Littoral Environments Research Articles

A new Miocene turtle from Colombia sheds light on the evolutionary history of the extant genus Mesoclemmys Gray, 1873

ABSTRACTMesoclemmys is the most diverse extant genus of South American pleurodires or side-necked turtles, with at least 10 species inhabiting fluvial to littoral environments. Despite this high extant diversity and extensive geographic distribution, the evolutionary history and fossil record of this genus are completely unknown. Here, we describe the first fossil record of this genus, which supports a previous molecular-based hypothesis that indicates a minimum split time of 13.5 Ma between this and other genera of South American chelids. Mesoclemmys vanegasorum, sp. nov., is represented by a nearly complete shell (carapace and plastron) and some postcranial bones found in the middle Miocene (13.6 ± 0.2 Ma), La Victoria Formation, Tatacoa Desert, Colombia, increasing the turtle paleodiversity of La Venta Fauna. It differs from all extant species of Mesoclemmys by vertebral scute 1 reaching the sutural boundary between peripherals 1 and 2; shorter cervical and marginal scutes 1 to 3; pleurals 1 very advanced over the peripherals; pygal bone with a posteromedial shallow notch; vertebral 5 covering half of the pygal bone; small extragulars reaching only half of the epiplastra length; and a fine microvermiculation of the shell. Our phylogenetic results show a close relationship between M. vanegasorum, sp. nov., and the extant M. hogei. The overall morphology and size of Mesoclemmys genus have remained relatively constant for at least the last 13.6 million years. However, its geographic distribution has decreased drastically in northwestern South America, being restricted today to the lower region of the Magdalena River Basin.

Study of wind direction factor based on sea clutter in littoral environments

Study of wind direction factor based on sea clutter in littoral environments

Classification of aerosol population type and cloud condensation nuclei properties in a coastal California littoral environment using an unsupervised cluster model

Abstract. Aerosol particle and cloud condensation nuclei (CCN) measurements from a littoral location on the northern coast of California at Bodega Bay Marine Laboratory (BML) are presented for approximately six weeks of observations during the boreal winter–spring as part of the CalWater-2015 field campaign. The nature and variability of surface (marine boundary layer, MBL) aerosol populations were evaluated by classifying observations into periods of similar aerosol and meteorological characteristics using an unsupervised cluster model to derive distinct littoral aerosol population types and link them to source regions. Such classifications support efforts to understand the impact of changing aerosol properties on precipitation and cloud development in the region, including during important atmospheric river (AR) tropical moisture advection events. Eight aerosol population types were identified that were associated with a range of impacts from both marine and terrestrial sources. Average measured total particle number concentrations, size distributions, hygroscopicities, and activated fraction spectra between 0.08 % and 1.1 % supersaturation are given for each of the identified aerosol population types, along with meteorological observations and transport pathways during time periods associated with each type. Five terrestrially influenced aerosol population types represented different degrees of aging of the continental outflow from the coast and interior of California, and their appearance at the BML site was often linked to changes in wind direction and transport pathways. In particular, distinct aerosol populations, associated with diurnal variations in source regions induced by land- and sea-breeze shifts, were classified by the clustering technique. A terrestrial type representing fresh emissions, and/or a recent new particle formation event, occurred in approximately 10 % of the observations. Over the entire study period, three marine-influenced population types were identified that typically occurred when the regular diurnal land and sea-breeze cycle collapsed and BML was continuously ventilated by air masses from marine regions for multiple days. These marine types differed from each other primarily in the degree of cloud processing evident in the size distributions, and in the presence of an additional large-particle mode for the type associated with the highest wind speeds. One of the marine types was associated with a multi-day period during which an atmospheric river made landfall at BML. Differences between many of the terrestrial and marine population types in total CCN number concentrations active at a specific supersaturation were often not as pronounced as the associated differences in the corresponding activated fraction spectra, particularly for supersaturations below about 0.4 %. This finding was due to the generally higher number concentrations in terrestrial air masses offsetting the lower fraction of particles activating at low supersaturations. At higher supersaturations, CCN concentrations for aged terrestrial types were typically above those of the marine types due to their higher number concentrations.

Provenance, shallow to deep diagenesis, and chemical mass balance in supermature arenites and pelites, Ordovician Simpson Group, Oklahoma and Kansas, U.S.A.

