Humans as the third evolutionary stage of biosphere engineering of rivers

We examine three fundamental changes in river systems induced by innovations of the biosphere, these being: (1) the evolution of oxygenic photosynthesis; (2) the development of vascular plants with root systems; and (3) the evolution of humans. The first two innovations provide context for the degree of human-induced river change. Early river systems of the Precambrian Archean Eon developed in an atmosphere with no free oxygen, and fluvial sediments accumulated ‘reduced detrital’ minerals. By 2.4 Ga the evolution of oxygenic photosynthesis produced an oxygenated atmosphere and ‘reduced detrital’ minerals mostly disappeared from rivers, affording a distinct mineralogical difference from subsequent fluvial deposits. Rivers of the Precambrian and early Phanerozoic were dominantly braided, but from 0.416 Ga, the evolution of vascular plants with roots bound floodplain sediments and fostered fine-grained meandering rivers. Early meandering river deposits show extensive animal activity including fish and arthropod tracks and burrows. Homo sapiens, appearing about 150 ka BP, has, in recent millennia, profoundly modified river systems, altering their mineralogical, morphological and sedimentary state. Changes in sediment fluxes caused by human ‘reverse engineering’ of the terrestrial biosphere include deforestation, irrigation and agriculture. Sediment retention has been encouraged by the construction of dams. Modern river systems are associated with extensive human trace fossils that show a developing complexity from ancient civilizations through to megacities. Changes induced by humans rank in scale with those caused by earlier biosphere innovations at 2.4 and 0.416 Ga, but would geologically soon revert to a “pre-human” state were humans to become extinct.This is the author accepted manuscript. The final version is available from Elsevier at http://www.sciencedirect.com/science/article/pii/S2213305415000089

Coral Uptake of Inorganic Phosphorus and Nitrogen Negatively Affected by Simultaneous Changes in Temperature and pH

The effects of ocean acidification and elevated seawater temperature on coral calcification and photosynthesis have been extensively investigated over the last two decades, whereas they are still unknown on nutrient uptake, despite their importance for coral energetics. We therefore studied the separate and combined impacts of increases in temperature and pCO2 on phosphate, ammonium, and nitrate uptake rates by the scleractinian coral S. pistillata. Three experiments were performed, during 10 days i) at three pHT conditions (8.1, 7.8, and 7.5) and normal temperature (26°C), ii) at three temperature conditions (26°, 29°C, and 33°C) and normal pHT (8.1), and iii) at three pHT conditions (8.1, 7.8, and 7.5) and elevated temperature (33°C). After 10 days of incubation, corals had not bleached, as protein, chlorophyll, and zooxanthellae contents were the same in all treatments. However, photosynthetic rates significantly decreased at 33°C, and were further reduced for the pHT 7.5. The photosynthetic efficiency of PSII was only decreased by elevated temperature. Nutrient uptake rates were not affected by a change in pH alone. Conversely, elevated temperature (33°C) alone induced an increase in phosphate uptake but a severe decrease in nitrate and ammonium uptake rates, even leading to a release of nitrogen into seawater. Combination of high temperature (33°C) and low pHT (7.5) resulted in a significant decrease in phosphate and nitrate uptake rates compared to control corals (26°C, pHT = 8.1). These results indicate that both inorganic nitrogen and phosphorus metabolism may be negatively affected by the cumulative effects of ocean warming and acidification

Ancient ports of trade on the red sea coasts -the ‘parameters of attractiveness’ of site locations and human adaptations to fluctuating land- and sea-scapes. Case study berenike troglodytica, Southeastern Egypt

© Springer Nature Switzerland AG 2019. The Red Sea region is unfavourable for long-shore nautical activity as it lacks natural topographic features that could be used as harbours; there are only a few suitable bays for landing along its coasts, where wadi mouths allow for a break in the reef. However, experiencing seasonally variable winds and currents, parts of the Red Sea constituted favourable marine environments for sea voyaging, contact and trade for millennia. This paper focuses on the influence that the local environmental and climatic context (including land- and sea-scape), had on the location, development, and ultimate success or decline of key Classical (Greco-Roman) ports of trade on the Red Sea coast, most pertinently those involved in exchange on the Spice, Incense and Maritime Silk Routes. The importance of changes in geomorphological, climatic, landscape and sea level configurations that led to the alternation of these human-adapted landscapes will be discussed within the new theoretical framework of ‘Parameters of Attractiveness’ developed whilst focusing on a case study, the Greco-Roman port town of Berenike Troglodytica on the southern Red Sea coast of Egypt. These parameters- grouped into 4 main categories: Sea, Land, Resources, and Socio-Economic and Political-were designed in order to statistically quantify the attractiveness of particular sites along the rims of the Red Sea for use as trade ports