加拿大女王大學(xué)和約克大學(xué)的科學(xué)家聯(lián)合研究發(fā)現(xiàn),，湖水中鈣含量下降導(dǎo)致湖水中食物網(wǎng)的破壞，對水生生物的生存構(gòu)成了嚴(yán)重威脅,。
科學(xué)家戲稱水中鈣元素的含量下降為“湖水骨質(zhì)疏松癥”,。科學(xué)家認(rèn)為,，當(dāng)湖水中的鈣元素含量下降至一定的危險值,，一些主要的水中生物的生存將難以為繼，而以食用這些生物為生的其它生物體的生存也將處于危險之中,。相關(guān)研究文章發(fā)表在最新出版的《科學(xué)》（Science）雜志上,。
加科學(xué)家對水中食物網(wǎng)中最重要的底端動物水蚤的生存狀況進(jìn)行了實驗評估?？茖W(xué)家在實驗室中事先確定了可能影響水蚤生存的最低鈣含量水平,。同時，他們在加拿大安大略省各大湖設(shè)立了數(shù)百個監(jiān)測點,，監(jiān)測當(dāng)?shù)睾械拟}含量變化和水蚤的生存情況,。研究人員發(fā)現(xiàn)，從上世紀(jì)70年代以來,，隨著湖水中鈣含量的持續(xù)降低,，湖水中許多主要的無脊椎生物體一直處于消亡之中。
湖水的鈣含量一直處于下降之中已是不爭的事實,，只是以前人們還未認(rèn)識到鈣含量對水中生物生存的重要性,，也沒有對水中鈣含量進(jìn)行監(jiān)測,。因此，研究人員對湖底的沉積物進(jìn)行取樣分析,，獲得了200年來湖水鈣含量變遷的歷史數(shù)據(jù),。研究人員認(rèn)為，湖水中鈣含量下降的原因包括酸雨,、伐木,、新生林木生長等。而且,，湖水含鈣水平越低,，越不利于湖水從酸化的環(huán)境中得到恢復(fù)。
研究人員認(rèn)為,，正是由于湖水鈣水平下降,，導(dǎo)致了湖中水生物食物網(wǎng)發(fā)生了很大的變化。目前他們的研究主要是針對鈣含量對水蚤的生存影響,，但是魚類等水中生物對于鈣都有非常高的需求,，可以說它們都處于危險之中。水中鈣含量的危險值到底是多少,，科學(xué)家目前還不能給出明確答案,。（生物谷Bioon.com）
生物谷推薦原始出處：
Science，Vol. 322. no. 5906, pp. 1374 - 1377,，Adam Jeziorski,，John P. Smol
The Widespread Threat of Calcium Decline in Fresh Waters
Adam Jeziorski,1 Norman D. Yan,2,3 Andrew M. Paterson,3 Anna M. DeSellas,1,3 Michael A. Turner,4 Dean S. Jeffries,5 Bill Keller,6 Russ C. Weeber,7 Don K. McNicol,7 Michelle E. Palmer,2 Kyle McIver,1 Kristina Arseneau,1 Brian K. Ginn,1 Brian F. Cumming,1 John P. Smol1*
Calcium concentrations are now commonly declining in softwater boreal lakes. Although the mechanisms leading to these declines are generally well known, the consequences for the aquatic biota have not yet been reported. By examining crustacean zooplankton remains preserved in lake sediment cores, we document near extirpations of calcium-rich Daphnia species, which are keystone herbivores in pelagic food webs, concurrent with declining lake-water calcium. A large proportion (62%, 47 to 81% by region) of the Canadian Shield lakes we examined has a calcium concentration approaching or below the threshold at which laboratory Daphnia populations suffer reduced survival and fecundity. The ecological impacts of environmental calcium loss are likely to be both widespread and pronounced.
1 Paleoecological Environmental Assessment and Research Lab, Department of Biology, Queen's University, Kingston, ON, Canada, K7L 3N6.
2 Department of Biology, York University, 4700 Keele Street, Toronto, ON, Canada, M3J 1P3.
3 Ontario Ministry of the Environment, Dorset Environmental Science Centre, 1026 Bellwood Acres Road, Post Office Box 39, Dorset, ON Canada, P0A 1E0.
4 Experimental Lakes Area, Fisheries and Oceans Canada, 501 University Crescent, Winnipeg, MB, Canada, R3T 2N6.
5 Environment Canada, National Water Research Institute, Post Office Box 5050, Burlington, ON, Canada, L7R 4A6.
6 Ontario Ministry of the Environment, Cooperative Freshwater Ecology Unit, Laurentian University, Sudbury, ON, Canada, P3E 2C6.
7 Canadian Wildlife Service (Ontario), Environment Canada, 335 River Road, Ottawa, ON, Canada, K1A 0H3.
