Assessing the relationship between the δ 18 O signatures of siliceous sponge spicules and water in a~tropical lacustrine environment (Minas Gerais, Brazil)
Assessing the relationship between the δ 18 O signatures of siliceous sponge spicules and water in a~tropical lacustrine environment (Minas Gerais, Brazil)
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评估热带湖泊环境中硅质海绵骨针和水的 δ 18 O 特征之间的关系（巴西米纳斯吉拉斯州）
DOI：
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
H. Miche
中科院分区：
文献类型：
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作者：
M. C. Matteuzzo;A. Alexandre;A. Varajão;C. Volkmer;A. C. S. Almeida;C. Varajão;C. Vallet;C. Sonzogni;H. Miche
抽象的。硅质海绵骨针与广泛分布的硅藻硅藻壳一起构成了湖相沉积物中重要的硅质组分。与硅藻细胞壳相反，硅质骨针在海绵中以酶促方式形成。以前尝试使用它们的氧同位素特征（δ 18 Osilica）作为古环境代用指标，导致了相互矛盾的结论。这些尝试表明，需要进一步评估海绵是否在与水的氧同位素平衡中形成其二氧化硅。出于这个原因，我们测量的δ 18 O签名的海绵骨针从一个单一的淡水物种（Metania spinata）生长在天然和人工支持超过9个月的巴西小池塘（拉戈阿佛得角，西北部米纳斯吉拉斯）。δ 18 O二氧化硅值是在受控同位素交换（CIE）后使用红外（IR）激光加热法测得的。在海绵生长的整个过程中，定期测量和重建了池塘水的δ 18 O值（δ 18 Owater）和温度。假设硅可以在骨针中连续形成，使用先前为Metania spinata建立的海绵生长系数对生长月份的温度和δ 18 O水值进行加权。同时生长的海绵和在相似基底上生长的海绵的δ 18 O SiO2值是分散的。当考虑重建值时，未观察到Δ 18 O硅水与水温之间的关系。反之，当考虑δ 18 O值和样品采集时的水温时，得到了正相关，相关系数为0.3‰ °C-1（R2 = 0.63）。这种正的温度系数清楚地表明，淡水海绵Metania spinata不形成其硅质骨针的氧同位素平衡与池塘水。相反，一种或几种生物控制的动力学分馏机制可能在二氧化硅形成的各个步骤中起作用。我们的研究结果表明，最新的降水给它的δ 18 O的印记，整个骨针组合。表观分馏的幅度随温度的增加，但其他控制参数，如溶解硅浓度和养分的可用性，随温度的变化可能会干预。这些结果阻止了使用来自米纳斯吉拉斯西北部海绵岩的δ 18 O二氧化硅值作为过去δ 18 O水和/或温度变化的直接代表。
Abstract. Siliceous sponge spicules constitute an important siliceous component of lacustrine sediments, together with widespread diatom frustules. In contrast to diatom frustules, siliceous spicules are formed in sponges in an enzymatic way. Previous attempts to use their oxygen isotopic signature (δ18Osilica) as a paleoenvironmental proxy have led to contradictory conclusions. These attempts demonstrated the need to further assess whether sponges form their silica in oxygen isotopic equilibrium with water. For this reason, we measured the δ18O signature of sponge spicules from a single freshwater species (Metania spinata) grown on natural and artificial supports over nine months in a small Brazilian pond (Lagoa Verde, northwestern Minas Gerais). The δ18Osilica values were obtained using the infrared (IR) laser-heating fluorination technique following a controlled isotopic exchange (CIE). The δ18O values (δ18Owater) and temperature of the pond water were periodically measured and reconstructed over the course of the sponge growth. Assuming that silica may form continuously in the spicules, temperature and δ18Owater values over the months of growth were weighted using a sponge growth coefficient previously established for Metania spinata. The δ18Osilica values of sponges grown simultaneously and on similar substrates were scattered. No relationships were observed between the Δ18Osilica-water and water temperature when the reconstructed values were considered. Conversely, a positive correlation was obtained, with a coefficient of 0.3‰ °C–1 (R2 = 0.63), when δ18Owater values and water temperature at the time of sample collection were considered. Such a positive temperature coefficient clearly indicates that the freshwater sponge Metania spinata does not form its siliceous spicules in oxygen isotopic equilibrium with the pond water. Instead, one or several biologically controlled kinetic fractionation mechanisms may be in play during the various steps of silica formation. Our results suggest that the latest precipitation gives its δ18O imprint to the entire spicules assemblage. The amplitude of the apparent fractionations increases with temperature, but other controlling parameters, such as dissolved Si concentration and nutrient availability, co-varying with temperature may intervene. These results prevent the use of δ18Osilica values from the spongillites of northwestern Minas Gerais as a direct proxy for past δ18Owater and/or temperature changes.
影响因子：
4.1
作者：
Schröder, HC;Perovic-Ottstadt, S;Müller, WEG
通讯作者：
Müller, WEG