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  • 1
    Electronic Resource
    Electronic Resource
    Influence of environmental parameters on the biomass development ofRuppia drepanensis populations in Doñana National Park: the importance of conditions affecting the underwater light climate (1996)
    Springer
    International journal of salt lake research 5 (1996), S. 157-180 
    Details
    ISSN: 1573-8590
    Keywords: brackish marsh ; growth ; light attenuation ; submerged macrophyte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract The development of submerged plant communities dominated byRuppia drepanensis Tineo in the brackish marsh of the Doñana National Park (SW Spain) was coupled to seasonal variation in environmental factors for two consecutive years. Plant biomass increased rapidly in early spring (March), with steady biomass yields (up to 100 g afdw m−2) together with abundant flowering and fruiting in late spring (April–May). Wind-induced sediment resuspension and periphyton growth strongly influenced the light climate experienced by the submerged vegetation, while a phytoplankton effect was generally negligible. Development of the submerged vegetation coincided with a decrease in water extinction coefficient and in bicarbonate concentration. Thus, where dense macrophyte meadows develop, light climate probably is the limiting factor in the early spring, while temperature and bicarbonate levels are so by the end of the season. Interannual variation was found to be very high, both in abundance and distribution of the submerged vegetation, mainly because of differences in rainfall which influenced the inundation cycle. Grazing by waterfowl accounted also for this effect, as in dry years birds concentrate in the few wetlands still containing water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01995828
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  • 2
    Electronic Resource
    Electronic Resource
    Leaf dynamics and standing stocks of intertidal Zostera noltii Hornem. and Cymodocea nodosa (Ucria) Ascherson on the Banc d'Arguin (Mauritania) (1993)
    Springer
    Hydrobiologia 258 (1993), S. 59-72 
    Details
    ISSN: 1573-5117
    Keywords: Zostera noltii ; Cymodocea nodosa ; growth ; seagrass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leaf dynamics and standing stocks of intertidal seagrasses were studied in the Baie d'Aouatif (Parc National du Banc d'Arguin, Mauritania) in April and September 1988. Standing stocks of Zostera noltii Hornem. suggest a unimodal seasonal curve similar to what is found for populations at higher latitudes. Also, leaf growth rates (0.03 cm2 cm−2 day−1 on average) were similar to those found at higher latitudes in these months. Variation in leaf loss over tidal depth, time and different locations in the Baie d'Aouatif was larger and more often significant than variation in leaf growth. In general, Z. noltii beds in the Baie d'Aouatif had comparable leaf growth rates and standing stocks. In both months losses were almost always higher than or equal to growth. Variation in leaf loss over time was much higher in the plots that were situated high in the intertidal than in lower plots. This is explained by differences in susceptibility to sloughing, which is presumably higher in periods with low tide around noon for shallow depths. In an experiment using artificial shading nets, in situ leaf growth was affected negatively from 94% shading onwards. This shading was observed to reduce the light intensity reaching the seagrass bed to a level below the reported range of light compensation points for Z. noltii. Cymodocea nodosa (Ucria) Ascherson on average had higher leaf area and relative growth rates than Z. noltii and much lower loss rates, resulting in a positive net increase in September. Standing stocks were also higher than for Z. noltii. A mixed seagrass bed containing the above two species and Halodule wrightii Ascherson had the highest observed total biomass: 335 g m−2 ash-free dry weight.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00006186
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The influence of ammonia on the growth and photosynthesis of Ruppia drepanensis Tineo from Doñana National Park (SW Spain) (1994)
    Springer
    Hydrobiologia 275-276 (1994), S. 219-231 
    Details
    ISSN: 1573-5117
