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Ross Sea Essay

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The Ross Sea is one of the most productive regions of the Southern Ocean, accounting for 25–30% of annual Southern Ocean primary production (Moore and Abbott 2000, Arrigo et al. 1998a, Arrigo et al. 2008). Because this region is covered by sea ice for much of the year, the bulk of annual production is restricted to austral spring and to summer blooms of phytoplankton that develop at the marginal ice zone (MIZ) and within polynyas (open water surrounded by ice) along the Victoria Land Coast and north of the Ross Ice Shelf. These blooms follow a predictable spatial and temporal pattern over the season of growth. In general, a large phytoplankton bloom forms by mid- November north of the Ross Sea Ice Shelf in the central Ross Sea Polynya and…show more content…
1999, 2000). This spe- cies is also found in sea ice, but usually in relatively low numbers and mostly in association with newly formed ice near the Ross Sea polynya (Arrigo et al. 2003). Conversely, diatoms dominate the sea-ice mi- crobial community as well as waters of the MIZ and coastal polynyas where surface stratification is in- tense and MLDs are shallow (520m). The specific conditions that determine the distinct species composition of phytoplankton blooms in the southwestern Ross Sea are not well understood. The high correlation reported between species distribution and MLD suggests that diatoms are better adapted than P. antarctica to the higher irra- diance characteristics of a shallow MLD, whereas P. antarctica is better adapted to low light levels and may be inhibited at high irradiance (Arrigo et al. 2000). However, field evidence to support this contention is equivocal (Van Hilst and Smith 2002; Robinson et al. 2003). Alternative hypotheses include species-specific differences in requirements for micronutrients, differences in the composition of pre-bloom phytoplankton seed populations, and differential rates of grazing by zooplankton (Van Hilst and Smith 2002). In addition, Robinson et al. (2003) suggested that the degree of variability of the light fields produced in deeply (more variable) and shallowly mixed (less variable) water columns, rather than the
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