關(guān)于全球二氧化碳排放量增加的影響,,許多科學家的關(guān)注點落在全球氣候變暖及隨之而來的海平面上升方面,。據(jù)美國物理學家組織網(wǎng)近日報道,斯坦福大學的研究者發(fā)現(xiàn),,二氧化碳含量的日益增長,,還可能導致海水酸性增大,,從而改變水下的生態(tài)系統(tǒng),。該研究發(fā)表在美國《國家科學院院刊》(PNAS),。
研究者選取了靠近伊斯基亞島、意大利的海水為研究對象,。這些海域的淺水層中位于地中海板塊上的火山口,,大量的二氧化碳由此噴出,并以該地為中心形成一個海水化學梯度,,越靠近噴發(fā)口,,酸性越大。
研究者發(fā)現(xiàn),,不同的物種對酸性日增的海水反應不一,,有的反而興盛起來,如無脊椎動物會沿著從酸性濃度最大的噴發(fā)口到方圓200米開外的酸性分布帶形成棲息區(qū),,但整體而言生物群落的前景堪憂,。
由碳酸鈣構(gòu)成殼體的生物體首當其沖,它們的殼體會在酸性水域中被消解掉,。蝸牛、蛤蚌,、貽貝和扇貝在極酸的水域未見蹤影,;生活在附著于巖石的碳酸鈣導管中的小蟹類、海膽,、基圍蝦也消失不見,;在酸度比周圍水域適度高些的中間地帶,一些蠕蟲也難覓蹤跡,。而且,,從一個水域到另一個水域,變化更加明顯,,在酸性最強的地方,,即使相距一米,變化也非常顯著,。
這毫無疑問會影響到整個海洋生態(tài)系統(tǒng),。即使較小的生物體能日漸豐富,但群落的總體生物量因為較大型生物的缺失而減少了,。這一方面可能減少食物鏈中更高一級的生物體的食物供給量,,另一方面也可能導致生物群落里的生物多樣性減少。能夠存活并壯大的生物體多為廣食性物種,而一些專食性物種在這種極高酸性區(qū)域會減少,。
同時,,由于生物多樣性的減少,每個物種會以不同比例在生態(tài)系統(tǒng)中扮演更為重要的角色,,任何一個物種的變化,,都可能對生態(tài)系統(tǒng)造成重要影響,如降低其穩(wěn)定性等,。
研究者還稱,,在近岸海域,由于上升流會把強酸性的海水從深海帶到表層,,以及生物進程如藻類經(jīng)光合作用從水中吸收二氧化碳,、動物經(jīng)呼吸作用釋放二氧化碳等,海水的pH值會發(fā)生急劇變化,。這預示著不僅近岸海域的生物體會遭受影響,,依賴這片海域的生物為生的人們也會受到影響。(生物谷 Bioon.com)
doi:10.1073/pnas.1107789108
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Divergent ecosystem responses within a benthic marine community to ocean acidification
Kroeker, Kristy J.; Micheli, Fiorenza; Gambi, Maria Cristina; Martz, Todd R.
Ocean acidification is predicted to impact all areas of the oceans and affect a diversity of marine organisms. However, the diversity of responses among species prevents clear predictions about the impact of acidification at the ecosystem level. Here, we used shallow water CO2 vents in the Mediterranean Sea as a model system to examine emergent ecosystem responses to ocean acidification in rocky reef communities. We assessed in situ benthic invertebrate communities in three distinct pH zones (ambient, low, and extreme low), which differed in both the mean and variability of seawater pH along a continuous gradient. We found fewer taxa, reduced taxonomic evenness, and lower biomass in the extreme low pH zones. However, the number of individuals did not differ among pH zones, suggesting that there is density compensation through population blooms of small acidification-tolerant taxa. Furthermore, the trophic structure of the invertebrate community shifted to fewer trophic groups and dominance by generalists in extreme low pH, suggesting that there may be a simplification of food webs with ocean acidification. Despite high variation in individual species’ responses, our findings indicate that ocean acidification decreases the diversity, biomass, and trophic complexity of benthic marine communities. These results suggest that a loss of biodiversity and ecosystem function is expected under extreme acidification scenarios.