Lagoon Formation Research Articles

Coastal Evolution of Satingpra Peninsula, Songkhla Province: Implications for Understanding Songkla Lagoon Formation

Songkhla Lagoon has been studied for decades, but there is no clear evidence of its origin. As a barrier to the lagoon, the Satingpra Peninsula plays a crucial role in understanding its formation. Eleven sediment samples from sand ridges and tidal flats on the Satingpra Peninsular were collected and analysed for granulometry and geochronology. Both coarse-grained and fine-grained quartz-rich fractions were utilised to prepare samples of aliquots. The optically stimulated luminescence (OSL) dating was performed using the single-aliquot regenerative dose method for a determined (deposited) age. In addition, previous research, geological surveys and geochronological data were combined to explain their formation in this region. The OSL ages in the present study indicated that the late Holocene regression occurred between 0.36 and 3.27 ka (ka stands for 1,000 years). Integrated with previous studies, recorded ages dating back to the mid-Holocene sea level rise (ca. 6.5 ka) and the subsequent late-Holocene decline, indicate that both the old lagoon and middle beach ridge exhibit a sand ridge formation that runs parallel to the shoreline, extending from the south to the north. The middle sand, in this study, formed from about 3.02 to 1.5 ka ago resulting in the lagoon being isolated from the sea during that time. The lagoonal tide led the deposition as the present tidal flat from 3.3 to 1.7 ka. About 2.19 ka ago, the inner and middle ridges formed due to wind-driven processes influenced by a dry climate. This was followed by a continued sea level regression, leading to the formation of the outer ridge around 1.5 ka ago when the sea level was 1.4 m below the present sea level. However, it’s essential to consider this sea level data in relation to the tectonic and human-induced land motions in the surrounding area. HIGHLIGHTS OSL ages, based on average dose model at the Northern Satingpra Peninsula were 1.04 - 3.27 ka. The old sand ridges of the Satingpra Peninsula prograde northward after mid Holocene sea level highstand. Paleo sea level based on wind-wave sediments contact was 1.4 m lower than present day at 1.46 ka. GRAPHICAL ABSTRACT

Flood mapping of the lower Mejerda Valley (Tunisia) using Sentinel-1 SAR: geological and geomorphological controls on flood hazard

Understanding the influence of the hydrological regime changes, encompassing both the duration and spatial extent of floods, is explored, through this paper, in the context of the complex interactions of the geological, geomorphological and climate change conditions. Integrating these parameters and their combined influence becomes paramount for effective flood risk management and disaster prevention, as highlighted in the broader context of the study’s conclusions. Over the past decade, despite prevailing drought conditions in North African countries, the Mejerda Valley in Tunisia has experienced several major flood events. The valley geomorphological history is presented, within the landscape evolution. This study explores the use of Sentinel-1 radar data for detecting and managing floods in the region, with a particular emphasis on the vulnerability of the Lower Mejerda Valley. Sentinel-1 radar data, owing to their continuous monitoring capabilities independent of weather conditions, prove highly effective in tracking the temporal evolution of floods and accurately mapping the extent of affected areas. The methodology utilized in this study has proven to be highly effective in accurately identifying areas susceptible to flooding, both spatially and temporally. In generating classified flood images, water objects are highlighted by applying a specific formula. The study delves into significant flood events in the Mejerda Valley, including occurrences in 2015, 2017, 2019, and 2020, examining their profound impacts on various regions. For instance, the floods of 2015 recorded precipitation levels reaching up to 141 mm, contributing to the overall understanding of flood evolution in the region. In conclusion, the Mejerda Delta’s relief is primarily due to tectonism, influencing both Mio-Pliocene and Quaternary processes, shaping the current delta configuration. The Valley’s topography results from extensive geomorphological evolution, with the eastward shoreline advance leading to the formation of sebkhas and lagoons, indicators of high flood risk, supported by detailed flood event analysis. Moreover, The climate change and anthropic activity are non-negligible parameters influencing flood occurrence and intensity.

