro, De Ezcurra & Parolin, 2007 ) and the best results are obtained when an uninterrupted spicule record is available. It seems that absolutely-dated sediment cores are the best way to obtain continuous record of the changes in spicule assemblages ( Bertolino et al, 2014 , 2017a , 2017b , 2019 ; Gaino et al, 2012 ; Łukowiak et al, 2018 ; Rasbold et al, 2019a ).…”

“…For example, Koltun (1960) already pointed out the existence of sponge taxa of specific environmental requirements which make them potential indicators of water salinity, temperature, or depth. Recognized sponge communities can provide information about the water regime, flow, and velocity (lentic vs. lotic conditions; for example, Parolin, Volkmer-Ribeiro & Stevaux, 2007 , 2008 ; Machado, Volkmer-Ribeiro & Iannuzzi, 2012 ; Kuerten et al, 2013 ), pH ( Harrison & Warner, 1986 ; Pisera & Saez, 2003 ), light intensity (e.g., Harrison, 1974 ; Supplemental Information 2 ), temperature (e.g., Gammon, James & Pisera, 2000 ; Gaino et al, 2012 ), currents (e.g., Molina-Cruz, 1991 ), salinity (e.g., Cumming, Wilson & Smol, 1993 ), and depth (e.g., Hinde & Holmes, 1892 ; Pisera, Cachao & Da Silva, 2006 ; Łukowiak, Pisera & Schlögl, 2014 ; Łukowiak, 2016a ; see Fig. 6 ).…”

Spatially explicit genetic structure in the freshwater sponge Ephydatia fluviatilis (Linnaeus, 1759) within the framework of the monopolisation hypothesis

“…1), is the most common and widespread freshwater sponge in the world, mostly inhabiting temperate regions (Lopp et al, 2007). it is a gonochoric species and performs both sexual and asexual reproduction, depending on environmental conditions (Gaino et al, , 2011.…”

Table 1: The number of records obtained through Google Scholar and PubMed using the search terms “sponge spicules”, “glass ramp”, “spiculite” and “spongillite”.

“…Such studies require spicule-rich sediment portions (Volkmer-Ribeiro, De Ezcurra & and the best results are obtained when an uninterrupted spicule record is available. It seems that absolutely-dated sediment cores are the best way to obtain continuous record of the changes in spicule assemblages (Bertolino et al, 2014(Bertolino et al, , 2017a(Bertolino et al, , 2017b(Bertolino et al, , 2019Gaino et al, 2012;Łukowiak et al, 2018;Rasbold et al, 2019a).…”

“…For example, Koltun (1960) already pointed out the existence of sponge taxa of specific environmental requirements which make them potential indicators of water salinity, temperature, or depth. Recognized sponge communities can provide information about the water regime, flow, and velocity (lentic vs. lotic conditions; for example, Parolin, Volkmer-Ribeiro & Stevaux, 2007Machado, Volkmer-Ribeiro & Iannuzzi, 2012;Kuerten et al, 2013), pH (Harrison & Warner, 1986;Pisera & Saez, 2003), light intensity (e.g., Harrison, 1974; Supplemental Information 2), temperature (e.g., Gammon, James & Pisera, 2000;Gaino et al, 2012), currents (e.g., Molina-Cruz, 1991), salinity (e.g., Cumming, Wilson & Smol, 1993), and depth (e.g., Hinde & Holmes, 1892;Pisera, Cachao & Da Silva, 2006;Łukowiak, Pisera & Schlögl, 2014;Łukowiak, 2016a; see Fig. 6).…”