Long-term changes in a trochid gastropod population affected by biogenic sediment stability on an intertidal sandflat in regional metapopulation context

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

“…After 1988 on Tomioka sandflat, the grand mean density of N. harmandi decreased and regained until 1995, from which it continued to decline until 2001, crossing 160 shrimp m À2 between 1997 and 1998 (Figure 4a). The decrease from 1995 well agreed with the abrupt increase in pits formed by the stingray, Hemitrygon akajei, over the sandflat from 1994 onward and is ascribable to its predation on ghost shrimp (Figure 3e; Takeuchi & Tamaki, 2014;Tamaki, Harada, et al, 2020;Tamaki et al, 2021). These pits are of half a spheroid in shape, with a 1060-cm 2 mean elliptical plane area and a 20-cm mean depth.…”

“…The present gastropod regional population might now be approaching a demise. Recently increased wet‐monsoonal heavy rains probably has brought about acute riverine mud deposition on U6 and U7 sandflats, which could suffocate epibenthic suspension‐feeding mollusks (Tamaki et al, 2021; possibility of abiotic conditionality for that source local population [Section 1, seventh paragraph]).…”

“…(f) Tubes of the chaetopterid polychaete, Mesochaetopterus minutus (reproduced from fig. 2a of Tamaki et al, 2021, with the permission of Springer Nature) [Color figure can be viewed at wileyonlinelibrary.com]…”

“…The use of fig. 2a of Tamaki et al (2021) for Figure 3e was permitted by Springer Nature. This study was partly supported by the Environment Research and Technology Development Fund (4D‐1104) of the Environmental Restoration and Conservation Agency of Japan and the JSPS KAKENHI Grant‐in‐Aid for Scientific Research JP26440244.…”

“…Based on a 40‐year (1979–2019) monitoring of the macrobenthic community on an intertidal sandflat of medium size (56 ha in area) in an estuary to inner‐shelf region, southern Japan, the present author recorded the local extinctions and recoveries of the population of one numerically dominant species with lecithotrophic and anchiplanic larvae, the trochid gastropod, Umbonium moniliferum . These extinctions and recoveries were caused by the population boom and decline, respectively, of another dominant species with planktotrophic and actaeplanic larvae, the callianassid decapod shrimp (or ghost shrimp), Neotrypaea harmandi (e.g., Tamaki, 1994; Tamaki et al, 2021; Tamaki & Takeuchi, 2016). Small to medium‐sized intertidal sandflats between rocky headlands like the present study's sandflat tend to be formed on the shoreline under moderately sheltered conditions, subject to medium wave action.…”