Studies on the submerged plant community in Lake Biwa. I. Distribution and productivity of Egeria densa. A submerged plant invader in the south basin [Translation from: Physiol.Ecol.Japan 17, 283-290, 1976]

Egeria densa (PLANCH.) ST. JOHN, a submerged plant invader, forms a wide submerged plant zone, particularly along the west coast of the south basin, Lake Biwa. The macrophyte occupies over 82% of the plant zone in the basin and its biomass reaches 93% of the total. The estimated annual net production was approximately 1 kg dry wt./m2 in a dense area, which is about 4.5 times as much as the net production by phytoplankton in an offshore area of the basin. Although the area covered by the macrophyte is only 5.8% of the total of the basin, it produced about one-tenth of the total annual primary production. In the most productive season Egeria produced 46% of the total primary productivity. Thus, the macrophyte never be neglected when one considers the energy flow or material circulation in the basin. This study was initiated in order to clarify the role of submerged macrophytes, particularly E. densa, in Lake Biwa. The following points are reported in this paper: the distribution of macrophytes in the south basin; seasonal change in standing crop of E. densa; seasonal change in values related to production, utilizing a model proposed by Ikushima with its parameters experimentally determined.

Copépodes pélagiques du plateau ivoirien. Utilisation de I'analyse des correspondances dans l'étude des variations saisonnières

Several 'analyses factorielles des correspondences' were used with the numerical data of planktonic copepods issued from a 1 year sampling programme at different stations of the Ivorian shelf. The main results were the following: (1) 'Ecological seasons' approximately corresponding to hydrological seasons may be defined for planktonic populations. (2) Each 'season' is characterized by one group of species, whose maximum abundance occurs in this period. (3) The same definition of ecological season is obtained whether all species present are used or whether only the most important ones are used. (4) The first principal axes may be interpreted as temperature and salinity or as the station's distance from shore.