Table 1.

The morphological descriptions of A. catenella, A. fundyense, and A. tamarense provided by Balech (1995).

	Alexandrium catenella	Alexandrium fundyense	Alexandrium tamarense
Current authority	Alexandrium catenella (Whedon & Kofoid) Balech 1985: p. 34, figure 2	Alexandrium fundyense Balech 1985: p. 37, figure 18	Alexandrium tamarense (Lebour) Balech 1985, p. 37, figure 20
Cell Characteristics From Balech 1995	Cell small- to medium-sized, somewhat flattened anterior-posteriorly. Usually forms curved chairs. Epitheca has more or less noticeable shoulder and a rather upraised apical region. Cigulum is very excavated, descending (one, sometimes a little more). It generally has an overlapping membrane or curtain fin that extends from the projecting flange on the epitheca to the corresponding flange on the hypotheca. Sulcus is rather deep, abruptly widened on the posterior. The 1′ lacks a ventral pore and directly contacts the Po. It is asymmetrically rhomboidal. Usually, the anterior right margin is clearly concave. Plates 2′, 3′ and 4′ have raised flanges and support the Po. 2′ is the largest apical plate and usually connected with 3′ by sinuous margin that is mostly concave. 3′ is hexagonal and clearly asymmetrical with the anterior left side up to twice as long as the anterior right side. 4′ is relatively short and wide. 6″ is medium wide; its internal margin border with the S.a. and has a barely pronounced concavity. In the hypotheca, the 5‴ is wide and has a somewhat reinforced internal margin that is slightly S-shaped and supports a narrow list. 1″″ is rather narrow, long and very oblique. Its sulcal list is moderately wide, wider anteriorly than posteriorly. 2″″ is transversely elongated.	“By its shape and size, it cannot be distinguished from A. tamarense. Therefore, instead of providing a detailed description, I will note only its variations and differences from the last species.” (Balech et al. 1995). Most specimens that are not obviously collapsed are as wide or wider than they are long. The L/W ratio is almost always less than one. “The primary difference from A. tamarense is the lack of the ventral pore, which hardly seems enough to separate them as species. However, I believe that the proven consistency of this character justifies separation of A. fundyense from the Lebour species. Some other small differences occur, but they are not consistent.”	Cell small- to relatively large-sized and is somewhat isodiametric. In lateral view, the shape is irregularly pentagonal and convex. The cell frequently has one or two shoulders that may or may not be very noticeable. The hypotheca is regularly trapezoidal with convex and sometime irregular sides. A concavity may be located on the left side of the hypothecae; sometimes a protuberance is above it. The concavity is not deep, but is noticeable. The posterior margin is very often asymmetric, sloped forward and to the right. The descending cingulum is excavated and has a very narrow list. The sulcus is variably deep and has moderately developed lists. The Po is often very wide and markedly angular. The 1′ has a relatively variable width. Usually, the anterior angle and, especially, the posterior angle are rather extensively truncated. The anterior right margin is often rather concave. Sometimes, the margin is abruptly angled at the location of the ventral pore. The ventral pore is small and always exists. Both its position on the margin and the degree of its indentation on the plate may vary. 3′ is always clearly asymmetrical, but the degree of asymmetry varies. 1″″ is somewhat narrow. The most variable feature is the development of the left sulcal list which is rather wide in some cases and rather narrow in others. The right sulcal list, supported by the 5‴ plate, is usually barely conspicuous. 2″″ is variable. It is transversely extended in some thecae or dorsoventrally in others, with some in transition. This species is widely distributed and therefore its characteristics are more variable.
Cellular Dimensions From (Balech 1995)	Length 20–39.5 μm, but generally 24 to 34 μm; width 22–44 μm. The length/width (L/W) ratio varies, but the species is generally wider than long and the anterior-posterior flattening is often rather conspicuous. However, length can equal the width in some specimens. Some specimens can be difficult to distinguish from A. tamarense.	Length 39–50 μm, but generally 27 to 37 μm; Width not given only the L/W ratio of 0.87–1, but generally 0.93 to 0.98. Interestingly, the larger cells usually have a rather different shape. They are somewhat elongated and the L/W ratio in almost all of them is equal to or greater than one (generally 1.01 to 1.09) averaging approximately 1.04. Additionally, their hypothecae are more regularly convex.	Length 22–51 μm, but generally 28 to 35 μm; Width 22–44 μm, but usually between 35 and 44 μm. [Width] is almost equal to L, but may be a little larger or smaller.