RAPID RECRUITMENT OF BENTHIC FORAMINIFERA TO EXPERIMENTAL ARRAYS IN MCMURDO SOUND, ROSS SEA, ANTARCTICA

The shallow benthos of McMurdo Sound, Ross Sea, Antarctica, is identified as a natural laboratory for deep-sea ecological processes because of the region’s low productivity, low recruitment, persistently cold temperatures, and relatively stable water-mass properties. This region is also a natural laboratory for studying paleoecological and taphonomic processes that affect carbonate preservation and biotic diversity. Studies on the initial recruitment of benthic organisms are essential to understand how organisms contribute to community structure. In McMurdo Sound, benthic recruitment is thought to take place on the order of decades.

Here we report our findings on foraminiferal recruitment to experimental arrays that were deployed for two years (2008-2010) at 9m (30ft) at three sites within McMurdo Sound: Herbertson Glacier (HG), Explorers Cove (EC), and Bay of Sails (BOS). The settling arrays were composed of similar-sized pieces of the Antarctic scallop (Adamussium colbecki) each enclosed in mesh bags (1-mm² openings). After two years, recruitment of calcareous (e.g., Cibicides, Rosalina) and agglutinated (e.g., Tritaxis, saccamminids, hemisphaeramminids) foraminifera occurred at all three sites, indicating that recruitment of encrusting foraminifera was rapid, occurring within two years despite persistently very cold water (-1.96^oC). These protistan recruits also form the dominant members of the mature encrusting foraminiferal communities in this region. Despite differences in water-mass properties, recruitment of calcareous foraminifera was not significantly different among sites (ANOVA, P = 0.30). While calcareous and agglutinated foraminifera recruited in similar abundance at HG and BOS, agglutinated foraminifera recruited at significantly higher numbers at EC, accounting for 70% of the recruits (ANOVA post-hoc Tukey HSD, P < 0.001 for EC*HG and EC*BOS). Our results show that foraminifera that encrust substrates recruit within two years, and not on the order of decades, in these very cold waters of Antarctica. For the fossil record, these early recruits are integral members of the mature polar benthic community and provide a scalar for addressing the recovery of these communities after perturbations from ice, or other disturbance regime.