Evidence of recent sea-level rise and the formation of a classic Maya canal system inferred from Boca Paila cave sediments, Sian Ka'an biosphere, Mexico

Cave sediments along the eastern coast of the Yucatán Peninsula contain important records of paleoenvironmental change that have not been fully explored. Reconstructing environmental changes in Boca Paila lagoon reveals details about sea level, flooding of the Sian Ka'an Biosphere, and the timeline of occupation at Muyil, an important Classic Maya maritime trading site. Three sediment cores (BP1, BP2, and BP3) were collected from a cave system beneath Boca Paila lagoon in the Sian Ka'an Biosphere. Radiocarbon dating, geochemical (X-Ray Fluorescence Core Scanning, δ13C, C/N), and microfossil (foraminifera, diatoms, pollen) analyses were performed. The combined results show three distinct phases of coastal evolution. Phase 1 (1157 BCE or earlier), an upland area with mangrove associate Conocarpus erectus, grasses, and ferns, is characterized by: organic-rich detrital peat; a relative absence of foraminifera and diatoms; organic geochemistry results within terrestrial ranges (δ13C values of −28‰ to −26‰); and low Sr/Ca, Si/Ti, and Ti/K ratios. These indicate dry conditions at the karst surface. Phase 2 (1157 BCE – 312 CE), a shallow wetland, is represented by: an increase in weathering products (Ti/K) and diatom productivity (Si/Ti); more positive δ13C values (−27‰ to −22‰) and decreasing C/N ratios; and increased marine foraminifera (e.g., Ammodiscus sp.). These indicate more open water conditions. Phase 3 (>312 CE), a wetland/lagoon environment, is characterized by: carbonate-rich marl; a greater diversity of foraminifera (Ammonia spp., Elphidium spp., Rosalina spp., and Bolivina spp.), diatoms (Cyclotella meneghiniana, Craticula spp., Amphora spp., Hyalosynedra laevigata, and Grammatophora spp.) and pollen (from mangroves, ferns, grasses, palms, and pine); increased Si/Ti and Sr/Ca values; and mixed marine and terrestrial organic geochemistry values (δ13C values of −22‰ to −20‰). These indicate increased input of marine organic sediment during sea-level rise. Sea-level and climate records support the interpretation of a dry upper karst environment prior to ∼1157 BCE, with sea-level rise forming shallow (<50 cm) wetlands by ∼312 CE. Previous archaeological analysis estimates that the first settlers arrived at Muyil ∼350 BCE, but that population expansion and construction of most structures occurred during the Postclassic (925–1550 CE). Sea-level rise would have been an important factor in the expansion of coastal settlements and trade routes; continued sea-level rise after ∼312 CE allowed for the formation of deeper lagoons and channels connecting the coast to Muyil and other inland sites which would likely not have been navigable prior to the Early Classic period (250–600 CE) as they would be too shallow. This study highlights the impacts of environment on society, as well as the importance of karst cave systems for obtaining paleoenvironmental records.

Microbial methane cycling in sediments of Arctic thermokarst lagoons.

Thermokarst lagoons represent the transition state from a freshwater lacustrine to a marine environment, and receive little attention regarding their role for greenhouse gas production and release in Arctic permafrost landscapes. We studied the fate of methane (CH4 ) in sediments of a thermokarst lagoon in comparison to two thermokarst lakes on the Bykovsky Peninsula in northeastern Siberia through the analysis of sediment CH4 concentrations and isotopic signature, methane-cycling microbial taxa, sediment geochemistry, lipid biomarkers, and network analysis. We assessed how differences in geochemistry between thermokarst lakes and thermokarst lagoons, caused by the infiltration of sulfate-rich marine water, altered the microbial methane-cycling community. Anaerobic sulfate-reducing ANME-2a/2b methanotrophs dominated the sulfate-rich sediments of the lagoon despite its known seasonal alternation between brackish and freshwater inflow and low sulfate concentrations compared to the usual marine ANME habitat. Non-competitive methylotrophic methanogens dominated the methanogenic community of the lakes and the lagoon, independent of differences in porewater chemistry and depth. This potentially contributed to the high CH4 concentrations observed in all sulfate-poor sediments. CH4 concentrations in the freshwater-influenced sediments averaged 1.34 ± 0.98 μmol g-1 , with highly depleted δ13 C-CH4 values ranging from -89‰ to -70‰. In contrast, the sulfate-affected upper 300 cm of the lagoon exhibited low average CH4 concentrations of 0.011 ± 0.005 μmol g-1 with comparatively enriched δ13 C-CH4 values of -54‰ to -37‰ pointing to substantial methane oxidation. Our study shows that lagoon formation specifically supports methane oxidizers and methane oxidation through changes in pore water chemistry, especially sulfate, while methanogens are similar to lake conditions.

