Amsassia (calcareous alga) from the Lower Ordovician (Tremadocian) of western Newfoundland, and the biologic affinity and geologic history of the genus

Modular coral-like fossils from Lower Ordovician (Tremadocian) thrombolitic mounds in the St. George Group of western Newfoundland were initially identified as Lichenaria and thought to include the earliest tabulate corals. They are here assigned to Amsassia terranovensis n. sp. and Amsassia? sp. A from the Watts Bight Formation, and A. diversa n. sp. and Amsassia? sp. B from the overlying Boat Harbour Formation. Amsassia terranovensis n. sp. and A. argentina from the Argentine Precordillera are the earliest representatives of the genus. Amsassia is considered to be a calcareous alga, possibly representing an extinct group of green algae. The genus originated and began to disperse in the Tremadocian, during the onset of the Great Ordovician Biodiversification Event, on the southern margin of Laurentia and the Cuyania Terrane. It inhabited small, shallow-marine reefal mounds constructed in association with microbes. The paleogeographic range of Amsassia expanded in the Middle Ordovician (Darriwilian) to include the Sino-Korean Block, as well as Laurentia, and its environmental range expanded to include non-reefal, open- and restricted-marine settings. Amsassia attained its greatest diversity and paleogeographic extent in the Late Ordovician (Sandbian–Katian), during the culmination of the Great Ordovician Biodiversification Event. Its range included the South China Block, Tarim Block, Kazakhstan, and Siberia, as well as the Sino-Korean Block and Laurentia, and its affinity for small microbial mounds continued during that time. In the latest Ordovician (Hirnantian), the diversity of Amsassia was reduced, its distribution was restricted to non-reefal environments in South China, and it finally disappeared during the end-Ordovician mass extinction. UUID: http://zoobank.org/ef0abb69-10a6-46de-8c78-d6ec7de185fe

Calcareous meiofauna associated with the calcareous alga Corallina officinalis on bedrock and boulder-field shores of Ceredigion, Wales, UK

The intertidal coastline of Ceredigion, Wales, comprises a patchwork of unstable sand and cobble beaches, and stable bedrock areas and boulder-fields. The last two shoreline types support rock-pools with growths of the red alga Corallina officinalis, the thalli of which are a popular substrate for calcareous epiphytes. Replicate samples of C. officinalis (four per site) were taken from (a) three bedrock sites (Ceinewydd, Aberystwyth Victoria Rocks and Castle Rocks) and (b) three boulder-fields (Llanon, Aberaeron lower shore (Aberaeron LS), Llanina) on the lower shore. The middle shore boulder field at Aberaeron (Aberaeron MS) was also sampled. These replicates were examined for calcareous meiofauna (63–2000 μm) not previously examined as a community: spirorbids, foraminifera, gastropods, bryozoans, ostracods and ophiuroids. These were assigned to sessile and vagile modes of life. The sessile association overwhelmingly dominated bedrock coastlines and the Aberaeron MS, while the vagile association was at its most abundant on the Corallina from lower shore, stable boulder-fields. Gastropods were almost entirely limited to Corallina on boulder-fields. We hypothesize that the boulders induce low-energy turbulence among breaking waves, allowing the less firmly attached vagile meiofauna to dominate on C. officinalis in rock-pools in lower shore boulder-fields. The small attachment area of sessile organisms allows them to settle bedrock sites in greater densities than do vagile organisms at boulder-field sites, which are presumed to require larger foraging areas.

The “earliest tabulate corals” are not tabulates

Putative tabulate-like corals dating to the Cambrian Explosion are not true tabulates. Early Ordovician fossils identified as Lichenaria and previously accepted as the earliest tabulate corals actually belong to Amsassia, which may be a calcareous alga. The earliest definite tabulates appeared in the latest Middle Ordovician as part of the Great Ordovician Biodiversification Event, prior to the earliest confirmed occurrence of tabulate species that do belong to Lichenaria in the Late Ordovician. With Cambrian (Epoch 2) tabulate-like fossils being separated from the appearance of true tabulates by a time span of ~50 m.y., a direct phylogenetic connection is unlikely. Thus, the prevailing understanding of the origin and evolutionary history of tabulate corals needs to be reconsidered. The appearance of both major groups of Paleozoic corals, tabulates and rugosans, at the same time on separate paleocontinents must be taken into account in determining biological and geological factors involved in the Great Ordovician Biodiversification Event.

Environmental sensitivity of Neogoniolithon brassica-florida associated with vermetid reefs in the Mediterranean Sea

Vermetid reefs in the Mediterranean Sea are increasingly affected by both anthropogenic actions and global climate change, which are putting this coastal ecosystem at risk. The main species involved in building these reefs are two species of intertidal vermetid gastropods and the crustose calcareous alga, Neogoniolithon brassica-florida, which cements the gastropod shells and thus solidifying the reef edges. In the present study, we examined the pattern of distribution in the field and the environmental sensitivity (thermal tolerance, resilience to low pH, high light intensity and desiccation) of N. brassica-florida along the coasts of Sicily and Israel by means of chlorophyll fluorescence and total alkalinity measurements in situ and in the laboratory. Tidal regimes did not affect photosynthesis of N. brassica-florida but light intensity in the intertidal did. Sensitivity to increased light intensity was amplified by elevated temperature and reduced pH. Winter temperature above 16 °C caused a decrease in the photosynthetic performance of photo-system II. Similarly, a decrease in pH resulted in decreased maximum photosynthetic yield and electron transport rate. Calcification was significantly lower at pH 7.9 as compared with ambient (8.1) pH. In fact, dissolution at pH 7.9 at night was higher than net calcification during the day, suggesting that N. brassica-florida may not be able to contribute to reef accretion under the levels of seawater warming and ocean acidification projected by the end of this century.

Use of calcareous algae and monensin in Nellore cattle subjected to an abrupt change in diet

ABSTRACT: Additives are used in high concentrate diets to prevent metabolic disorders in cattle. This study was designed to evaluate the effect of calcium sources and monensin on the control of ruminal acidosis in Nellore cattle that were abruptly shifted to a high (92.3%) concentrate diet. Eight cannulated steers were randomly assigned to two contemporary 4x4 Latin square. Treatments involved the addition of a calcium source, either limestone (LI) or a product derived from calcareous algae (CA), to the basic diet with or without the presence of monensin. Calcareous alga (Lithothamnium calcareum) is a natural and renewable product and a source of calcium carbonate. The quantity of added limestone, calcareous algae and monensin was 7.1g kg-1, 7.4g kg-1 and 30mg kg-1 DM, respectively. There was no effect of calcium source (P=0.607) or monensin (P=0.294) on feed intake or on the concentration of short chain fatty acids. Treatments with calcareous algae resulted in a higher mean ruminal pH (P=0.039), a shorter amount of time with the ruminal pH under 5.2 (P<0.001) and a better control of blood pH (P=0.006). Treatments with monensin also resulted in a shorter amount of time with the ruminal pH below 5.2 (P=0.023). Calcareous algae were shown to be effective in controlling adverse changes in the rumen and in blood variables for Nellore cattle that were subjected to an abrupt change to a high concentrate diet.