Do we have enough pieces of the jigsaw to integrate CO2 fluxes in the Coastal Ocean ?

Annually integrated air-water CO2 flux data in 44 coastal environments were compiled from literature.
Data were gathered in 8 major ecosystems (inner estuaries, outer estuaries, whole estuarine systems, mangroves, salt
marshes, coral reefs, upwelling systems, and open continental shelves), and up-scaled in the first attempt to integrate
air-water CO2 fluxes over the coastal ocean (26 3 106 km2), taking into account its geographical and ecological diversity.
Air-water CO2 fluxes were then up-scaled in global ocean (362 3 106 km2) using the present estimates for the coastal
ocean and those from Takahashi et al. (2002) for the open ocean (336 3 106 km2). If estuaries and salt marshes are not
taken into consideration in the up-scaling, the coastal ocean behaves as a sink for atmospheric CO2 (21.17 mol C m22
yr21) and the uptake of atmospheric CO2 by the global ocean increases by 24% (21.93 versus 21.56 Pg C yr21). The
inclusion of the coastal ocean increases the estimates of CO2 uptake by the global ocean by 57% for high latitude areas
(20.44 versus 20.28 Pg C yr21) and by 15% for temperate latitude areas (22.36 versus 22.06 Pg C yr21). At subtropical
and tropical latitudes, the contribution from the coastal ocean increases the CO2 emission to the atmosphere from the
global ocean by 13% (0.87 versus 0.77 Pg C yr21). If estuaries and salt marshes are taken into consideration in the upscaling,
the coastal ocean behaves as a source for atmospheric CO2 (0.38 mol C m22 yr21) and the uptake of atmospheric
CO2 from the global ocean decreases by 12% (21.44 versus 21.56 Pg C yr21). At high and subtropical and tropical
latitudes, the coastal ocean behaves as a source for atmospheric CO2 but at temperate latitudes, it still behaves as a
moderate CO2 sink. A rigorous up-scaling of air-water CO2 fluxes in the coastal ocean is hampered by the poorly constrained
estimate of the surface area of inner estuaries. The present estimates clearly indicate the significance of this
biogeochemically, highly active region of the biosphere in the global CO2 cycle.