This study, considering original detrital compositions and diagenetic alterations, relates sandstone and shale mineral and chemical composition to provenance and mass balance between the sedimentary assemblage and its provenance. Mature quartz-rich sandstones and siltstones with clay-rich shales in cores at depths of 60 m–5.2 km and burial temperatures of <50 to >150 °C from over 50 wells were utilized in this work. These provide the material for analysis of compositions and alterations in coastal and shallow marine clastic sedimentary rocks of the Middle Ordovician Simpson Group in Oklahoma and Kansas, U.S.A. Mineral and geochemical data were obtained by optical petrography, X-ray diffraction, scanning electron microscopy, electron microprobe, and whole rock X-ray fluorescence and ICP/MS analyses. Results of the study show significant progressive diagenetic changes with increased burial depth and temperature. Mineralogically and chemically, less altered rocks are comparable to modern quartz-rich sands and kaolinitic muds in siliciclastic sediments developed during humid tropical weathering in crystalline basement shield provenance in Africa and South America. By analogy to modern tropical cases, muds composed of major kaolinite with minor smectite and illite at deposition, were diagenetically transformed to illite-rich rocks by possible microbial action, at surface to shallow (<200 m, <40 °C) burial with influx of K, Rb and Mg from seawater. In sandstones, early open system diagenesis with calcite cementation and quartz overgrowths occurred at <1 km depth and < 40 °C. Further closed system silica diagenesis and K-metasomatism, occurred with deeper burial (to 3+ km and 100 °C) in the Pennsylvanian and Permian and later, during and following uplift of the Arbuckle and Wichita Mountains, with establishment of a new fold and thrust belt structural and hydrologic regime. Pressure solution of quartz and the illite to muscovite transformation in shales in the depth range 3–8 km, yielded silica for later generation quartz cement (10- >20%) in sandstone buried >3 km. During deep burial, high temperature (>110 °C) calcite cement from deep basin sources was precipitated in sandstones. Geochemical mass balance estimates, physical, and chemical evidence suggest quartz cement was sourced from within clastic rocks of the Simpson Group with minor external contribution of SiO2. Na is in low abundance due to loss in solution during weathering in the provenance. Rare earth elements (REE) have typical abundances and distributions in shales with enrichment in light REE; littoral environment siltstones and matrix-rich sandstones display enrichment of heavy REE in phosphatic brachiopod shell fragments.

First record of carbonates with spherulites and cone-in-cone structures from the Precambrian of Arctic Norway, and their palaeoenvironmental significance

We report for the first time carbonates from the upper Ediacaran sedimentary succession of Finnmark, Arctic Norway. Carbonates occur as calcareous siliciclastic beds, lenses, and concretions, some with calcite spherulites and cone-in-cone (CIC) calcite, in a mudrock to fine-grained sandstone succession from approximately 3 m to 26 m above the base of the 2nd cycle of the Manndrapselva Member of the Stáhpogieddi Formation (Vestertana Group). They occur c. 40 m below the Ediacaran–Cambrian boundary, which is well defined by trace fossils. Thin-section petrography and scanning micro X-ray fluorescence elemental mapping reveal a layered composition of the calcareous sedimentary rocks. In some of those, well-developed nested cones of CIC calcite form the outer layer. Thin clay coatings outline individual cones. The inner layers are composed of (1) carbonate with calcite spherulites (grainstone) and (2) thinly laminated fine-grained calcareous siliciclastics (mudstone and wackestone) indicated by elevated concentrations of Al, Si, Fe, and Ti. The inner siliciclastic layers contain framboidal pyrite and probably organic matter. Formation of calcite spherulites took place probably at the sediment–water interface either in a coastal littoral environment or in situ in the sublittoral zone under high alkaline conditions whereas CIC calcite formed during burial diagenesis and clearly in pre-Caledonian time before metamorphism and cleavage formation. This new record of carbonates with calcite spherulites and CIC structures from the Ediacaran of Arctic Norway adds to their rare occurrences in the geological record.

