加拿大女王大学和约克大学的科学家联合研究发现，湖水中钙含量下降导致湖水中食物网的破坏，对水生生物的生存构成了严重威胁。
科学家戏称水中钙元素的含量下降为“湖水骨质疏松症”。科学家认为，当湖水中的钙元素含量下降至一定的危险值，一些主要的水中生物的生存将难以为继，而以食用这些生物为生的其它生物体的生存也将处于危险之中。相关研究文章发表在最新出版的《科学》（Science）杂志上。
加科学家对水中食物网中最重要的底端动物水蚤的生存状况进行了实验评估。科学家在实验室中事先确定了可能影响水蚤生存的最低钙含量水平。同时，他们在加拿大安大略省各大湖设立了数百个监测点，监测当地湖水中的钙含量变化和水蚤的生存情况。研究人员发现，从上世纪70年代以来，随着湖水中钙含量的持续降低，湖水中许多主要的无脊椎生物体一直处于消亡之中。
湖水的钙含量一直处于下降之中已是不争的事实，只是以前人们还未认识到钙含量对水中生物生存的重要性，也没有对水中钙含量进行监测。因此，研究人员对湖底的沉积物进行取样分析，获得了200年来湖水钙含量变迁的历史数据。研究人员认为，湖水中钙含量下降的原因包括酸雨、伐木、新生林木生长等。而且，湖水含钙水平越低，越不利于湖水从酸化的环境中得到恢复。
研究人员认为，正是由于湖水钙水平下降，导致了湖中水生物食物网发生了很大的变化。目前他们的研究主要是针对钙含量对水蚤的生存影响，但是鱼类等水中生物对于钙都有非常高的需求，可以说它们都处于危险之中。水中钙含量的危险值到底是多少，科学家目前还不能给出明确答案。（生物谷Bioon.com）
生物谷推荐原始出处：
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.
