據物理學家組織網7月2日報道,,南加州大學科學家一項最新研究稱,,氣候變化可能會把某些構成海洋食物鏈基礎的細菌淘汰,,而那些能適應環(huán)境的特殊細菌在未來海洋中會更加繁榮昌盛,。相關論文發(fā)表在6月30日的《自然·地質科學》上,。
在氣候變化的大環(huán)境下,,一切事物都有“贏家”和“輸家”,。隨著大氣二氧化碳水平和全球氣溫的升高,科學家也越來越關心未來哪些生物會繁榮,,而哪些會毀滅,。
這個問題的答案是固氮藍藻(通過光合作用獲取能量的細菌,也叫“藍綠藻”),,它們將變成影響海洋所有生物的重要角色,。固氮是由藍藻等生物將空氣中不活潑的氮氣(生物無法利用)轉化為大部分生物賴以生存的活潑形式。沒有這種固氮者,,海洋生物也無法長期生存,。
“我們的研究結果顯示,在海洋生物中,,二氧化碳有可能控制這些關鍵性的基礎生物,。我們的化石燃料排放可能是造成固氮細菌種類改變的原因,海洋中這些細菌正在增加。”論文第一作者,、南加州大學棟賽夫文理藝學院海洋環(huán)境生物學教授大衛(wèi)·哈欽斯說,,“海洋食物鏈和生產力的變化可能會造成各種各樣衍生的結果,甚至潛在影響我們從海洋獲取的資源,,如漁業(yè)產量,。”
哈欽斯和他的小組研究了兩種主要的固氮藍藻群:束毛藻(Trichodesmium)和鱷球藻(Crocosphaera),前者能形成大的飄浮群落,,用肉眼可以看到,,并在開放海域造成大的爆發(fā);后者數量也很大,,但是一種單細胞的顯微生物,。
以往的研究顯示,這兩種藍藻應屬于氣候變化的最大“贏家”之列,,在二氧化碳濃度更高和更溫暖的海洋中茁壯成長,。但以往研究只考察了它們中的一兩個品系。南加州大學有一個大型的生物種質培養(yǎng)庫,。利用這一獨特的資源優(yōu)勢,,研究小組找出了哪些菌株在工業(yè)革命以前的二氧化碳濃度水平下生長得更好,哪些在未來的“溫室”地球上能繁榮昌盛,。
“我們發(fā)現(xiàn),,氣候變化不會除掉所有的固氮者,自然系統(tǒng)中還會有剩余,。隨著大氣二氧化碳濃度增加,,某些特殊的固氮者可能會繁榮。”哈欽斯說,,“但我們還不能完全確定,,未來的海洋會怎樣變化。”(生物谷 Bioon.com)
生物谷推薦的英文摘要
Nature Geoscience doi:10.1038/ngeo1858
David A. Hutchins, Fei-Xue Fu, Eric A. Webb, Nathan Walworth & Alessandro Tagliabue
Taxon-specific response of marine nitrogen fixers to elevated carbon dioxide concentrations
Much of the bioavailable nitrogen that supports open ocean food webs and biogeochemical cycles is fixed from the atmosphere by marine cyanobacteria of the genera Trichodesmium and Crocosphaera. In previous experiments carried out with a limited set of cyanobacterial isolates, rates of cyanobacterial nitrogen fixation were shown to increase with carbon dioxide concentrations. Here, we report results from a series of laboratory experiments in which we grew seven strains of Trichodesmium and Crocosphaera from the Atlantic and Pacific oceans under a wide range of carbon dioxide concentrations, and monitored rates of nitrogen fixation and growth. We document large, strain-specific differences in the relationship between nitrogen fixation and carbon dioxide concentration, suggesting that individual strains within each genus are adapted to grow and fix nitrogen at different concentrations of carbon dioxide. We apply kinetic constants from the individual carbon dioxide response curves to an illustrative biogeochemical model of the ocean in 2100, which suggests that strains adapted to high carbon dioxide concentrations could potentially be favoured in a future acidified ocean. We suggest that surface ocean carbon dioxide concentrations could constitute a previously unrecognized selective force that shapes the community composition and diversity of nitrogen-fixing cyanobacteria.