Factors influencing seed germination of Cyperus capitatus, inhabiting the moving sand dunes in southern Europe

Cyperus capitatus Vandelli (Cyperaceae) is distributed in coastal sandy habitats and mobile dunes of south Europe. Its seed germination ecology is not known, despite its potential to be used in re-vegetation projects. Laboratory experiments were conduced to assess the effects of salinity, light regime, cold stratification and burial on seed germination of this species. Overall, increasing salinity delayed germination, increased seed dormancy and mean time to germination (MTG), and reduced final germination percentage, inhibiting it completely above 1% of salinity; although it did not affect seed viability. C. capitatus seeds exhibited their greatest germination at levels between 0 and 1% in non-stratified seeds, and between 0 and 0.5% for stratified seeds. Thus, the effect of salt was greater for stratified seeds at 5 °C. Germination in light/darkness conditions was similar to that in full darkness. Finally, burial in sand of C. capitatus seeds appeared to have a significant effect on cumulative percentage of germination. Seeds buried at depths greater than 2 and 3 cm showed a lower germination success than those on sand surface or buried at shallower depths. Burial also affected the beginning and speed of seed germination.     

Dynamics of chromophoric dissolved organic matter in Mandovi and Zuari estuaries — A study through in situ and satellite data

The spatial and temporal distribution of absorption of chromophoric dissolved organic matter at 440 nm (a_CDOM (440)) in the Mandovi and Zuari estuaries situated along the west coast of India, has been analysed. The study was carried out using remotely sensed data, obtained from the Ocean Colour Monitor (OCM) on board the Indian Remote Sensing satellite — P4, together with in situ data during the period January to December 2005. Satellite retrieval of CDOM absorption was carried out by applying an algorithm developed for the site. A good correlation (R=0.98) was obtained between satellite derived CDOM and in situ data. Time series analysis revealed that spatial distribution of CDOM has a direct link with the seasonal hydrodynamics of the estuaries. The effect of remnant fresh water on CDOM distribution could be analysed by delineating a plume in the offshore region of the Zuari estuary. Though fresh water flux from terrestrial input plays a major role in the distribution of CDOM throughout the Mandovi estuary, its role in the Zuari estuary is significant up to the middle zone. Other processes responsible for feeding CDOM in both the estuaries are coastal advection, in situ production and resuspension of bottom settled sediments. The highest value of a_CDOM(440) was observed in the middle zone of the Mandovi estuary during the post-monsoon season. The relation between a_CDOM(440) and S (spectral slope coefficient of CDOM) could differentiate CDOM introduced in to estuaries through multiple sources. The algorithm developed for the Mandovi estuary is S=0.003 [a_CDOM(440)^−0.7091] while for the Zuari estuary, S=0.0031 [a_CDOM(440)^−0.777], respectively.     

Climate warming and the onset of salinization: Rapid changes in the limnology of two northern plains lakes

Water resources of the interior plains region of North America may be adversely affected by climate warming. The climate records of the Battleford region (west central Saskatchewan) indicate that mean annual temperatures have risen by 0.71 °C and mean annual minimum temperatures have risen by 1.03 °C from 1894 to 2007. Snowfall has also increased but total precipitation has not. Concomitant with periodic declines in precipitation, lake elevation has declined and salinity has increased in Jackfish and Murray lakes from 1938 to 2004. This long term increase in salinity is predicted to have caused an approximate 30% loss in diversity of macrobenthos. Phosphorus concentrations have also increased significantly, and Jackfish and Murray lakes would be classified as eutrophic by freshwater trophic indices. However, despite large increases in nutrients in both lakes, algal biomass has not increased and water transparency has not decreased. Although the total amount of planktonic biomass in Jackfish and Murray’s food web is similar to that of freshwater lakes, these lakes contain very low algal biomass (measured as chlorophyll a). In fact, such low algal biomass has not been previously observed in such dilute systems. The algal community in these shallow Prairie lakes appears to be very sensitive to slight changes in climate, and future climate driven increases in salinity of prairie lakes may result in large reductions in algal primary productivity.     

