On the relationship between the diversity and structure of benthic macroinvertebrate communities and sediment enrichment with heavy metals in Gabes Gulf, Tunisia

2014 ◽  
Vol 95 (2) ◽  
pp. 233-245 ◽  
Author(s):  
Lotfi Rabaoui ◽  
Radhouane El Zrelli ◽  
Mohammed Ben Mansour ◽  
Rafik Balti ◽  
Lamjed Mansour ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Benthic Communities ◽  
Central Area ◽  
Macroinvertebrate Communities ◽  
Benthic Assemblages ◽  
Gulf Of Gabes ◽  
Gulf Of Gabès ◽  
Composition And Structure ◽  
Ecological Quality Status ◽  
The Relationship

The variations in the composition and structure of macroinvertebrate benthic communities in relationship with the marine sediment enrichment with heavy metals were investigated in the Gulf of Gabes, Tunisia. Standard community parameters as well as the trophic and ecological structure were analysed in 18 stations sampled in six localities. Highest values of diversity descriptors (S, N and H′) were recorded in the less-polluted localities and vice versa. Besides, the results of AMBI and BENTIX indexes were also concordant with those obtained with the classical diversity parameters and matched with the sediment heavy metals distribution in the Gulf of Gabes. Compared with the northern and southern parts of the Gulf, the central area was found to be the most polluted and to host the most-affected benthic community. In addition, biotic indexes were found to be very useful tools to monitor the ecological quality status of benthic assemblages.

Impact of Heavy Metals on Insect Communities in Streams: A Comparison of Observational and Experimental Results

1988 ◽  
Vol 45 (11) ◽  
pp. 2017-2025 ◽  
Author(s):  
Williams H. Clements ◽  
Donald S. Cherry ◽  
John Cairns Jr.
Keyword(s):  
Heavy Metals ◽  
Benthic Communities ◽  
Macroinvertebrate Community ◽  
Experimental Results ◽  
Macroinvertebrate Communities ◽  
Insect Communities ◽  
Copper And Zinc ◽  
Stream Mesocosms ◽  
Clinch River ◽  
Number Of Individuals

This research compares effects of heavy metals on macroinvertebrate communities in outdoor experimental streams with those observed at impacted field sites. Natural assemblages of aquatic macroinvertebrates were established on substrate-filled trays which were then transferred to outdoor stream mesocosms. Exposure of these communities to low levels of copper and zinc (target concentration = 12 μg/L) significantly reduced the number of taxa, number of individuals, and abundance of most dominant taxa within 4 d. After 10 d, control streams were dominated by Ephemeroptera and Tanytarsini chironomids, whereas treated streams were dominated by Hydropsychidae and Orthocladiini. Responses of benthic communities to metals observed at the Clinch River (Russell Co., Virginia), a system impacted by copper and zinc, were similar to those in experimental streams. Ephemeroptera and Tanytarsini, which comprised 38–46% of the macroinvertebrate community at upstream reference stations, were significantly reduced at all effluent sites. As in treated experimental streams, impacted stations were dominated by Hydropsychidae and Orthocladiini. The similarity of our experimental results to those obtained from Clinch River field sites suggests that outdoor stream mesocosms may be employed to predict macroinvertebrate community responses to heavy metals.

scholarly journals Diversity of Oligotrichia and Choreotrichia Ciliates in Coastal Marine Sediments and in Overlying Plankton

2010 ◽  
Vol 76 (12) ◽  
pp. 3924-3935 ◽  
Author(s):  
Mary Doherty ◽  
Maiko Tamura ◽  
Jan A. C. Vriezen ◽  
George B. McManus ◽  
Laura A. Katz
Keyword(s):  
New England ◽  
Spatial Scale ◽  
Marine Sediments ◽  
Benthic Communities ◽  
Molecular Approach ◽  
Marine Ciliate ◽  
Benthic Assemblages ◽  
Marine Systems ◽  
Coastal Marine ◽  
The Relationship

