Evaluating spatial variability of subsurface carbon stock and free-phase gas using ground-penetrating radar and direct measurements in coastal landforms of South-West Indian peatlands

Organic rich soils (peat) store significant amount of global soil carbon (C) in the form of methane (CH4) and carbon dioxide (CO2). Peat soils act as sinks and are a source of greenhouse gases (GHG) which occur in the form of Free Phase Gas in coastal landforms. South-West India has an extensive wetland system and is the primary source of GHG emissions, and CH4, in particular, has high potential to contribute to global climate change. In this scenario, this study sheds light on how SW Indian peatlands contribute to the global carbon cycle. The soil C stock and GHG spatial distribution in three distinct topographic coastal landforms within the peatland region were investigated: site 1, Muthukulam in the wetland boundary; site 2, Ramapuram in the paleo-sand ridge, and site 3, Eruva in the paleo-drainage channel. The combination of non-destructive Ground Penetrating Radar (GPR) and direct measurement (coring) in conjunction with the C core analysis helped in building the relationship between the GHG storage in the landforms of varying C stocks. Moreover, Common offset GPR has the ability to image subsurface features, lithological boundaries, coastal landforms, and peat-forming environments. The result from this study depicts the importance of different landforms in the storage of C and GHG in SW Indian peatlands.

Coastal Landform Constrains Dispersal in Mangroves

Mangrove forests are dynamic ecosystems found along low-lying coastal plains along tropical, subtropical, and some warm-temperate coasts, predominantly on tidal flats fringing deltas, estuaries, bays, and oceanic atolls. These landforms present varied hydrodynamic and geomorphological settings for mangroves to persist and could influence the extent of within-site propagule transport and subsequent local regeneration. In this study, we examined how different landform characteristics may influence local genetic diversity, kinship, and neighborhood structure of mangrove populations. To do so, we considered independent populations of Avicennia marina, one of the most abundant and widespread mangrove species, located in estuarine and coastal bay environments spread across the Western Indian Ocean region. A transect approach was considered to estimate kinship-based fine-scale spatial genetic structure using 15 polymorphic microsatellite markers in 475 adult A. marina trees from 14 populations. Elevated kinship values and significant fine-scale structure up to 30, 60, or 90 m distances were detected in sheltered systems void of river discharge, suggesting a setting suitable for very local propagule retention and establishment within a neighborhood. Slopes of a linear regression over restricted distance within 150 m were significantly declining in each sheltered transect. Contrastingly, such a spatial structure has not been detected for A. marina transects bordering rivers in the estuarine systems considered, or alongside partially sheltered creeks, suggesting that recruitment here is governed by unrelated carried-away mixed-origin propagules. South African populations showed strong inbreeding levels. In general, we have shown that A. marina populations can locally experience different modes of propagule movement, explained from their position in different coastal landforms. Thus, the resilience of mangroves through natural regeneration is achieved by different responses in coastal landforms characterized by different hydrodynamic conditions, which can be important information for their management and protection within the variety of coastal environments.

Between Natural and Anthropogenic Coastal Landforms: Insights from Ground Penetrating Radar and Sediment Analysis

Both natural and anthropogenic coastal landforms characterize Penang Island. As years have passed it is a challenge to differentiate the genuineness of landmasses created by natural geological formations or by coastal reclamation projects. An account is given of the environmental impact of solid wastes used for reclaiming land in coastal areas of Penang and of the impact of a major sewage outfall in the western channel. Leaching of heavy metals was shown to be one of the main sources of contamination from solid wastes. This paper presents eight lines of ground penetrating radar (GPR) surveys and sediment analysis to identify the anthropogenic interventions that shaped the urban landscape of Penang Island by excavations, filling, and embankment construction along the coastline and differentiate it from the natural one. The surveys were implemented in two locations, the Batu Ferringhi area, representing the natural coastline, and Persiaran Bayan Indah (the Queensbay Mall area), representing the anthropogenic coastal landform. The apparent depth of penetration that was achieved using a 250-MHz antenna is limited (less than 5 m). The results show between natural and anthropogenic sediment recorded different radar facies. In complement mode, mean grain size distribution, sorting, skewness, and kurtosis graphics of sediment samples from both sites correspond with the GPR data. This technique can likely be applied to the developing coast, where natural and anthropogenic coastal landform data is incomplete, considering future coastline development.

