Environmental Engineering Reference
In-Depth Information
Vertical Migration
Passive Sinking
Respiration
Aggregate Formation
Diffusion
Grazing/Ingestion
Mixing
CO 2
Euphotic Zone
CO 2
Small Phytoplankton
(Cyanobacteria,
Flagellates, Haptophytes)
Large Phytoplankton
(Diatoms)
POC
Microzooplankton
(Ciliates, Tintinnids)
Mesozooplankton
(Copepods)
DOC
Aggregates
Higher Trophic
Levels
Fecal Pellets
Aphotic Zone
Particulate Organic Carbon (POC)
Fig. 12.2 Schematic of the biological pump showing the biological and chemical components and
processes involved in the transformation of carbon dioxide (CO 2 ) to organic matter, and the
subsequent transformation, movement, and oxidation of particulate organic carbon (POC) and
dissolved organic carbon (DOC). The CO 2 is absorbed from the atmosphere across the air-ocean
interface ( wavy lines ) and is transformed by processes in the euphotic (above dashed line ) and
aphotic zone (below dashed line ). The migration of zooplankton and higher trophic levels within
the water column ( light blue lines ) and unidirectional passive sinking of particles of different sizes
to depth ( green dot-dashed line ) redistribute organic material. Processes of grazing/ingestion ( red
dashed line ), aggregate formation ( red line ), respiration and CO 2 generation ( orange line ),
physical mixing (heavy blue line ), and solubilization, and DOC generation ( dark blue line ) modify
the rate at which POC is exported to depth from the surface waters. The POC pool at depth is
generally composed of unidentifiable, small particles, whereas the POC pool in the surface
is composed of recognizable biota (bacteria, phytoplankton, zooplankton) and variable amounts
of detritus
acidification [ 5 , 6 ]. A decrease in pH would seriously impact calcification, likely
increasing dissolution of CaCO 3 found in skeletons and shells because the material
is unprotected from seawater, and decreasing the rate at which calcification can
occur by altering the concentrations of the necessary minerals in the water column.
As a result, decreased pH has a great capacity to alter the ecology of marine systems
such as coral reefs. In addition, decreased pH levels have been shown to alter the
growth, reproduction, efficiency, and survival of those organisms that require
CaCO 3 to survive, and these effects vary among organisms, suggesting that sub-
stantial and unexpected impacts on biodiversity could occur [ 7 ].
It is now recognized that many phytoplankton can remove only CO 2 for use in
photosynthesis. Under preindustrial pH levels, free CO 2 levels could have been at
 
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