The diatom types of M. Giffen from Kidd’s Beach, Eastern Cape, South Africa
Abstract
Marine littoral diatoms are rarely studied and are important in the littoral zone ecosystem.
Diatoms contribute to numerous aquatic ecosystem functions including: primary productivity,
sediment binding, and stability. There is relatively little taxonomic work related to marine
littoral diatoms, especially in South Africa (SA).
Malcolm Giffen was one of the pioneers in this field of study and described many marine
littoral diatoms taxa in South Africa. Giffen collected 10 marine littoral diatom samples from
the Kidd’s Beach area between 1946 and 1963. These were documented with line diagrams
which could be potentially misinterpreted. Recently several of Giffen’s taxa have been reexamined;
however, this research is restricted mostly to the West Coast of South Africa. For
this reason, this present project focus on taxa that he described from Kidd’s Beach in the
Eastern Cape. Of the 10 marine littoral diatom samples Giffen had collected from Kidd’s
Beach area, 8 were used to describe 27 new diatom species. Twenty-six of these taxa were
documented with light microscopy and 23 with electron microscopy.
Taxa were evaluated, descriptions emended and some were re-described or transferred to
more appropriate genera, based on morphological characteristics observed with LM and SEM.
After examinations of the SEM micrographs, 8 of the 27 species were transferred to more
appropriate genera (Niztschia erosa to Entomoneis erosa; Amphiprora galerita to Entomoneis
galerita; Navicula pragmatica to Fallacia pragmatica; Stauroneis exilissima to Olifantiella
exilissima; Navicula pseudogamma to Moreneis pseudogamma; Amphora tenellula to
Seminavis tenellula; Opephora perlonga to Tabularia perlonga and Opephora perlonga var.
clavata to Tabularia perlonga var. clavata). One status change Petroneis capensis (synonym:
Navicula humerosa f. capensis) was also made after the examination of the cell morphology
under SEM.
Additionally, the 8 sites as described by Giffen were re-sampled in October of 2018 and
October 2019, to determine if any temporal changes occurred during the past circa 57 years.
DCA bi-plots were used to illustrate the temporal changes of the two re-sampled years also
comparing these samples with those collected by Giffen. Physico-chemical data were also
measured in 2019 to determine if there was any external driving factor influencing the diatom
community at Kidd’s Beach. A CCA bi-plot was used to present the influence of the physicochemical
variables on the diatom community. From the DCA bi-plots, it was apparent that the
diatom community structure in 2018 was remarkably different from the diatom community
structure sampled by Giffen. However, the diatom community structure in 2019 was in some
respects more similar to the diatom community structure sampled by Giffen. It was found that
there was no direct external factor influencing the diatom community and that the main
internal driving factor determining community structure is salinity. The resampling of the 8
sites in question only yielded 6 of the 27 taxa described as new by Giffen. From these results,
it was clear that the diatom community at Kidd’s Beach is constantly in flux and that the
resampling at original sites where type material was collected is not guaranteed to contain the
species in question, therefore, the preservation, maintenance and documentation of extant
types is of the utmost importance.