. -⢠TOTAL DIATOMS - CHAETOCERACEAE -' 'PENNATAE" >â â BIDDULPHIINEAE o DISCINEAE â SOLENIINEAE SO 160 SEA MILES FROM LAND Fig. 77. Estimated total diatoms and diatom group totals, survey II. A. Mowe Point line, 9-11 October 1950. B. Northern Intermediate line, 8-9 October 1950. The dominance of this solenoid community at offshore stations persisted in very marked degree at the outer end of the Walvis Bay line, where, however, there was a larger proportion of Thalassiothrix longissima, perhaps the most oceanic of the ' Pennatae', among the small fraction of the total not accounted for
. -⢠TOTAL DIATOMS - CHAETOCERACEAE -' 'PENNATAE" >â â BIDDULPHIINEAE o DISCINEAE â SOLENIINEAE SO 160 SEA MILES FROM LAND Fig. 77. Estimated total diatoms and diatom group totals, survey II. A. Mowe Point line, 9-11 October 1950. B. Northern Intermediate line, 8-9 October 1950. The dominance of this solenoid community at offshore stations persisted in very marked degree at the outer end of the Walvis Bay line, where, however, there was a larger proportion of Thalassiothrix longissima, perhaps the most oceanic of the ' Pennatae', among the small fraction of the total not accounted for by the solenoids. Indeed it would appear that with minor modifications the solenoids predominated in the offshore plankton from about the middle of the area to the northern limit of our serial observations at the time of this second survey (cf. Table 17, Figs. 76-8). The inshore stations on both the Walvis Bay and mid-intermediate lines also displayed common features that differed markedly from those observed in autumn. In spring the rich coastal flora of Chaetoceros spp., with Asterionella and Fragilaria karsteni among the 'Pennatae', etc., was confined to the innermost stations, with an abrupt diminution seawards before the shelf-edge was reached. There was thus a pronounced narrowing of the rich coastal belt here in spring, where it had been wide, and fanned out seaward to the shelf-edge on the Walvis Bay line, during the first (autumnal) survey (cf. Fig. 57 and Fig. 65). The spring results resembled more the extreme contrast within a relatively short distance out from the coast, that had been shown on the Sylvia Hill line, immediately to the southward, in autumn. The distributional pattern is consistent with the active upwelling which was demonstrated by the hydrological results from this region. Within the upwelling water, the larger
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