Canonical cylindrical target acoustic backscattering investigations

In littoral environments where visibility can be low and objects of interest are often either partially or fully buried with respect to the water-sediment interface, the task of identifying unexploded ordinances (UXOs) is a challenging one. Downward looking sonar (DLS) systems have been shown to be capable of penetrating the seafloor of various littoral environments and therefore could be an effective tool for searching for UXOs. However, although DLS’s can penetrate the seafloor, classification and identification (C&amp;I) of targets of interest versus clutter are still a technical obstacle of interest. To address this, researchers at the Naval Surface Warfare Center Panama City Division (NSWC PCD) have been working on algorithms that can identify an object based on its acoustic backscatter response. The concept is similar to identifying the material composition of an object with optical spectroscopy but in this case using the acoustic response rather than the optical spectra. Initial investigations, analysis, and algorithm development have focused on the analysis of acoustic backscattering measurements conducted on various targets in the free-field using linear frequency modulated (LFM) interrogation pulses. Experimental measurements are compared with model results derived from a paper by Lecroq [1]. Data/model results as well as a process for potentially aiding automatic target recognition development will be discussed in this presentation. [1] F. Lecroq, L. Fernand, D. Décultot, and G. Maze, J. Acoust. Soc. Am. 91, 1388 (1992).

Middle Jurassic charophytes from southern Tunisia: Implications on evolution and paleobiogeography

The Middle Jurassic section from the Kef El Anéba in southern Tunisia, near the Beni Kheddache area, provided exceptionally species-rich charophyte assemblages that are studied here for the first time. The Krachoua Formation yielded a Bajocian assemblage composed of Porochara fusca, P. schudackii nov sp., P. kimmeridgensis, P. westerbeckensis, Auerbachichara saidakovskyi, Stenochara sp., Stellatochara aff. subsphaerica, Aclistochara longiformis and Aclistochara africana. A second assemblage from the Krechem El Miit Member (Foum Tataouine Formation), of Late Callovian age, includes Auerbachichara tataouinensis nov. sp., Porochara kimmeridgensis, P. westerbeckensis, P. douzensis, P. obovata var. gondwanensis nov. var. and Mesochara voluta. Taphonomic and paleoenvironmental data suggest autochthony of these two assemblages in a brackish lagoon and a temporary freshwater pond from a littoral environment, respectively. In addition, these floras suggest that Middle Jurassic charophyte biodiversity formed an evolutionary bridge between Upper Triassic charophyte floras dominated by genera Stellatochara, Stenochara and Auerbachichara and Upper Jurassic floras dominated by Porochara, Aclistochara and Mesochara. Furthermore, the biogeography of Middle Jurassic charophytes from southern Tunisia provides further arguments to support the hypothesis of significant biological exchanges between Laurasian and Gondwanan islands, indicating that Peri-tethyan biogeography remained relatively uniform during the Middle Jurassic.

Regional Planning and the Environmental Impact of Coastal Tourism: The Mission Racine for the Redevelopment of Languedoc-Roussillon’s Littoral

Research on the coast has highlighted the role of mass tourism as a driver of littoral urbanization. This article emphasizes the role of public policy by focusing on Languedoc-Roussillon in Mediterranean France. This littoral was the target of a state-driven development initiative known as Mission Racine, which aimed to promote the growth of what was seen as a backward area via the development of seaside tourism. For that purpose, the Mission promoted coordinated interventions including forest management, eradication of mosquitoes, construction of resorts, and transport infrastructure. This large-scale redevelopment significantly reshaped the littoral environment, severely impacted pre-existing forms of coastal activities and launched a new tourism industry. The legacy of the Mission, however, also included innovative land-use planning, which established protected areas and sought to contain urbanization. This case study illustrates the ambiguities of public policies for the coast, which can act alternatively as drivers of development or conservation and at times of both, and therein lies the importance of a contextual analysis of their role.

The use of Unmanned Aerial Vehicles for CASEVAC in the future urban and littoral environments

AbstractThe recent development of Unmanned Aerial Vehicles (UAVs) and their potential use for casualty evacuation (CASEVAC) has exciting implications for the United Kingdom Defence Medical Services (DMS). When compared to existing technology, the unique attributes of small size, increased manoeuvrability and lack of a human pilot would be extremely useful in congested and hazardous settings. There are ethical and practical considerations to be taken into account, but harnessing the full potential of this technology may improve the chances of survival from some battlefield injuries.UAVs could be of most benefit in a congested and complex battlespace, allowing evacuation of casualties from high risk environments. In addition to CASEVAC, a UAV could be used for critical care transfers, Search and Rescue (SAR) and Humanitarian And Disaster Relief (HADR) operations. Given the vast array of potential applications and a lower risk profile compared with current CASEVAC platforms, the DMS should actively monitor the development of UAV technology and plan ahead for integration within current doctrine.

