4.2. Variability in kelp physiological condition
The dynamic environment of the California coast leads to changes in the physiological state of the giant kelp canopy throughout the year. Elemental analysis of kelp blades in the SBC shows that blade organic nitrogen follows a similar pattern as available nitrate in the water column, while blade carbon remains relatively constant through the year (Brzezinski et al., 2013). This leads to elevated C:N during the summer and fall, when many kelp fronds lack active growing tips, blades become lighter in color, and photosynthetic rates decline (Clendenning, 1971). Increased ambient NO3 concentrations and decreased PAR flux are known to positively influence the concentrations of photosynthetic pigments in giant kelp (e.g., Shivji, 1985). The nitrogen and pigment status of the giant kelp canopy changes seasonally and may be subject to the fluctuations in nutrient delivery to the inner shelf, thus it is critical to measure these indicators of physiological state at timescales relevant to the dynamics of the local environment. Measurements of kelp pigments and nutrient status at a few sites are not sufficient to explain these patterns on the scales of environmental variability affecting giant kelp populations.
4.2. Variability in kelp physiological conditionThe dynamic environment of the California coast leads to changes in the physiological state of the giant kelp canopy throughout the year. Elemental analysis of kelp blades in the SBC shows that blade organic nitrogen follows a similar pattern as available nitrate in the water column, while blade carbon remains relatively constant through the year (Brzezinski et al., 2013). This leads to elevated C:N during the summer and fall, when many kelp fronds lack active growing tips, blades become lighter in color, and photosynthetic rates decline (Clendenning, 1971). Increased ambient NO3 concentrations and decreased PAR flux are known to positively influence the concentrations of photosynthetic pigments in giant kelp (e.g., Shivji, 1985). The nitrogen and pigment status of the giant kelp canopy changes seasonally and may be subject to the fluctuations in nutrient delivery to the inner shelf, thus it is critical to measure these indicators of physiological state at timescales relevant to the dynamics of the local environment. Measurements of kelp pigments and nutrient status at a few sites are not sufficient to explain these patterns on the scales of environmental variability affecting giant kelp populations.
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