Coastal changes at the Sulina mouth of the Danube River as a result of human activities

Sulina, the middle distributary of the Danube Delta, has been significantly changed by human activities over the past 150 yr. These include engineering works in the second half of the 19th century, when the channel was transformed for navigation and the construction of jetties which nowadays extend 8 km seawards. These interventions have strongly affected the natural processes of the Black Sea coast near the Sulina mouth. To the south of the Sulina mouth, the natural mild erosion has been reversed in the area close to the jetties where accretion is occurring, while southwards the greatest erosion rate along the entire Romanian coast, of more than 20 m/yr, has been recorded. Sediment accumulation in the northern part of the mouth is also huge and has brought to the creation and swift elongation of a sediment spit in several decades. Thus, the bay located here suffers from a rapid transformation into a lagoon.     

The power of low‐resolution spectroscopy: On the spectral classification of planet candidates in the ground‐based CoRoT follow‐up

Planetary transits detected by the CoRoT mission can be mimicked by a low‐mass star in orbit around a giant star. Spectral classification helps to identify the giant stars and also early‐type stars which are often excluded from further follow‐up. We study the potential and the limitations of low‐resolution spectroscopy to improve the photometric spectral types of CoRoT candidates. In particular, we want to study the influence of the signal‐to‐noise ratio (SNR) of the target spectrum in a quantitative way. We built an own template library and investigate whether a template library from the literature is able to reproduce the classifications. Including previous photometric estimates, we show how the additional spectroscopic information improves the constraints on spectral type. Low‐resolution spectroscopy (R ≈ 1000) of 42 CoRoT targets covering a wide range in SNR (1–437) and of 149 templates was obtained in 2012–2013 with the Nasmyth spectrograph at the Tautenburg 2 m telescope. Spectral types have been derived automatically by comparing with the observed template spectra. The classification has been repeated with the external CFLIB library. The spectral class obtained with the external library agrees within a few sub‐classes when the target spectrum has a SNR of about 100 at least. While the photometric spectral type can deviate by an entire spectral class, the photometric luminosity classification is as close as a spectroscopic classification with the external library. A low SNR of the target spectrum limits the attainable accuracy of classification more strongly than the use of external templates or photometry. Furthermore we found that low‐resolution reconnaissance spectroscopy ensures that good planet candidates are kept that would otherwise be discarded based on photometric spectral type alone. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Real-time drilling mud gas monitoring for qualitative evaluation of hydrocarbon gas composition during deep sea drilling in the Nankai Trough Kumano Basin

Background

Riverine particles undergo a rapid transformation when they reach estuaries. The rapid succession of hydrodynamic and biogeochemical regimes forces the particles to flocculate, settle and enter the sediment pool. The rates and magnitudes of flocculation depend on the nature of the particles which are primarily affected by the types and quantities of organic matter (OM). Meanwhile, the OM characteristics vary widely between environments, as well as within a single environment due to seasonal climate and land use variability. We investigated the effect of the OM types and quantities through laboratory experiments using natural estuarine particles from the Mississippi Sound and Atchafalaya Bay as well as model mixtures of montmorillonite and organic molecules (i.e., biopolymers (guar/xanthan gums) and humic acid).

Results

Biopolymers promote flocculation but the magnitude depends on the types and quantities. Nonionic guar gum yields much larger flocs than anionic xanthan gum, while both of them exhibit a nonlinear behavior in which the flocculation is the most pronounced at the intermediate OM loading. Moreover, the effect of guar gum is independent of salinity whereas the effect of xanthan gum is pronounced at higher salinity. Meanwhile, humic acid does not affect flocculation at all salinity values tested in this study. These results are echoed in the laboratory manipulation of the natural estuarine particles. Flocculation of the humic acid-rich Mississippi Sound particles is unaffected by the OM, whereas that of biopolymer-rich Atchafalaya Bay particles is enhanced by the OM.

Conclusions

Flocculation is positively influenced by the presence of biopolymers that are produced as the result of marine primary production. Meanwhile, humic acid, which is abundant in the rivers that drain the agricultural soils of Southeastern United States, has little influence on flocculation. Thus, it is expected that humic acid-poor riverine particles (e.g., Mississippi River, and Atchafalaya River, to a lesser degree) may be prone to rapid flocculation and settling in the immediate vicinity of the river mouths when mixed with biopolymer-rich coastal waters. It is also expected that humic acid-rich riverine particles (e.g., Pearl River) may resist immediate flocculation and be transported further away from the river mouth.     

