An assessment of indices of nutrientsufficiency in symbiotic dinoflagellates

A variety of methods for assessing the nutrient status ofmarine plants have been applied to zooxanthellae fromcorals and sea anemones. Mitotic indices increase withnutrient supply, while chI a levels decrease. Elementalratios (C:N, C:P) increase· with N(P) limitation, as docellular inclusions associated with carbon storage(starch, lipids). Internal amino acid (IAA) pools, particularlythe relative amounts of basic amino acids, arereliable indicators of N-sufficiency in zooxanthellae.Basic IAA form a greater percentage of the pool in symbiontsfrom well-fed sea anemones. Ammonium enhancementof dark carbon fixation is greater in N-limited zooxanthellae,as does the uptake of dissolved inorganic nitrogen.Most of these techniques have been used in experimentalwork under laboratory conditions, and their applicationto field situations is needed.