scholarly journals Spatial and seasonal changes of brackish peracaridan assemblages and their relation to some environmental variables in two tidal channels of the Ria de Aveiro (NW Portugal)

1999 ◽  
Vol 190 ◽  
pp. 69-87 ◽  
Author(s):  
MR Cunha ◽  
JC Sorbe ◽  
MH Moreira
Keyword(s):  
Seasonal Changes ◽  
Environmental Variables ◽  
Tidal Channels ◽  
Ria De Aveiro ◽  
Nw Portugal

scholarly journals Slave to the Tides: Spatiotemporal Foraging Dynamics of Spring Staging Black Brant

The Condor ◽  
2006 ◽  
Vol 108 (3) ◽  
pp. 661-677 ◽  
Author(s):  
Jeffrey E. Moore ◽  
Jeffrey M. Black
Keyword(s):  
Seasonal Changes ◽  
Negative Binomial ◽  
Bird Species ◽  
Negative Binomial Regression ◽  
Nutrient Content ◽  
Latitudinal Gradients ◽  
Tidal Channels ◽  
Branta Bernicla ◽  
Black Brant ◽  
Site Use

AbstractArctic-nesting geese depend on nutrients acquired during spring migration for reproduction, and thus should attempt to maximize nutrient intake while on staging areas. We investigated site use of Black Brant (Branta bernicla nigricans) at an important staging location—Humboldt Bay, California—to determine whether birds selected the most profitable feeding areas available. Migrating Brant feed almost exclusively on eelgrass (Zostera marina), which is restricted in availability due to daily and seasonal tidal cycles. We mapped foraging Brant locations during low tides and collected eelgrass samples to describe food resources in 31 areas in the bay. We used negative binomial regression to evaluate goose densities during different tidal levels and times of season as a function of food biomass and nutrient content, distance from grit sites, and substrate elevation. Results varied by time of season and tidal depth, but Brant densities were positively correlated with eelgrass protein, calcium, and biomass in most analyses. Brant usually fed in the deepest possible areas permitted by tides, and closer to tidal channels, where biomass and nutrient content of eelgrass were greater and where depletion from grazing was probably less. During higher low tides, Brant fed closer to previously visited grit sites. Tide cycles change over the course of the Brant's staging period on the bay, enabling longer and more frequent access to deeper eelgrass meadows as spring progresses. These seasonal changes in tidal pattern coincide with seasonal changes in Brant use of the bay. Thus, migration patterns for estuarine bird species might be shaped by latitudinal gradients in both food phenology and seasonal tidal patterns.

Numerical Changes and Resource Utilization in Orchard Populations of Drosophila.

1985 ◽  
Vol 33 (6) ◽  
pp. 875 ◽  
Author(s):  
KM Nielsen ◽  
AA Hoffmann
Keyword(s):  
Resource Utilization ◽  
Endemic Species ◽  
Seasonal Changes ◽  
Environmental Variables ◽  
Laboratory Experiments ◽  
Climatic Variables ◽  
Partial Agreement ◽  
Larval Stages

Drosophila were collected monthly at a south-east Australian orchard site over 30 months. D, melanogaster was predominant in spring-summer, D. simulans in autumn, and D. immigrans in winter. These seasonal changes are consistent with trends described in an earlier study by McKenzie and Parsons (1974). Numbers of the endemic species D. lativittata tended to follow those of D. melanogaster. Comparisons of numbers of each species with environmental variables indicate that D. melanogaster is positively correlated, and D. immigrans negatively correlated, with temperature parameters. D. simulans and D. lativittata numbers were independent of all climatic variables tested. These associations are consistent with collections by McKenzie and Parsons (1974) from an orchard site, but not from their suburban sites. The associations of numbers of adults of each species with climatic variables are only in partial agreement with results from laboratory experiments on stress in adults. Sampling within the orchard indicates that D. melanogaster and D. simulans are differentially associated with fruit resources at both adult and larval stages, with D. melanogaster predominating on peach resources.

Relative influence of weather and season on anuran calling activity

2013 ◽  
Vol 91 (7) ◽  
pp. 462-467 ◽  
Author(s):  
David A. Steen ◽  
Christopher J.W. McClure ◽  
Sean P. Graham
Keyword(s):  
Seasonal Changes ◽  
Environmental Variables ◽  
Reproductive Activity ◽  
Environmental Variable ◽  
Relative Influence ◽  
Ephemeral Wetlands ◽  
Temperature And Precipitation ◽  
South Central ◽  
Multiple Hypotheses ◽  
Calling Activity

Drivers of anuran reproductive activity may include multiple and independent environmental variables. To determine the relative influence of season, temperature, and precipitation in initiating frog reproduction, we monitored a species-rich frog assemblage in south-central Alabama for 3 years and modeled calling activity of vocalizing males, who call to attract mates. We evaluated multiple hypotheses potentially explaining calling activity and we were able to identify significant influences of calling activity for all 11 anuran species considered in the analysis. Eight species were significantly influenced by month of survey and four of these were influenced by at least one additional environmental variable. In our study, precipitation was relatively unimportant in influencing calling activity, likely because breeding pools at the site are semipermanent and the species we sampled are not generally reliant on ephemeral wetlands. In general, our data suggest that different species within the same wetlands respond to different cues when initiating reproduction and calling activity is largely based on a combination of both environmental conditions and either seasonal changes or endogenous drivers.

Seasonal Changes in Epipelic Diatoms Along an Intertidal Shore, Berrow Flats, Somerset

1991 ◽  
Vol 71 (3) ◽  
pp. 579-596 ◽  
Author(s):  
Deborah R. Oppenheim
Keyword(s):  
Organic Matter ◽  
Salt Marsh ◽  
Water Content ◽  
Seasonal Changes ◽  
Environmental Variables ◽  
Interstitial Water ◽  
Seasonal Pattern ◽  
Environmental Variable ◽  
Assemblage Structure ◽  
Epipelic Diatoms

Seasonal changes in the assemblage structure of dominant epipelic diatoms were studied along a transect crossing a salt marsh, sandflat, and mudflat of an estuarine intertidal shore at Berrow Flats, Somerset, UK. Seasonal changes in cell numbers displayed different patterns in the salt marsh and sandflat/mudflat. At salt marsh sites highest numbers of individuals were recorded in summer followed by a smaller autumn growth, while in the sandflat lower numbers showed no seasonal pattern. Repeated annual patterns in the succession of taxa were not observed as environmental conditions changed at the study site with time. Measurements of salinity, pH, interstitial water content, air and soil temperature were taken together with the diatom samples. A canonical correspondence analysis was employed to relate seasonal changes in assemblage structure to measured environmental variables. Total percentage variation in the first four axes of the species/site-environmental biplots ranged between 54 and 66°. In winter, sites and species separated most significantly along gradients of salinity and levels of organic matter. In spring and autumn, interstitial water content became a more significant environmental variable. By summer steep gradients in pH, levels of organic matter, and hypersaline conditions separated sites and assemblages into more discrete groups when compared to the more even spread of points in the other seasons. The results indicate that different combinations of environmental variables influence diatom assemblage structure seasonally.

Chemical and Biological Characterization of Estrogenicity in Effluents from WWTPs in Ria de Aveiro (NW Portugal)

2009 ◽  
Vol 58 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Ana Sousa ◽  
René Schönenberger ◽  
Niels Jonkers ◽  
Marc J.-F. Suter ◽  
Shinsuke Tanabe ◽  
...  
Keyword(s):  
Biological Characterization ◽  
Ria De Aveiro ◽  
Nw Portugal
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