    Keywords: Ruppia drepanensis ; ammonia toxicity ; temperature effects ; photosynthesis ; growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a laboratory experiment, Ruppia drepanensis Tineo seedlings from a brackish marsh in Southern Spain were grown at 20 and 30 °C, at three different nitrogen levels. These levels were obtained by the addition of a slow release fertilizer (23% NH4NO3 by weight) to a sediment mixture of sand and clay (3:1). Several morphometric parameters were recorded during the first five weeks of the experiment, and photosynthesis and respiration were measured after 7 weeks of growth. Results showed a significant reduction of growth and development with increasing nitrogen and temperature levels. Dark respiration increased strongly at high nitrogen levels. At the same time, net photosynthesis at 250 and 500 µE m-2 s-1, Pm, Km and LCP were not affected by either factor. We attribute these phenomena to ammonia toxicity, since relatively high total ammonia (NH3 + NHf4 p+) levels were found in the interstitial water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026713
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Photosynthetic plasticity in Potamogeton pectinatus L. from Argentina: strategies to survive adverse light conditions (1996)
    Springer
    Hydrobiologia 340 (1996), S. 1-5 
    Details
    ISSN: 1573-5117
    Keywords: light climate manipulation ; Potamogeton pectinatus ; photosynthesis ; turbidity ; weed management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Argentine Potamogeton pectinatus L. was grown in The Netherlands under laboratory conditions at four light intensities (50, 100, 150 and 200 µE m−2 s−1), and photosynthetic performance was evaluated after about 1, 2 and 3 months of growth. At these moments, chlorophyll-a and -b and tissue N and P content were also determined. During the growing period, plant lengths and number of secondary shoots were measured. In the field in Argentina, photosynthetic performance of P. pectinatus was also measured at different light intensities created by artificial shading at various times during the growing season. Field and laboratory photosynthetic results were in good agreement. P. pectinatus showed a significant plasticityin its photosynthesis, rather than in morphology. A fairly constant maximum photosynthetic rate with reduced light enabled the plants to maintain netproduction rates rather unaffected at low light intensities. Still, it can be predicted that increasing turbidity from 1–2 m−1 at present to 3 m−1 could lead to a strongly light-limited growth which should reduce the present weed problem considerably. Such a turbidity increase might be achieved by the introduction of a fairly dense bottom-feeding fish population like Common carp (Cyprinus carpio L.).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00012725
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Periphyton density and shading in relation to tidal depth and fiddler crab activity in intertidal seagrass beds of the Banc d'Arguin (Mauritania) (1993)
    Springer
    Hydrobiologia 258 (1993), S. 73-80 
    Details
    ISSN: 1573-5117
    Keywords: extinction coefficient ; grazing ; periphyton ; seagrasses ; Uca tangeri ; Zostera noltii
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Periphyton development was studied on microscopic glass slides and leaves of Zostera noltii Hornem. in an intertidal area in the Banc d'Arguin (Mauritania). The effects of shading, tidal depth and grazing activities by the fiddler crab Uca tangeri Eydoux were evaluated. For all experiments, periphyton ash content was high (52–93%) and ash-free dry weight ranged between 0.10–0.63 mg cm−2. Slides accumulated more periphyton than leaves. Artificial shading (62–99%) for 13 days had no effect on periphyton densities on leaves. Increased tidal depth resulted in higher ash-free dry weight on slides, but in lower ash-free dry weight on leaves. Significant variation along the coastline also existed. The effect of fiddler crabs was studied using exclosures. Presence of fiddler crabs reduced periphyton density on slides, whereas light transmittance was increased. On leaves, no significant fiddler crab effect was found. This difference between leaves and slides was probably caused by a storm at the day before the end of the experiment, and by the higher periphyton density on slides as compared with leaves. As visual inspection during the experiment showed clear differences in appearance of leaves inside and outside the exclosures, the storm probably sloughed off mainly the older leaves, i.e. those on which the differences in periphyton cover were the highest. It is hypothesized that periphyton accumulation is higher with increased tidal depth, whereas fiddler crab grazing pressure also increases in this direction. The result is a decreased periphyton density with increased tidal depth. The presently found light extinction coefficients (mean 0.8 m−1) and periphyton light attenuance (up to 25%) in Banc d'Arguin are not likely to affect seagrass leaf growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00006187
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    Paper (German National Licenses)
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