Search

A spring-fed, headwater stream in central Rhode Island was examined during the period from June to October, 1979 to 1982. In the first two summers, a dense riparian canopy reduced the light penetration at the stream surface to a range of 5 to 18% of incident radiation. The lotic macroalgal community during this period was limited to 1 to 4 species covering A spring-fed, headwater stream in central Rhode Island was examined during the period from June to October, 1979 to 1982. In the first two summers, a dense riparian canopy reduced the light penetration at the stream surface to a range of 5 to 18% of incident radiation. The lotic macroalgal community during this period was limited to 1 to 4 species covering <1 to 35% of the stream bottom. However, in June and July, 1981, the surrounding leaf canopy was removed by a massive gypsy moth larval outbreak. Light penetration to the stream during this summer increased to 73% by early July, there by resulting in a rise in water temperatures by 3.7°C. Even though there was a partial regrowth of leaves in late July and August of 1981, macroalgal cover values continued to rise to an early august peak of 80%. During the third summer, 88% of the macroalgal abundance could be attributed to illumination and water temperature. The filamentous diatom Eunotia pectinalis (O.F. Müll) Rabh. Was the predominant species in the mid summer of all four years, accounting for at least 60% of the total cover. In 1981, an important taxon was the desmid Hyalotheca dissilines (S. Smith) Bre´b., a species which was not seen in other years. A less severe gypsy moth defoliation occurred in 1982 but did not produce significant differences in light, temperature or macroalgal cover from 1979 and 1980. [ABSTRACT FROM AUTHOR]

Focuses on the distribution, seasonality and reproductive phenology of Bangia atropurpurea in Rhode Island. Bangia populations in winter; Upper intertidal populations from September to May; Maximum diameter of asexual and carpogonial filaments; Correlation of monosporogenesis to temperature; Relationship of gametogenesis to photoperiod.

The diatom Eunotia pectinalis (O. F. Müll.) Rabh. exhibited considerable morphological variability in samples collected over a 13-month period from a software Rhode Island stream. All observed morphotypes were classified into three main complexes based upon their valve configuration. These grouping were confirmed by discriminant analysis using quantitative value characteristics and were named in accordance with their associated varieties: minor (Kü]tz.) Rabh., pectinalis and ventricosa Grun. Clonal cultures were subjected to a defined series of temperatures, agitation rates and light intensities in order to assess inherent morphological variability. Similar trends were evident for all complexes. Over time, valve length decreased, valve breadth enlarged, and striae number per 10 μm at valve center and apex increased. Morphological plasticity was evident in culture and appeared to be more a function of the clone genotype than the environmental conditions to which it was subjected. One clone originally identified as E. pectinalis var. minor assumed certain morphological features of E. vanheurckii Patr, after four months in culture. [ABSTRACT FROM AUTHOR]