Oceanographic surveys in the Black Sea during 1998, 2002, and 2004 in the framework of a French-Romanian joint project, and recently in the framework of the European project ASSEMBLAGE, complement previous seabed mapping and subsurface sampling studies undertaken in the Black Sea by various international expeditions. Until the Ryan and Pitman flood theory and prior to this project, it was proposed that the Black Sea was predominantly a fresh-water lake interrupted by possible marine invasions coincident with high sea level during the Quaternary. From the recent surveys carried out on the western part of the Black Sea it is evident that the Black Sea's lake level rose on the shelf to at least the isobath −40 to −30 m as ascertained by the landward limit of extent of the Dreissena layer characteristic of brackish to fresh-water conditions. This rise in the lake level could coincide with the answer of the Black Sea catchment's basin to the meltwater drained from the thawing of the ice cap ensuing Melt Water Pulse 1A ( Bard et al., 1996 ). It is possible that at that time the lake level filled by fresh water reached the level of its outlet and spilled into the Mediterranean Sea. Later, in the mid-Holocene at 7.5 k.y. B.P., the onset of salt-water conditions is clearly evident in the Black Sea. From these observations Ryan et al. (1997) came to the conclusion that the Black Sea could have been filled by salt water cascading from the Mediterranean. Even though this hypothesis has been challenged ( Aksu et al., 2002b , 1999b ), the recent confirmation of the excellent preservation of drowned beaches, sand dunes, and soils during Ifremer (Institut français de recherche pour l'exploitation de la mer) surveys seems to support the Ryan and Pitman hypothesis ( Ryan and Pitman, 1999 ). The multibeam echo-sounding and the seismic reflection profiles acquired on the Romanian margin during our surveys revealed wave-cut terraces at an average water depth of 100 m. More evidence of seawater penetration is marked at the Bosphorus outlet by the presence of recent canyon heads mapped during the last cruise in 2002. The cores recovered on the Romanian continental shelf penetrated an erosion surface, indicating subaerial exposure well below the level of the modern Bosphorus outlet. The 14 C ages documented a simultaneous colonization of the terrestrial surface by marine mollusks at 7.1 k.y. B.P. The most recent palynology analysis and studies of the dynocyst population ( Popescu, 2004 ) document a real onset of fresh-water arrival during the Younger Dryas and abrupt replacement of Black Sea dynocyst by Mediterranean population, coincident with the onset of the marine mollusks.

The Dead Sea is an extremely dynamic hydrologic system, where the base level is currently declining at a rate of ∼1 m/yr. The groundwater level follows this drop within a relatively short time (a few days in the case of the extensive floods in the winter of 1991–1992). The fresh-saline water interface is very shallow, compared to that of the ocean, due to the large density difference between the fresh and saline water bodies. The interface was found to be steeper near the marginal faults, tracked in a time domain electromagnetic geophysical survey, due to the relatively low horizontal hydraulic conductivity at the fault zone. SUTRA code simulations support this result. Near the shoreline of the Dead Sea, a new coastal area is exposed, whereby the main processes are flushing of most of the section and evaporation and precipitation of salts near the surface. The effect of flushing is seen in several in situ profiles that show much lower concentrations than the original Dead Sea brine, which existed only a few decades ago. Preliminary simulations on a larger scale imply that the Dead Sea water level drop will influence groundwater levels at least several kilometers from the shoreline, increasing the hydraulic gradient and thus also the discharge to the Dead Sea.

A geochemical investigation (major cations and anions, stable isotopes of oxygen and hydrogen, pH, and salinity) was conducted to identify the sources of groundwater recharge to the surficial aquifer system in Everglades National Park. The weighted mean values of δ 18 O and δD of rainfall were −2.83‰ and −10.59‰, respectively. A mean deuterium excess value of 12 suggests that evaporation of Everglades surface water contributes between 7% and 12% to the local precipitation. Most shallow groundwater in the surficial aquifer system (<28 m) is recharged throughout the year by Everglades surface water and or canal water exposed to evaporation. Recharge rates between 2 cm/yr and 12 cm/yr were obtained, with the higher rates in areas of little to no standing water. Deep groundwater in the surficial aquifer system (>28 m) is recharged directly from rainfall far upgradient of the northern boundary of Everglades National Park. Groundwater from the underlying Hawthorn Group is geochemically distinct from the surficial aquifer system and recharges the surficial aquifer system from below. There is no geochemical evidence of surface water or shallow groundwater flow between the two major waterways (Shark Slough and Taylor Slough) in Everglades National Park. In this investigation, a combination of stable isotopes (δ 18 O and δD) and major-ion data was necessary to identify different sources of groundwater recharge to the karst aquifer. The stable isotopes (δ 18 O and δD) were most useful in deciphering between rainfall and surface-water recharge to the shallow aquifer, whereas the major-ion data were used to identify recharge from deeper aquifers and seawater intrusion.