Effect of habitat architecture on mobile benthic macrofauna associated with patches of barnacles and ascidians

Abstract

The physical structure of a habitat strongly affects species composition and diversity in benthic assemblages. In the shallow subtidal zone in the White Sea in northwestern Russia, barnacles Balanus crenatus are often found in clusters on empty bivalve shells or small stones, sometimes overgrown by solitary ascidians (mainly Styela spp. and Molgula spp.). These epibenthic patches are surrounded with muddy sediment. Sediment also fills the space between barnacle shells within the patches. The assemblages of mobile macrofauna associated with epibenthic patches and surrounding unstructured sediment are different in species composition and abundance. We hypothesised that epibenthic patches at least partially affect mobile benthic organisms with their architectural properties as complex cavity-loaded structures. In a field experiment we assessed the strength of this effect, comparing unmanipulated natural epibenthic patches (E), unmanipulated patches of bare sediment (S), and patches of bare sediment with artificial imitation structures (mimics) added (M). Mimics were made of polyvinyl chloride (PVC) tubes and exposed for 1 and 2 yr (half-buried in sediment; 50 tubes × 8 to 9 sets × 2 replications). After 1 or 2 yr of exposure, the assemblages in E and M were much more similar to each other than to S (analysis of similarities, non-metric multidimensional scaling). Most species that were constantly abundant in E responded positively to the treatments. The bivalve Musculus discors and the sigalionid polychaete Pholoe minuta dominated numerically both in E and M, whereas maldanid Rhodine loveni and spionid-like Apistobranchus tullbergi dominated in S. Like many other large aggregated benthic suspension feeders, patched barnacles shape the associated assemblage of mobile benthic fauna with their architectural effect.

Bored to Death: Community-Wide Effect of Predation on a Foundation Species in a Low-Disturbance Arctic Subtidal System

“…It would be generally expected, if in the absence of harsh environmental stress live and dead barnacles had similar effects on the associated organisms. For instance, in the White Sea subtidal, adding simple structures made of PVC tubes to the bare soft sediment assembles the species composition rather similar to the one observed within the patches of live barnacles [ 55 ]. Yet, our present data show that the effect of barnacles in a subtidal habitat is far from purely architectural, and the biogenic activity of the live ones does make the difference.…”

Epibenthic predators control mobile macrofauna associated with a foundation species in a subarctic subtidal community

“…The increase of Sphaerosyllis abundance in predator exclosures, however, was only marginally insignificant (Tables and ). In the field, Pholoe and Sphaerosyllis inhabit barnacle clusters rather than surrounding muddy sand (Yakovis et al, ), while all the three species significantly increase their abundance in response to adding structure (PVC tubes) to unstructured sediment (Yakovis et al, ). Given that some crab species can prey at least on Pholoe (Quijón & Snelgrove, ), it is likely that structural traits of barnacle clusters effectively protect these potentially vulnerable mesopredators from crabs and shrimp compared with less structured habitats.…”

“…To test the effect of predators on mobile macrofauna of barnacle clusters, we conducted a year‐long field experiment at a 12‐m‐deep subtidal site in the White Sea near the Solovetsky Islands (the Onega Bay, 65°01.180′N, 35°39.721′E, see Site 1 in Yakovis & Artemieva, ). The exposure duration was selected according to the results of previous colonization and caging experiments on the same system (Yakovis & Artemieva, ; Yakovis et al, ). While caging experiments at lower latitudes typically last shorter, the rates of succession and predation in subtidal of the severely cold White Sea are very slow (Varfolomeeva et al, ; Yakovis & Artemieva, ; Yakovis et al, ) and require longer experiments to detect changes.…”

“…Equally complex patches of live barnacles and their empty tests develop strongly different assemblages of associated species, with live barnacles accommodating several times more juvenile bivalves Musculus discors and polychaetes Cirratulis cirratus and Pygospio elegans than empty tests (Yakovis & Artemieva, ). Also, field experiments with barnacle mimics show that species composition of mobile fauna inhabiting barnacle clusters is largely determined solely by the presence of structurally complex habitat (Yakovis, Artemieva, Fokin, Varfolomeeva, & Shunatova, ), potentially rich in refuges from predation.…”

Comparative efficiency of Mytilus edulis as engineering species for shallow-water fouling communities on artificial structures in the White Sea

“…Mass aggregations of some epibenthic organisms are commonly known to serve as a habitat for a variety of motile, sessile and sedentary fauna providing food and refuge from predators or adverse environmental conditions (Gutiérrez et al ., 2011). These properties have been shown for the populations of ascidians (Monteiro et al ., 2002; Castilla et al ., 2004), sponges (Abdo, 2007; Gerovasileiou et al ., 2016), algae and seagrass (Crowe et al ., 2013; McCloskey & Unsworth, 2015), corals (Curdia et al ., 2015; Ponti et al ., 2016), tubicolous worms (Albano & Obenat, 2009; Gravina et al ., 2018), shared populations of barnacles and ascidians (Yakovis et al ., 2007). The environmental modification caused by these organisms and their impact on the associated and surrounding fauna are so significant that these organisms have been termed ecosystem engineers, bioengineers or foundation species (Jones et al ., 1994, 2010; Crain & Bertness, 2006).…”