A Recent Shellfish Toxin Investigation in China

A shellfish toxin investigation along the Chinese coast has recently been conducted using both HPLC and mouse assay methods. The results showed that DSP was widely distributed in different shellfish species in China. 26 out of 89 samples had DTX1 (dinophysistoxin-1) or OA (okadaic acid) but the DSP content in most shellfish samples did not reach the regulatory limit for human consumption adopted in many countries (20 μg/100 g soft tissue). PSP was also found in 5 out of 96 samples along the coast. One sample, Chlamys nobilis from Hong Kong contained high levels of PSP (320 μg STX equivalent/100 g soft tissue), compared to the regulatory limit (80 μg STX equivalent/100 g soft tissue). After the recent outbreak of red tide in Hong Kong waters, three further shellfish samples were collected within 40 days to investigate the impacts of this event. It was shown that high levels of PSP continued to exist in Hong Kong waters. This report provides the first report of DSP and PSP distribution along the Chinese coast.     

Warm winds from the Pacific caused extensive Arctic sea-ice melt in summer 2007

During summer 2007 the Arctic sea-ice shrank to the lowest extent ever observed. The role of the atmospheric energy transport in this extreme melt event is explored using the state-of-the-art ERA-Interim reanalysis data. We find that in summer 2007 there was an anomalous atmospheric flow of warm and humid air into the region that suffered severe melt. This anomaly was larger than during any other year in the data (1989?C2008). Convergence of the atmospheric energy transport over this area led to positive anomalies of the downward longwave radiation and turbulent fluxes. In the region that experienced unusual ice melt, the net anomaly of the surface fluxes provided enough extra energy to melt roughly one meter of ice during the melting season. When the ocean successively became ice-free, the surface-albedo decreased causing additional absorption of shortwave radiation, despite the fact that the downwelling solar radiation was smaller than average. We argue that the positive anomalies of net downward longwave radiation and turbulent fluxes played a key role in initiating the 2007 extreme ice melt, whereas the shortwave-radiation changes acted as an amplifying feedback mechanism in response to the melt.     

Snow,runoff, and mass balance modeling for the entire Mittivakkat Glacier (1998–2006), Ammassalik Island,SE Greenland

Geografisk Tidsskrift, Danish Journal of Geography 108(1):121–136, 2008

SnowModel, a physically-based snow evolution modeling system that includes four submodels—MicroMet, EnBal, SnowPack, and SnowTran-3D—was used to simulate eight full-year (1998/99 through 2005/06) evolutions of snow accumulation, blowing snow sublimation, evaporation, snow and ice surface melt, runoff, and mass changes on the entire Mittivakkat Glacier (31 km²) in southeast Greenland. Meteorological observations from two meteorological stations inside the glacier catchment were used as model input, and glaciological mass balance observations were used for model calibration (1998/99 through 2001/02) and validation (2002/03 through 2005/06) of winter snow simulations. As confirmed by observations, the spatially modeled end-of-winter snow water equivalent (SWE) accumulation increased with elevation up to 700–800 m a.s.l. in response to elevation, topography, and dominating wind direction, and maximum snow deposition occurred on the lee side of the ridge east and south of the glacier. Simulated end-of-summer cumulative runoff decreased with elevation and minimum runoff occurred on the shadowed side of the ridge east and south of the glacier. The modeled test period averaged annual mass balance was 65 mm w. eq. y^?1 or ～8% more than the observed. For the simulation period, the glacier net mass balance varies from -199 to -1,834 mm w.eq. y^?1, averaging -900 (±470) mm w.eq.y^?1. The glacier averaged annual modeled precipitation ranged from 1,299 to 1,613 mm w.eq. y^?1, evaporation and sublimation from 206 to 289 mm w.eq., and runoff from 1,531 to 2,869 mm w.eq. y^?1. The model simulated Mittivakkat Glacier net loss of900 mm w.eq. y^?1 contributes approximately 42% to the average simulated runoff of 2,140 mm w.eq. y^?1, indicating a mean specific runoff of 67.8 l s^?1 km^?2.     

Optimal planning and operation of irrigation systems under water resource constraints in Oman considering climatic uncertainty

In this contribution, we introduce a stochastic framework for decision support for optimal planning and operation of water supply in irrigation. This consists of (1) a weather generator for simulating regional impacts of climate change on the basis of IPCC scenarios, (2) a tailor-made evolutionary optimization algorithm for optimal irrigation scheduling with limited water supply, (3) a mechanistic model for simulating water transport and crop growth in a sound manner, and (4) a kernel density estimator for estimating stochastic productivity, profit, and demand functions by a nonparametric method. As a result of several simulation/optimization runs within the framework, we present stochastic crop-water production functions (SCWPF) for different crops which can be used as a basic tool for assessing the impact of climate variability on the risk for the potential yield for specific crops and specific agricultural areas. A case study for an agricultural area in the Al Batinah region of the Sultanate of Oman is used to illustrate these methodologies. In addition, microeconomic impacts of climate change and the vulnerability of the agro-ecological system are discussed.     

