scholarly journals Recent non-marine Ostracoda from Jamaica, West Indies

1997 ◽  
Vol 16 (2) ◽  
pp. 137-143 ◽  
Author(s):  
Jonathan A. Holmes
Keyword(s):  
Water Chemistry ◽  
Water Depth ◽  
West Indies ◽  
Lake Level ◽  
Aquatic Macrophyte ◽  
Late Quaternary ◽  
Habitat Characteristics ◽  
Clear Distinction ◽  
Large Fluctuations ◽  
Spatial Zonation

Abstract. Ostracods were sampled qualitatively at 22 sites from 15 waterbodies in the western part of Jamaica and determinations of the water chemistry and habitat characteristics were made at each locality. Most of the ostracods found belong to the Cypridinae, Cypridopsinae, Cyclocypridinae and Darwinulidae. There is a clear distinction between the faunas found in the larger, permanent lakes and the smaller ponds. The latter are subject to large fluctuations in volume and may desiccate either seasonally or interannually. Within the largest lake, Wallywash Great Pond, there is some degree of spatial zonation in the ostracod faunas that appears to be related to water depth and aquatic macrophyte occurrence. The distribution of modern ostracods within Wallywash Great Pond suggests that the late Quaternary faunal sequence from this lake is primarily a function of lake-level changes.

scholarly journals Late Quaternary tectonic activity and lake level change in the Rukwa Rift Basin

1998 ◽  
Vol 26 (3) ◽  
pp. 397-421 ◽  
Author(s):  
D. Delvaux ◽  
F. Kervyn ◽  
E. Vittori ◽  
R.S.A. Kajara ◽  
E. Kilembe
Keyword(s):  
Lake Level ◽  
Late Quaternary ◽  
Tectonic Activity ◽  
Rift Basin ◽  
Lake Level Change ◽  
Level Change

Late Pleistocene and Holocene Paleoenvironments of Chalco Lake, Central Mexico

1993 ◽  
Vol 40 (3) ◽  
pp. 332-342 ◽  
Author(s):  
Maria Socorro Lozano-Garcı́a ◽  
Beatriz Ortega-Guerrero ◽  
Margarita Caballero-Miranda ◽  
Jaime Urrutia-Fucugauchi
Keyword(s):  
Volcanic Activity ◽  
Lake Level ◽  
Environmental Changes ◽  
Late Quaternary ◽  
Cold Climate ◽  
Central Mexico ◽  
Pollen Record ◽  
Loss On Ignition ◽  
Southeastern Part ◽  
Saline Marsh

AbstractIn order to establish paleoenvironmental conditions during the late Quaternary, four cores from the Basin of Mexico (central Mexico) were drilled in Chalco Lake, located in the southeastern part of the basin. The upper 8 m of two parallel cores were studied, using paleomagnetic, loss-on-ignition, pollen, and diatom analyses. Based on 11 14C ages, the analyzed record spans the last 19,000 14C yr B.P. Volcanic activity has affected microfossil abundances, both directly and indirectly, resulting in absence or reduction of pollen and diatom assemblages. Important volcanic activity took place between 19,000 and 15,000 yr B.P. when the lake was a shallow alkaline marsh and an increase of grassland pollen suggests a dry, cold climate. During this interval, abrupt environmental changes with increasing moisture occurred. From 15,000 until 12,500 yr B.P. the lake level increased and the pollen indicates wetter conditions. The highest lake level is registered from 12,500 to ca. 9000 yr B.P. The end of the Pleistocene is characterized by an increase in humidity. From 9000 until ca. 3000 yr B.P. Chalco Lake was a saline marsh and the pollen record indicates warmer conditions. After 3000 yr B.P. the lake level increased and human disturbance dominates the lacustrine record.

Is it possible to predict habitat use by spawning salmonids? A test using California golden trout (Oncorhynchus mykiss aguabonita)

1999 ◽  
Vol 56 (9) ◽  
pp. 1576-1584 ◽  
Author(s):  
Roland A Knapp ◽  
Haiganoush K Preisler
Keyword(s):  
Oncorhynchus Mykiss ◽  
Water Depth ◽  
Parametric Model ◽  
Water Velocity ◽  
Habitat Characteristics ◽  
Nonparametric Model ◽  
Habitat Features ◽  
Substrate Size ◽  
Depth Water ◽  
Spawning Sites

