20 / 36
7. DEAD-FALL CARBON
When the Biomass Carbon of marine organisms is not already
removed by fishing, or redirected through the oceanic carbon
cycle by predation, their carcasses sink to depth and the carbon
stored in their biomass may enter deep sea ecosystems (>1500
m) (Figure 2, service 7), where it can be stored on timescales of
thousands to millions of years (Lutz
et al.
2007).
The carcass of a single large marine vertebrate transports
organic carbon, naturally accumulated in its body when it falls
to the sea floor. Here it represents a bounty of food for deep
sea and benthic organisms, and effectively sequesters carbon
from atmospheric release at ocean depth (Smith and Baco
2003). Primarily reported for whales (Smith and Baco 2003,
Pershing
et al.
2010, Roman
et al.
2014), Dead-Fall Carbon has
recently been reported for other marine vertebrates such as
whale sharks and mobulid rays (Higgs
et al.
2014).
It has been estimated that if whale populations were at pre-
whaling levels, an additional 160,000 tons of carbon would
be exported to the deep sea annually through whale dead-
falls alone (Pershing
et al.
2010). This figure is roughly
equivalent to the greenhouse gas emissions of 33 thousand
cars per year (EPA 2014).
Interactions between Dead-Fall Carbon and the broader
carbon cycle are yet to be established and quantified,
however the implication for oceanic carbon cycling is
that maintenance of healthy populations of large marine
vertebrates will enhance levels of carbon transfer to the deep
ocean through Dead-Fall Carbon.
Carbon can be transported into deep sea ecosystems through
marine vertebrate carcasses that sink to the ocean floor