Thermokarst Lagoons: A Core-Based Assessment of Depositional Characteristics and an Estimate of Carbon Pools on the Bykovsky Peninsula

Permafrost region subsurface organic carbon (OC) pools are a major component of the terrestrial carbon cycle and vulnerable to a warming climate. Thermokarst lagoons are an important transition stage with complex depositional histories during which permafrost and lacustrine carbon pools are transformed along eroding Arctic coasts. The effects of temperature and salinity changes during thermokarst lake to lagoon transitions on thaw history and lagoon deposits are understudied. We analyzed two 30-m-long sediment cores from two thermokarst lagoons on the Bykovsky Peninsula, Northeast Siberia, using sedimentological, geochronological, hydrochemical, and biogeochemical techniques. Using remote sensing we distinguished between a semi-closed and a nearly closed lagoon. We (1) characterized the depositional history, (2) studied the impact of marine inundation on ice-bearing permafrost and taliks, and (3) quantified the OC pools for different stages of thermokarst lagoons. Fluvial and former Yedoma deposits were found at depth between 30 and 8.5 m, while lake and lagoon deposits formed the upper layers. The electrical conductivity of the pore water indicated hypersaline conditions for the semi-closed lagoon (max: 108 mS/cm), while fresh to brackish conditions were observed beneath a 5 m-thick surface saline layer at the nearly closed lagoon. The deposits had a mean OC content of 15 ± 2 kg/m3, with higher values in the semi-closed lagoon. Based on the cores we estimated a total OC pool of 5.7 Mt-C for the first 30 m of sediment below five mapped lagoons on the Bykovsky Peninsula. Our results suggest that paleo river branches shaped the middle Pleistocene landscape followed by late Pleistocene Yedoma permafrost accumulation and early Holocene lake development. Afterward, lake drainage, marine flooding, and bedfast ice formation caused the saline enrichment of pore water, which led to cryotic talik development. We find that the OC-pool of Arctic lagoons may comprise a substantial inventory of partially thawed and partially refrozen OC, which is available for microbial degradation processes at the Arctic terrestrial-marine interface. Climate change in the Arctic leading to sea level rise, permafrost thaw, coastal erosion, and sea ice loss may increase the rate of thermokarst lagoon formation and thus increase the importance of lagoons as biogeochemical processors of former permafrost OC.

ПРОИСХОЖДЕНИЕ “ВРЕЗАННЫХˮ ИЛИ СЛЕПЫХ ДЕЛЬТ НА ВОЛГО-УРАЛЬСКОМ МЕЖДУРЕЧЬЕ В СВЕТЕ НОВЫХ ПРЕДСТАВЛЕНИЙ ОБ ИСТОРИИ КОЛЕБАНИЙ УРОВНЯ КАСПИЯ

