Trace fossils in the Ecca of northern Natal and their palaeoenviromental significance

Because of the rarity of body fossils in the Ecca Group fossil burrows, tracks and trails are of potential value in supplementing primary sedimentary evidence concerning the palaeoenvironmental factors of bathymetry, energy level and food supply. The three most important ichnogenera are Skolithos, Corophioides and Scolicia. The first two are restricted to the upper portions or Middle Ecca upward-coarsening regressive cycles attributed to delta progradation. They arc representatives of Seilacher's (1967) Skolithos and Glossijungites communities, indicating shallow water conditions with diastems. Scolicia occurs at lower levels in the cycles and corresponds to Seilacher's deeper water Cruziana community. Meandering trails Helminthopsis and Taphrhelminthopsis in the Lower Ecca belong to Seilacher's deep water Nereites community. Less common ichnogenera include the U-burrows Diplocraterion and Rhizocorallium. It has proved impossible positivelv to identify many trace fossils such as short ramifying burrows, chevron trails, dumbbell-shaped surface impressions, digitate tracks and problematic elliptical casts. Trace fossils have not been recognised with certainty in the fluviatile deposits which comprise the bulk or the coal-bearing strata of northern Natal.CSI

Differential Responses of Calcifying and Non-Calcifying Epibionts of a Brown Macroalga to Present-Day and Future Upwelling pCO2

Seaweeds are key species of the Baltic Sea benthic ecosystems. They are the substratum of numerous fouling epibionts like bryozoans and tubeworms. Several of these epibionts bear calcified structures and could be impacted by the high pCO2 events of the late summer upwellings in the Baltic nearshores. Those events are expected to increase in strength and duration with global change and ocean acidification. If calcifying epibionts are impacted by transient acidification as driven by upwelling events, their increasing prevalence could cause a shift of the fouling communities toward fleshy species. The aim of the present study was to test the sensitivity of selected seaweed macrofoulers to transient elevation of pCO2 in their natural microenvironment, i.e. the boundary layer covering the thallus surface of brown seaweeds. Fragments of the macroalga Fucus serratus bearing an epibiotic community composed of the calcifiers Spirorbis spirorbis (Annelida) and Electra pilosa (Bryozoa) and the non-calcifier Alcyonidium hirsutum (Bryozoa) were maintained for 30 days under three pCO2 conditions: natural 460±59 µatm, present-day upwelling1193±166 µatm and future upwelling 3150±446 µatm. Only the highest pCO2 caused a significant reduction of growth rates and settlement of S. spirorbis individuals. Additionally, S. spirorbis settled juveniles exhibited enhanced calcification of 40% during daylight hours compared to dark hours, possibly reflecting a day-night alternation of an acidification-modulating effect by algal photosynthesis as opposed to an acidification-enhancing effect of algal respiration. E. pilosa colonies showed significantly increased growth rates at intermediate pCO2 (1193 µatm) but no response to higher pCO2. No effect of acidification on A. hirsutum colonies growth rates was observed. The results suggest a remarkable resistance of the algal macro-epibionts to levels of acidification occurring at present day upwellings in the Baltic. Only extreme future upwelling conditions impacted the tubeworm S. spirorbis, but not the bryozoans

The micrometric formula and the classification of fenestrate cryptostomes

Volume: 9Start Page: 413End Page: 42

The phylogenetic affinities of fenestelloid bryozoans

Volume: 18Start Page: 1End Page: 1