At the individual, macroscopic level, increased leaf growth, production, shoot height, blade length and width, and biomass are the most commonly reported responses to increased nutrients (Orth, 1977; Bulthuis and Woelkerling, 1981; Perez et al., 1991; Tomasko and Lapointe, 1991; Murray et al., 1992; Agawin et al., 1996; Alcoverro et al., 1997; Udy and Dennison, 1997a; Terrados et al., 1999; Lee and Dunton, 2000). Another individual response is the change in the pattern of within-plant resource allocation. In effect, shoot: root ratio increases with fertility, both following nutrient gradients (Perez et al., 1994; Lee and Dunton, 2000) and in nutrient additions experiments (Powell et al., 1989; Short et al., 1990; Perez et al., 1991). This behavior implies that seagrasses allocate more biomass in leaf tissues under high-nutrient availability, but more below-ground biomass under low-nutrient conditions. Plants under sediment nutrient deficient conditions increase biomass allocation to below-ground tissues to expand surface area for nutrient uptake (Gleeson, 1993; Vogt et al., 1993), while they increase carbon allocation to the above-ground tissues as a result of nitrogen addition into sediment (Lee and Dunton, 1999a). Changes in seagrass biomass allocation thus reflect a kind of strategy: when nutrients are abundant, leaves seem to be the 'preferred' site for uptake; in contrast, when nutrients are scarce, root uptake is maximized.
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