Food supply and Feeding

Figure 8. Marine snow composed of detritus. As it falls, some particles clump together forming aggregates (Physical Oceanography).

Only 5% of energy created in the surface waters reaches the dark zone (Bylatt et al. 2001) so the food supply to this ecosystem is quite limited. Most of this energy reaches the deep in the form of marine snow (Figure 8), which is composed of detritus, living organisms and inorganic matter (Alldredge and Silver 1988). This is mostly formed in the highly productive surface waters via photosynthesis – despite never seeing the sun, the organisms that live at these depths still rely on it for food. Some matter like faecal pellets can sink at a rate of 1000m per day (Herring 2007) but most settle more slowly, 4-5mm aggregates settle at a rate of 1m per day and 1-2mm can settle at rates of 36m per day (Asper 1986). Large inputs such as the carcases of large organisms like whales, seals and dolphins are all important to this ecosystem (Herring 2007) as they are able to nourish organisms for sometimes several years (Goffredi et al. 2004).

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