GLOSSARY - Introduction to the Physical and Biological Oceanography of Shelf Seas - page 372

cyanobacteria Photosynthetic bacteria
(prokaryotes) with cell sizes typically
0.5-2 m m. In the ocean, cyanobacteria tend
to be the dominant autotrophs in nutrient-
stressed environments (e.g. the oligotrophic
open ocean, or the summer surface mixed
layer of the shelf seas), They are also
referred to as 'blue-green algae'. In the
ocean, the most important cyanobacteria
are Synechococcus and Prochlorococcus;
they are probably the most abundant
photosynthetic organisms on the planet.
deep water waves Waves with a wavelength
that is much less than the depth of water
through which they are propagating. Such
waves have circular particle orbits whose
amplitude decreases exponentially from the
surface.
degenerate amphidrome

dinoflagellates Single-celled phytoplankton,
typically 10s m m in diameter, and an
important part of the marine food chain.
About half of the dinoflagellates are
autotrophic, the rest being either
heterotrophic (part of the
microzooplankton) or mixotrophic.
Dinoflagellates have two whip-like
'flagella' that allow them to swim and to
control their swimming direction. (See also
flagellates.)
dissolved organic carbon (DOC) Very tiny
particles of organic carbon released by, for
instance, the break-up of phytoplankton
cells ('lysis') or sloppy feeding by
zooplankton. The distinction between
'particulate' and 'dissolved' organic matter
is defined operationally, with DOC being
able to pass through a filter with pore
size 0.45

An amphidrome
which is displaced to a position on land by
frictional effects in the tidal regime.
Energy lost to friction results in the Kelvin
wave reflected at the head of a gulf being
weaker than the incident wave, thus
producing an asymmetry in the tidal
response.
denitrification The conversion of nitrate
back to gaseous nitrogen (N 2 ) by bacteria.
diatom Single-celled autotrophic
phytoplankton that use silicate to build
their cell wall (called a 'frustule'). They
have no ability to swim, but some species
achieve vertical movement through
changes in cell buoyancy. Diatoms are
typically 10-100 m m in diameter,
sometimes aggregating into large
colonies.
dissolved inorganic carbon (DIC)

m.
dissolved organic matter (DOM)

m

Dissolved
organic compounds, such as carbon
(DOC), phosphate (DOP) and nitrogen
(DON). (See dissolved organic
carbon.)
dissolved organic nitrogen (DON) Fixed
organic nitrogen released during cell lysis
and grazing, and able to pass through a
0.45 m m filter. As with dissolved organic
carbon, DON is a component of dissolved
organic matter (DOM).
diffuse attenuation coefficient Parameter
with units of m 1 expressing the rate of
exponential decay of the downward flux of
diffuse light energy.
DOC See dissolved organic carbon.
DOM See dissolved organic matter.
eddy diffusivity Dissolved

inorganic carbon in the water made up of
carbon dioxide, carbonic acid, bicarbonate
and carbonate. These different forms of
inorganic carbon arise from the transfer of
atmospheric CO 2 into the sea, followed by
chemical reactions between the CO 2 and
the water, About 88% of DIC is
bicarbonate, 11% is carbonate and the
remaining 1% is CO 2 and carbonic acid.

A parameter that describes
the transfer of a scalar property by
turbulent eddies down the property
gradient. It arises from an analogy with
the molecular diffusivity in molecular
diffusion.
eddy viscosity A parameter that describes
the transfer of fluid momentum by
turbulent eddies down momentum
gradients in the water.