Lacerda Luiz D, Santos Janaína A, Marins Rozane V, Silva Francisco A T F DA
Instituto de Ciências do Mar, Universidade Federal do Ceará/UFC, Av. Abolição, 3207, Meireles, 60165-081 Fortaleza, CE, Brazil.
Faculdade de Filosofia Dom Aureliano Matos, Universidade Estadual do Ceará/UECE, Av. Dom Aureliano Matos, 2058, Centro, 62930-000 Limoeiro do Norte, CE, Brazil.
An Acad Bras Cienc. 2018 Aug;90(2 suppl 1):2073-2096. doi: 10.1590/0001-3765201820180085.
This work reviews the limnology of the largest multi-use reservoir in NE Brazil, the Castanhão Reservoir in Ceará State, during 5 years of an extended drought when the reservoir's volume decreased from 88% to about 30%. Major physical and chemical parameters of the water column, phytoplankton community, trophic state and sediment geochemistry were monitored, as well as the impact from extensive aquaculture. Water quality of the full reservoir was maintained due to hydrodynamics, which transport nutrients to the hypolimnion of a stratified water column, rendering an oligotrophic state to the reservoir, notwithstanding the large nutrient inputs from aquaculture and irrigated agriculture. However, with the extension of the drought period, the reservoir volume reduced, decreasing water depth leading to breaking of the thermocline due to wind forcing, and mixing the entire water column. This increased turbidity, nutrient availability and primary productivity, also changed phytoplankton functional groups. As a result, at the end of the monitoring period, when the reservoir attained its lowest volume, its trophic state became eutrophic. Under a scenario of climate change, where annual precipitation is decreasing, human uses of reservoirs in the semiarid should be very restricted to maintain water quality proper for human use.
本研究回顾了巴西东北部最大的多用途水库——塞阿拉州的卡斯塔尼奥水库在长达5年的干旱期间的湖沼学情况，在此期间，水库蓄水量从88%降至约30%。对水柱的主要物理和化学参数、浮游植物群落、营养状态和沉积物地球化学进行了监测，同时也监测了大规模水产养殖的影响。尽管水产养殖和灌溉农业带来大量营养物质输入，但由于水动力作用将营养物质输送到分层水柱的下层，使水库保持贫营养状态，从而维持了整个水库的水质。然而，随着干旱期的延长，水库蓄水量减少，水深降低，导致温跃层因风力作用而破裂，整个水柱混合。这增加了浊度、营养物质可用性和初级生产力，也改变了浮游植物功能群。结果，在监测期结束时，当水库达到最低蓄水量时，其营养状态变为富营养。在气候变化导致年降水量减少的情况下，半干旱地区水库的人类用途应受到严格限制，以维持适合人类使用的水质。
