scholarly journals Contraction-expansion dynamics of reef species in response to sea-level changes

2021 ◽  
Author(s):  
Thierry B Hoareau ◽  
Petrus Pretorius
Keyword(s):  
Sea Level ◽  
Subsequent Development ◽  
Population Level ◽  
Marine Species ◽  
Late Glacial ◽  
Sea Level Changes ◽  
Radiocarbon Dates ◽  
Last Glacial ◽  
Sea Level Fluctuations ◽  
The Last Glacial

The contraction-expansion model (CEM) describes the dynamics of species that survived in refugia during the last glacial maximum (LGM) and expanded their range when environmental conditions slowly improved from the Late Glacial through to the Holocene. The CEM has been proposed to describe the dynamics of reef species in response to sea-level fluctuations from a range of disciplines, but genetic inferences rather suggest stable population sizes since the last glacial period. Here, we address this paradox by providing a new model of modern reef development, by assessing the effect of LGM bottlenecks using genetic simulations, and by using a survey of the literature on reef species to compile both estimates of times to expansion and applied rates of molecular evolution. Using previously published radiocarbon dates of core data, we propose a synthetic model for the dynamics of modern coral reefs in the Indo-Pacific region. This model describes both an initiation at 9.9 ka and subsequent development that confirms a strong influence of sea-level fluctuations on reef dynamics. Simulations based on mtDNA datasets showed that pre-LGM genetic signatures of expansion are lost. Recent literature shows that, although genetic expansions of tropical marine species are frequent (>95%), the onset of these expansions is old (median ~110 ka), which indicates that most populations have remained stable since before the LGM. These pre-LGM expansions are explained by the low mutation rates (1.66% changes/site/Myr) known to be inadequate to calibrate time at population level. Specific calibrations should help solve the paradox and generalise the CEM for reef species.

Late-Glacial and Early Holocene Sea-Level Fluctuations in the Central Puget Lowland, Washington, Inferred from Lake Sediments

1994 ◽  
Vol 42 (2) ◽  
pp. 149-161 ◽  
Author(s):  
Karl Anundsen ◽  
Sally Abella ◽  
Estella Leopold ◽  
Minze Stuiver ◽  
Sheila Turner
Keyword(s):  
Sea Level ◽  
Late Glacial ◽  
Early Holocene ◽  
Pollen Record ◽  
Sea Level Changes ◽  
Radiocarbon Dates ◽  
Sea Level Fluctuations ◽  
Lake Outlet ◽  
Basal Section ◽  
Holocene Sea Level

AbstractAnalyses of sediments, diatoms, and pollen in a 12.65-m-long sediment core taken from Lake Carpenter in the central Puget Lowland, Washington, provide detailed information regarding the history of deglaciation and late-glacial/early Holocene sea-level changes. The lake outlet, now 8.2 m above sea level, has been lowered 1-1.5 m by postglacial erosion. The lithology and pollen record suggest that no lengthy hiatuses in sedimentation have occurred. The basal sediments are glacialmarine and contain shell fragments and brackish/marine diatoms. Freshwater sediments above the basal section are interrupted only by a short section containing few fossils, most of which are brackish to marine indicators, and by the Mazama tephra at 9.5 m. The pollen record in the basal 4 m reveals a Pinus zone (ca. 13,850-11,000 yr B.P.) with a brief peak of Picea at ca. 13,700 yr B.P., and an Alnus/Pseudotsuga zone (ca. 11,000-6500 yr B.P.). The chronology is based on nine radiocarbon ages. A relative lowering of sea level below the 9.5-m threshold is recorded in the core at 12.41 m and dates 13,850 to 13,700 yr B.P. A marine episode occurred about 13,600 yr B.P., implying that relative sea-level temporarily rose above 9.5 m. No subsequent transgressions above the 9.5-m level have been recorded. Comparison of six radiocarbon dates ≥13,600 yr B.P. suggest that the marine reservoir correction of 760 yr currently used for this area may be too high for this time period.

Sediment record of precipitation and changes in circulation in Bohol Sea area since the Last Glacial Maximum

2020 ◽  
Author(s):  
Sarahmae Buen ◽  
Fernando Siringan ◽  
Ronald Lloren
Keyword(s):  
Sea Level ◽  
Last Glacial Maximum ◽  
Accumulation Rate ◽  
The Philippines ◽  
Glacial Maximum ◽  
Radiocarbon Dates ◽  
Last Glacial ◽  
Sediment Input ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p>Deep marine sediments may provide insights of past climate and oceanographic events. Knowledge of the past events can aid in scenario setting of future climate and their oceanographic consequences. A deep sea sediment core from the western side of Bohol Sea, a marginal sea located south of the Philippines, was used to reconstruct precipitation and identify the impacts of sea level rise on the circulation of Bohol Sea.  Five radiocarbon dates from bulk organic matter provide age control spanning back to the Last Glacial Maximum. Sedimentological (lithics and carbonate fractions; bulk density; sedimentation rate and mass accumulation rate) and geochemical (Ti, Al, Zr, Ti/Al and Y/Ni) data were used to reconstruct the sediment input for the area. Sediment input was decreasing from 20-15ka, followed by a relatively stable trend until ~9ka. After ~9ka sediment input increased up until the most recent years. Sedimentation trend follows the average winter (DJF) insolation curve at 10<sup>o</sup>N. This signifies that the sediment input reflects the general changes in precipitation in the area. Lithics and carbonate contents reflect a shift in sediment source that could be attributed to the change in circulation in the basin as the sea level rose to overtop the Surigao Strait located at the northeastern side of the basin. Greater westward transport of suspended material from large rivers to the east would contribute to the sedimentation in the western part of Bohol Sea.</p>

