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坦噶尼喀湖的捕鱼量与气候变暖
【发布时间:2016-10-08 】 【 】【打印】【关闭

  一项研究发现,持续的气候变暖正在减少非洲坦噶尼喀湖的捕鱼量,这个湖是一个关键的生态系统,为该地区提供了至多60% 的动物蛋白。位于非洲中部的坦噶尼喀湖每年出产20多万吨鱼,它对于该地区的居民来说,是一个关键的蛋白质来源。尽管报告中渔业生产力的衰退反映了诸如过度捕鱼、森林砍伐以及水温上升等因素,几乎没有研究对这些变化进行记录并得出因果联系。Andrew Cohen及其同事分析了来自这个湖的沉积物岩芯,并且构建出了一个大约1500年的古气候学记录,它是追踪温度和藻类与鱼类生产的关键替代指标。这个记录表明,持续的变暖与该湖的混合减少、藻类生产的停滞以及这个湖的软体动物和甲壳纲动物等关键底栖动物的氧合栖息地缩小了38% 存在关联。此外,由于过去500年间该湖的温度增加与鱼类和软体动物化石数量的减少具有相关性,气候变化与这个湖的湖泊分层很可能对目前捕鱼量的衰退以及支持该湖生物多样性的关键栖息地濒临危险具有相关性。这项研究证明了气候变化对热带湖泊生态系统的影响,并且提出,急需实施干预措施从而维持坦噶尼喀湖对这个地区的重要贡献。

Warming climates are rapidly transforming lake ecosystems worldwide, but the breadth of changes in tropical lakes is poorly documented. Sustainable management of freshwater fisheries and biodiversity requires accounting for historical and ongoing stressors such as climate change and harvest intensity. This is problematic in tropical Africa, where records of ecosystem change are limited and local populations rely heavily on lakes for nutrition. Here, using a ~1,500-y paleoecological record, we show that declines in fishery species and endemic molluscs began well before commercial fishing in Lake Tanganyika, Africa’s deepest and oldest lake. Paleoclimate and instrumental records demonstrate sustained warming in this lake during the last ~150 y, which affects biota by strengthening and shallowing stratification of the water column. Reductions in lake mixing have depressed algal production and shrunk the oxygenated benthic habitat by 38% in our study areas, yielding fish and mollusc declines. Late-20th century fish fossil abundances at two of three sites were lower than at any other time in the last millennium and fell in concert with reduced diatom abundance and warming water. A negative correlation between lake temperature and fish and mollusc fossils over the last ~500 y indicates that climate warming and intensifying stratification have almost certainly reduced potential fishery production, helping to explain ongoing declines in fish catches. Long-term declines of both benthic and pelagic species underscore the urgency of strategic efforts to sustain Lake Tanganyika’s extraordinary biodiversity and ecosystem services.

(来源:PNAS, 2016, 113 (34): 9563-9568)

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