OBLIQUE BREAKWATERS FOR MULTI-PURPOSE BEACH RECREATION AND SHORE PROTECTION

Breakwaters, jetties, and groins have long been used in the littoral environment as port, navigation, shoreline stabilization and beach protection structures. Customarily however, the recreational benefits of structures such as these have been realized only incidentally. For example, jetties built solely to stabilize an inlet almost immediately attract surfers who exploit the break created by waves reflecting from the structure. This is the case at Sebastian Inlet, Florida, where the world renowned ‘First Peak’ was created when the north jetty was lengthened in the early 1970’s. Often when the waves elsewhere are too small to surf, one can rely on First Peak to be surfable. Also, under conditions of large, long-period swell, although the normally incident surfbreak elsewhere tends to ‘close-out’, not only is First Peak an excellent break, but sometimes a second and third surfable peak appear.

Analysis of sonar clutter using backscattered spatial correlation

Sonar clutter events are one of the primary limitations of long-range active sonar systems within the littoral environment. For this reason, research towards understanding their acoustic return characteristics and ultimately their mitigation are of high importance. This paper discusses measurements and modeling of the backscattered horizontal correlation function from clutter events and comparison with returns from the littoral environment. A statistical model for returns from boundaries, as well as general expectations of returns from common clutter sources will be discussed. The horizontal correlation function is estimated via sub-aperture beamforming of the Five Octave Research Array (FORA), a towed line array system owned and operated by Penn State and funded by the Office of Naval Research. [Work supported by Office of Naval Research.]

Improving the speed of acoustic propagation modeling, for sonar training applications, with a 3D Gaussian ray bundling model

This research improves the calculation speed of acoustic propagation modeling, for sonar training applications in littoral environments, by implementing a 3D Gaussian ray bundling model in the geodetic coordinates of the environmental databases. Tactical decision aids currently transform the three-dimensional environment into two dimensional radials, then compute acoustic propagation as a function of range and depth. This allows them to analyze millions of range, depth, and bearings for potential targets locations in a few minutes. But, it assumes that the cost of transformation is small compared to the speed benefit of computing propagation in Cartesian coordinates. This assumption is violated in applications where the geometry of the sensors and targets is rapidly evolving, results are strongly dependent on location, and answers must be produced faster than real time. Instead of relying on advancements in computer hardware, this research focuses on the development of a new algorithm to compute bistatic, broadband, transmission loss, and reverberation for 100 active sonar acoustic contacts on commodity laptop hardware, at rates ten times faster than the speed of sound, with no measurable impact on accuracy. [Work supported by the High Fidelity Active Sonar Training (HiFAST) Project at the U.S. Office of Naval Research.]

A critical review and re-investigation of the Pleistocene deposits between Cranfield Point and Kilkeel, Northern Ireland: Implications for regional sea-level models and glacial reconstructions of the northern Irish Sea basin

The coastline of County Down includes sites that are pivotal to understanding the history of the last glaciation of the northern Irish Sea Basin in relation to relative sea level and regional glacial readvances. The cliff sections display evidence that has been used to underpin controversial models of glaciomarine sedimentation in isostatically-depressed basins followed by emergent marine and littoral environments. They also provide crucial evidence claimed to constrain millennial-scale ice sheet oscillations associated with uniquely large and rapid sea-level fluctuations. This paper reviews previous work and reports new findings that generally supports the ‘terrestrial’ model of glaciation, involving subglacial accretion and deformation of sediment beneath grounded ice. Deep troughs were incised into the till sheet during a post Late Glacial Maximum draw-down of ice into the Irish Sea Basin. Ice retreat was accompanied by glaciomarine accretion of mud in the troughs during a period of high relative sea level. The trough-fills were over-ridden, compacted, deformed and truncated during a glacial re-advance that is correlated with the Clogher Head Readvance. Grounding-line retreat accompanied by rapid subaqueous ice-proximal sedimentation preserved a widespread subglacial stone pavement. Raised beach gravels cap the sequence. The evidence supports an uninterrupted fall in relative sea level from c. 30 m that is consistent with sea level curves predicted by current glacio-isostatic adjustment modelling. Critical evidence previously cited in support of subaerial dissection of the troughs, and hence rapid fall and rise in relative sea level prior to the deposition of the glaciomarine muds, is not justified.

