49
Table 2.4 Empirical classification of sediment organic matter based on the susceptibility to remineralization during early diagenesis
Class
Definition
Main sources
Examples
Stability in
Oxic layer
Anoxic layer
Mineral-free labile
organic matter
Organic materials that can be
enzymatically hydrolyzed and
consumed by microorganisms
and are not protected by
sorptive interactions with
sediment minerals
Detrital particles derived
from plankton, seagrasses,
macroalgae, coral mucus,
microphytobenthos,
terrestrial plants, etc.
Low- molecular- weight
carbohydrates and proteins,
short-chain hydrocarbons
and fatty acids
Remineralized within
a relatively short
period
Remineralized
into inorganic
carbon or
decomposed
into simple
organic
molecules
Mineral- associated
labile organic
matter
Organic materials that are
essentially degradable by
microorganisms but are
protected by sorptive
interactions with sediment
minerals
Secondary organic products
produced from primary
organic matter by
microorganisms
High- molecular- weight
polysaccharides and
polypeptides, DNA,
long-chain lipids
Relatively resistant to
decomposition but
slowly and constantly
remineralized over a
long period
Somewhat
stable
Refractory organic
matter
Structurally recalcitrant organic
matter that strongly resists
against biodegradation
Lignin and other phenolic
polymers contained in
vascular plants, especially
xylem, bark, and cones of
arborous species; artificial
durable polymers such as
plastics
Lignin, plastics, kerogens
Degraded only
conditionally and very
slowly
Stable
2 Carbon Sequestration in Sediment as an Ecosystem Function of Seagrass Meadows