南洞庭湖区软体动物物种多样性评估及保护对策

洞庭湖孕育和维持了较高和独特的软体动物多样性。尽管有关该湖软体动物的调查较多, 但多分散于各文献中。本文结合文献调研和现场调查(2013-2018年), 系统评估了南洞庭湖区软体动物物种多样性, 解析驱动群落格局演变的关键因子, 并提出合理的保护对策。共记录2纲5目14科33属87种(腹足纲41种, 双壳纲46种), 其中本调查记录54种, 隶属于2纲5目12科31属, 包括腹足纲22种, 双壳纲32种。评估结果显示处于近危和受威胁等级物种21种, 包括腹足纲4种和双壳纲17种。调查区域软体动物平均密度和生物量分别为173.1 ind./m ²和279.3 g/m ²。优势种为河蚬(Corbicula fluminea)、大沼螺(Parafossarulus eximius)、铜锈环棱螺(Bellamya aeruginosa)、卵河螺(Rivularia ovum)。基于距离的冗余分析(distance-based redundancy analysis, dbRDA)结果显示, 局域环境因子(底质类型、水深、pH、总溶解固体和总磷)制约软体动物的群落变异。另外, 区域内的人类活动(如商业采砂、建坝和沿岸土地利用、过度捕捞和非法电捕等)亦深刻影响软体动物的生存。这些人类干扰已导致软体动物物种多样性显著下降, 可能造成一些特有物种的局域性灭绝。为了恢复和保护软体动物物种多样性和资源, 应采取一系列对策, 包括管控合法的挖沙业和取缔非法挖沙业、禁止过度捕捞和非法电捕、维持水文的自然节律、恢复沿岸自然湖滨带和控制点源和面源污染物排入等。我们呼吁尽快在南洞庭湖区建立软体动物国家级自然保护区, 以保护该湖区(可能是整个洞庭湖)残存的软体动物物种多样性和特有性。

Diversity assessment and protection strategies for the mollusk community in the southern Dongting Lake

Being the second largest freshwater lake in China, the Dongting Lake supports high biodiversity of endemic mollusks. Although surveys concerning mollusk diversity in this region are plentiful, there is no comprehensive resource for cataloging their diversity. Here, we carried out a comprehensive mollusk diversity assessment in the southern Dongting Lake and identified potential factors driving the observed community patterns, based on combined historical datasets and a five-year field survey (2013-2018). We identified a total of 87 species (Gastropoda: 41 species and Bivalvia: 46 species) belonging to 5 orders, 14 families, 33 genera. Fifty-four species (Gastropoda: 22 species and Bivalvia: 32 species) of mollusks were found, belonging to 5 orders, 12 families, 31 genera. Twenty-one species were in vulnerable condition (Gastropoda: 4 species and Bivalvia: 17 species). Dominant species were Corbicula fluminea, Parafossarulus eximius, Bellamya aeruginosa, Rivularia ovum. Distance-based redundancy analysis (dbRDA) shows that some local physical (substrate and water depth) and chemical (pH, total dissolved solid and total phosphate) factors seemed to regulate mollusk community. Additionally, human activities in the region (such as commercial sand-mining industry, dam construction and coastal land use, overfishing and illegal electric fishing) also have a profound impact on the survival of mollusk. More importantly, anthropogenic pressures have caused a dramatic decline in mollusk diversity in recent decades, possibly leading to local extinction of some previously recorded endemic species. To protect the lake’s mollusk diversity, a series of strategies and practices should be taken by local authorities and the public. These practices could include control and regulation of the illegal sand-mining industry, a ban on overfishing and illegal electric fishing, maintaining the naturally hydrology, recovery of natural riparian zones, and control the discharge of point source and non-point source pollutants. We argued that a mollusk-based reserve should be established to protect mollusk diversity and endemism of the benthos, and possibly the lake as a whole.