The effect of a thermal effluent on the attached algae of the Provo River, Utah, USA, was studied from 1975 to 1977 . Data for macroscopic and microscopic algae were collected and analyzed . Diatoms, Cladophora glomerata, and Hydrurus foetidus dominated the flora . The thermal effluent significantly affected the algal flora in a section of river 100 to 135 meters long immediately below the discharge point . Cladophora growth was increased and Hydrurus was absent in this area. In addition, diatom production was often higher and diversity lower than in the rest of the river . Community structure was unique from all other adjacent areas . Small temperature increases which occurred as effluent and river waters mixed farther downstream were apparently not as important to the algal flora as other environmental factors .
Phytoplankton samples were collected from ice-covered Utah Lake during February and March, 1979 in order to characterize the winter algal flora. These samples were analyzed for presence and abundance of diatoms and non-diatom algae as well as selected water chemical parameters. A total of 159 diatom taxa and 20 non-diatoms was found in the water column under the ice. The flagellates Carteria stellifera, Euglena gracilis and Chlamydomonas globosa dominated the winter non-diatom flora while Stephanodiscus cf. dub&, Cyclotella meneghiniana, Navicula minima, Fragilaria construens var. venter, and Melosira granulata var. angustissima dominated the winter diatom flora. Species richness and abundance were elevated in the major bays of the lake.
The diatom flora in the lower Damour River, a small coastal river in Lebanon, was studied during 1981 . The study area included the Damour estuary and a tributary, the el-Hamam River . Achnanthes minutissima was the most abundant diatom in the flora . Other dominant taxa included Nitzschia dissipata and Navicula cryptocephala var. veneta in the spring and Anomoeoneis vitrea in the fall . The diatom community structure was characterized by 1 or 2 dominant taxa, a few common and many rare taxa, but the taxa in these categories varied according to season and locality. The freshwater flora had a group of 20 taxa which were widely distributed in the study area throughout the study period . These taxa, in addition to a few taxa of more restricted seasonal occurrence, were the major contributers to the flora and are characteristic of this river system . Certain aspects of the flora were resistant to change. Others were more sensitive to environmental conditions . The estuarine flora reflected brackish conditions beginning in June and extending through October .
Mt. St. Helens, a volcanic peak in the Cascade Range in southern Washington erupted violently on May 18, 1980, causing enormous damage to both terrestrial and aquatic ecosystems. The initial explosion evaporated, scoured or buried all springs and streams in the blast impact area. Ash fall and erosion from defoliated hillsides subsequently filled most of the lotic habitats with organic debris and volcanic ash. Recolonization of springs and streams by algae occurred quickly in areas where erosion through the ash progressed down to bedrock. Within 15 months or less of the eruption, algal communities were established throughout the blast impact area. However, as a result of the initial and continued disturbance these communities remained in an early successional stage. Floral assemblages were highly variable except that they were composed mostly of diatoms, with Achnanthes minutissima dominating most lotic sites. Springs showed the most rapid development toward stable floras.
Mt. St. Helens, a volcanic peak in the Cascade Range in southern Washington erupted violently on May 18, 1980, causing enormous damage to both terrestrial and aquatic ecosystems. The initial explosion evaporated, scoured or buried all springs and streams in the blast impact area. Ash fall and erosion from defoliated hillsides subsequently $filled most of the lotic habitats with organic debris and volcanic ash. Recolonization of springs and streams by algae occurred quickly in areas where erosion through the ash progressed down to bedrock. Within 15 months or less of the eruption, algal communities were established throughout the blast impact area. However, as a result of the initial and continued disturbance these communities remained in an early successional stage. Floral assemblages were highly variable except that they were composed mostly of diatoms, with Achnanthes minutissima dominating most lotic sites. Springs showed the most rapid development toward stable Joras.
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