The relief of the Volga-Ural interfluve is considered, where the rivers in the mouths form “embedded” or blind deltas. These deltas terminate close to the Volga-Ural Sands. During spring snowmelt floods, large lakes appear at the mouths of rivers. Therefore, it is difficult to agree with the opinion that the rivers disconnected from the sea during the regression phases due to the low water levels in rivers. Sea regression led to the downcutting of the delta channels into the alluvial and marine deposits. Analysis of the outcrops, taking into account the coastal geomorphology and the impact of the sea level fluctuations on the coast has led to the conclusion that there was no deep Atelian regression and Great Early Khvalynian transgression. It was a Great Khazarian transgression, after which lagoon-transgressive terraces formed sequentially at the background of the gradual lowering of the Caspian Sea. Positive oscillations of sea level led to the formation of lagoons, where the chocolate clays accumulated. All tributary rivers formed deltas that prograded into such lagoons. Therefore, Sea the rivers could not follow the coastline during the subsequent lowering of the Caspian Sea. The shallowing of the lagoons resulted in the drainage of the deltas. When the water level in the lagoons dropped, rivers cut in deltaic deposits and “embedded” or blind deltas were formed.

Comparative population genetics and demographic history of two polychaete species suggest that coastal lagoon populations evolve under alternate regimes of gene flow

Here, we compare the population genetic structure and the demographic history of two polychaete species along one bay and eight coastal lagoons distributed over ~ 200 km of the Southwest Atlantic to understand the evolution of discontinuous and confined inland ocean-connected waters populations. A total of 515 sequences of COI and 16S were obtained for Laeonereis culveri and Capitella nonatoi. Levels of genetic diversity and population genetic structure were higher for C. nonatoi than L. culveri, possibly reflecting the differences in life-history strategies. Furthermore, the genetic diversity of both species was, in general, smaller in more confined populations. Populations of both species showed signs of recent demographic expansion, although it was more pronounced in C. nonatoi. As the population size of both species may reach high densities in highly eutrophic environments, these expansions are probably associated to the coastal lagoon formation, which favors the process of organic matter accumulation and the water oxygenation reduction. The general pattern of haplotype distribution revealed high levels of haplotype sharing among populations, mainly in L. culveri. On the other hand, the observed number of exclusive haplotypes indicates that the genetic exchange among populations is not as high as it may seem. This result suggests that coastal lagoons populations evolve under alternate regimes of soft (physiological barriers) and strong (physiological and physical barriers) gene flow restriction.

Landscape and environmental changes along the Eastern Primorye coast during the middle to late Holocene and human effects

Several stages are recognizable in landscape evolution along the Eastern Primorye coast, Kit Bay and its surrounding mountains in terms of climatic changes and related sea level fluctuations during the middle–late Holocene. The last 3.8–3.5 cal ka years were marked by a notable effect of the pyrogenic factor. The sea level rise at the maximum phase of the Holocene transgression led to the formation of lagoons at stream mouths, which underwent a complicated development. At that time, the coast’s principal topographic elements came into being, and the modern landscape’s pattern was laid on the coastal lowlands. The authors trace the changes in the vegetation in the process of short-term warmings and coolings. Korean pine appeared in the forests surrounding Kit Bay much earlier than in other regions of the Eastern Primorye. During the considered period, warmer phases were marked by increasing importance of broadleaf species, while at the cooler phases, a proportion of the Korean pine grew in the low mountains. In the last 2.3 cal ka, at greater elevations in the middle mountains, dark coniferous forests became more widespread, particularly spruce. At the same time, larch groves existed around the coastal sphagnum bog, probably due to seasonally frozen ground persisting for the greater part of a year. Extreme events with a considerable effect on the coastal landscape evolution include floods, whose frequency has been growing for the last 1.75 cal ka. Strong tsunamis are another factor influencing coastal evolution. Finally, changes in landscapes have been recorded related to human activities in the last few decades.

Evaluating Scientific Value of Geodiversity for Natural Protected Sites: the Biga Peninsula, Northwestern Turkey

This study aims to report on an inventory of geodiversity features of natural protected sites distributed in the Biga Peninsula in Northwestern Anatolia (Turkey). There are 37 natural sites with their own data sets. Data of the sites describing their boundaries and administrative features were acquired from the national authority. The criteria scale was established for geoscience value for the methodology applied. A conceptual (qualitative) geosite inventory was established for intrinsic geosite potential according to representativeness, rarity, integrity, and scientific knowledge. Then, a semi-quantitative assessment was carried out to compare and parameterize the potential geosites in the scope of representativeness, key locality, geological diversity, rarity, integrity, scientific knowledge, and limitations. From these results, a total of seven sites is highlighted due to their scores for different geodiversity assets. The sites located inland represent endogenous assets labeled lithological, fault, or geothermal, whereas the sites located along the coast are dominated by their exogenous asset (lagoon formation) or simply a geomorphological feature.

