The structural aspect in the ecology of sea-grass communities
In: Helgoländer Wissenschaftliche Meeresuntersuchungen. Biologische Anstalt Helgoland: Hamburg. ISSN 0017-9957, more
Also appears in:Kinne, O.; Aurich, H. (Ed.) (1967). Vorträge und Diskussionen. Erstes Europäisches Symposion über Meeresbiologie = Papers and discussions. First European Symposium on Marine Biology = Rapports et discussions. Premier symposium européen sur biologie marine. European Marine Biology Symposia, 1. Helgoländer Wissenschaftliche Meeresuntersuchungen, 15(1-4). 669 pp., more
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| Abstract |
1. Sea-grasses are aquatic angiosperms which are completely adapted to life in the marine environment. They belong to 2 families, the Potamogetonaceae with 9 marine genera and the Hydrocharitaceae with 3 marine genera.2. All sea-grasses satisfy the following indispensable conditions for a successful existence in the sea: (a) high salt tolerance, (b) ability to grow when fully submerged, (c) well-developed rhizomes, (d) hydrophilous pollination, and (e) sufficient competitive power in the marine environment.3. Plant taxa which fulfill the first 4 conditions excellently, but have a reduced competition capacity, are unable to establish themselves successfully in the marine environment and are restricted to poikilohaline environments, such as brackish waters and continental salt waters. Moreover, some of these taxa occur in instable fresh-water environments.4. Within the group of the sea-grasses 6 different growth-forms can be distinguished: parvozosterids, magnozosterids, syringodiids, enhalids, halophilids and amphibolids.5. The growth-forms are linked with the environmental conditions: they show a distinct horizontal zonation and in the succession series they follow each other in a fixed sequence.6. The structure of the communities is also dependent on the dominating growthforms. The communities of parvozosterids and halophilids are very simple in structure. The magnozosterid vegetations show some differentiation. In the enhalid and amphibolid communities a marked stratification occurs, as an upper layer, characterized by photophilous epiphytes on the leaves, and a lower layer with sciophilous epiphytes on the rhizomes can be distinguished.7. Sea-grass communities alter the physical environment by stabilizing the bottom, slackening the water movements and increasing the sedimentation.8. Sea-grass vegetations form a food resource for many marine organisms and water fowl, and are also of some importance as shelter and nurseries for a number of animal species. |
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