21-YEAR DYNAMICS OF MARINE BENTHIC CILIATE COMMUNITY IN THE WHITE SEA INTERTIDAL FLAT: GRADUAL OR DISCRETE?

Abstract

Changes in the composition, structure and seasonal succession patterns were observed in a local community of interstitial ciliates over a period of 21 years (1991–2011). General trends in species structure transformation were revealed. During 1991–2004 years Trachelocerca incaudata, Remanella margaritifera, Coleps tesselatus, and Uronema marina, dominated in the community. However, in 2005–2011 the number of specific interstitial ciliate species, and of Apotrachelocerca arenicola in particular, increased considerably. These changes were caused by the increase in the silt content in the sediments. Long-term changes were realized at different stages of seasonal development of the community including both, more structurally simple earlier period (in the beginning of spring) and more structurally complex mature period (at the end of summer). The most mature state of ciliate community was temporally (in the inter-year scale) stable, but discretely (drastically) transformed from one variant (in 1991–2004) to another one (in 2005–2011). The simpler state of ciliate community was more variable between years and transformed gradually from one polymorphic variant (in 1991–1995, 1998, 2000–2005, 2009–2010) to another one (in 2006–2008, 2011). This suggests that discrete and stable mature communities can be assembled via different annual trajectories.

Keywords

• ciliates
• community
• long-term dynamics
• White Sea
• intertidal flat