The Genesis and Evolution of the Caspian Sea Lagoons as Avifauna Refuges at the Transboundary Scale

The article summarizes 34 years (1980-2014) of the original observations of the genesis and evolution stages of the Caspian lagoons. A model of the formation and evolution of the coastal lagoons has been worked out. It can be applied to the modelling of the global geoecological scenario along all the world’s coasts characterized by a steady transgression of their marine areas. The lagoons had been formed in a “bottleneck”, a narrow migration corridor, traversed by the largest migration route of trans-Palearctic species in Russia. This route is part of the West Siberian-East African migration range. Year round bird censuses (n = 746) were taken by the author in 1995-2014 along two key routes in the regions of Turalinskaya and Sulakskaya lagoons of Daghestan (the western coast of the Middle Caspian Sea). The meridional orientation of lagoons, location of the migration trajectory and a wide range of habitats in the study area contribute to the preservation of 294 Eurasian bird species. After formation of the lagoons, the breeding avifauna of the Caspian Sea Region of Central Daghestan has added 32 taxa. Among the species recorded at the lagoons, 50 are included in the IUCN Red List, Red Data Books of Russia and Daghestan. The reconstruction analysis of the migration trajectory compiled according to the data of the Russian Bird Ringing Centre allowed us to determine the population distribution geography for the birds regularly migrating along the western coast of the Caspian Sea and refine borders of theWest Siberian-East African migration range. Thus, according to the information received, the current migratory range should be greatly extended to cover the area from the British Isles in the West Palearctic to Lake Baikal in the east, including the extreme west and south of Africa.

LAGOON-TRANSGRESSIVE TERRACES

During the sea-level rise lagoon formation is taking place if the dip of the coastal land is less than the dip of the offshore. Under such condition lagoon and coastal bar appear simultaneously. They are genetically associated and form joint transgressive system. The sediments of bar and lagoon are of different types, though their accumulation occurs at the same hypsometric level. Thence, lagoon sediments in the transgressive train have a seat rock from previous regressive phase; they are overlay by shelly and sandy loose beach deposits of the same transgressive stage as lagoon loam and have the same age. Such paragenesis should be taken into account while interpreting geological data and paleogeographical reconstructing.

Late-Holocene record of lagoon evolution, climate change, and hurricane activity from southeastern Cuba

A sediment core from a lagoon in southeastern Cuba was the focus of a multi-proxy paleoenvironmental study to investigate lagoon response to sea-level change and climate change and also to infer changes in the frequency of past hurricane strikes. The proxy data examined included benthic foraminifera, fossil pollen, particle size analysis, and macrocharcoal influx values. The core was dated using 137Cs and accelerator mass spectrometry (AMS) radiocarbon methods. The results show that lagoon formation began approximately 4000 years ago and that the lagoon environment evolved through four phases: (1) from ~4000 to 2800 cal. yr BP, the lagoon was a shallow polyhaline to euryhaline system with limited mangrove coverage; (2) from ~2800 to 2000 cal. yr BP, there was a decrease in salinity which facilitated the expansion of red mangrove; (3) from ~2000 to 1000 cal. yr BP, sea-level rise resulted in an increase in water depth and possibly salinity; and (4) from ~1000 cal. yr BP to the present, water level continued to rise and the mangrove environment diversified. The shift to lower salinity conditions from ~2800 to 2000 cal. yr BP may have been climate driven as similar changes are seen at lagoons elsewhere in Cuba. The particle size data show several periods where sand-sized particles are more abundant; these periods are similar to data from Puerto Rico that document times of relatively frequent hurricanes. This paper shows that coastal lagoons are useful archives of paleoclimatic and paleoenvironmental information in the Caribbean region and that they should be the focus of additional research efforts.

