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KurzfassungAls „Parvosilvosa“ werden taxonomisch komplexe, rasenartige Pflanzenbestände bezeichnet, die aus kleinen Algen und mikroskopischen Entwicklungsstadien größerer Algen bestehen. Die vorliegende Untersuchung erörtert die ökologische Bedeutung dieser Pflanzenkomponente als Teil der örtlichen Gesamtflora; sie basiert auf Schwimmtauch-Studien und Laboratoriumsexperimenten. Mit „Parvosilvosa“ bedeckte Felsstücke und Molluskenschalen wurden unter Laboratoriumsbedingungen natürlichem und künstlichem Licht ausgesetzt. In den Kulturen konnten sowohl luxurierende Formen von bereits aus dem Biotop bekanntem Material als auch neue Formen festgestellt werden. Einige dieser Algen wuchsen sehr gut in Kultur und schritten zur sexuellen Fortpflanzung. Offenbar existieren viele benthonische Algen zeitweise in Form von Ruhestadien. Unter günstigen Bedingungen — wie sie beispielsweise in unseren Kulturen geboten werden — wachsen sie dann zu adulten Pflanzen heran. Die Erfassung des gesamten Algenbestandes eines Biotops dürfte durch die hier angewandten Methoden erleichtert werden. Die durchgeführten Untersuchungen ergeben neue Ansatzpunkte für experimentelle Arbeiten im Litoral.Summary1. Ecological studies of the kelp forests of Pacific North America have understandably stressed the larger vegetational components. An important vegetational component, previously neglected, is a taxonomically complex “turf” or parvosilvosa (Gislén 1930), composed of small algae and microscopic reproductive or developmental forms of larger algae.2. This report considers the ecological importance of this smaller plant component within the framework of the overall vegetational structure. Both diving studies and the cultivation of experimental material in the laboratory under controlled conditions have been utilized to probe the questions involved.3. Rocks and shells covered with representative algal turf have been cultured in the laboratory in naturally or artificially-illuminated tanks provided with a continuous supply of filtered seawater, and the resulting species composition has been compared with that occurring in nature.4. Both luxuriant forms of previously collected material and new forms have been observed in these cultures. Certain of these algae grow extremely well in culture and in some cases continue to reproduce, generating successive crops of plants. Growth rates under laboratory conditions for a few species have been measured and approach what might be expected in the field.5. Elective culture results suggest that many benthic algae may well exist for periods of time as “resting” or “resistant” stages, awaiting favorable environmental conditions. Stages such as those postulated have been produced in the laboratory.6. Complete taxonomic or ecological surveys of subtidal areas, and particularly the deeper benthic regions near the lower limits of plant distribution would benefit from culture studies of the type described. Subtidal benthic algae also lend themselves readily to experimental manipulation, and the results obtained to date, although preliminary, suggest possible experimental approache to subtidal ecology.

Composition and growth of subtidal parvosilvosa from Californian kelp forests