Trace metal concentrations in the tropical sponge Spheciospongia vagabunda at a sewage outfall: synchrotron X-ray imaging reveals the micron-scale distribution of accumulated metals

Abstract

Major and trace elements were measured in sponges, seawater and sediment in Darwin Harbour (Australia) to test the hypothesis that metals are elevated in sponges closer to a sewage outfall compared with unimpacted sites. Seawater and sediment at the sewage discharge site contained high, but localised, concentrations of phosphorus (P), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As) and lead (Pb) compared with background sites. Metal concentrations in the sponge Spheciospongia vagabunda were highly elevated compared with other sponges and, although site specific, high metal concentrations were unrelated to the presence of sewage effluent. X-ray fluorescence microprobe imaging was used to investigate the metal distribution pattern in S. vagabunda. High Fe, Ni and Zn concentrations were either localised in circular patches (100-200 lm size) near water canals or in the pinacoderm, or scattered in spots (approximately 10 lm) throughout the tissue. This supports a microflora-mediated metal bioaccumulation hypothesis. In contrast, Co and Mn were highly dispersed and probably associated with aluminium-and iron-oxide rich sediment inclusions. Although the lack of association between sewage effluent and metal accumulation precludes the use of S. vagabunda as a biomonitor, the apparent differential mechanisms of metal accumulation warrants further investigation.

Marine sponges as a powerful tool for trace elements biomonitoring studies in coastal environment

“…Value of 1 was set as threshold for all analytes, with results equal or above 1 being considered indicative of bioconcentration. When TE concentration in seawater is included in the study, the BAF are also calculated by dividing the TE sponge's content by the one found in seawater (Padovan et al, 2012;Venkateswara Rao et al, 2009;Batista et al, 2014).…”

“…Sponges pump large quantities of seawater (100-1200 mL h −1 g −1 ), more than any other marine invertebrates (Olesen and Weeks, 1994). These organisms have a high capacity for TEs accumulation (Patel et al, 1985;Padovan et al, 2012), exhibiting higher filtering capacity than bivalves (Negri et al, 2006;Gentric et al, 2016). They are considered as "biological particle traps" due to their ability to concentrate a wide range of chemicals from both the suspended and dissolved phases of the water, with usually high bioconcentration factors (BCF) (Perez et al, 2005;Cebrian et al, 2003).…”

Maia X-ray fluorescence imaging: Capturing detail in complex natural samples

“…Using a collimated beam, larger objects, such as works of art, have been imaged at 50-100 µm resolution [18] over areas up to 600 × 300 mm 2 . This method has been applied to studies in the earth [23][24][25][26][27][28][29][30], planetary [31], environmental [32,33], medical [19,34], biological [20][21][22][35][36][37][38][39][40][41] and material [42] sciences as well as cultural heritage [18,43]. A similar capability has been established on the P06 beamline (e.g.…”

Determination of elemental composition of Lake Baikal sponges by wavelength dispersive X‐ray fluorescence spectrometry

“…As a matter of fact, marine sponges have been studied more comprehensively than those from the Baikal Lake. The structure of sponge spicules, the water content in sponges, density, and biochemical and element composition have been identified.…”

“…The average chemical composition of their spicules was 85.2% SiO 2 , 12.3% water, and 2.5% of some other elements such as S, Al, K, Ca, and Na. References refer to marine sponges as biomonitors of environment, for they are known to have a strong ability to concentrate metals in their tissues . The metal concentrations were measured by ICP‐MS, AAS, X‐ray fluorescence microprobe analysis, and energy‐dispersive X‐ray fluorescence spectrometry (EDXRF).…”