Sedimentary Patterns and Evolution of Coastal Environments during the Holocene in Central Belize, Central America

ABSTRACT Adomat, F. and Gischler, E., 2015. Sedimentary patterns and evolution of coastal environments during the Holocene in central Belize, Central America. Coastal lagoons, marshes, and swamps cover large areas of the Belize coast. Twenty-six sediment cores collected along five transects along the central Belize coast and 58 radiocarbon dates from these cores reveal stratigraphic details of coastal sediment deposition. Marine inundation of the mainland and coastal lagoon formation started between 7980 calendar years before present (cal BP) and >5547 cal BP. As a response to sea-level rise during the Holocene transgression, facies retrograded toward the coast, as seen in marginal marine overlying brackish mollusk faunas. Evidence for late Holocene progradation of facies due to sea-level stagnation is largely lacking. The occurrence of landward thinning sand beds, hiatuses, and marine fauna in lagoonal successions are indications of event (overwash) sedimentation. Sediments recovered are largely of Holoc...

New Light on the Evolutionary History of the Common Goby (Pomatoschistus microps) with an Emphasis on Colonization Processes in the Mediterranean Sea

Through the study of the phylogeographic structure and demographic history of the common goby, Pomatoschistus microps, the influence of Quaternary climatic changes on the evolutionary history of coastal and marine fishes is investigated. Because of its sedentary life cycle in Mediterranean lagoons, it is also a good model to study more specifically if the formation of lagoons during the Holocene had an impact on population structure and demography. Mitochondrial sequences of Northeastern Atlantic and Western Mediterranean specimens were used for phylogenetic reconstructions as well as divergence time estimates, demographic history and population structure analyses. Pomatoschistus microps was a highly supported monophyletic clade including four lineages. It may have appeared 77,000 yr ago, and the divergence of its lineages likely occured shortly thereafter (between 61,000 and 54,000 yr). Most lineages had polytomic topologies, low nucleotide diversity and demographic analyses providing evidence of population expansion. Each lineage was characterized by a large number of private haplotypes. Most haplotypes found in Mediterranean localities were endemic, and one was dominant. Complex reticulated relationships connecting North European, Atlantic and Mediterranean haplotypes were observed. Moderate to high population structure was underlined. Contrary to previous published studies, no significant differentiation was observed between Atlantic and Mediterranean populations, indicating that the Gibraltar Strait is not a phylogeographic break for P. microps. Indeed, molecular dating combined with the tree topologies, phylogeographic and demographic analyses as well as high haplotype diversity underline a recent and rapid population divergence during the last glacial. However, population structure indicates that differentiation is an ongoing process. From an ancestral population trapped in the Atlantic, this goby colonized first northern Europe and later the Mediterranean Sea. Shared haplotypes could have dispersed in the western Mediterranean basin before the lagoon formation, while most private haplotypes, evidencing a recent isolation, probably diverged in lagoons after their closure.

Development of spit–lagoon complexes in response to Little Ice Age rapid sea-level changes in the central Guilan coast, South Caspian Sea, Iran

The central Guilan coast along the Iranian Caspian coastline is characterized by sandy beaches and the development of spit–lagoon complexes, which are prone to preserve past sea-level fluctuations. The morphology of three spit–lagoon complexes along the central Guilan coast was studied using ground penetrating radar (GPR) and sediment sequences to understand the effects of past sea-level changes on spit–lagoon development. The results showed the prominent role of coastal setting in conditioning the development of spit–lagoon formation in response to sea-level change. When the Caspian Sea experienced a highstand in the Little Ice Age, the coast of central Guilan recorded fluctuations in sedimentation which are reflected, for example, by river avulsion and beach ridge formation depending on physical setting. In the western half of the central Guilan, eastward longshore currents and strong wave action on a W–E coastline coupled with sea-level changes shaped the Anzali spit–lagoon complex; while in the eastern part of the studied area river avulsion and changing the coastline orientation are responsible for development of the Amirkola and Kiashahr spit–lagoon complexes under the same sea-level fluctuations. Although sea-level change has a major role in spit–lagoon development, an increase in the frequency of storms, changes in sediment supply due to more precipitation, and river avulsion are other players in spit–lagoon development in the central Guilan during the Little Ice Age and more recent times.