Dynamics of global coastline: Dynamics of Global Coastline: An Exposition of Erosional and Depositional Landforms Along The Komenda Coastline in The Central Coastal Plains of Ghana

The coast is a dynamic region where various processes with their origin from the land, atmosphere and sea interact. The interactional nature of these processes gives rise to one of the most spectacular forms along coastlines and these are coastal landforms. However, there has not been much research that unearths and describes the coastal landforms caused by deposition and erosion along the about 1 km stretch of the Komenda Ghana coastline. The study is an exposition of the coastal landforms caused by both deposition and erosion along the coastline. The study thrived on a descriptive research design coupled with observations, measurements and photographic presentation. The study revealed diverse coastal erosional landforms along the Komenda shoreline which encapsulate caves, geo, a blowhole, a stack and stumps while the only depositional landforms found were rocky and sandy beaches. Also, the study revealed the massive operation of sub-aerial processes such as weathering and mass wasting as the main forces operating along the shoreline. The study recommends increased research along the area to ensure a better understanding of its climatic, hydrodynamical, geological and geomorphological conditions which will provide a more and comprehensive understanding of coastal landforms and the factors shaping the coastline at every point in time. The study area has high nature conservation and recreational value. Therefore, it is crucial to sustainably monitor and to improve the planning processes in these vulnerable landscapes.

Coastal landforms evolution during the Holocene marine transgression: a witness from the past to understand the future

<p>The continental shelves submerged during the last marine transgression could constitute a unique laboratory to analyse how coastal landforms developed and evolved within the framework of a rising sea level. Such features therefore represent precious witnesses in the light of the high rates of sea-level rise predicted for the end of the century. Unfortunately, the majority of the coastal landforms have been wiped away during and soon after their submersion as a consequence of the pervasive wave and tidal action. Therefore, only few examples of well-preserved submerged coastal landforms are available.</p><p>In this study we focused our attention on the Italian side of northern Adriatic Sea, where a wide, low-gradient continental shelf, coupled to a very rapid marine ingression, allowed the partial conservation of the transgressive coastal landforms. Such study was carried out through the analysis of almost 10,000 km of high-resolution geophysical surveys (CHIRP-sonar profiles) and tens of stratigraphic cores carried out in the area during the last 30 years.</p><p>We recognized a series of almost 100 remnants of paleo tidal inlets which formed during the post-LGM transgression that led to the submersion of the Adriatic shelf. Despite paleo tidal inlets are often almost completely erased by the wave ravinement processes, when preserved they represent ideal markers for reconstructing the timing and impact of sea-level rise on the transgressed coastal plain. A wealth of information can be obtained by their analysis, such as the paleo coastlines locations, the dimensions of the paleo lagoon systems and, in particular conditions, the relative paleo sea-level. Such features therefore represent valid means to reconstruct the impact of the transgressive sea on the coastal area.</p><p>In particular, the paleo tidal inlets recognized in the northern Adriatic Sea suggest the recurrent formation followed by rapid overstepping of large lagoon systems during the early Holocene. Moreover, these features can be subdivided into clusters based on the depth of their top, thus allowing to infer the position of a series of paleo coastlines and suggesting the occurrence of periods of stasis of the relative sea-level rise, which allowed the formation of such inlets.</p><p>Although remnants of paleo tidal inlets are common on the northern Adriatic Shelf, they are almost absent in the northernmost portion of the basin (i.e. the Gulf of Trieste), where a series of paleo fluvial systems have been identified, thus providing a direct witness on the evolution of the coastal plain during a transgressive phase and right before its rapid submersion.</p><p>This research provides new insights on two main topics: i) it improves our knowledge on the post-LGM marine transgression, therefore contributing to reconstruct the history of sea-level rise and to constrain the modelling of future behaviour; ii) it contributes to understand the evolution of tidal inlets and lagoon-barrier island systems under the forcing of high rates of sea-level rise.</p>