Linking watershed disturbance with nearshore sedimentation and the shell beds of Lake Tanganyika (Mahale Mountains, Tanzania)

Extensive deposits of shell-rich sediments in the nearshore environment of Lake Tanganyika, Africa, form a unique habitat for a diverse group of endemic gastropods, crustaceans, fish and sponges, among other organisms. Anthropogenic alteration of the lake’s hinterland from deforestation, fires, and agriculture threaten this crucial habitat through sediment pollution of the littoral environment. This study examines the sedimentology of these nearshore shell beds along a study area north of the Mahale Mountains (Tanzania) to test whether varying levels of watershed disturbance, determined by analysis of satellite imagery, within three moderately sized watersheds (> 100 km2) results in sedimentological differences offshore. The results show that shell beds adjacent to disturbed watersheds (Lagosa and Rukoma) contain more fine-grained sediment compared to shell beds offshore of the undisturbed watershed (Katumbi). Widespread burning, clearance, and land cultivation, and rains of the wet season are causal factors that result in significant differences in fine-grained sedimentation, larger sediment plumes offshore, and increased shoreline progradation. In areas most affected by sedimentation, sponges are largely absent, and shell coverage, which is a measure of fish-nesting capabilities, is lower. The discovery of a small population of live Neothauma tanganyicense offshore of the Katumbi river suggests that the presence of shell-bed forming gastropods in front of a relatively low disturbance watershed, and their conspicuous absence offshore of the other two watersheds, could be related to recent watershed disturbance and increased sedimentation. The increased fine-grained sedimentation and limited shell production by the reduced modern gastropod populations may signal that the shell-bed ecosystem of Lake Tanganyika is at risk.

The optimal sampling design for littoral habitats modelling: A case study from the north-western Mediterranean.

Species distribution models (SDMs) have been used to predict potential distributions of habitats and to model the effects of environmental changes. Despite their usefulness, currently there is no standardized sampling strategy that provides suitable and sufficiently representative predictive models for littoral marine benthic habitats. Here we aim to establish the best performing and most cost-effective sample design to predict the distribution of littoral habitats in unexplored areas. We also study how environmental variability, sample size, and habitat prevalence may influence the accuracy and performance of spatial predictions. For first time, a large database of littoral habitats (16,098 points over 562,895 km of coastline) is used to build up, evaluate, and validate logistic predictive models according to a variety of sampling strategies. A regularly interspaced strategy with a sample of 20% of the coastline provided the best compromise between usefulness (in terms of sampling cost and effort) and accuracy. However, model performance was strongly depen upon habitat characteristics. The proposed sampling strategy may help to predict the presence or absence of target species or habitats thus improving extensive cartographies, detect high biodiversity areas, and, lastly, develop (the best) environmental management plans, especially in littoral environments.

Why the damselfish Chromis chromis is a key species in the Mediterranean rocky littoral-a quantitative perspective.

The damselfish Chromis chromis is typically the most abundant fish species in the rocky littoral environment of the Mediterranean Sea, where it feeds in huge shoals on incoming zooplankton and rests near the seabed each night. Research has shown that large populations of C. chromis play a fundamental role by transferring carbon, nitrogen and phosphorus directly from the pelagic system to the littoral in the form of solid and liquid wastes and therefore that this species acts as a vital conduit for nutrients. In addition, C. chromis represents a major prey item for predatory fish and seabirds, it has been shown to exert significant predation pressure on coastal zooplankton populations, but it is also a major consumer of fish eggs and hence may have a strong influence on the dynamics of other fish species. In this review paper the contention is that C. chromis represents a key species in the Mediterranean Sea rocky littoral. This view is supported by quantitative evidence that has been amassed over a number of years, but is collated here for the first time. Chromis chromis is of only minor importance to commercial fisheries (it is usually discarded), but trends in population abundance of this species can be indicative of levels of fishing pressure on other commercial species. It has been demonstrated that where predator numbers are able to recover from intensive fishing (e.g.in marine protected areas; MPAs), this is often mirrored by lower densities of C. chromis. Several papers have championed C. chromis as a possible indicator species for human disturbance. As well as being directly and indirectly affected by fishing, the species is also sensitive to a number of other anthropogenic pressures, most notably poor water quality and noise pollution.

