|Carbon flow in fjords|
Burrell, D.C. (1988). Carbon flow in fjords. Oceanogr. Mar. Biol. Ann. Rev. 26: 143-226
In: Oceanography and Marine Biology: An Annual Review. Aberdeen University Press/Allen & Unwin: London. ISSN 0078-3218, more
Carbon cycle; Fjord dynamics; Fjords; Marine
"Fjords" embrace a wide variety of higher latitude, geologically immature marine inlets. This review is concerned primarily with carbon flow to and within deep, silled, ice-impacted estuaries located in mountainous boreal-polar terrain.The primary external source of carbon to fjords is from the surrounding watershed.Mean annual influx may be small in polar and glacial inlets, but very high in those located in the boreal-subarctic climatic zone. Sediment influx, both organic and inorganic, is seasonally skewed, and frequently the bulk of the annual transport occurs over intervals of weeks or days. Silled fjords are net repositories of sediment:sedimentation rates can locally exceed 1 m.yr-1 in glacial regions, and fjords may be globally significant carbon sinks where influx of terrigenous, refractory organic material is high. Because of their topography, fringing community production is relatively slight, and autochthonous carbon is primarily due to phytoplankton production. An annual spring bloom is the most distinctive feature of phytoplankton carbon uptake. Primary production and grazing are characteristically poorly coupled at this time of year and substantial phytodetritus may be sedimented out of the euphotic zone.In essence fjord basins are partially isolated marine regions underlying an estuarine environment. The deep basins emphasized in this review receive particulate material from the above-sill estuarine and intermediate zones (the sole energy source for the quantitatively dominant sub-euphotic benthos), but are generally poorly coupled hydrodynamically. Under ideal circumstances the basin soft-bottom environment is physically (and, in well-ventilated fjords, chemically) stable, but in practice is commonly subject to episodic bedload transports. The resultant benthic community structure, and mean productivity levels, are poorly known. Direct sedimentation of phytodetritus is an important seasonal benthic energy source in shallow fjords but the supply of labile carbon to the deep basin benthos is typically small, even through the summer. Deep fjords appear to be primarily pelagic systems, although secondary and higher order mesopelagic production has been quantitatively studied in very few localities.