Productivity and nutrient limitation
Hillman, K., Walker, D.I., Larkum, A.W.D. and McComb, A.J. (1989) Productivity and nutrient limitation. In: Larkum, A.W.D., McComb, A.J. and Shephard, S.A., (eds.) Biology of seagrasses : a treatise on the biology of seagrasses with special reference to the Australian region. Elsevier Science Pub., Amsterdam, The Netherlands, pp. 635-685.
Research in the last decade has firmly established the importance of seagrass meadows to shallow coastal and estuarine ecosystems (Kemp, 1983 and references cited therein). Early studies (Westlake, 1963; McRoy and McMillan, 1977; Zieman and Wetzel, 1980) suggested that some seagrasses had primary productivities comparable with those of terrestrial crops, though more recent estimates (Larkum and West, 1983) set a more realistic upper limit while still acknowledging that seagrasses are amongst the most productive of submerged aquatic ecosystems. A number of authors (Wood et al., 1969; Thayer et al., 1975; den Hartog, 1977 ;Kemp, 1983) have outlined ways in which seagrass meadows function to maintain the productivity of coastal waters and estuaries and stabilize sediments, but the cornerstone of all these functions is the high productivity of the seagrasses themselves.
The high productivity of seagrasses implies a high nutrient demand, and some seagrass meadows may be nutrient limited, principally by the macronutrients nitrogen or phosphorus (Orth, 1977; Bulthuis and Woelkerling, 1981; Harlin and Thorne-Miller, 1981; Short et al., 1985). Seagrasses can tap both sediment and water column nutrients (McRoy and McMillan, 1977; lizumi and Hattori, 1982; Thursby and Harlin, 1982; Brix and Lyngby, 1985), and efficient uptake and utilization of essential nutrients, dynamic cycling and/or well developed nitrogen fixation must be important attributes of seagrass meadows (see Chapter 15).
The following account reviews Australian research on the primary production of seagrasses and nutrient limitation. Elsewhere, the majority of such research has involved the two species Thalassia testudinum and Zostera marina, neither of which occur in Australian waters. The results reviewed here therefore broaden the data base, to allow more meaningful generalizations and predictions about seagrass productivity in different ecosystems. The term 'primary production' is defined as in Larkum (1981) and is used where actual measurements on specific seagrasses are referred to. The term 'primary productivity' is used in the more general context, as when comparing different genera of seagrasses.
|Publication Type:||Book Chapter|
|Murdoch Affiliation:||School of Biological and Environmental Sciences|
|Publisher:||Elsevier Science Pub.|
|Copyright:||© Elsevier Science Publishers B.V. 1989|
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