Corrigendum.

Corrigendum.

Structural changes in Mediterranean marine communities: lessons from the Ligurian Sea

The most important structural changes of the marine communities of the Ligurian Sea (Mediterranean Sea) are described and discussed, stemming from scientific contributions published in the last decades. The main causes of disturbance and stress along the coastline were, since long time ago: huge urban, touristic and industrial developments, harbour activities, building of littoral rail- and motorways, beach replenishments, presence of several polluted drainages, impact of fishery activities. Nevertheless, the EQR-CARLIT index recently evidenced a moderate seawater quality and ecological status, indicating a slow, but progressive improvement of the littoral environment. But, in a changing climate, thermal stress anomalies in 1999, 2003 and 2006 determined major changes in the structure of benthic and fish communities. In addition, the plankton showed significant changes, especially in terms of primary production, while the disappearance of some species and the arrival of others, even of commercial interest, were recorded. Starting from the late 1980s, some thermophilous and/or Lessepsian species reached the Ligurian Sea, often determining processes of “meridionalization” and “tropicalization” of the basin. In a relatively short time span, i.e., 30–40 years, the structural complexity of Ligurian marine communities changed dramatically as never observed before in historical times.

Can bioturbation be responsible for thicker freshwater lenses than expected in littoral environments?

A study of hydrological and lithological characteristics that allow the development of freshwater lenses in littoral ridges underneath clay sediments of the coastal plain was undertaken, considering as a case of study the freshwater lenses located in the coastal sector of Samborombón Bay (Argentina). Geological characteristics were studied at a regional scale, as well as detailed sedimentological and ichnological aspects. Thickness of the lens and the freshwater–saline water interface were determined by salinity measurements in exploration wells located at different depths. Results obtained suggest that the infiltration of rainwater into the littoral ridges causes the formation of freshwater lenses that deepen below the clayey layers of the coastal-plain deposits. The key to answering this question are the crustacean burrows, which regionally occur in the fine sediments of the coastal plain. The burrows create an interconnected system of galleries and tunnels filled with sandy-silt material that favours seepage. Because the alternation of coastal-plain deposits and littoral ridges is a frequent situation throughout the world, the data provided by the present work do not represent just a simple case study; on the contrary, they show that biological structures promote bigger freshwater lenses in coastland environments, thus increasing water reserves.

Dynamics of dissolved inorganic nitrogen in bioturbated littoral surface sediments at a selected tourist destination of Northern Coastal Bay of Bengal, India: An ecologically significant case study

A case study was undertaken to observe the variations in the concentrations of the dissolved inorganic nitrogen species in the surface sediments of the littoral compartments at Bakkhali and Frasergunj situated within the single coastal stretch at the southernmost tip of West Bengal, India. Effects, if any, of the presence or absence of bioturbations on the variability of the dissolved nitrate-nitrogen, nitrite-nitrogen, ammonia-nitrogen, total dissolved nitrogen and the cumulative concentration of former three variables in the beach surface sediments were also noted. On site nitrite-nitrogen was found in alternate fluctuating patterns throughout the beach zonations with gradual lowering and peaking within each zone. An evidently prominent fact was the independence of dissolved inorganic nitrogen species from bioturbatory influences in the surface sediments of wave exposed littoral environments at the study sites. That effect might become significant in a vertical profile but from the data procured it can be stated that inorganic nitrogen species concentrations in surface beach sediments are not entirely perturbed by bioturbations and are governed by many other environmental parameters. A Pearson correlation performed on the normalized data sets revealed that there existed a fairly significant correlation in between the both the beach sediments with r-values ranging from -0.97 to +0.99 among the five variables considered at 95% confidence level. ANOVA Single factor yielded values in support of the rejection of the null hypothesis.