Spatial variation in population dynamics of the sand‐burrowing amphipodHaustorioides japonicus

Abstract

Densities of sandy beach organisms along coastlines often vary considerably even within small local scales. In order to understand the demographic basis of density variations in shore animals, we examined the population dynamics of the amphipod Haustorioides japonicus Kamihira, which is an ideal subject because it lacks a planktonic dispersal stage in its life history. Quantitative sampling at three adjacent sandy beaches along the Sea of Japan coast revealed that the spring density, i.e., the density of overwintered individuals, was similar among the three beaches. However, the amount of recruitment of newly hatched juveniles from late spring to summer greatly differed among the beaches, resulting in large spatial variations in the summer density. Cohort analyses revealed that at all beaches, young‐of‐the‐year (YOY) individuals reproduced and then died, and that individuals which recruited in late summer overwintered. Moreover, growth, fecundity, and survival schedules of overwintered and YOY individuals were very similar among beaches. These observations suggest that the difference in recruitment success, i.e., the survival of newly hatched juveniles, is the primary cause of the inter‐population variation in the summer density. It is likely that variations in salinity and sandy sediment affect the recruitment success of newly hatched individuals. This study indicates that biological productivity may differ substantially even among adjacent sandy beaches, with important implications for beach management.

Universality of the linkage between geoenvironment and the distributions of three <i>Haustorioides</i> amphipods: <i>H. japonicus</i>, <i>H. munsterhjelmi</i>, and <i>H. koreanus</i>

“…Among them, two species, H. japonicus and H. munsterhjelmi, and four species, H. koreanus, H. latipalpus, H. indivisus, and H. nesogenes, are found in Japan and South Korea, respectively. Haustorioides japonicus occurs on the intertidal zones of sandy beaches on the coast of the Sea of Japan, Kyushu and Honshu; the coast of the Oshima Peninsula, Hokkaido; and the Pacific coast on the northeastern part of Honshu (Kamihira 2000, Kaneko & Omori 2003, Suzuki et al 2013, Takada et al 2016. Haustorioides munsterhjelmi is distributed only in the easternmost part of Hokkaido, and H. koreanus is most common on intertidal sandy beaches throughout the southern half of the Korean Peninsula, except for the east coast of South Korea (Jo 1988, Kamihira 2000.…”

Estimates of mortality in sandy beach populations of <i>Haustorioides japonicus</i> (Amphipoda: Crustacea) and <i>Excirolana chiltoni</i> (Isopoda: Crustacea) during winter storm seasons

“…A demographic study of H. japonicus in Niigata demonstrated that the populations increased from spring to summer as a result of multiple events of recruitment of juveniles; then, from fall to winter, recruitment did not occur and the populations decreased (Suzuki et al 2013). A similar seasonal life history was observed in E. chiltoni (Kaneko & Omori 2005): its recruitment occurred only in the warm season.…”

Zonation of macrofaunal assemblages on microtidal sandy beaches along the Japan Sea coast of Honshu

“…We investigated the zonation pattern in summer, but seasonal variations may be considerable (Brazeiro & Defeo 1996, Giménez & Yannicelli 1997. Because of the harsh wind-driven waves in winter (Naganuma 2000) and seasonal variations in abundance and vertical distribution of sandy beach macrofauna (e.g., A. kokuboi: Takahashi & Kawaguchi 1995, Donax semigranosus: Hasegawa & Yajima 2000, E. chiltoni: Kaneko & Omori 2005, H. japonicus: Kamihira 1992, Suzuki et al 2013, Tylos granuliferus: Kuramochi 2006, Talitridae: Tsubokura et al 1997, zonation patterns in winter may be different from the present results obtained in summer. Especially in winter, assemblage C2 may not be recognizable because of a decrease in the density of its indicator, H. japonicus (Suzuki et al 2013).…”