*Received: 22 December 2010; in revised form: 25 January 2011 / Accepted: 4 February 2011 / Published: 10 February 2011*

**Abstract:** The new pigment "moraxanthin" was found in natural samples from a fish mortality site in the Inland Bays of Delaware, USA. Pure cultures of the species, tentatively named *Chattonella cf. verruculosa*, and natural samples contained this pigment as a dominant carotenoid. The pigment, obtained from a 10 L culture of *C. cf. verruculosa*, was isolated and harvested by HPLC and its structure determined from MS and 1Dand 2D-NMR. The data identified this pigment as a new acylated form of vaucheriaxanthin called moraxanthin after the berry like algal cell. Its presence in pure cultures and in natural bloom samples indicates that moraxanthin is specific to *C. cf. verruculosa* and can be used as a marker of its presence when HPLC is used to analyze natural blooms samples. 

**Keywords:** *Chattonella cf. verruculosa*; Raphidophyceae; toxic algae; carotenoids; moraxanthin 
