ABSTRACT: Leaf litter consumption has implications for growth and nutrient balances of mangrove crabs and mangrove trophic pathways. This study (1) addressed the impact of leaf litter quality and quantity on crab life history and growth, and (2) proposed keystone roles of crabs in mangrove material fluxes. Estimates of crab standing stocks, growth, and carbon and nitrogen mass balances were obtained for a field population of Parasesarma messa, a primary consumer of leaf litter in Queensland mangroves. P. messa exhibited slow growth and individuals took >>4 yr to reach maximum size. Females appeared to breed once per year with high reproductive effort relative to other crabs. An apparent trade-off between growth and reproduction in the dry-wet transition season was caused by a shortage of available leaf litter. A nitrogen mass balance indicated that the population ingested twice the amount of nitrogen that could be supplied by leaf litter. Assuming mortality was mainly due to predation, the estimated loss to predators (28 kg ha^-1 yr^-1) supported a hypothesis that crab consumption by fish short-circuits mangrove food chains. Faecal production by crabs (0.48 Mg C ha^-1 yr^-1 and 0.03 Mg N ha^-1 yr^-1) represents a substantial contribution to deposit-feeding food chains. P. messa is a keystone species whose impact on ecosystem processes is large relative to its abundance and biomass.

中文翻译：

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落叶消费减缓了螃蟹的生长，但改变了红树林的食物链

摘要：落叶物消耗对红树林蟹和红树林营养途径的生长和营养平衡有影响。本研究 (1) 解决了落叶质量和数量对螃蟹生活史和生长的影响，以及 (2) 提出了螃蟹在红树林物质通量中的关键作用。对昆士兰红树林落叶的主要消费者Parasesarma messa的野外种群进行了螃蟹常备种群、生长以及碳和氮质量平衡的估计。P.messa表现出缓慢的增长，个体需要 >>4 年才能达到最大尺寸。相对于其他螃蟹，雌性似乎每年繁殖一次，繁殖力很高。干湿过渡季节生长和繁殖之间的明显权衡是由于可用落叶的短缺造成的。氮质量平衡表明，该种群摄入的氮量是落叶所能提供的氮量的两倍。假设死亡主要是由于捕食，捕食者的估计损失（28 kg ha ^-1 yr ^-1）支持鱼类食用螃蟹会使红树林食物链短路的假设。螃蟹产生的粪便（0.48 Mg C ha ^-1 yr ^-1和 0.03 Mg N ha ^-1 yr ^-1) 代表了对存款喂养食物链的重大贡献。P. messa是一种关键物种，其对生态系统过程的影响与其丰度和生物量有关。