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首页> 外文期刊>Journal of Experimental Marine Biology and Ecology >Interactive effects of episodic hypoxia and cannibalism on juvenile blue crab mortality
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Interactive effects of episodic hypoxia and cannibalism on juvenile blue crab mortality

机译：间歇性缺氧和食人症对青蟹幼蟹死亡率的相互作用

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We hypothesized that as the spatial extent of hypoxic bottom water increased, (1) adult blue crab predator densities would increase in shallow habitats as they avoided hypoxia, and that (2) juvenile blue crabs, which use shallow unvegetated habitat as a predation refuge from adult conspecifics, would experience increased mortality rates during crowding by cannibalistic adult blue crabs. These hypotheses were tested along a depth gradient of sandy-mud shoreline in the Neuse River Estuary (NRE), North Carolina, USA using a combination of (1) hydrographic measurements to characterize the spatial extent of hypoxia, (2) beach seines to quantify the density of adult blue crab predators in relatively shallow water as a function of 1, and (3) tethering experiments to quantify relative rates of predation on juvenile blue crabs as a function of 1 and 2. During our seven tethering experiments, the NRE study site experienced a range of DO scenarios including normoxia, chronic hypoxia, and hypoxic upwelling. No known predators of juvenile blue crabs, other than adult conspecifics, were collected in any of our shallow-water seines. During the transition from normoxia to chronic hypoxia, blue crab predator densities in shallow refuge habitats increased 4-fold, and relative mortality rates of juvenile blue crabs in shallow habitats increased exponentially with the density of adult conspecifics. Conversely, during hypoxic upwelling events, the density of adult blue crabs in shallow water declined, which may explain why the relative mortality of juvenile crabs did not increase significantly with the increasing spatial extent of hypoxia. Thus, juvenile blue crabs may be relatively safe from adult conspecifics during hypoxic upwelling events, but not during chronic hypoxia. These experimental results highlight the need to consider the effects of dynamic water quality on mobile consumers emigrating from degraded habitats when considering indirect trophic impacts beyond the immediate area of impact.
机译：我们假设随着缺氧底水的空间范围的增加，（1）成年蓝蟹的食肉动物密度会由于避免缺氧而在浅生境中增加，并且（2）幼年蓝蟹将无植被的浅生境用作捕食的避难所。成年物种，在食人成年蓝蟹拥挤期间，死亡率会增加。这些假设是在美国北卡罗来纳州Neuse河河口（NRE）沿沙泥海岸线的深度梯度上进行测试的，结合使用（1）水文测量来表征低氧的空间范围，（2）沙滩围网进行量化相对浅水区成年蓝蟹捕食者的密度与1的函数关系，以及（3）拴系实验以定量对幼小蓝蟹的相对捕食率与1和2的函数关系。在我们的七个拴系实验中，NRE研究该站点经历了一系列DO场景，包括常氧，慢性低氧和低氧上升。在我们的任何浅水围网中，除了成年同种外，没有其他已知的幼年蓝蟹捕食者。在从常氧到慢性低氧的过渡过程中，浅海避难所生境中的蓝蟹捕食者密度增加了4倍，浅海生境中的幼体蓝蟹的相对死亡率随成虫的成虫密度呈指数增加。相反，在低氧上升过程中，成年蓝蟹在浅水中的密度下降，这可以解释为什么随着低氧空间范围的增加，幼蟹的相对死亡率没有显着增加。因此，在低氧上升事件中，幼体蓝蟹相对于成年犬更安全，但在慢性低氧时则不是。这些实验结果强调，在考虑影响范围以外的间接营养影响时，有必要考虑动态水质对从退化栖息地迁移的流动消费者的影响。

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