New threats of an old enemy: the distribution of the shipworm Teredo navalis L. (Bivalvia: Teredinidae) related to climate change in the Port of Rotterdam area, the Netherlands

The effects of four climate change scenarios for the Netherlands on the distribution of the shipworm upstream of the Rhine-Meuse estuary are described. Global warming will cause dry and warmer summers and decreased river discharges. This will extend the salinity gradient upstream in summer and fall and may lead to attacks on wooden structures by the shipworm. Scenarios including one or two degree temperature increases by 2050 compared to 1990 with a weak change in the air circulation over Europe will lead to an increased chance of shipworm damage upstream from once in 36 years to once in 27 or 22 years, respectively; however, under a strong change in air circulation, the chance of shipworm damage increases to once in 6 or 3 years, respectively. The upstream expansion of the distribution of the shipworm will also be manifested in other northwest European estuaries and will be even stronger in southern Europe.     

Macroalgal diversity along the Baltic Sea salinity gradient challenges Remane's species-minimum concept

Remane’s species-minimum concept, which states that the lowest number of taxa occurs at the horohalinicum (5-8 psu), was tested by investigating macroalgal diversity on hard substrates along the natural salinity gradient in the Baltic Sea. Field data on species occurrence and abundance were collected by SCUBA diving along 10 transects of the Finnish, Swedish and German coasts, covering a salinity range from 3.9 to 27 psu. Macroalgal species numbers declined steadily with salinity, decreasing until 7.2 psu was reached, but in the horohalinicum, a marked reduction of species number and a change in diversity were indicated by the Shannon index and evenness values. The non-linear decrease in macroalgal diversity at 5-8 psu and the lack of increase in species numbers at salinities below 5 psu imply a restricted applicability of Remane’s species-minimum concept to macroalgae.     

A 30,000 yr record of land–ocean interaction in the eastern Gulf of Guinea

A 30,000 yr dinocyst and pollen record from the eastern equatorial Atlantic (off Cameroon) has been investigated in order to identify land–ocean linkages during the last deglacial transition. A strong correlation between the abundance of Brigantedinium spp. and the Ca/Fe ratio during the last glacial period suggests enhanced marine productivity in association with cool seawater temperatures and nutrient input linked to coastal upwelling and/or a proximal river mouth. Dry conditions are recorded on the adjacent continent with a significant representation of open vegetation indicators and the Afromontane taxon Podocarpus. After 17 cal ka BP these indicators register a sharp decline as a result of a climatic transition from the dry/cooler conditions of the last glacial period to the wetter/warmer conditions of the deglaciation. Simultaneously, dinocysts show a significant shift from dominant heterotrophs to an increasing abundance of autotrophs, reflecting warmer conditions. Significant changes are observed during the Younger Dryas, with a return to drier conditions and higher salinities. The start of the Holocene is marked by very low-salinity conditions, reflecting optimal monsoonal conditions over west equatorial Africa. The end of the African Humid Period is observed between 6 and 5 cal ka BP, followed by significant fluctuations in both terrestrial and oceanic proxies.     

Lago Mare and the Messinian Salinity Crisis: Evidence from the Alboran Sea (S. Spain)

This paper provides a new environmental, sedimentological and stratigraphic context of the Lago Mare deposits from the North Alboran region and clarifies their chronologic location with respect to the Messinian Salinity Crisis. We present new micropalaeontological data (dinoflagellate cysts, calcareous nannoplankton, planktonic foraminifers), correlated with field observations and offshore seismic interpretations. We show that the Lago Mare event known in three onshore localities (Río Mendelín near Malaga, Zorreras near Sorbas, Gafares near Níjar) follows the marine reflooding of the Mediterranean Basin which ended the Messinian Salinity Crisis. Chronologically, these Lago Mare deposits last from the latest Messinian to the early Zanclean. In fact, the first influx of Paratethyan organisms is revealed by the dinoflagellate cyst record from near Malaga within a Gilbert-type fan delta overlying the Messinian Erosional Surface. Invading molluscs and/or ostracods may have persisted in lagoonal coastal areas more or less affected by discontinuous marine influxes (Sorbas and Níjar). The Malaga area is convenient for a palaeogeographic and sedimentary reconstruction which shows the prevalent forcing of sea-level changes during the time-interval 5.600–5.332 Ma at the difference of the usually solicited prevalent tectonics. The studied Lago Mare event is the third episode resulting in such a palaeobiological assemblage in the Mediterranean region and corresponds to the final two-way water exchange at high sea level between the Mediterranean and the former Paratethys. It documents the onset of the modern marine circulation in the Mediterranean after the reflooding ending the Messinian Salinity Crisis.     

