Deep Sea Minerals - Vol 2 - Manganese Nodules

Global geographic context 2.2

Nodule regions sustaining different levels of particulate organic carbon flux appear to have different levels of species diversi- ty and substantially different faunal communities, both in the soft sediments and on the nodules themselves. (Figure 16; Mul- lineaux 1987; Veillette et al . 2007a; UNESCO 2009; Ebbe et al . 2010). The CCZ, the area of most intense interest for manganese nodule mining in the Pacific, experiences substantial east-west and south-north gradients in overlying primary production and the flux of food to the abyssal sea-floor (UNESCO et al . 2009; Watling et al . submitted). Based on these gradients, as well as on patterns of faunal turnover, the CCZ is expected to harbour distinct faunas and levels of biodiversity in different subre- gions. The CCZ is also thought to straddle a major biogeograph- ic provincial boundary in the abyssal Pacific (UNESCO 2009; Watling et al . in press).

Normalized parameter value

1.5

Abyssal sea cucumber wresting – Psychropotes versus Adrian Glover. Photo courtesy of C. Smith.

Megafaunal abundance

r 2 = 0.94 y = 41.86x - 9.507

1.0

Macrofaunal biomass r 2 = 0.96 y = 112.0x + 47.92

Microbial biomass r 2 = 0.58 y = 9.024x + 11.11

0.5

Macrofaunal abundance

r 2 = 0.672 y = 250.552x + 1751.954

0

0

0.5

1.0

1.5

2.0

2.5

Poc ux (g CM -2 yr -1 )

Figure 16 Links between abyssal benthic ecosystems and particulate organic matter. Regression relationships demon- strating the strong dependence of abyssal benthic ecosystem structure and function on the level of particulate organic matter (expressed as carbon) flux to the sea-floor. All relationships are statistically significant (p < 0.05). Bioturbation intensity is based on 210Pb Db SCOC = sediment community oxygen consumption Modified from Smith et al. (2008a).

Tiny holothurians that live on the spines of sea urchins at abys- sal depths in the CCZ. Photo courtesy of Adrian Glover.

MANGANESE NODULES 22

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