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The evolution of the bottom water in Amvrakikos Gulf in Ionian Sea at western Greece for a 50-year timespan was assessed by benthic foraminifera assemblages. The degradation of the bottom water of Amvrakikos has been a catalyst for the surface water degradation. The east basin has shown permanent low environmental quality in bottom waters since 1980, while the west basin has been under seasonal hypoxic regime since 2000. The most adverse environmental conditions occurred in 1990-2000 and 2005-2010 coinciding with the recorded fish mortality events. The major cause of the environmental quality improvement of the bottom water is the intrusion of seawater. In western areas of the gulf, where the influence of the seawater is high, the decreased temperature improves the environmental conditions, while in the areas influenced by river discharges (east and northern), the environmental conditions are depended on multiple causes like organic matter input and surface salinity., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

High-resolution data for planktonic foraminifera and their groups of ecological interest, including Herbivores and Carnivores, combined with benthic foraminifera and a great variety of biogeochemical indices from the SE Aegean sediment core ST5, contribute to a detailed study concerning major and minor climatic episodes during Holocene. The ST5 sediment record, retrieved from the Tilos-Symi marine basin, evidences the impact of the nearby land, the local climate, and the Rhodes Gyre imprint on the eastern Mediterranean water circulation. Pronounced environmental changes are detected during a preconditioning period of ~400 years before the onset of sapropel S1 deposition and during the deposition phases S1a (10.0–8.4 ka BP) and S1b (8.0–6.1 ka BP). Major freshwater influx episodes (10.5 ka BP, 9.2–8.9 ka BP, 7.4 ka BP, 4.5–4.3 ka BP, and few additional during the Late-Holocene) are revealed, prominent oxygen deficiency time intervals (including a distinct brief anoxic period) as well as several drier, cooler and warmer climatic events. Herbivore planktonic foraminifera alternate their dominance with the Carnivores at the preconditioning period before the S1 onset and at the Late-Holocene (2.0–1.5 ka BP) when conditions of good seawater circulation, oxygenation, and productivity alternate with stratified low oxygenation waters and high freshwater influx from the land. [ABSTRACT FROM AUTHOR]

The Gulf of Corinth represents an ideal setting for studying the impact of sea level changes and regional climate on a semi-enclosed, syn -rift basin. Here we investigate the stratigraphic and paleoceanographic variability recorded in the sedimentary succession of the basin over the Marine Isotope Stage (MIS) 5 period when global sea level and climatic conditions along the eastern Mediterranean exhibited pronounced fluctuations. We used sedimentological (granulometry, composition), micropaleontological (planktic and benthic foraminifera), and isotopic (stable δ18O, δ13C, and clumped isotope) proxies on core samples from site M0079A (IODP Expedition 381) combined with additional data from the expedition overview and records from the surrounding area. The sedimentary succession comprises an alternating pattern of a) bioturbated, biogenic-rich deposits associated with increased hemipelagic sedimentation with b) partly bedded, detrital-rich sediments attributed to intercalated sediment gravity flows within the hemipelagic background under low oxic sea-surface conditions, and c) aragonite-rich laminated deposits, indicating either transitional conditions between marine and isolated environment or a highly stratified seawater column and low oxygen seafloor conditions. We find that the Gulf of Corinth lay under marine conditions for nearly the entire MIS 5 period, while the Rion sill would have been possibly shallower, even 10 m, than the current depth. Nevertheless, water exchange was restricted during the MIS 5a – MIS 4 transition when the sea level fluctuated very close to the sill height. The hydrological conditions within the Gulf during most of the highstands MIS 5a, 5c, and 5e reflect higher oxygen levels and/or increased nutrient availability compared to the Holocene and present-day regime. The combined effects of Ionian Sea inflows and enhanced riverine runoff led to increased water column stratification and low oxygen, eutrophic seafloor conditions in the Gulf of Corinth during times of high precipitation in southern Europe and deposition of sapropels S3, S4, and S5 throughout the eastern Mediterranean. In contrast, during periods of widespread cold and arid conditions in the eastern Mediterranean, water column mixing was intense within the Gulf. Prevalent marine conditions are also proposed during the MIS 5b and 5d lowstands, yet associated with predominately bedded-detrital sediments in the Gulf. A complementary investigation in the adjoining Patras Gulf is suggested to fully comprehend the dynamics of climate and sea level changes in complex rift systems. • The Gulf of Corinth lay under marine conditions for nearly the entire MIS 5 period. • Three sedimentary facies associations characterize the MIS5 succession in the Gulf. • Hydrological conditions reflect eastern Mediterranean Sea trends and regional climate. • Higher sea-surface O 2 and/or nutrients at MIS5 highstands compared to the Holocene. • The western sill-boundary (Rion) had possibly been even 10 m shallower than present. [ABSTRACT FROM AUTHOR]

Abstract: High-resolution palaeoenvironmental changes, corresponding to a mean time interval of 450 years covering the last 48,000 years, were examined in a core from the Cretan Basin in the southern Aegean Sea. The intensity and duration of the climatic and oceanographic events were determined by examining the compositional changes in the planktonic foraminifera and pollen assemblages, along with the δ18O signal of Globigerinoides ruber. A reconstruction of sea-surface temperatures was attempted using the Modern Analogue Technique (MAT). In total, 10 stadials and 6 interstadials occurred over the last 48,000 years. These fluctuations in climatic conditions coincide with fluctuations documented in the western and central Mediterranean and seem to be associated with Dansgaard–Oeschger events. Some of these climatic fluctuations are correlated with changes in the vegetation in the surrounding land. Between 48 and 10 cal kyr BP the most pronounced stadials occurred at 41 cal kyr BP (C69-ST10) and at 13 cal kyr BP (C69-ST4). These events are characterized by: (i) high positive δ18O values of Globigerinoides ruber, (ii) drops in SST and (iii) increases in aridity. These events may be correlated with the Heinrich H4 event and the Younger Dryas event, respectively. Two other stadials at 23 cal kyr BP (C69-ST6) and at 16 cal kyr BP (C69-ST5) which are characterized by increases in the abundance of the cold plaktonic foraminifera species and increases in aridity may be correlated with the H2 and H1 events, respectively. The dominant planktonic foraminiferal species during the stadials witch are correlated with the Heinrich events were Turborotalita quinqueloba and Globorotalia scitula. The most pronounced interstadials occurred between 39.5 and 38.5 cal kyr BP (C69-IST6) and between 25 and 24 cal kyr BP (C69-IST3) and are characterized by depletion in δ18O values, increases in SST and increases in humidity. The former event coincides with the formation of the sapropelitic layer S2. In the Holocene the most pronounced stadial occurred between 8 and 6.5 cal kyr BP (C69-ST2), during the interruption of S1 and is characterized by a reduction in SST and an increase in aridity. The most pronounced interstadials of Holocene occurred during the formation of S1a and S1b between 9 and 8 cal kyr BP (C69-IST1) and between 6.5 and 5.5 cal kyr BP (C69-IST2), respectively. These events are characterized by depletion in δ18O values, increased SST and an increase in humidity as is indicated by the expansion of temperate evergreen and Mediterranean taxa in the pollen record. [Copyright &y& Elsevier]