Species of Staurastrum from Bryant Bog.

Abstract

Bogs of the Great Lakes are usually small in area and rarely exceed one mile in diameter. Often these bogs, like Bryant Bog, are only of the magnitude of ponds. Water within the bog is relatively calm and fluctuates seasonally in temperature. Bog mats are usually thick, firm and compact. Sphagnum mats are typically found in bogs and have great water retention capabilities. The 'false bottom', another feature of bogs, consists of plant material suspended in the water giving the bog the appearance of a continuous bottom. Water above the false bottom is usually well-illuminated (10). Typically bogs are poor in nutrients and derive their minerals solely from the atmosphere and are acidic habitats with a pH around 4.0 (1). Bogs offer a diverse array of organisms often differing greatly from lakes, streams, fens, and other freshwater aquatic habitats. The phytoplankton and sphagnum mats are especially abundant in desmids. George Nichols contends that bogs possess by far the richest desmid flora of any habitat--richest in both total number of species and in number restricted to a particular type of habitat.(4). One particular species of desmid, Staurastrum, is particularly abundant in the plankton and Sphagnum mat of bogs of the Cheboygan area. Staurastrum, a member of the Order Zygnematales and Family Desmidiaceae, shares common characteristics with desmids. These include division of the cell in to two semicells united at an isthmus, which varies in width. Semicells are usually symmetrical and drawn out into processes, or arms (3). Staurastrum species typically vary greatly in shape, size and ornamentation(6). Species share characteristics of being solitary organisms, generally longer than broad, radially symmetrical, and variable in constriction of the median. Semicells are usually oval-, elliptical-, or triangular-shaped. Almost all species are deeply constricted in the middle of the cell (8). Some species have smooth cell walls, while others are granulate, and still others are covered with spines. Chloroplasts are usually axial, one in each semicell, with usually a single pyrenoid in each. Three or four arm-like, long projections extending from each semicell generally distinguish Staurastrum from other desmids. In order to gain an understanding of the variety of Staurastrum species that can be obtained within a freshwater habitat, I conducted a survey of the Staurastrum of Bryant Bog.