Applicability of the source–sink population concept to marine intertidal macro‐invertebrates with planktonic larval stages

Abstract

AbstractLocal populations of marine benthic macro‐invertebrates with planktonic larvae are believed to be in source–sink relationships via larval dispersal in a regional population complex. Practically, such a region is definable only after connectivity of constituent local populations is explored. Numerical simulations abound for hydrodynamic connectivity by larvae between local/regional populations. Empirical studies have scarcely integrated inter‐local connectivity and intra‐local population dynamics into demographic connectivity analysis. I review the current research and indicate fundamental and technical problems to demonstrate that some source–sink systems in intertidal shores, which are most accessible among benthic habitats, are a good model. The challenge in benthic source–sink research comes from that existent local populations may not be self‐sustaining because of low larval self‐seeding rates and/or low benthos' survival rates and yet can persist as latent sinks. They may receive larvae leaking from sources at good‐quality habitat patches with stationary larval retention areas for self‐recruitment. On an intertidal sandflat in an estuary–coastal ocean region, Kyushu, Japan during 1979–2019, the population of a trochid gastropod with 3‐ to 9‐day larval duration became extinct and recovered. The extinction was caused by sediment destabilization by a callianassid shrimp population which increased in the early 1980s. The gastropod recovery was owing to the shrimp decline by stingray predation and the transport of larvae from some self‐sustainable populations with lower shrimp densities 30 km away. It was estimated that the gastropod population before the shrimp proliferation on that sandflat might be a latent sink requiring allochthonous larval subsidy due to epi‐benthic predation on juveniles.