A comparison of natural and human determinants of phytoplankton communities in the Kentucky River basin,USA

Physical, chemical, and biological characteristics of the Kentucky River and its tributaries were assessed for one year to compare effects of seasonal, spatial, and human environmental factors on phytoplankton. Phytoplankton cell densities were highest in the fall and summer and lowest in the winter. Cell densities averaged 1162 (± 289 SE) cells m1^–1. Cell densities were positively correlated to water temperature and negatively correlated to dissolved oxygen concentration and to factors associated with high-flow conditions (such as, suspended sediment concentrations). Chrysophytes, diatoms, and blue-green algae dominated winter, spring, and summer assemblages, respectively. Ordination analyses (DCCA) indicated that variation in taxonomic composition of assemblages was associated with stream size as well as season.Spatial variation in phytoplankton assemblages and effects of humans was investigated by sampling 55 sites in low flow conditions during August. Phytoplankton density increased with stream size. Assemblages shifted in composition from those dominated by benthic diatoms upstream to downstream communities dominated by blue-green algae and small flagellates. Human impacts were assumed to cause higher algal densities in stream basins with high proportions of agricultural or urban land use than in basins with forested/mined land use. While density and composition of phytoplankton were positively correlated to agricultural land use, they were poorly correlated to nutrient concentrations. Phytoplankton diversity changed with water quality: decreasing with nutrient enrichment and increasing with conditions that probably changed species composition or inhibited algal growth. Human impacts on phytoplankton in running water ecosystems were as great or greater than effects by natural seasonal and spatial factors. Our results indicated that phytoplankton could be useful indicators of water quality and ecosystem integrity in large river systems.     

River/land ecotones: scales and patterns

On a continental scale a river system itself is an ecotone, mediating between the terrestrial system and the sea. On the landscape scale, ecotones appear between terrestrial and river systems. At decreasing scales, the number and diversity of ecotones increases. Ecotone processes are discussed in relation to the entire river ecosystem, on scales ranging from the activity range of fish fry up to that of adult fish.The introduction of patch theory into the River Continuum Concept (RCC) allows for the proper consideration of hydraulics and time. The relationships between stream order and patch distribution, patch size and lifetime and age diversity of patches are described. This combination model is much better adjusted to the situations occurring in nature than the original, very abstract RCC-model.Dedicated to Professor Franz Berger on the occasion of his 90th birthday     

The effects of recreated instream and ecotone structures on the fish fauna of an epipotamal river

Investigations of fifteen sections of seven Austrian epipotamal (barbel region) streams between 1981 and 1984 demonstrate the impact of instream river bed structures on fish communities. Reduced spatial heterogeneity due to river straightening resulted in decreasing species number, diversity, stock density and biomass. Reincreased variability of the river bed in the frame of a subsequent restructuring project improved all community-specific values significantly within a 3-year investigation period (1988–1990). Besides the regained habitat variability in form of riffle pool sequences and other instream structures, the newly created riparian zones obviously provided important niches, e.g. as refuge areas during flooding and as nursery grounds for fish fry. The positive effects of the recreated land/water ecotone are discussed with respect to river restoration projects.     

Culturing the fairy shrimp Streptocephalus dichotomus Baird using livestock waste – a reclamation study

The present study describes a defined culturetechnique for the fairy shrimp, Streptocephalusdichotomus. It emphasizes reclamation of low-cost organiclive-stock waste(cow-dung), lime powder, and urea. These compounds wereused to enrich algal and diatom populations in themedium. These algae and diatoms were fed to filter feedingfairy shrimps to yield anostracanbiomass. A production of 262 ± 6 animals l^–1was obtained in an experimental tank compared to 36 ± 4animals l^–1 in the controls. Interestingly,the total number of clutches in experimentalfemales (12 ± 2), relative to the control (7 ± 1),increased too.     

Ecological degradation and agricultural intensification in the Andean highlands

Andean cultural ecologists have made two claims in recent years: ecological decomposition is absent due to effective indigenous management of communal resources, and agricultural intensification is inversely related to altitude. Drawing on material from the Jukumani Indians of Northern Potosi, Bolivia, these assertions are challenged. First, there is little evidence to prove or disprove ecological degradation. Second, the location of agricultural intensification, as the Jukumani data suggests, is influenced by altitude as well as by the presence of market.Fieldwork in Bolivia was carried out between January 1979 and May 1981. This essay was originally presented at a conference entitled, How Communities Resolve Common Property Problems, sponsored by the Harvard Institute for International Development and the Center for Population Studies of Harvard University in the spring semester of 1983.     

