Role of larval dispersal and on-shore transport in the explosion and extinction of marine benthic matapopulations

自1979年以来，在日本九州有里克-海湾河口系统的富冈湾滩涂，随着日本鬼虾Nihonotrypaea harmandi(十足纲)的数量激增，其密度一直保持到1994年。从1995年开始，人口开始下降，1999年的人口密度恢复到1979年的水平。这可能是由于黄貂鱼的捕食，Dasyatis akajei自1995年以来突然增加。鬼虾是底栖动物群落中一个强大的生物扰动关键物种，并对许多物种产生了负面影响，包括另一个群落关键物种--串珠腹足类。虽然腹足类的数量在1986年灭绝，但从1997年开始已经恢复。本河口系统潮间带沙洲的任何物种的本地种群，包括富冈湾沙滩种群，都可以通过交换幼虫来相互作用。关于富冈湾沙洲与其他沙洲当地种群的源-汇关系与河口系统海洋条件的关系，揭示出：(1)对于具有2天幼虫周期的串珠线虫，由于强潮流的幼虫快速运输，这种关系是互惠的，而富冈湾沙滩种群的恢复归功于有里克海湾现有的种群，以及(2)对于幼虫周期为3-4周的富冈湾沙洲，富冈湾沙洲种群只能是一个来源，这是由于时间平均水流场。对于最近整个河口系统中幽灵虾种群的爆炸性增长，幼虫存活率的增加被认为是一个主要原因(例如，富营养化造成的大范围自下而上效应)。对于最近黄貂鱼种群的普遍增加，也提出了它对当地每个底栖群落的自上而下的影响。

Since 1979, on the Tomioka Bay sandflat in the Ariake-Sound estuarine system, Kyushu, Japan, following the population explosion of the callianassid ghost shrimp, Nihonotrypaea harmandi (Decapoda), its constant high density has been maintained until 1994. From 1995 the population began to decline, with the density in 1999 returning to that in 1979. This would be due to the predation by a stingray, Dasyatis akajei, which has suddenly increased since 1995. The ghost shrimp was a powerful bioturbating key species of the benthic community and has negatively affected many species, including another community key species, the gastropod Umbonium moniliferum. Although the gastropod population went extinct in 1986, it has recovered from 1997. Local populations of any species metapopulation of intertidal sandflats in the present estuarine system, including the Tomioka Bay sandnflat population, can interact through exchanging their larvae. Concerning the source-sink relationship of the local populations between the Tomioka Bay sandflat and other sandflats in relation to the oceanographic conditions of the estuarine system, it was revealed that (1) in the case of U. moniliferum with a 2-d larval period, the relationship is reciprocal due to a swift larval transport due to the strong tidal currents, and the recovery of the Tomioka Bay sandflat population owes its larval source to the extant populations in Ariake Sound, and (2) in the case of N. harmandi with a 3-4-wk larval period, the Tomioka Bay sandlat population can only be a source due to the time-averaged water current field. For the recent population explosion of the ghost shrimp in the entire estuarine system, an increased survival of larvae was suggested as a principal causal factor (e.g. a broad-scale bottom-up effect due to eutrophication). Concerning the recent widespread increase in the stingray population, its top-down effect on each local benthic community was also suggested.