Eustatic control of late Quaternary sea-level change in the Arabian/Persian Gulf

2014 ◽  
Vol 82 (1) ◽  
pp. 175-184 ◽  
Author(s):  
Thomas Stevens ◽  
Matthew J. Jestico ◽  
Graham Evans ◽  
Anthony Kirkham
Keyword(s):  
Sea Level ◽  
Persian Gulf ◽  
Late Quaternary ◽  
Osl Dating ◽  
Sea Level Changes ◽  
Last Interglacial ◽  
Coastal Evolution ◽  
Last Glacial ◽  
Sea Level Variations ◽  
The Last Glacial

AbstractAccurate sea-level reconstruction is critical in understanding the drivers of coastal evolution. Inliers of shallow marine limestone and aeolianite are exposed as zeugen (carbonate-capped erosional remnants) on the southern coast of the Arabian/Persian Gulf. These have generally been accepted as evidence of a eustatically driven, last-interglacial relative sea-level highstand preceded by a penultimate glacial-age lowstand. Instead, recent optically stimulated luminescence (OSL) dating suggests a last glacial age for these deposits, requiring >100 m of uplift since the last glacial maximum in order to keep pace with eustatic sea-level rise and implying the need for a wholesale revision of tectonic, stratigraphic and sea-level histories of the Gulf. These two hypotheses have radically different implications for regional neotectonics and land–sea distribution histories. Here we test these hypotheses using OSL dating of the zeugen formations. These new ages are remarkably consistent with earlier interpretations of the formations being last interglacial or older in age, showing that tectonic movements are negligible and eustatic sea-level variations are responsible for local sea-level changes in the Gulf. The cause of the large age differences between recent studies is unclear, although it appears related to large differences in the measured accumulated dose in different OSL samples.

scholarly journals Late Glacial Marine Transgression and Ecosystem Response in the Landlocked Elefsis Bay (Northern Saronikos Gulf, Greece)

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1505
Author(s):  
Katerina Kouli ◽  
Maria V. Triantaphyllou ◽  
Olga Koukousioura ◽  
Margarita D. Dimiza ◽  
Constantine Parinos ◽  
...  
Keyword(s):  
Sea Level ◽  
Late Glacial ◽  
Ecosystem Response ◽  
Sea Level Changes ◽  
Marine Transgression ◽  
Sea Level Fluctuations ◽  
Geological Processes ◽  
Marginal Areas ◽  
Coastal Landscapes ◽  
Marine Realm

Coastal landscapes are sensitive to changes due to the interplay between surface and submarine geological processes, climate variability, and relative sea level fluctuations. The sedimentary archives of such marginal areas record in detail the complex evolution of the paleoenvironment and the diachronic biota response. The Elefsis Bay is nowadays a landlocked shallow marine basin with restricted communication to the open Saronikos Gulf. A multi-proxy investigation of a high-resolution sediment core recovered from the deepest part of the basin offered a unique opportunity to record the paleoenvironmental and aquatic ecosystem response to climate and glacioeustatic sea level changes since the Late Glacial marine transgression. The retrieved sedimentary deposits, subjected to thorough palynological (pollen, non-pollen palynomorphs, dinoflagellates), micropaleontological (benthic foraminifera, calcareous nannoplankton, ostracods), and mollusc analyses, indicates isolation of the Elefsis Bay from the Saronikos Gulf and the occurrence of a shallow freshwater paleolake since at least 13,500 cal BP, while after 11,3500 cal BP the transition towards lagoon conditions is evidenced. The marine transgression in the Elefsis Bay is dated at 7500 cal BP, marking the establishment of the modern marine realm.

scholarly journals Submarine Geomorphology of the Southwestern Sardinian Continental Shelf (Mediterranean Sea): Insights into the Last Glacial Maximum Sea-Level Changes and Related Environments

Water ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 155
Author(s):  
Giacomo Deiana ◽  
Luciano Lecca ◽  
Rita Teresa Melis ◽  
Mauro Soldati ◽  
Valentino Demurtas ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Sea Level ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Sea Level Changes ◽  
Side Scan Sonar ◽  
Last Glacial ◽  
Depositional Processes ◽  
The Last Glacial Maximum ◽  
The Last Glacial

During the lowstand sea-level phase of the Last Glacial Maximum (LGM), a large part of the current Mediterranean continental shelf emerged. Erosional and depositional processes shaped the coastal strips, while inland areas were affected by aeolian and fluvial processes. Evidence of both the lowstand phase and the subsequent phases of eustatic sea level rise can be observed on the continental shelf of Sardinia (Italy), including submerged palaeo-shorelines and landforms, and indicators of relict coastal palaeo-environments. This paper shows the results of a high-resolution survey on the continental shelf off San Pietro Island (southwestern Sardinia). Multisensor and multiscale data—obtained by means of seismic sparker, sub-bottom profiler chirp, multibeam, side scan sonar, diving, and uncrewed aerial vehicles—made it possible to reconstruct the morphological features shaped during the LGM at depths between 125 and 135 m. In particular, tectonic controlled palaeo-cliffs affected by landslides, the mouth of a deep palaeo-valley fossilized by marine sediments and a palaeo-lagoon containing a peri-littoral thanatocenosis (18,983 ± 268 cal BP) were detected. The Younger Dryas palaeo-shorelines were reconstructed, highlighted by a very well preserved beachrock. The coastal paleo-landscape with lagoon-barrier systems and retro-littoral dunes frequented by the Mesolithic populations was reconstructed.

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