Benthic Algal Communities Research Articles

A Direct Method of Measuring Benthic Primary Production in Streams1

This paper describes a method of direct measurement of the primary production of the benthic algal community in the lotic environment that eliminates calculations of diffusion and is adaptable to the various chemical analyses used to indicate rates of production.

Accumulation of dieldrin by benthic algae in laboratory streams

The accumulation of dieldrin by benthic algal communities was studied in laboratory streams. Dieldrin concentrations ranging from 0.05 to 7.0 ppb were maintained in the water of laboratory streams for periods of two to four months. Analyses of algal samples by gas chromatography showed dieldrin concentrations ranging from 0.1 to 200 ppm. These results indicated that increases in concentration up to 30,000 times that of the water had occurred. Quantitative evaluation of species composition revealed that communities dominated by filamentous algae accumulated greater amounts of the insecticide than those in which unicellular diatoms were prevalent.

Structural Characteristics of Benthic Algal Communities in Laboratory Streams

Effects of light intensity and current velocity on the species composition and ecological properties of communities of benthic algae were investigated in laboratory streams. Of the 15 diatom taxa studied, only Melosira varians, Meridion circulare, and Navicula radiosa were more abundant in streams receiving 700 ft—c of illumination than in those receiving 150 ft—c. Achnanthes exigua, A. minutissima, Meridion circulare, Rhoicosphenia curvata, and Navicula radiosa were indifferent to current velocity, while current velocity had a positive effect on the abundance of Nitzschia linearis, Achnanthes lanceolata, Navicula cryptocephala, N. minima, N. seminulum, Synedra ulna, Gomphonema parvulum, G. angustatum, Cocconeis placentula, and the lanceolate Nitzschia. Melosira varians exhibited a negative response to current and was more abundant in standing water. Of the six taxa other than diatoms, Anabaena variabilis and Tribonema minor were more abundant in streams at the higher light intensity, but only one species, Phormidium retzii, was more abundant in streams with a current than in standing water. At a particular season, light intensity, and current velocity, conditions in a laboratory stream allow the establishment of an algal community with a more or less unique species composition and a characteristic biomass, pigment concentration, and increment of export. In order to understand the factors which influence productivity in these communities, it is necessary to have some knowledge of the autecologies of the community constituents and the mechanisms which regulate species composition and diversity of the flora.

An Investigation of Two Benthic Algal Communities in Malham Tarn, Yorkshire

An Investigation of Two Benthic Algal Communities in Malham Tarn, Yorkshire