Coccolith determination of ODP Site 184-1143

The slides are observed under a polarized light microscope (Leica DM6000B) at ×1,000 magnification. In each sample, a total of ~50 to >500 Noelaerhabdaceae coccoliths are counted in 6 one-quarter fields of view (FOVs). Coccolith abundance (CA, coccoliths g-1) can be calculated as: CA=(NC/n)×(A/(f×W)), where Nc/n is the average number of coccolith counted per FOV, A is the area of a coverslip, f is the area of an FOV, and W is the dry sediment weight.

Coccolith flux (export production) (CF) (cm-2 kyr-1) can be calculated as: CF=CA×LSR×DBD, where linear sedimentation rate (LSR, cm kyr-1) is resolved by the age model at Site 1143; DBD is dry bulk density (g cm-3). For coccolith morphological analysis. The slides are photographed under circular-polarized light (Zeiss Axio light microscope) using an 8-bit black-white digital camera (Mrc5) at ×1,250 magnification with a resolution of 0.088 μm pixel-1.

For each sample, approximately 150–250 Noelaerhabdaceae coccoliths are measured for coccolith thickness, coccolith area, and coccolith length using Image J software. Coccolith thickness is determined based its brightness under the light microscope. Coccolith mass (CM, pg) can be calculated as: CM=2.7×AC×CT, where AC is coccolith area (μm2) and calcite density is 2.7 pg μm-3.

Finally, Noelaerhabdaceae coccolith calcite export production or coccolith mass accumulation rate (MAR, g CaCO3 m-2 yr-1) can be calculated based on CF and average CM: MAR=CF×CM.