Temporal evolution of the area of Capo Peloro (Sicily, Italy) from pristine site into urbanized area

1 - The area of Capo Peloro was examined as a natural system subjected to an increasing anthropogenic pressure, resulting in alteration of its ecological characteristics. According to the hypothesis of Barrier (1995), Capo Peloro was originated by tectonic movements along the Straits of Messina during the Pliocene and the Pleistocene times. Two different models of littoral barrier construction, were suggested by Bottari & Carveni (2009) and by Chillemi (1995). Both of them have lead to the formation of brackish lagoons along the coastline similar to those existing now. 2 - Historical evidence of Greek and Roman times, supports the existence of a bay able to accommodate vessels up to the I century B.C. The evolution into brackish lagoons appears accomplished in the V century A.D., as documented in 1864 by Solino. The salt marsh along with the two adjacent lakes, formed a complex ecosystem able to support local hunting and fishing. At the same time, swordfish fishing in the Straits of Messina became a fashionable leisure for the Elders of the city and their famous guests. 3 - A series of channels linking the lakes to each other and to the neighbouring sea can be found at the beginning of XIX century A.D., during the British occupation; they were focused to protect the Bourbons from possible invasions of Sicily made by the French. A marshland between the two lakes was claimed due to the achievement of military fortresses built along the coast from Messina to Capo Peloro. During the same period, the Bourbons gave permission to clean up the area to create a fishing reserve in the Ganzirri lake. 4 - Gradually, in the second half of the XIX century, the drained marshy area was used as farmland. In the two lakes, the harvesting of clams from spontaneous became shellfish farming. The rearing process involved the tampering of the lake bottom to create the mounds in which to enter the clams for their growth. In addition to local species, the introduction of allochthonous species (oysters, mussels ...) is mentioned in some documents of the late XIX century. 5 - The intensification of shellfish farming has led to significant influences also on autotrophic biomass. Legal disputes also arose as to the rights of property resulting from the division into parcels granted to individual owners. The violent impairment of the territory has developed over the last 50 years through the intense urbanization extended to all the area of Capo Peloro.

Long-term water monitoring in two Mediterranean lagoons as an indicator of land-use changes and intense precipitation events (Adra, Southeastern Spain)

During recent historical times the Adra river delta, a detrital coastal aquifer of nearly 32 km 2 located in a semi-arid, mountainous area of SE Spain, has undergone different changes caused by human activity. Within this context, both the river dynamics in the plain and the geomorphology of the coastline have at various times resulted in the formation of small lagoons. At present only two small (<0.5 km 2) lagoons exist, at the eastern edge of the aquifer, which, although closely surrounded by commercial market-garden greenhouses, are protected under international agreements. During the last 30 years of the twentieth century traditional agricultural irrigation techniques have undergone significant changes to improve their efficiency. Surface-water resources in the Adra river basin are regulated via the Beninar reservoir. In addition, the use of groundwater is increasing progressively. Both these factors affect the recharge of the coastal aquifer. To monitor these changes measurements of electrical conductivity and water level fluctuations have been recorded in these lagoons for the last 35 years (1975–2010). A comparison of the hydrochemical characteristics of the water in the lagoons and of the surrounding groundwater from 2003 to 2010 shows marked differences induced by the different hydrological dynamics in each lagoon, as well as by the hydrogeological impact of changes in land use in the delta. The increase in water demand is a consequence of the extension of irrigated areas from the fluvio-deltaic plain to its slopes, originally occupied by unirrigated crops. A reduction in irrigation return-flow is linked to the use of new irrigation techniques. These modifications affect both the recharge regime of the aquifer and its water quality. Moreover, extreme precipitation events, which are characteristic of Mediterranean semi-arid environments, can affect the lagoons’ hydrological dynamics to a considerable extent. One such example is the unusually rainy period from January to March 2010 (>600 mm). This event, along with other effects, has dramatically lowered the salinity of the water in both lagoons. This case study reveals the extreme vulnerability of deltaic environments and also how lagoons can reflect anthropogenic changes over the whole river basin.

