The ecology of delta marshes The ecology of delta marshes of coastal Louisiana : a community profile ecologyofdeltama00goss Year: 1984 BIOLOGICAL PRODUCTIVITY AS A FUNCTION OF THE DELTA CYCLE SALINITY SUBAERIAL DEVELOPMENT LENGTH OF LAND - WATER INTERFACE BIOLOGICAL PRODUCTIVITY Maringouin /?\ ^ ^ . (3) St. Bernard (D Teche W Lafourche Plaquemines High (0 UJ z - 2 UJ = a ± o Low Marine ^XD> Subaqueous Growth NATURAL ENVIRONMENTS OPEN BAY SUBAQUEOUS LEVEES MUDFLATS FRESH MARSH BRACKISH MARSH SALINE MARSH SWAMP LAKES OYSTER REEFS MARGINAL BEACHES BARRIER ISLANDS Rapid Subaerial Growth Tim
The ecology of delta marshes The ecology of delta marshes of coastal Louisiana : a community profile ecologyofdeltama00goss Year: 1984 BIOLOGICAL PRODUCTIVITY AS A FUNCTION OF THE DELTA CYCLE SALINITY SUBAERIAL DEVELOPMENT LENGTH OF LAND - WATER INTERFACE BIOLOGICAL PRODUCTIVITY Maringouin /?\ ^ ^ . (3) St. Bernard (D Teche W Lafourche Plaquemines High (0 UJ z - 2 UJ = a ± o Low Marine ^XD> Subaqueous Growth NATURAL ENVIRONMENTS OPEN BAY SUBAQUEOUS LEVEES MUDFLATS FRESH MARSH BRACKISH MARSH SALINE MARSH SWAMP LAKES OYSTER REEFS MARGINAL BEACHES BARRIER ISLANDS Rapid Subaerial Growth Time Span Deterioration Figure 25. Environmental Van Beek 1975). succession of an idealized delta cycle (fiagliano and delta becomes saline and is modified by marine processes which typically rework the delta edge into a series of barrier reefs and islands that protect the inner estuary. Riverine hydraulic energy is much reduced and sediment loads decline. Further marsh development is increasingly controlled by the productivity of the vegetation, which forms peat. This is especially true at the landward edge of the basin. Here, too far from the coast to experience much tidal activity and with the river's sediment supply cut off, organic material produced in situ is the only material available for marsh accretion. Thus, as Figure 26 shows, fresh marshes start out as highly mineral, but as the delta lobe ages become increasingly organic. Salt marsh sediments, subject turbid tidal washes, are high in mineral content. to frequent, always fairly The general sequence is clear in the figure, but some exceptions deserve com- ment. Sediment mineral content decreases with distance from the river source (that is, from fresh toward salt marshes) in active deltas (units II and V) but de- creases with distance from the marine sediment source in the abandoned basins. This trend is consistent in all basins. However, compared to the low mineral contents in the recently abandoned basins III and IV
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