Gastrochaenolites ichnofacies from intertidal seashells, Al-Khobar coastline, Saudi Arabia
Introduction
Bioerosion identifies every form of biological erosion of hard substrates and encrustation is the behavior by which organisms attach to hard substrates (Bromley, 1992; Demircan, 2012; El-Sorogy et al., 2019). Shells can provide the only hard substrate available for colonization by epi- and endoskeletozoans in areas where the bottom consists of unconsolidated sediments (Lopes, 2011; El-Sorogy, 2015). Formation of scrape traces, borings and other biogenic structures are the resultant byproduct of mechanical or chemical erosion of hard substrates by organisms. Modern biogenic hard substrates in intertidal and shallow subtidal environment may be colonized by a diverse endobionts, in addition to suspension feeding epibionts (Svane and Petersen, 2001; Santos and Mayoral, 2008).
Rocky shores represent major flooding surfaces in the geological record and offer excellent conditions for colonization by bioeroders and encrusters in shallow marine environments, as they associated with null or low sedimentation (Cachão et al., 2008; Demircan, 2012). The bioeroders including mechanical and/or chemical processes are the primary agent of shell destruction (Cutler and Flessa, 1995). They attack the living and dead shell materials, and their importance increases with productivity and decreases with higher rates of sedimentation (Lescinsky et al., 2002; Santos and Mayoral, 2008).
Al-Khobar coastline has subjected to three environmental studies (Alharbi and El-Sorogy, 2017; Alharbi et al., 2017; El-Sorogy et al., 2019). These studies assessed the anthropogenic sources of trace and heavy metals in coastal sediments, seawaters, and bivalve and gastropod shells. In general, the published articles on bioerosion and encrustation processes in the Aabian Gulf is very scarce (El-Gendy et al. 2015; El-Sorogy et al., 2018), therefore, the present contribution aims to: (1) identify and describe the bioerosion structures with their tracemakers on seashells in the coastal environment of the Al-Khobar area; (2) document the spatial distribution of borers and encrusters on mollusc shells in the study area, and (3) distinguish between the skeletobiont colonization of living and dead seashells.
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Materials and methods
Seashells were collected from 15 stations in the intertidal zone of Al-Khobar coastline, Saudi Arabia, between 50°12′59″E − 26°15′49″N and 50°6′55″E − 25°57′15.497″N (Fig. 1). Al-Khobar coastline is subdivided into sandy dominated and rocky dominated shores (Fig. 2). The sandy dominated shores are composed of medium to coarse sands and gravels in parts. Seashells ranged from scarce to completely cover the coastline, and composed mostly of cerithiids, venerids, and other biogenic fragments. The
Bioerosion
The total percentage of bioerosion in the investigated samples is high, giving an average value of 78% for bivalves, and 47% for gastropods (Table 1, Fig. 3). A total of eight ichnospecies were identified on seashells from the study area, which were grouped into five ichnogenera. To characterize the documented biotic relationships, the present borings were divided by their producers, including structures produced by clionaid sponges (Entobia geometrica, and Entobia isp), duraphagous drillers (
Discussion
Shells of marine molluscs along the coastline of Al-Khobar, Saudi Arabian Gulf were subjected to bioerosion and encrustation by a wide array of organisms, while the individuals are still alive and also after death, provided that the shells exposed in the water-sediment interface long enough. Surfaces of the investigated seashells act as the hard substrate for larval settlement and ontogeny development. Skeletobiont larvae tend to settle in protected zones of disarticulated seashells, either in
Conclusions
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The Al-Khobar coastline along the Saudi Arabian Gulf is differentiated into sandy dominated and rocky dominated shores, which are characterized by accumulation of seashells and other biogenic fragments. Shells of 14 bivalve species (A. lacunose, P. nigra, P. margaritifera, A. antiquata, D. ceylonica, G. pectunculus, C. rugifera, P. sinuosa, D. subrotundata, C. bicolor, C. divergens, F. fragile, M. flammea, and P. australis) and 6 gastropod ones (H. kuesterianus, F. arabicus, B. ampulla, T.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
The authors extend their appreciation to the Deanship of Scientific Research at King Saud University for funding this work through research group No. (RG-1439-031).
References (38)
- et al.
Assessment of metal contamination in coastal sediments of Al-Khobar area, Arabian Gulf, Saudi Arabia
J. Afr. Earth Sci.
(2017) - et al.
Metal pollution in Al-khobar seawater, arabian Gulf, Saudi Arabia
Mar. Pollut. Bull.
(2017) - et al.
Prey selection by drilling predators: a case study from Miocene of Kutch, India
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(2013) Determination of a late Miocene rocky palaeoshore by bioerosion trace fossils from the bozcaada island, canakkale, Turkey
C. R. Palevol
(2012)- et al.
Molluscan assemblage as pollution indicators in Al-Khobar coastal plain, Arabian Gulf, Saudi Arabia
J. Afr. Earth Sci.
(2019) - et al.
Bioerosion structures in high-salinity marine environments: A case study from the Al–Khafji coastline, Saudi Arabia. Estuarine
Estuar. Coast Shelf Sci.
(2018) - et al.
Bioerosion versus colonisation on Bivalvia: a case study from the Upper Miocene of Cacela (southeast Portugal)
Geobios
(2008) - et al.
Palaeoecology and evolution of marine hard substrate communities
Earth Sci. Rev.
(2003) - et al.
Geographic variation of shell bionts in the deep–sea snail Gaza
Deep-Sea Res., Part I
(1995) - et al.
Bioerosion in the Miocene reefs of the northwest red sea, Egypt
Lethaia
(2015)
Parasitic gastropod bioerosion trace fossil on Cenomanian oysters from Le Mans, France and its ichnologic and taphonomic context
Acta Palaeontol. Pol.
Bioerosion of Bermuda reefs
Palaeogeogr. Palaeoclimatol. Palaeoecol.
Concepts in ichnotaxonomy illustrated by small round holes in shells
Acta Geol. Hisp. Concept method. Paleontology
Bioerosion: eating rocks for fun and profit
The palaeoecology of bioerosion
Endolithic community replacement on a Pliocene rocky coast
Ichnos
The ichnogenus Entobia from the Miocene, pliocene and Pleistocene of southern Italy
Riv. Ital. Paleontol. Stratigr.
Lethaea geognostica. 2. Das Kreide und Molassen - Gebirge
The bioeroded megasurface of Oura (Alvarge, South Portugal): implications for the Neogene stratigraphy and tectonic evolution of Southwest Iberia
Facies
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