Great Calcite Belt
When these organisms die, their shells sink to the bottom of the ocean, and over time, they accumulate to form a thick layer of calcite sediment.
For example, variations in the CCD depth over time can indicate changes in the amount of carbon dioxide in the atmosphere and the ocean's ability to absorb it.
The belt is also home to a diverse range of contemporary marine life, including deep-sea corals and fish that are adapted to the unique conditions found in this part of the ocean.
[8][9][10] Hence, if model parameterizations are to improve to provide accurate predictions of biogeochemical change, a multivariate understanding of the full suite of environmental drivers is required.
[11][2] The Southern Ocean has often been considered as a microplankton-dominated (20–200 μm) system with phytoplankton blooms dominated by large diatoms and Phaeocystis sp.
and Thalassiosira spp., tend to dominate numerically, whereas large diatoms with higher silicic acid requirements (e.g., Fragilariopsis kerguelensis) are generally more abundant south of the polar front.
[20][12][13][21] Rather, the focus has often been on the larger and noncalcifying species in the Southern Ocean due to sample preservation issues (i.e., acidified Lugol’s solution dissolves calcite, and light microscopy restricts accurate identification to cells > 10 μm.
[6] These fronts divide distinct environmental and biogeochemical zones, making the GCB an ideal study area to examine controls on phytoplankton communities in the open ocean.
The GCB is clearly observed in satellite imagery [3] spanning from the Patagonian Shelf [30][31] across the Atlantic, Indian, and Pacific oceans and completing Antarctic circumnavigation via the Drake Passage.
While coccolithophores have been observed to have moved polewards in recent decades,[55][56][34] their response to the combined effects of future warming and ocean acidification is still subject to debate.
[57][55][58][59][60] As their response will also crucially depend on future phytoplankton community composition and predator–prey interactions,[61] it is essential to assess the controls on their abundance in today's climate.
Bottom-up factors directly impact phytoplankton growth, and diatoms and coccolithophores are traditionally discriminated based on their differing requirements for nutrients, turbulence, and light.
The greenish area south of the Polar Front shows the extension of the subpolar opal belt where sediments have a significant portion of silicous plankton frustules.
