Burger Joanna
Division of Life Sciences, Rutgers University, 604 Allison Road, Piscataway, NJ 08854, USA.
Environmental and Occupational Health Sciences Institute, Rutgers University, 170 Frelinghuysen Road, Piscataway, NJ 08854, USA.
Toxics. 2023 Jul 14;11(7):614. doi: 10.3390/toxics11070614.
Understanding variations in metal levels in biota geographically and under different environmental conditions is essential to determining risk to organisms themselves and to their predators. It is often difficult to determine food chain relationships because predators may eat several different prey types. Horseshoe crab () eggs form the basis for a complex food web in Delaware Bay, New Jersey, USA. Female horseshoe crabs lay thumb-sized clutches of eggs, several cm below the surface, and often dislodge previously laid eggs that are brought to the surface by wave action, where they are accessible and critical food for migrant shorebirds. This paper compares metal and metalloid (chromium [Cr], cadmium [Cd], lead [Pb], mercury [Hg], arsenic [As] and selenium [Se]) concentrations in horseshoe crab eggs collected on the surface with concentrations in eggs from clutches excavated from below the sand surface, as well as examining metals in eggs from different parts of the Bay. The eggs were all collected in May 2019, corresponding to the presence of the four main species of shorebirds migrating through Delaware Bay. These migrating birds eat almost entirely horseshoe crab eggs during their stopover in Delaware Bay, and there are differences in the levels of metals in blood of different shorebirds. These differences could be due to whether they have access to egg clutches below sand (ruddy turnstones, ) or only to eggs on the surface (the threatened red knot [] and other species of shorebirds). Correlations between metals in clutches were also examined. Except for As and Cd, there were no significant differences between the metals in crab egg clutches and eggs on the surface that shorebirds, gulls, and other predators eat. There were significant locational differences in metal levels in horseshoe crab eggs (except for Pb), with most metals being highest in the sites on the lower portion of Delaware Bay. Most metals in crab eggs have declined since studies were conducted in the mid-1990s but were similar to levels in horseshoe crab eggs in 2012. The data continue to provide important monitoring and assessment information for a keystone species in an ecosystem that supports many species, including threatened and declining shorebird species during spring migration.
了解生物群中金属含量在地理上以及不同环境条件下的变化，对于确定生物体自身及其捕食者所面临的风险至关重要。由于捕食者可能会食用几种不同类型的猎物，所以通常很难确定食物链关系。在美国新泽西州特拉华湾，鲎的卵构成了一个复杂食物网的基础。雌性鲎产下拇指大小的卵块，埋在地表以下几厘米处，并且常常会弄松先前产下的卵，这些卵会被海浪冲到海面，而这正是迁徙滨鸟可获取的关键食物。本文比较了从海面收集的鲎卵与从沙面以下挖出的卵块中的金属和类金属（铬[Cr]、镉[Cd]、铅[Pb]、汞[Hg]、砷[As]和硒[Se]）浓度，同时还检测了海湾不同区域的卵中的金属含量。所有卵均于2019年5月收集，此时正值四种主要滨鸟物种迁徙经过特拉华湾。这些迁徙鸟类在特拉华湾中途停留期间几乎完全以鲎卵为食，并且不同滨鸟血液中的金属含量存在差异。这些差异可能是由于它们能否获取沙面以下的卵块（翻石鹬），还是只能获取海面上的卵（濒危的红腹滨鹬和其他滨鸟物种）所致。研究人员还检测了卵块中各种金属之间的相关性。除了砷和镉之外，鲎卵块中的金属与滨鸟、海鸥及其他捕食者食用的海面卵中的金属并无显著差异。鲎卵中的金属含量存在显著的位置差异（铅除外），大多数金属在特拉华湾下游区域的含量最高。自20世纪90年代中期开展相关研究以来，鲎卵中的大多数金属含量有所下降，但与2012年鲎卵中的含量相似。这些数据继续为一个生态系统中的关键物种提供重要的监测和评估信息，该生态系统支持着许多物种，包括春季迁徙期间濒危和数量减少的滨鸟物种。
