caa a22 4500 465762077 CHVBK 20180323111902.0 cr unu---uuuuu 170327e19900901xx s 000 0 eng 10.1007/BF00877284 doi (NATIONALLICENCE)springer-10.1007/BF00877284 Planktoneustonic algae in the surface films of Lake Zürich: Occurrence and dependence on phytoplankton succession [Elektronische Daten] [Astrid Nägeli, Ferdinand Schanz] Samples of surface films and of the underlying bulk water at 0.2 m depth were taken in Lake Zürich on 48 occasions in 1986, 1988 and 1989, with the aim of assessing the appropriateness of applying existing neuston nomenclature to the organisms found in these films, of determining which organisms accumulate there during which periods of time, and of assessing the importance of the phytoplankton community in the development of neustonic biocoenoses. Lake Zürich surface films were found to support a community of high population density, consisting of organisms which had migrated from the benthal or pelagial, or which had entered the film via the atmosphere or inflowing rivers. In all samples, species originating from within the phytoplankton community accounted for the greatest proportion of the total abundance. Several of these species were found to exhibit a special preference for the surface biotope, viz. those with a relative frequency (rF) exceeding 10%, a mean enrichment factor (Ef) exceeding 100, and, in the majority of cases, with a greater concentration of individuals in the surface film than in the underlying bulk water layer. We suggest that only those organisms occurring in the surface films of large water bodies which fulfil the above criteria should be considered as belonging to the planktoneuston, in order to distinguish them from other species, the occurrence of which in surface films is merely coincidental. The fact that planktoneustonic algae are dominant in the surface films of Lake Zürich means that changes in the species composition of the planktonic algal biocoenosis directly affect the species composition of the neustonic algal biocoenosis. Thus, just as in the underlying bulk water, a succession can be observed in the algal biocoenosis of the surface films. However, because of the higher abundance of planktoneustonic algae there, this succession is distinct from that occurring in the pelagial. Factors bringing about these differences which are discussed for the case of the dominant planktoneustonic algae are: alterations in specific gravity; positive phototaxis; and enhancement of growth rates in surface films as compared with the underlying bulk water. Birkhäuser Verlag, 1990 Neuston nationallicence surface film nationallicence surface-film enrichment nationallicence phytoplankton succession nationallicence Lake Zürich nationallicence Nägeli Astrid Hydrobiologisch-limnologische Station, Seestrasse 187, CH-8802, Kilchberg, Switzerland aut Schanz Ferdinand Hydrobiologisch-limnologische Station, Seestrasse 187, CH-8802, Kilchberg, Switzerland aut Aquatic Sciences Birkhäuser-Verlag 52/3(1990-09-01), 269-286 1015-1621 52:3<269 1990 52 27 https://doi.org/10.1007/BF00877284 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00877284 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Nägeli Astrid Hydrobiologisch-limnologische Station, Seestrasse 187, CH-8802, Kilchberg, Switzerland aut NATIONALLICENCE 700 1- Schanz Ferdinand Hydrobiologisch-limnologische Station, Seestrasse 187, CH-8802, Kilchberg, Switzerland aut NATIONALLICENCE 773 0- Aquatic Sciences Birkhäuser-Verlag 52/3(1990-09-01), 269-286 1015-1621 52:3<269 1990 52 27 Metadata rights reserved Springer special CC-BY-NC licence nationallicence SWISSBIB 346032156 BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer