Multivariate analysis of biogenic constituents in recent sediments off Ras Burka, Gulf of Elat, Red Sea

The shallow shelf area to a water depth of 40 m off Ras Burka, Gulf of Elat, comprises several depositional zones. In order of increasing water depth these include: sand dune (on shore); swash; dead reef platform; sand channel; live coral reef; Cymodoceaslope; reef knolls; and Halophilalawn. The abundance of 64 biogenic constituents, comprising 48 genera of Foraminifera and a variety of other taxa, was recorded in 16 samples representing the sediments presently forming in the various environments. Nodal ordination and association analysis were applied to classify the samples and to examine whether the present day zonation of sedimentary environments can be objectively recognized on the basis of the assemblages of biogenic constituents. The analyses classified the samples consistently into three classes, identified as the shallow near-shore, the upper slope, and the lower slope zones. Association analysis, utilizing only discrete binary presence or absence scores, yielded better results than nodal ordination analysis utilizing continuous metric modal data. In the study area, biogenic grains other than Foraminifera do not contribute to the environmental discrimination. The results suggest that crude presence scores, as contrasted with refined metric data, are informative enough for differentiating sedimentary environments.