In situ experimental evidence of nutrient limitation of seagrasses in Cape Bolinao, NW Philippines
1995
Agawin, N.S.R.
Nutrient limitation of Enhalus acoroides, Thalassia hemprichii and Cymodeocea rotundata at two mixed seagrass beds (Silaqui and Lucero) in Cape Bolinao, NW Philippines was investigated through 4-5 months in situ sediment fertilizations. Leaf growth of T. hemprichii and E. acoroides increased significantly following fertilization by 40-100 percent and 160 percent, respectively. Leaf biomass also increased significantly by 60 percent to as much as 240 percent following nutrient additions. These results demonstrated nutrient limitations of seagrass growth at the two sites in Cape Bolinao. The increased growth and biomass with fertilization was supported by enhanced photosynthetic activity, consequently by higher chlorophyll and nutrient concentrations in the photosynthetic tissues. The extent of responses differed between sites and among species. Results indicate that plants in Lucero were mostly phosphorus deficient relative to those at Silaqui. This was consistent with the higher ambient nutrient concentration in the pore water and sediment nutrient and organic matter content in Silaqui. This differences between sites emphasizes the importance of local differences in the factors controlling nutrient losses and gains in seagrass meadows. Results also indicate that the nature and extent of nutrient deficiency varied greatly among co-occurring species. Both E. acoroides and T. hemprichii were shown to be N and P deficient, but deficiency was greater for E. acoroides than T. hemprichii. Moreover, phosphorus appeared to be the primary limiting nutrient for T. hemprichii and nitrogen for E. acoroides. These results also emphasize the importance of identifying the species-specific traits that generate the interspecific plasticity of nutrient status
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