IS BURIAL VELOCITY A MASTER PARAMETER FOR BIOTURBATION

The intensity of biological mixing in a marine sediment is widely believed to be related to the flux of labile organic matter. At the same time, this flux has been shown to be strongly correlated to the burial velocity. One would then expect a significant correlation between biological mixing coefficient, D(B), and burial velocity, omega. A nonlinear regression of existing data with a power law (Eqns. 2 and 3 of the text) produces a statistically significant correlation. The statistical significance of the regression in no way implies causation and, in fact, it accounts for only about 22% of the total variance in the dataset, thus reducing its physical significance. A number of additional processes contribute to the large observed variance, including timing of mixing events, temporal and spatial heterogeneity, differences in temporal scales, sampling artifacts, and specific particle associations. With due care, the D(B)-omega relationship may prove useful in defining the likely range of D(B) values in a particular environment. A similar analysis of the tracer-identified surface mixed-depth shows that it is essentially independent of burial velocity with a worldwide mean of 9.8 +/- 4.5 cm. Depth of mixing is probably more closely related to the energetic costs of deep burrowing.