Saint-Paul, Ulrich
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Saint-Paul, Ulrich
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Saint-Paul, Ulrich
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Saint-Paul, U.
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Item-typ:Veröffentlichung, Ecology and culture of giant clams (Tridacnidae) in the Jordanian sector of the Gulf of Aqaba, Red Sea(2005-08-29); ; This thesis is on the ecology and culture of giant clams in the northern Gulf of Aqaba. Giant clams are scarce (0.3 - 0.5 ind. per 100 m-2) in Jordan, decreasing12-fold over three decades. Two-third higher abundances in restricted (1.04 0.4 ind. 100 m-2), suggest a decline caused by overfishing and habitat loss related to urban development over four decades. In the wider Red Sea, the impact of human activities are also evident. There is a distinct reproductive seasonality of giant clams in Jordan with species-specific spawnings: T. squamosa has an extended bi-modal spawning (June-Nov.) and T. maxima a shorter unimodal spawning (Jun-Sep). Regression of the ovarian follicles is protracted over winter and maturation commenced in late winter, culminating in spring. Likewise, the landbased culture showed reproductive success in summer (Jun-Sep), with protracted larval development and mortality in winter. Modifications done on existing culture techniques for the Red Sea conditions have been successful. Molecular mitochondrial rDNA analysis, morphological taxonomic classification, and, reproductive periodicity provided for the existence of a new species of giant clam in the northern Red Sea. The molecular analysis and amended taxonomic classification are consistent in placing Tridacna nov. sp. in the subgenus Chametrachea. This is strongly supported by the similar morphological and behavioural characteristics of Tridacna nov. sp with the two members of the subgenus, T. maxima and T. squamosa, the only two extant species in the Red Sea. Furthermore, Tridacna nov. sp showed species-specific reproductive seasonality with a shorter summer spawning (May-July), smaller ova diameter (75 2 µm) and earlier ovarian maturation (Aug.) compared to the other two species.Dissertation485 543 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Foraging ecology and habitat use of wading birds and shorebirds in the mangrove ecosystem of the Caeté Bay, Northeast Pará, Brazil(2004-07-27); ; ; Only little is known of migratory shorebirds in the tropics. The objective of this thesis was to describe the environment, the food availability, the bird community, the relationship between birds and environment and the avian consumption at tropical tidal flats. The study was conducted at tidal flats in the Northeast of Brazil.The study area comprised a low content of organic material and high fluctuations of sediment conditions and salinity. The benthic diversity, abundance and biomass was very low and variable compared to other tropical areas.Over 90% of the observed birds were migratory shorebirds, most residential birds were wading birds. Their spatial distribution could not be linked to environmental variables, however, birds had preferences for some sites and microhabitats.The harvestable fraction of the prey, the items accessible and ingestible, was very low, especially for small birds relying on small prey. The avian diets included a large variety of prey items and the attempt to find a relationship between the spatial distribution of the birds and their prey failed, presumably due to the resulting complex relationship.The avian community was split into residential wading birds and predominantly migratory shorebirds. Also, less distinct niches appeared within the shorebird community, however, most birds occupied broad niches. Birds not able to forage on large prey items had to feed opportunistically, a restriction on few prey items probably would have led to food shortages.Most species did not spend the entire ebb tide at the study area, but probably used also other, more profitable areas to obtain food. This might be crucial, since some birds cannot gain enough energy with the observed intake rates. Also, the food stock would have been depleted in a few weeks, if the birds would have foraged exclusively in the study area. However, an exclosure experiment did not show an impact, another indicator that the birds might forage elsewhere.Dissertation580 243 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Nutritional state and organic matter diagenesis in an ecotone of halophyte and planted mangrove in Bac Lieu province, Vietnam(2014-10-09); ; ; Mangroves play many significant roles in human life and socio-economical activities. However, their coverage has seriously declined worldwide due to various reasons while understanding of the roles and functions of this ecosystem is still insufficient. With a vast area of mangroves along the coast line, several studies on this ecosystem have been done in Viet Nam. Notwithstanding, the knowledge of nutrient and organic matter dynamics in the mangroves of Viet Nam, in general, and in the Mekong Delta, in particular, is still a gap. This study was conducted to understand the nutrient dynamics in a mangrove replanted in an abandoned salt-pan in Ganh Hao, Bac Lieu province a coastal area in the South of Viet Nam. Sediments and fresh leaves were collected from 8 different landscapes along a transect which was ca. 700 m in length. Sampling was conducted in the dry and rainy season in 2009. The nutrient contents (NH4 , NO2-, NO3- and available P for plant uptake), total organic carbon and total nitrogen were determined to assess the nutritional state in the study area. The composition and concentration of the amino acids in the sediments were quantified to understand the organic matter diagenesis in the area. Glucosamine, galactosamine and amino acids in the fresh leaves were analyzed to find the source of the organic matter. The chitin content in the sediments was determined by 2 methods to calculate the contribution of chitin to the N pool. Chitin was directly quantified through the binding of N-acetylglucosamine and WGA-FITC. On the other hand, chitin was calculated from the concentration of glucosamine in the sediments. The study area was subject to a serious deficiency of nutrients, especially nitrogen. The deficiency of nitrogen resulted in the deficiency of phosphorus in the sediments. The nitrogen and phosphorus contents in the sediments were controlled by the physico-chemical properties of the sediments and the vegetation. The carbon-to-nitrogen ratios showed that the organic matter in the deep sediments (30-35 cm) mostly derived from marine sources. The organic matter derived from terrestrial plants was found mostly in the surface sediments. The forestation and the invasion of Sesuvium portulacastrum, therefore, have recently contributed to the pool of organic matter in the sediments. The organic matter content in the study area was lower compared to other coastal areas, probably due to the higher turnover rate in the sediments, which resulted from the high temperature and the aeration in the sediment. The composition and contents of the sedimentary amino acids were affected by the composition and contents of the amino acids in leaves. In general, the contents of sedimentary amino acids decreased with depth. However, the soil preparation for mangrove plantation resulted in a disturbance in the variation trend with depth in the amino acid contents under the planted mangrove. The chitin content directly quantified through the binding between N-acetylglucosamine and WGA-FITC exceeded the organic carbon content in the sediments. However, these chitin data revealed an ecological relationship between chitin and the diatom frustules. The content of chitin calculated from glucosamine concentration showed that chitin contributes less than 2% to the OC pool and less than 3% to the N pool. In the deep sediments (30-35 cm), the crustacean sheaths was the major source of chitin while in the shallow sediments, chitin mostly derived from diatoms. In conclusion, this study showed that the nutritional state and the organic matter dynamics in a mangrove planed in extreme conditions was driven by tides, vegetation and the physico-chemical properties of the sediments. These effects might relate to the activities of sediment bacteria functioning in the nitrogen and phosphorus mineralization and solubilization. Improving the sediment conditions by irrigational solutions will help to maximize the bacterial activities and enhance the efficiency of mangrove plantation in abandoned salt-pans.Dissertation372 130