The Variation on Sediment Reworking with Influencing Factors by a Sand Bubbler Crab, Scopimera globosa, in Intertidal Sediments of the Anmyeon Island, Korea

Jaehwan Seo,Bon Joo Koo

doi:10.3390/su13105703

Abstract

Though biological and ecological characteristics of Scopimera globosa have been intensively investigated, little has been understood on bioturbation, especially sediment reworking. This study was designed to evaluate variation on sediment reworking of S. globosa based on feeding pellet production (FP) and burrowing pellet production (BP) with influencing factors and estimating the chlorophyll content reduction within the surface sediment by its feeding. The FP and BP largely fluctuated according to chlorophyll a concentration and crab density, but both were not influenced by temperature. The FP was enhanced by chlorophyll a concentration, whereas both FP and BP were restricted by crab density. The daily individual production was highest in spring, followed by fall and summer, with values of 25.61, 20.70 and 3.90 g ind.−1 d−1, respectively, while the total daily production was highest in fall, followed by summer and spring 2150, 1660 and 660 g m−2 d−1, respectively. The daily sediment reworking based on the FP and BP of Scopimera was highest in fall, followed by summer and spring, with values of 1.91, 1.70 and 0.77 mm d-1 and the annual sediment reworking rate of this species was calculated 40 cm year−1 based on its density in this study area. The chlorophyll a reduction ratio was estimated from 11 to 24% in one day by its feeding. These results imply that the sediment reworking of S. globosa is regulated by food abundance and its density, and Scopimera is an important bioturbator, greatly influencing biogeochemical changes in the intertidal sediments.

Highlights

Bioturbation by the activities of benthic organisms, such as feeding and burrowing, is one of the important processes influencing the physical, chemical and biological characteristics of intertidal sediments
Organic matter decomposition in intertidal sediments is mediated by the activity of macrofauna, which increases the capacity of organic matter degradation and transport processes via burrow dwelling
A few studies have investigated the biological and ecological information of this species such as population ecology, life history and behavioral characteristics [19,20,21,22]. It lives in the sandy intertidals and ingests surface sediments and egests the remaining particles around the burrow in the shape of beans [23]. The recruitment of this crab occurs from July to August resulting in a high juvenile proportion in the population during summer

Summary

Introduction

Bioturbation by the activities of benthic organisms, such as feeding and burrowing, is one of the important processes influencing the physical, chemical and biological characteristics of intertidal sediments. Through feeding and burrowing activities, macrofauna increase the surface area of sediment exposed to overlying water or air and modify the surface sediments. The sediment reworking that results from feeding and burrowing of macrofauna is essential to the organic matter mineralization, microphytobenthos reduction and nutrient exchange from the sediment to the water column [4,5,6,7]. Organic matter decomposition in intertidal sediments is mediated by the activity of macrofauna, which increases the capacity of organic matter degradation and transport processes via burrow dwelling. Sediment disturbance and particle erosion through burrowing, feeding and movement of burrowing crabs enhance both the direct release of nutrients

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