Changing abundant ecotypes during the warm anomaly period
We further investigated the interannual turnover during the periods of
highest POC flux in spring and summer of some of the abundant OTUs and
their correlation with the temperature changes observed in Fram Strait
during the period 2003 - 2011. One of the interesting patterns that
emerged was the alternating abundances between some of the most abundant
phytoplankton OTUs. For example, chlorophyte OTUs in the Wolf938 dataset
showed that the temperate Clade C represented by OTU 2 had higher read
counts (t-test, p <0.05) in both spring and summer from
2005-2008, while the cold adapted Clade Ea represented by OTU 268
dominated the chlorophyte communities in the other years (Figures 5A and
5C). The same general pattern was observed in the OTUs identified from
the Stoeck dataset, where Clade C was more dominant among the
Chlorophyta in the years 2006-2009 for both seasons (t-test,p <0.05), while Clade Ea was prominent in the other
years. Similar observation however was not apparent in any of the OTUs
in the Wolf964 dataset.
Interestingly, alternating dominance of some OTUs was also observed in
the haptophytes based on the Wolf964, but was not observed in the Stoeck
and Wolf964 datasets. Specifically, Emiliania sp. (OTU 36) andPhaeocystis sp. (OTU 29) followed that of the chlorophytes where
the former becoming more prominent in 2006-2008 and the latter in both
seasons for the other years (Figure 5B and 5D). No similar pattern was
observed for the diatoms at the OTU level. However, their abundances
were generally higher before 2004 and after 2008 when haptophytes and
chlorophytes were more dominant.