Molecules,fossils, and the origin of tetrapods

Summary Since the discovery of the coelacanth, Latimeria chalumnae, more than 50 years ago, paleontologists and comparative morphologists have debated whether coelacanths or lungfishes, two groups of lobe-finned fishes, are the closest living relatives of land vertebrates (Tetrapoda). Previously, Meyer and Wilson (1990) determined partial DNA sequences from two conservative mitochondrial genes and found support for a close relationship of lungfishes to tetrapods. We present additional DNA sequences from the 12S rRNA mitochondria gene for three species of the two lineages of lungfishes that were not represented in the first study: Protopterus annectens and Protopterus aethiopicus from Africa and Neoceratodus forsteri (kindly provided by B. Hedges and L. Maxson) from Australia. This extended data set tends to group the two lepidosirenid lungfish lineages (Lepidosiren and Protopterus) with Neoceratodus as their sister group. All lungfishes seem to be more closely related to tetrapods than the coelacanth is. This result appears to rule out the possibility that the coelacanth lineage gave rise to land vertebrates. The common ancestor of lungfishes and tetrapods might have possessed multiple morphological traits that are shared by lungfishes and tetrapods [Meyer and Wilson (1990) listed 14 such traits]. Those traits that seem to link Latimeria and tetrapods are arguably due to convergent evolution or reversals and not to common descent. In this way, the molecular tree facilitates an evolutionary interpretation of the morphological differences among the living forms. We recommended that the extinct groups of lobe-finned fishes be placed onto the molecular tree that has lungfishes and not the coelacanth more closely related to tetrapods. The placement of fossils would help to further interpret the sequence of morphological events and innovations associated with the origin of tetrapods but appears to be problematic because the quality of fossils is not always high enough, and differences among paleontologists in the interpretation of the fossils have stood in the way of a consensus opinion for the branching order among lobefinned fishes. Marshall and Schultze (1992) criticized the morphological analysis presented by Meyer and Wilson (1990) and suggest that 13 of the 14 morphological traits that support the sister group relationship of lungfishes and tetrapods are not shared derived characters. Here we present further alternative viewpoints to the ones of Marshall and Schultze (1992) from the paleontological literature. We argue that all available information (paleontological, neontological, and molecular data) and rigorous cladistic methodology should be used when relating fossils and extant taxa in a phylogenetic framework. Offprint requests to: Axel Meyer     

Correlation of rotifer associations in a chain of lakes fed by reclaimed sewage

The quantitative composition of the rotifer fauna of seven interconnected lakes located in southern California was studied in a preliminary investigation. The lakes are fed by reclaimed sewage, and the water quality increases rapidly from the first lake, barely able to support life, to a series of lovely lakes stocked with fish and utilized for recreation. The Shannon index of rotifer population diversity showed an appropriate increase. Up to 24 – 28 different rotifer taxa in each lake provided a rich community dominated by Brachionids, Keratella and Trichocerca. The diversity and quantity of the rotifer association then declined again in the last lake. Comparison of the lakes using the Bray and Curtis index of similarity and cluster analysis supported the picture of a lake-chain evolution, a biotic development showing a maximum curve.     

Shell-banding polymorphism of the land snail Xeropicta vestalis along the coastal plain of Israel

Along the coastal plain of Israel, shell darkness of the polymorphic land snail Xeropicta vestalis is positively related to the extent of perennial vegetation. It is not related to rain, temperature, geographic position or darkness of the ground.
White shells reflect more radiation than dark ones do, and therefore in Israel's coastal plain, where solar radiation is very strong, they are favoured. Perennial vegetation, where it occurs, shields the snails from the sun by absorbing radiation, so that snails amongst them can afford to be darker, and thus more cryptic. Hence, the more perennial vegetation in the habitat, the darker the shells.
Also during the Pleistocene, when temperatures were 5–10°C lower than today, the shells of the coastal plain were as pale as recent ones are. The distribution of a snail-predator, Gerbillus allenbyi , which is restricted to sandy biotopes where perennial bushes occur, and which was absent from Israel during the Pleistocene, could perhaps explain the distribution of X. vestalis morphs, both today and in the past.     

A phylogenetic analysis of the land plants

Phylogenetic systematics (cladistics) is a theory of phylogeny reconstruction and classification widely used in zoology. Taxa are grouped hierarchically by the sharing of derived (advanced) characters. The information is expressed in a cladogram, a best estimate of a phylogeny. Plant systematists generally use a phenetic system, grouping taxa on overall similarity which results in many groups being formed, at least in part, on the basis of shared primitive characters.
The methods of phylogenetic systematics are used to create a preliminary cladogram of land plants. The current classification of land plants is criticized for its inclusion of many groups which are not monophyletic.
Objections to the use of phylogenetic systematics in botany, apparent convergences within major groups and frequent hybridization, are shown to be invalid. It is concluded that cladistic analysis presents the best estimate of die natural hierarchy of organisms, and should be adopted by plant systematists in their assessment of plant interrelationships.