Valves are arcuate, symmetric about the trans-apical axis and asymmetric about the apical axis. Apices are capitate and deflexed to the ventral side. The capitate ends are recurved slightly toward the dorsal side. The dorsal margin is tumid at the valve center and the ventral margin has a distinct central inflation. Striae are alternate and parallel, occurring 16-18 in 10 µm throughout the valve. In some specimens, a hyaline area is present in the central inflation on the ventral side. A rimoportula is present at one of the valve apices, a feature visible only in SEM.
Hannaea superiorensis forms rosette colonies and grows in planktonic, epilithic and periphytic habitats throughout the upper Laurentian Great Lakes. It was described from Lake Superior, but occurs more rarely in northern Lake Michigan and Lake Huron (Bixby et al. 2005). This diatom is especially common in the wave zone along the Minnesota North Shore of Lake Superior. Although this species was originally thought to be endemic to the upper Laurentian Great Lakes, it has been reported from lakes of northern Ellesmere Island and Ellef Ringnes Island, Canada (Antoniades et al. 2008).
Cells attached at the end forming rosette colonies (Fig. 4). Chloroplast central, plate-like, along the dorsal side of frustule (Fig. 3). Nucleus central, ventrally located (Fig. 3). Lipid droplets one or more, positioned at distal ends of the chloroplast. Cingula open with valvocopula crenate on advalvar margin, with single row of punctae abvalvar to crenate margin. Valves arcuate with secondary reflexion towards dorsal margin, capitate ends, central unilateral inflation (Figs 3-9). Valves 111.8-170.2 µm length, 4.9- 7.8 µm breadth (at inflation), length/breadth ratio approximately 22:1, degree of curvature 0.0033-0.0065 µm-1. Raphe absent. Axial area narrow. Central inflation with occluded striae. Striae punctate and parallel, uniseriate on valve face and mantle, 10.3-15.1 in 10 µm (Figs 10-11). Spines between striae, occasional (Fig. 11). Valve apices with a single polar, sessile rimoportula per valve (Figs 9-10), with modified ocellulimbi on mantle of both valve apices (Fig. 10)
Burge, D., Edlund, M. (2017). Hannaea superiorensis. In Diatoms of North America. Retrieved April 26, 2024, from https://diatoms.org/species/hannaea_superiorensis
The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Hannaea superiorensis from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:
ELEVATION = stream reach elevation (meters)
STRAHLER = distribution plot of the Strahler Stream Order
SLOPE = stream reach gradient (degrees)
W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.
PHSTVL = pH measured in a sealed syringe sample (pH units)
log_COND = log concentration of specific conductivity (µS/cm)
log_PTL = log concentration of total phosphorus (µg/L)
log_NO3 = log concentration of nitrate (µeq/L)
log_DOC = log concentration of dissolved organic carbon (mg/L)
log_SIO2 = log concentration of silicon (mg/L)
log_NA = log concentration of sodium (µeq/L)
log_HCO3 = log concentration of the bicarbonate ion (µeq/L)
EMBED = percent of the stream substrate that is embedded by sand and fine sediment
log_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).
DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.
