Portskewett The village lost its railway station (on the Newport to Gloucester line) when it was closed under the Beeching Axe in 1964. Black Rock, on the Severn estuary immediately south east of the village, has been an important crossing point of the River Severn for many centuries. Numerous coins found in the mud show that it was in constant use throughout the Roman period, on the route between Aquae Sulis (Bath) and Venta Silurum (Caerwent). By the 18th century, a regular ferry service crossed the Severn estuary from Black Rock to New Passage on the Bristol side, carrying passengers, cattle
Aphanizomenon flos-aquae (dietary supplement) from the air, and water to synthesize proteins, carbohydrates, and lipids. AFA is also able to directly use molecular nitrogen from the air to produce proteins and other nitrogen-containing biomolecules. This ability is widespread in prokaryotes, but unknown in eukaryotes. "Aphanizomenon flos-aquae" as a species has both toxic and non-toxic forms. While benefits have been indicated, toxicity has been shown in some strains of the species "Aphanizomenon flos-aquae", with cylindrospermopsin and saxitoxins present, and microcystins found contaminating AFA dietary supplements. The World Health Organization's "Guidelines For Drinking Water Quality" note Anatoxin-a, saxitoxins, and cylindrospermopsins are present in the Aphanizomenon genus.