Dealing with erosion along the Danube Delta coast. The CONSCIENCE experience towards a sustainable coastline management

The most severe shoreline retreat (over 20 m/year) along the Danube Delta coast has been recorded in the coastal stretch confined by the Sulina branch (north) and Sahalin spit island (south). This erosive trend is caused by the natural evolution of some stretches of the Danube Delta coast, but strongly enhanced by the human activities. Human interventions result in the dramatic decrease in quantity of sediments reaching the coast and in the disruption of natural sediment circulation in the coastal area. EUROSION FP5 Project developed four concepts to be used in coastal studies: coastal sediment cell, coastal resilience, favourable sediment status and strategic sediment reservoir. The main objectives of this study regard the application of the CONSCIENCE methodology and test of the concepts in order to identify and understand the main threats for Sulina - Sahalin littoral cell, especially the coastal erosion one, as well as to provide a sound working methodology for coastal managers to deal with these threats. The sediment budget computed in previous studies, as well as the field observations, indicate a lack of sediments for the littoral cell (unfavourable sediment status). In order to asses the vulnerability of the coast to short term extreme events (especially storms), simulations of water level changes were performed and calibrated with the field observations. A processes based numerical model was used to simulate the storm induced water level variations and the main input data were the bathymetry of the active beach, wind direction and speed (storm scenarios) and the characteristics of water and air. The results show large water level increases for the central part of the study zone, especially for northern wind directions.The main solution proposed to deal the problems arising from a sediment-starved coast, vulnerable to the extreme events, is artificial nourishment. Two strategic sediment reservoirs were identified, both of them at the northern boundary of the cell: the sediments dredged periodically from Sulina mouth and the sediments accumulated in Musura Bay, just north of Sulina jetties. The transfer of these sediments towards the central part of the littoral cell Sulina - Sahalin would decrease the erosion rates to a natural level and restore the natural coastal resilience. The methodology developed in CONSCIENCE Framework and applied to Danube Delta coastal zone provided good results when problems and solutions for the coastal zone were to be identified and tested. This methodology and its related results can be applied by the local coastal managers to Sulina - Sahalin littoral cell, while this experience can be extended to other similar environments facing the same problems.     

Surface reflectance of sea ice and under-ice irradiance in Kongsfjorden, Svalbard

Initial results from a field experiment on fast ice in Kongsfjorden, Svalbard, in March 2002 are presented. We measured surface reflectance and under-ice irradiance using an advanced, portable spectroradiometer sensitive in the visible and near-infrared parts of the electromagnetic spectrum, i.e. 350-1100 nm. Under-ice irradiance (UV-A, UV-B and photosynthetically active radiation [PAR]) was measured down to depths of 7.5 m by vertical profiling using a six-channel radiometer. We also present model results of wavelength-dependent transmittance of radiation through a combined snow and sea ice layer for various thicknesses of snow. Model results show that the snow and sea ice is more transparent for solar radiation in the PAR region (400-700 nm) than at shorter and longer wavelengths. This is confirmed by the field measurements. Even very thin snow layers on top of the sea ice efficiently prevent solar radiation from penetrating the snow–sea ice system. For example, a 5 cm thick snow layer reduces under-ice irradiance in the PAR region with a factor of about 10. Measurements of under-ice UV irradiance show that both UV-A and UV-B irradiance is reduced with a factor of more than 10 at depths of 7.5 m below the ice compared to at the ice-sea water interface.     

Lack of association between color morphs of the Jellyfish Cassiopea andromeda and zooxanthella clade

Understanding the ecology and evolution of the cnidarian-algal symbiosis is of major scientific interest as it is sensitive to temperature and strong light and may therefore be susceptible to climate change. The stability of this mutualism is often mediated by host color pigments that influence photosynthetic activity in symbiotic dinoflagellates either by providing the photosystem with irradiance of suitable wavelength or by protecting it from much too much and potentially damaging light. Like scleractinian corals, the upside-down jellyfish, Cassiopea andromeda, relies heavily on the nutrients provided by its symbionts of the dinoflagellate genus Symbiodinium. It occurs in several conspicuously different color morphs and is found in habitats with high levels of irradiation. We tested whether the color morphs of Cassiopea were correlated with the Symbiodinium distribution in the host and whether host color was associated with different clades of Symbiodinium. We found that the presence of color pigment did not correlate with the distribution of Symbiodinium in the host. Symbiodinium was found in both the colored tentacles of the jellyfish and the colorless feeding tentacles. At least six different color morphs co-occurred in the very shallow waters of the Red Sea, but they all hosted a single Symbiodinium clade (clade A1). Therefore, no correlation of host color morph and Symbiodinium clade could be found. Photoaccumulative or photoprotective functions of host pigments, as proposed for some scleractinian corals, thus seem unlikely in the colored tentacles (vesicles) of the upside-down jellyfish Cassiopea andromeda.