Algal beds, coral reefs and estuaries

More recently attention has been focussed on the production of biomass in coastal areas with their algal beds, reefs and estuaries. These ecosystems cover only 0.6% of the world s sea area, but they produce 7% of the marine 

The causes of the high productivity of coral-reef communities are still not clear. Concentrations of nitrogen and phosphorus in waters flowing over reefs are relatively low, but nevertheless there is a constant supply of nutrients. Lewis (1977) found some evidence to suggest that both these nutrients are recycled rapidly on the reef and that nitrogen is fixed by bacteria and primary producers. 

A crude estimate of the area of the world s estuaries indicates a total area of about 1.7 X 10 km of which 3.8 X 10 km is marsh and mangrove, and 1.4 X 10 km is open water, including such areas as Chesapeake Bay (U.S.A.), St. Lawrence Gulf (Canada) and the Baltic Sea (Europe). Despite the numerous research efforts in recent decades, an evaluation of all relationships between net primary production, gross production and various aspects 

Woodwell et al. (1973) summarised primary productivity data from a number of relevant papers and arrived at the following survey submei ed angiosperms in estuaries produce 880 to 1600 g C m yr , epiphytic and benthic algae have a production of 28 to 314 g C m yr (ratio dry weight to C is 2.5). 

The soft bottom ecosystem of the Northern Baltic proper with special reference to the macrofauna. Contrib. Asko Lab. 19 1—62. 

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