The distribution, morphology, and ecology of a non-native species, Thalassiosira lacustris (Bacillariophyceae), from benthic stream habitats in North America
Smucker, Nathan J.; Edlund, Mark B.; Vis, Morgan L.
Thalassiosira lacustris (Grunow) Hasle is reported for the first time from tributary streams of the Ohio River in southeastern Ohio, USA. Thalassiosira lacustris is more commonly reported from the plankton of northern continental shelf regions, coastal estuaries, and large brackish rivers, not the benthos of smaller inland streams as in our study. We document the distribution, morphology, ecology, and environmental preferences of T. lacustris in southeast Ohio streams. Cells attained maximum diameters of 57 μm in moderately high conductivity water (1550 μS cm−1), but in low conductivity water (507 μS cm−1) specimens only reached 34 μm in diameter. Specimens from highly conductive water were found in greater abundances and had more valve face fultoportulae than specimens of the same diameter from low conductivity waters, which may be a physiological response to increasingly brackish environments. Morphological variations of fultoportulae and rimoportulae were also observed. Measurements of morphological characters were similar to recent reports of a diminutive Thalassiosira allied with T. lacustris from northeastern Ohio, but not in all cases. The extent of its North American range, habitat, and environmental preferences are documented. The spread of T. lacustris in southeastern Ohio most likely coincides with the Mississippi-Ohio River drainage basin, and establishment of abundant large-celled populations is associated with moderately conductive waters.