Appendicularian species groups and southern Brazil water masses

Abstract

The distribution of 19 species of appendicularia sorted out of a series of plankton samples taken between Cabo Frio (lat. 23º S) and Rio Grande do Sul (lat. 36º S) is discussed in relation to temperature and salinity. Most species showed a wide spectrum of temperature and salinity tolerance. No species was found to be exclusive of a single water mass. Eleven species were present in coastal waters, 16 in shelf waters and 13 in tropical waters. Ten species were found in the three water masses. Oikopleura longicauda was the most abundant species and O. dimca was found only over the shelf. Species of the genus Fritillaria were more sensitive to lower salinities and in a general way the number of species decreases coastalwards. Different groups of species were present in the same water mass and conversely similar groups occurred in different water masses. Five, eight and nineteen different groups of species occurred exclusively in shelf, coastal and tropical waters respectively. There was suggested the occurrence of stratified distribution and consequently the presence of different ecological niches within a single water mass. Several species probably reproduce more than once, most species are proterandric. Parasites and predators are mentioned. It is suggested that the knowledge of the past history of the water mass and its biological dynamics are more important for the interpretation of the distribution of the appendicularian fauna than temperature and salinity factors alone.