ABSTRACT Elucidating the relationship between ciliate communities in the benthos and the plankton is critical to understanding ciliate diversity in marine systems. Although data for many lineages are sparse, at least some members of the dominant marine ciliate clades Oligotrichia and Choreotrichia can be found in both plankton and benthos, in the latter either as cysts or active forms. In this study, we developed a molecular approach to address the relationship between the diversity of ciliates in the plankton and those of the underlying benthos in the same locations. Samples from plankton and sediments were compared across three sites along the New England coast, and additional subsamples were analyzed to assess reproducibility of methods. We found that sediment and plankton subsamples differed in their robustness to repeated subsampling. Sediment subsamples (i.e., 1-g aliquots from a single ∼20-g sample) gave variable estimates of diversity, while plankton subsamples produced consistent results. These results indicate the need for additional study to determine the spatial scale over which diversity varies in marine sediments. Clustering of phylogenetic types indicates that benthic assemblages of oligotrichs and choreotrichs appear to be more like those from spatially remote benthic communities than the ciliate communities sampled in the water above them.

scholarly journals Foraminiferal-based biotic indices to assess the ecological quality status of the Gulf of Gabes (Tunisia): Present limitations and future perspectives

2020 ◽  
Vol 111 ◽  
pp. 105962 ◽  
Author(s):  
Akram El Kateb ◽  
Claudio Stalder ◽  
Michael Martínez-Colón ◽  
Guillem Mateu-Vicens ◽  
Fabio Francescangeli ◽  
...  
Keyword(s):  
Ecological Quality ◽  
Biotic Indices ◽  
Future Perspectives ◽  
Gulf Of Gabes ◽  
Gulf Of Gabès ◽  
Ecological Quality Status ◽  
Quality Status

Board of Director Characteristics, Institutional Ownership, and Fraud: Evidence from Australia

2004 ◽  
Vol 23 (2) ◽  
pp. 105-117 ◽  
Author(s):  
Vineeta D. Sharma
Keyword(s):  
Research Evidence ◽  
Institutional Ownership ◽  
Board Of Director ◽  
Composition And Structure ◽  
High Incidence ◽  
The Board Of Directors ◽  
Director Characteristics ◽  
The Relationship ◽  
The U.S

Due to the high incidence of fraud in Australia, regulatory reports suggest strengthening the monitoring role of the board of directors (BOD). These reports recommend greater independence and no duality (chairperson of the BOD should not be the CEO) on the BOD. While there is no Australian evidence, research evidence in the U.S. supports these suggested reforms. It is not clear whether the research evidence observed in the U.S. will generalize to the Australian setting because of contextual differences. This study extends the U.S. findings to the Australian context and investigates the relationship between two attributes of the BOD, independence and duality, and fraud. In addition, I examine whether institutional ownership plays a role in the context of fraud. The more highly concentrated institutional ownership in Australia suggests the presence of some relationship. Using a matched sample of fraud and no-fraud firms from 1988–2000, I find that as the percentage of independent directors and the percentage of independent institutional ownership increases, the likelihood of fraud decreases. As expected, the results show a positive relationship between duality and the likelihood of fraud. These results support the call for strengthening the composition and structure of the BOD in Australia.

Are circle hooks effective management measures in the pelagic longline fishery for sharks in the Gulf of Gabès?

2020 ◽  
Vol 30 (6) ◽  
pp. 1172-1181
Author(s):  
Bechir Saidi ◽  
Khaled Echwikhi ◽  
Samira Enajjar ◽  
Sami Karaa ◽  
Imed Jribi ◽  
...  
Keyword(s):  
Longline Fishery ◽  
Effective Management ◽  
Gulf Of Gabes ◽  
Gulf Of Gabès ◽  
Management Measures ◽  
Pelagic Longline Fishery ◽  
Pelagic Longline
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