Fig. 4. Effect of nutrient addition to the bioluminescent ratio (BLR) ratio of estuarine bacterial communities. Effect of (A) nitrate (•) and urea (), (B) glucose, and (C) a 5:1 mixture of peptone and yeast extract. Error bars represent one standard deviation of the mean. No difference between any of the treatments was statistically significant: nitrate (p = 0.57); urea (p = 0.55); glucose (p = 0.62); peptone and yeast extract (p = 0.9).