It is widely believed that stream salmonids select spawning sites based on water depth, water velocity, and substrate size. Attempts to predict spawning locations using these habitat features have met with little success, however. In this study, we used nonparametric logistic regression to determine what habitat features were associated with the locations chosen by spawning California golden trout (Oncorhynchus mykiss aguabonita). From this nonparametric model, we developed a parametric model that incorporated the habitat features most strongly associated with spawning sites and used this model to calculate the probability of use by spawning golden trout for specific stream locations. The overall nonparametric model was highly significant and explained 62% of the variation in spawning location. Four of the eight habitat variables, substrate size, water depth, water velocity, and stream width, had highly significant effects and alone explained 59% of the variation in spawning location. The results of a cross-validation procedure indicated that the parametric model generally provided a good fit to the data. These results indicate that location-specific probabilities of use were predictable based on easily measured habitat characteristics and that nonparametric regression, an approach still rarely used in ecological studies, may have considerable utility in the development of fish-habitat models. Given the escalating pace at which fish habitats are being altered, such models are increasingly important in predicting the effects of these alterations on populations.

scholarly journals Die plantgemeenskappe van die Ba-landtipe in die Mooirivieropvanggebied, Transvaal

1991 ◽  
Vol 10 (2) ◽  
pp. 85-92 ◽  
Author(s):  
H. Bezuidenhout
Keyword(s):  
Nature Conservation ◽  
Plant Communities ◽  
Soil Type ◽  
Habitat Characteristics ◽  
Clear Distinction ◽  
Conservation Practices ◽  
Numerical Classification ◽  
Habitat Types ◽  
Land Type ◽  
Vegetation Gradients

The aim of this study was to identify, characterize and interpret ecologically, by using habitat characteristics, the major vege­tation units and their variations of the Ba land type. Six plant communities were successfully distinguished through applying a numerical classification (TWINSPAN) and Braun-Blanquet procedures. The plant communities could easily be correlated with specific habitat types. A clear distinction could be made between plant communities of the upland and lowland areas. Vegetation gradients and associated gradients in habitat were identified by using an ordination technique (DECORANA). The studv emphasized the importance of topography and soil type for the delimitation of management units for farming or nature conservation practices.

scholarly journals The Biodiversity–Biomass Relationship of Aquatic Macrophytes Is Regulated by Water Depth: A Case Study of a Shallow Mesotrophic Lake in China

2021 ◽  
Vol 9 ◽  
Author(s):  
Fei Ma ◽  
Lei Yang ◽  
Tian Lv ◽  
Zhenjun Zuo ◽  
Haocun Zhao ◽  
...  
Keyword(s):  
Water Depth ◽  
Aquatic Macrophyte ◽  
Interspecific Interactions ◽  
Species Identity ◽  
Community Biomass ◽  
Macrophyte Communities ◽  
Macrophyte Community ◽  
Evenness Indices ◽  
Aquatic Macrophyte Community ◽  
The Relationship

The relationship between biodiversity and productivity (or biomass production) (BPR) has been a popular topic in macroecology and debated for decades. However, this relationship is poorly understood in macrophyte communities, and the mechanism of the BPR pattern of the aquatic macrophyte community is not clear. We investigated 78 aquatic macrophyte communities in a shallow mesotrophic freshwater lake in the middle and lower reaches of the Yangtze River in China. We analyzed the relationship between biodiversity (species richness, diversity, and evenness indices) and community biomass, and the effects of water environments and interspecific interactions on biodiversity–biomass patterns. Unimodal patterns between community biomass and diversity indices instead of evenness indices are shown, and these indicate the importance of both the number and abundance of species when studying biodiversity–biomass patterns under mesotrophic conditions. These patterns were moderated by species identity biologically and water depth environmentally. However, water depth determined the distribution and growth of species with different life-forms as well as species identities through environmental filtering. These results demonstrate that water depth regulates the biodiversity–biomass pattern of the aquatic macrophyte community as a result of its effect on species identity and species distribution. Our study may provide useful information for conservation and restoration of macrophyte vegetation in shallow lakes through matching water depth and species or life-form combinations properly to reach high ecosystem functions and services.

scholarly journals Plantegroeiklassifikasie van die A-landtipe van die Mooirivier - opvanggebied, Transvaal

1991 ◽  
Vol 10 (1) ◽  
pp. 4-10
Author(s):  
H. Bezuidenhout
Keyword(s):  
Nature Conservation ◽  
Plant Communities ◽  
Soil Type ◽  
Habitat Characteristics ◽  
Clear Distinction ◽  
Conservation Practices ◽  
Numerical Classification ◽  
Habitat Types ◽  
Land Type ◽  
Vegetation Gradients

The aim of this study was to identify, characterize and interpret ecologically, by using habitat characteristics, the major vege­tation units and their variations of the A land type. Five plant communities were successfully distinguished by applying a numerical classification and Braun-Blanquet procedures. The plant communities could easily be correlated with specific habitat types. A clear distinction could be made between plant communities of the upland and lowland areas. Vegetation gradients and associated gradients in habitat were identified by using an ordination technique. The study emphasized the importance of topography and soil type for the delimitation of management units for farming or nature conservation practices.

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