Benthic foraminifera in a deep-sea high-energy environment: the Moira Mounds (Porcupine Seabight, SW of Ireland)

Abstract

Cold-water coral ecosystems represent unique and exceptionally diverse environments in the deep-sea. They are well developed along the Irish margin, varying broadly in shape and size. The Moira Mounds, numerous small-sized mounds, are nestled in the Belgica Mound Province (Porcupine Seabight, North-East Atlantic). The investigation of living (Rose Bengal stained) and dead benthic foraminiferal assemblages from these mounds allowed to describe their distribution patterns and to evaluate their response to environmental variability. Quantitative data was statistically treated to define groups of species/genera associated to specific habitats. The Moira Mounds differ from their larger neighbours by the reduced spatial variability of benthic foraminiferal assemblages, living assemblages only distinguishing coral-rich and coral-barren areas. The ecological needs of corals are highlighted by the abundance of Alabaminella weddellensis and Nonionella iridea, phytodetritus-feeding species in coral supporting sediments. Living foraminifera in sediments from the Moira Mounds concentrate in the upper first centimetre. Infaunal species may be affected by bioturbation and/or reworking by the strong currents in the area. Dead foraminiferal assemblages from the Moira Mounds resemble those described for the sandwave facies in adjacent giant mounds, suggesting similar processes in facies deposition.

Cold-Water Coral Mound Archive Provides Unique Insights Into Intermediate Water Mass Dynamics in the Alboran Sea During the Last Deglaciation

“…The association of C. lobatulus, D. coronata, T. angulosa, Cassidulina spp. and CWCs is reported from the Porcupine Seabight (Margreth et al, 2009;Schönfeld et al, 2011;Fentimen et al, 2018), Norwegian margin (Spezzaferri et al, 2013;Stalder et al, 2014) and the Alboran Sea (Margreth et al, 2011;Stalder et al, 2015Stalder et al, , 2018. However, this assemblage is here observed in relation to a thick accumulation of the bryozoan Buskea dichotoma associated to the brachiopod G. vitreus, whilst CWCs are absent (Figure 2).…”

Impact of bottom water currents on benthic foraminiferal assemblages in a cold-water coral environment: The Moira Mounds (NE Atlantic)

“…Previously defined bio-sedimentary facies were deemed unsuitable for the aim of this research (e.g. Spezzaferri and Vertino, 2012;Vertino et al, 2014;Fentimen et al, 2018). Here, we utilize a bio-sedimentary facies classification that differentiates between the facies' ability to alter the hydrodynamic or sedimentological regime.…”

Benthic foraminiferal faunas associated with cold‐water coral environments in the North Atlantic realm

“…Benthic foraminiferal assemblages have hence been widely used to reconstruct past environmental conditions (Gooday, 1993;Jorissen et al, 2007 and references therein). Previous studies suggest that benthic foraminiferal assemblages are a useful and promising tool to identify the environmental conditions governing present and past CWC reef and mound development (Fentimen et al, 2018;2020a;Fink et al, 2012;Margreth et al, 2009Margreth et al, , 2011Rüggeberg et al, 2007;Schönfeld et al, 2011;Stalder et al, 2014Stalder et al, , 2015Stalder et al, , 2018. However, no integration of these results in one comparative study has yet been done.…”

“…For the Porcupine Seabight, surface benthic foraminiferal studies have focused on Galway Mound (Margreth et al, 2009;Schönfeld et al, 2011) and the downslope Moira Mounds (Fentimen et al, 2018(Fentimen et al, 2020b) within the Belgica Mound Province (see Dorschel et al, 2007;Eisele et al, 2008;Lim et al, 2018;Wheeler et al, 2011), Propeller Mound (Margreth et al, 2009;Schönfeld et al, 2011) within the Hovland Mound Province (see De Mol et al, 2002), unnamed buried mounds (Margreth et al, 2009) from the Magellan Mound Province (see De Mol et al, 2002;Huvenne et al, 2007), and adjacent off-mound areas (Figure 1; Table 2). In addition, Rüggeberg F I G U R E 1 Geographical location of foraminiferal studies related to cold-water coral environments.…”

“…Smeulders et al (2014) focused on total benthic foraminiferal assemblages from 4 to 5 cm depth in the sediment instead of the generally used top first centimetre (Table 2). Furthermore, the investigation of soft-shelled tests (Morigi et al, 2012) or biomineralized tests only (Fentimen et al, 2018;Margreth et al, 2009;Schönfeld et al, 2011;Smeulders et al, 2014;Spezzaferri et al, 2013), or the lack of inspection of bioclasts and pebbles for attached foraminifera (Morigi et al, 2012) can also have an impact on foraminiferal relative abundances. This diversity of sampling protocols handicaps comparisons between studies (Table 2).…”