Role of exchange flow in salt water balance of Urmia Lake

In this paper we examine how exchange flow in Urmia Lake plays a crucial role in dynamics of the lake. Urmia Lake, a very large hyper-saline lake of high ecological significance, is located in northwest of Iran with a 15-km causeway dividing it into north and south lakes. A 1250-m opening in the causeway near the east coast links the two lakes. The differences in mean water levels and densities of the two lakes increase in spring due to large freshwater inflows into the south lake. High evaporation dominates the lake in summer. By incorporating the results of a two-layer hydraulics theory into a mixing model of the lake, we show that the exchange flow through the opening diminishes the water level and salinity differences of the two lakes and hence helps restoration of the pre-construction state of the lake by the end of fall. The model results are confirmed by the field data. The north–south and south–north flows through the opening are equal in most of the year, except in spring when the south–north flow is greater due to the head difference of the two lakes.     

Estimating salinity stress in sugarcane fields with spaceborne hyperspectral vegetation indices

The presence of salt in the soil profile negatively affects the growth and development of vegetation. As a result, the spectral reflectance of vegetation canopies varies for different salinity levels. This research was conducted to (1) investigate the capability of satellite-based hyperspectral vegetation indices (VIs) for estimating soil salinity in agricultural fields, (2) evaluate the performance of 21 existing VIs and (3) develop new VIs based on a combination of wavelengths sensitive for multiple stresses and find the best one for estimating soil salinity. For this purpose a Hyperion image of September 2, 2010, and data on soil salinity at 108 locations in sugarcane (Saccharum officina L.) fields were used. Results show that soil salinity could well be estimated by some of these VIs. Indices related to chlorophyll absorption bands or based on a combination of chlorophyll and water absorption bands had the highest correlation with soil salinity. In contrast, indices that are only based on water absorption bands had low to medium correlations, while indices that use only visible bands did not perform well. From the investigated indices the optimized soil-adjusted vegetation index (OSAVI) had the strongest relationship (R² = 0.69) with soil salinity for the training data, but it did not perform well in the validation phase. The validation procedure showed that the new salinity and water stress indices (SWSI) implemented in this study (SWSI-1, SWSI-2, SWSI-3) and the Vogelmann red edge index yielded the best results for estimating soil salinity for independent fields with root mean square errors of 1.14, 1.15, 1.17 and 1.15 dS/m, respectively. Our results show that soil salinity could be estimated by satellite-based hyperspectral VIs, but validation of obtained models for independent data is essential for selecting the best model.     

利用地震数据反演海水温盐结构

利用地震剖面获取海水层温度、盐度、密度等物理参数成为地震海洋学研究的一个重要问题.本文提出了以CTD(Conductivity-Temperature-Depth)温盐深剖面仪观测资料为约束的波阻抗、温-盐结构反演方法.该方法包括两个步骤:首先把少量的CTD作为"约束井"进行地震数据的波阻抗反演;然后利用从CTD资料获得的研究海区的温-盐关系式,结合波阻抗数据反演得到温度和盐度剖面.通过合成数据的试算表明,基于少量的CTD资料控制,利用地震数据可以反演得到高分辨率的二维温度、盐度结构.基于地震数据的温-盐结构反演方法有望弥补传统物理海洋学观测方法的不足,为海洋学研究提供大量的基础数据,有广泛的应用前景.