Surette Céline, Lucotte Marc, Tremblay A
COMERN, Université du Québec à Montréal, Montréal, Québec, Canada.
Sci Total Environ. 2006 Sep 1;368(1):248-61. doi: 10.1016/j.scitotenv.2005.09.038. Epub 2005 Oct 10.
It has been demonstrated that intensive fishing, i.e., removing more than 25% of the fish biomass, can reduce mercury levels in predator fish in a lake. We test here the hypothesis that, by removing an important part of the fish biomass from a lake, a significant amount of methylmercury can be eliminated, therefore reducing the mercury available to the remaining biota, at least in the short term. A mass burden approach is used to evaluate the partitioning of total mercury and methylmercury in natural lake ecosystems. Three small natural lakes from the James Bay territory, in northern Québec, Canada, were selected for intensive fishing. Mercury (Hg) and methylmercury (MeHg) concentrations were evaluated for sediments, water column (dissolved fraction and suspended particulate matter), plankton, aquatic invertebrates, and fish. Biomasses were determined for fish, plankton, and aquatic invertebrates. Two case scenarios are presented using different mercury contributions from the sediment component (1 cm depth, and no sediment). Our results for the scenario including the sediment contribution show that lake sediments represent over 98% of the total mercury while the biotic components represent less than 0.1% of the same burden. For methylmercury, fish account for up to 5% of the burden, while sediments make up 84.6% to 93.1%. If we put aside the sediment contribution, the methylmercury in fish partitioning can represent up to 48%. As for invertebrates, they can account for up to 48% of the total MeHg burden. We do not observe any change in the partitionings or the quantities of Hg and MeHg before and after fishing in either of the two case scenarios even when we do not take into account dynamics of the ecosystems. This will be all the more the case when the dynamics of the system are included in the analyses. Therefore, biological parameters such as growth rates or fish diet must be considered.
业已证明，高强度捕捞，即捕捞超过25%的鱼类生物量，可降低湖泊中捕食性鱼类的汞含量。我们在此检验这样一个假设：通过从湖泊中移除一大部分鱼类生物量，可消除大量甲基汞，从而减少剩余生物群可获取的汞，至少在短期内如此。采用质量负荷法评估天然湖泊生态系统中总汞和甲基汞的分配情况。从加拿大魁北克省北部詹姆斯湾地区选取了三个小型天然湖泊进行高强度捕捞。对沉积物、水柱（溶解部分和悬浮颗粒物）、浮游生物、水生无脊椎动物和鱼类的汞（Hg）和甲基汞（MeHg）浓度进行了评估。测定了鱼类、浮游生物和水生无脊椎动物的生物量。给出了两种案例情景，使用了沉积物组分（1厘米深度，无沉积物）的不同汞贡献量。我们针对包含沉积物贡献量的情景所得到的结果表明，湖泊沉积物占总汞的比例超过98%，而生物组分占相同负荷的比例不到0.1%。对于甲基汞，鱼类占负荷的比例高达5%，而沉积物占84.6%至93.1%。如果不考虑沉积物贡献量，鱼类中甲基汞的分配比例可高达48%。至于无脊椎动物，它们可占甲基汞总负荷的比例高达48%。在两种案例情景中，无论是否考虑生态系统动态，我们都未观察到捕捞前后汞和甲基汞的分配情况或数量有任何变化。当在分析中纳入系统动态时，情况更是如此。因此，必须考虑生长速率或鱼类饮食等生物学参数。
