Novel Bathymetry of Lake Afdera Reveals Fault Structures and Volcano-Tectonic Features of an Incipient Transform Zone (Afar, Ethiopia)

Lake Afdera is a hypersaline endorheic lake situated at 112 m below sea-level in the Danakil Depression. The Danakil Depression is located in the northern part of the Ethiopian Afar and features an advanced stage of continental rifting. The remoteness and inhospitable environment explain the limited scientific research and knowledge about this lake. Bathymetric data were acquired during 2 weeks expeditions in January/February 2016 and 2017 using an easily deployable echosounder system mounted on an inflatable motorized boat. This study presents the first complete bathymetric map of the lake Afdera. Bathymetric results show that the lake has an average depth of 20.9 m and a total volume of 2.4 km3. The maximum measured depth is 80 m, making Lake Afdera the deepest known lake in Afar and the lowest elevation of the Danakil Depression. Comparison with historical reports shows that the lake level did not fluctuate significantly during the last 50 years. Two distinct tectonic basins to the north and the south are recognized. Faults of different orientations control the morphology of the northern basin. In contrast, the southern basin is affected by volcano-tectonic processes, unveiling a large submerged caldera. Comparison between the orientation of faults throughout the lake with the regional fault pattern indicates that the lake is part of two transfer zones: the major Alayta–Afdera Transfer Zone and the smaller Erta Ale–Tat’Ali Transfer Zone. The interaction between these Transfer Zones and the rift axis forms the equivalent of a developing nodal basin which explains the lake’s position as the deepest point of the depression. This study provides evidence for the development of an incipient transform fault on the floor of the Afar depression.

Revision of the genus Seminemacheilus, with the description of three new species (Teleostei: Nemacheilidae)

The nemacheilid genus Seminemacheilus is revised. Six species are recognised, three of them described herein as new. All species are endemic to Central Anatolia. Seminemacheilus lendlii from the Sakarya River drainage and the endorheic Lake Aksehir and Eber basins, S. ispartensis from Lake Eğirdir basin and S. ahmeti from Sultan Sazlığı are valid species. Although Seminemacheilus lendlii and S. ispartensis have almost identical COI sequences, they are distinguished by the shape of the caudal peduncle and the presence of scales on the caudal peduncle in S. ispartensis (vs. absent in S. lendlii). Seminemacheilus attalicus, new species, from Kırkgöz drainage, is distinguished by having a slightly emarginated caudal fin, a central pore in the supratemporal canal and a marbled flank pattern. Seminemacheilus ekmekciae, new species, from Lake Tuz basin is distinguished by having a roundish caudal fin, a short post-dorsal length and large brown blotches fused into stripes on the flank. Seminemacheilus tubae, new species, from Lake Beyşehir basin, is distinguished by having a truncate caudal fin and 2–5 (6) supraorbital head pores. Seminemacheilus dursunavsari from the Göksu River drainage is not a valid name and this population is identified as S. tubae.

Changes in Hydromorphological Conditions in an Endorheic Lake Influenced by Climate and Increasing Water Consumption, and Potential Effects on Water Quality

The study aims to analyse changes in the morphological conditions of the endorheic Lake Borówno (39.06 ha) that occurred in the 20th century and early 21st century. The analysis was based on bathymetric measurements carried out in 2018 and cartographic materials, and performed using QGIS 3.10 and SAGA GIS 6.4 software. Moreover, changes in physical (temperature, transparency), chemical (dissolved oxygen, phosphorus, and nitrogen content) and biological (chlorophyll a, phytoplankton) parameters were analysed based on the results of measurements conducted by the Voivodeship Inspectorate of Environment Protection (VIEP) in Bydgoszcz in the period 1984–2017. It was found that Lake Borówno is subject to a constant reduction in surface area and volume, the rate of which increased in the second decade of the 21st century. The lake’s progressive disappearance results from the co-occurrence of hydrological drought over the last several years and an increase in the use of groundwater resources. A decrease in the maximum depth of the lake entails a change in temperature distribution in the vertical profile, which contributes to the tendency toward the lake transforming into an unstratified reservoir. The increase in water temperature affects oxygen content in the bottom water, improves water transparency, and influences the maximum occurrence of chlorophyll a in spring.

Origin and behavior of contamination of Lake Neusiedl with PAH and PFAS

<p>Lake Neusiedl is the largest endorheic lake in Central Europe, straddling the Austrian–Hungarian border. The lake has an area of 315 km<sup>2</sup>, 52% of which is covered by a reed belt representing the second largest contiguous reed population in Europe. The lake's drainage basin has an area of about 1,120 km<sup>2</sup> and is strongly impacted by intensive agricultural production and urban settlements, especially in the catchment of the main inflow River Wulka. On average, the lake's surface lies 115.45 m above the Adriatic Sea and the lake is no more than 1.8 m deep. Due to its chemical composition Lake Neusield can be characterized as soda lake with typical pH values of 9.0-9.3 in the open lake.</p><p>In this contribution, we present results from investigations on selected PAH (Benzo(a)pyrene, Fluoranthene) and PFAS (PFOS and PFOA) in the lake with specific focus on sediment associated transport and legacy processes. We apply a holistic approach, by combining emission modelling, targeted monitoring, adsorption and mobilization experiments as well as a lake’s mass balance. We describe the current state of contamination of River Wulka and the lake, we identify the main emission pathways into both river and lake and we shed light on the complex environmental behavior within the coupled system lake - reed belt.</p><p>While PFOA and PFOS emissions into the river are dominated by effluents from waste water treatment plants, atmospheric deposition on the lake surface adds a significant contribution to the contamination of the lake. On the contrary, agricultural erosion is the dominant pathway of the contamination of river and lake for Benzo(a)pyrene, Fluoranthene. Our results show that the reed belt at the entrance of River Wulka to the lake acts as a significant sink for these substances due to suspended solid sedimentation.</p><p>Persistent chemicals entering the lake may undergo different fates. They may concentrate in water, because in this peculiar lake evaporation exceeds precipitation. They may also be stored in the sediments of the reed belt, from where they might be later re-mobilized. The fate of Benzo(a)pyrene and Fluoranthene is clearly dominated by the latter processes. While these processes cannot be neglected for PFOS and PFOA as well, PFOA shows a strong enrichment in the lake water. The behavior of PFOS is even more complex. Though highly persistent, its removal from the lake water cannot be explained by suspended solid associated transport to and sedimentation in the reed belt. It is removed from the lake water through degradation or conversion to metabolites to a significant extent as well.</p>