نتایج جستجو برای: trophic structure

تعداد نتایج: 1579737  

2013
Jennifer Dannheim Thomas Brey Alexander Schröder Rainer Knust E. Arntz

a r t i c l e i n f o The trophic structure of the German Bight soft-bottom benthic community was evaluated for potential changes after cessation of bottom trawling. Species were collected with van-Veen grabs and beam trawls. Trophic position (i.e. nitrogen stable isotope ratios, δ 15 N) and energy flow (i.e. species metabolism approximated by body mass scaled abundance) of dominant species wer...

2012
Amy A. Briggs Hillary S. Young Douglas J. McCauley Stacie A. Hathaway Rodolfo Dirzo Robert N. Fisher

While it is well established that ecosystem subsidies--the addition of energy, nutrients, or materials across ecosystem boundaries--can affect consumer abundance, there is less information available on how subsidy levels may affect consumer diet, body condition, trophic position, and resource partitioning among consumer species. There is also little information on whether changes in vegetation ...

2012
Carla M. Guenther Hunter S. Lenihan Laura E. Grant David Lopez-Carr Daniel C. Reed

Fishing can trigger trophic cascades that alter community structure and dynamics and thus modify ecosystem attributes. We combined ecological data of sea urchin and macroalgal abundance with fishery data of spiny lobster (Panulirus interruptus) landings to evaluate whether: (1) patterns in the abundance and biomass among lobster (predator), sea urchins (grazer), and macroalgae (primary producer...

Journal: :Brazilian journal of biology = Revista brasleira de biologia 2011
J P A Pagotto E Goulart E F Oliveira C B Yamamura

The present study analysed the relationship between morphology and trophic structure of Siluriformes (Pisces, Osteichthyes) from the Caracu Stream (22º 45' S and 53º 15' W), a tributary of the Paraná River (Brazil). Sampling was carried out at three sites using electrofishing, and two species of Loricariidae and four of Heptapteridae were obtained. A cluster analysis revealed the presence of th...

2015
Jerome Fiechter

While specifically focusing on trophic interactions affecting habitat utilization and foraging patterns of California sea lions (CSL) in the California Current Large Marine Ecosystem (CCLME), the long-term goal of our modeling approach is to better understand and characterize biological “hotspots” (i.e., the aggregation of multiple marine organisms over multiple trophic levels) off the U.S. wes...

Journal: :international journal of environmental research 2014
f. abdolahpur monikh m. hosseini j. kazemzadeh khoei a.f. ghasemi

in this study, three stations of the north persian gulf were analyzed in order to determinethe effect of trophic levels on the concentration of harmful pahs in fish and sediment. in all cases,similar distributions were observed in which benzo(a)pyrene largely predominated andbenzo(b)fluoranthene and pyrene were the second major compounds in fish tissues. the predominantcomponents of pahs in sed...

Journal: :The Journal of animal ecology 2015
Guadalupe Peralta Carol M Frost Raphael K Didham Arvind Varsani Jason M Tylianakis

Incorporating the evolutionary history of species into community ecology enhances understanding of community composition, ecosystem functioning and responses to environmental changes. Phylogenetic history might partly explain the impact of fragmentation and land-use change on assemblages of interacting organisms and even determine potential cascading effects across trophic levels. However, it r...

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه بیرجند - دانشکده ادبیات و علوم انسانی 1392

in new management approaches, in the organizations with inflexible structure, existing of red tapes and interruptions caused by limitations and also non-compliance with environmental changes, create demotivation among staff. with regard to the influence of job motivational potential and its relationship to the type of organizational structure( enabling and dissuasive), the goal of this research...

2002
David B. Jepsen Kirk O. Winemiller

Fish assemblages in tropical river food webs are characterized by high taxonomic diversity, diverse foraging modes, omnivory, and an abundance of detritivores. Feeding links are complex and modified by hydrologic seasonality and system productivity. These properties make it difficult to generalize about feeding relationships and to identify dominant linkages of energy flow. We analyzed the stab...

Journal: :PLoS ONE 2007
Jarrett E. Byrnes Pamela L. Reynolds John J. Stachowicz

The biodiversity of ecosystems worldwide is changing because of species loss due to human-caused extinctions and species gain through intentional and accidental introductions. Here we show that the combined effect of these two processes is altering the trophic structure of food webs in coastal marine systems. This is because most extinctions ( approximately 70%) occur at high trophic levels (to...

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