Effects of ethyl 2-methyl acetoacetate (EMA) on the growth of Phaeodactylum tricornutum and Skeletonema costatum

Abstract

We investigated the effects of ethyl 2-methyl acetoacetate (EMA) on growth of the marine diatom algae Phaeodactylum tricornutum (P. tricornutum) and Skeletonema costatum (S. costatum). Growth of P. tricornutum was significantly inhibited by the minimum concentration (3.5 mmol·L −1) of EMA at lower initial algal densities (IADs) (3.6×104 and 3.3×105 cells·mL −1). However, at the highest IAD, significant growth inhibition was found at above 7 mmol·L −1 of EMA exposure. In S. costatum, EMA concentrations of 10.5 mmol·L −1 or more significantly inhibited growth at lower IAD (3×104 and 1.8×105 cells·mL −1); at the highest IAD, only EMA concentrations above 14 mmol·L −1 obviously inhibited the growth of S. costatum. Changes in specific growth rates and pigment were consistent with algal growth, but only at higher EMA concentrations or lower IAD values was the ratio of chlorophyll a (Chla) to carotenoid significantly lower than the control. Medium effective concentration (EC 50) values were in the order 4.07, 8.03 and 12.27 mmol·L −1 for P. tricornutum and 7.48, 11.92 and 17.22 mmol·L −1 for S. costatum. All these results show that the effect of EMA on the growth of algae was species specific and mainly depended on IAD, which might be an important factor to influence algal growth.