First lake record of Holocene climate and vegetation change of the Northern Kuril Islands

Investigation of Pernatoe Lake sediments in the south of Paramushir Island has enabled us to obtain the first continuous pollen record of climate and vegetation changes in the north of the Kurile archi� pelago during the Holocene. Series of radiocarbon datings of between 10 000 ± 40 and 2180 ± 40 years ago are evidence that the beginning of sediments accumulation, found after borehole development, is related to the Early Holocene. Diatom analysis has shown several stages in the lake development: raised bog on the border of the Pleistocene and Holocene, lagoon formation resulting from the sea level rise over 9-6 ky, and freshwa� ter lake formation 6 ky and up to the present. Climate warming during the period attributed to the boreal and Atlantic periods of the Holocene is reflected by the dominance of Pinus pumila and Alnus serrulata assem� blages in vegetation cover. Wide dune fields were formed in the Sea of Okhotsk and the Pacific shores of Para� mushir Island 5-4 ky. Strengthening of atmogenic processes is related to cooling of the climate and drying of some areas of the underwater slope. DOI: 10.1134/S1028334X1002011X

Dinámica del manglar en el complejo lagunar de Cispatá(Caribe colombiano) en los últimos 900 años

The lagoon complex of Cispatá (old Sinú river delta) located at the Northwestern coast of the Colombian Caribbean, encloses one of the biggest mangrove areas in this region. This area has changed during the last 330 years because of several environmental and climatic causes, mainly changes in the position of the delta (Sinú River), which is the main freshwater source in this area, and sea level rise. We hypothesized that the climatic and geomorphologic dynamics has caused changes in the extension and composition of mangrove vegetation, especially during last 150 years. The dynamics of mangroves during the last 900 years was reconstructed based on the changes in the stratigraphy, pollen record, calcite concentrations (CaCO3) and C/N ratio, along two sediment cores from La Flotante and Navio lagoons, located in Cispatá complex. The age model was built based on lineal interpolation of 210Pb ages and changes in granulometry. Establishment and expansion of mangrove forests during the last 900 years were related to fluviomarine dynamics in the area and the lagoon formation. During the period encompassed between 1064 and 1762 A.D., the Mestizos spit was formed when marine conditions predominated in the surroundings of La Flotante Lagoon. At the site of Navío, a river dominated lagoon, terrigenous conditions dominated since 1830. Although the colonization of herbaceous pioneer vegetation started between 1142 and 1331 A.D., mangrove colonization only took place since 1717 A.D. Mangrove colonization was a result of the delta progradation. In 1849 A.D. the Sinú river delta migrated to the Cispatá bay. The eustatic sea level rise, the increase in river discharges and sedimentation rates produced the establishment of mangrove forests dominated by Rhizophora since 1849. Since 1900 a marine intrusion was recorded in both lagoons. In 1938, the migration of the delta toward its actual location in Tinajones gave place to the formation of the present lagoon system and to the expansion of mangrove forests, which reflects the balance between the high alluvial sediment input and the current sea level rise as has been recorded in similar ecosystems.

Pro-thrombolites from Laguna San Ignacio, B.C.S., Mexico.

New information is presented on the presence of prothrombolites in coastal lagoons of the Baja California Peninsula. The photographic records of prothrombolytic structures in Laguna San Ignacio, B.C.S. support the hypothesis that these promoted the formation of coastal lagoons throughout the Mexican northwest and that the cyanophyte species involved are the same.