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Growing in a saline environment causes changes in important physiological processes that are directly related to plant growth and development. In this study we evaluated the effect of salinity on transpiration of sorghum plants in semi-arid conditions and found that the highest rates of transpiration were observed in the hottest hours of the day, between 10 a.m. and 3 p.m., with plants subjected to the saline environment having their transpiration reduced by up to 70% when compared to the non-saline environment. This behavior can be reflected in reductions in plant growth and development due to reduced water absorption by the roots, consequently causing an imbalance of nutrients in the plant due to low absorption rate and competition between nutrients and salts in the preferred routes of absorption in the roots.
Postglacial changes in sea-surface conditions, including sea-ice cover, summer temperature, salinity, and productivity were reconstructed from the analyses of dinocyst assemblages in core S2528 collected in the northwestern Barents Sea. The results show glaciomarine-type conditions until about 11,300 ± 300 cal yr BP and limited influence of Atlantic water at the surface into the Barents Sea possibly due to the proximity of the Svalbard-Barents Sea ice sheet. This was followed by a transitional period generally characterized by cold conditions with dense sea-ice cover and low-salinity pulses likely related to episodic freshwater or meltwater discharge, which lasted until 8700 ± 700 cal yr BP. The onset of “interglacial” conditions in surface waters was marked by a major change in dinocyst assemblages, from dominant heterotrophic to dominant phototrophic taxa. Until 4100 ± 150 cal yr BP, however, sea-surface conditions remained cold, while sea-surface salinity and sea-ice cover recorded large amplitude variations. By ~4000 cal yr BP optimum sea-surface temperature of up to 4°C in summer and maximum salinity of ~34 psu suggest enhanced influence of Atlantic water, and productivity reached up to 150 gC/m2/yr. After 2200 ± 1300 cal yr BP, a distinct cooling trend accompanied by sea-ice spreading characterized surface waters. Hence, during the Holocene, with exception of an interval spanning about 4000 to 2000 cal yr BP, the northern Barents Sea experienced harsh environments, relatively low productivity, and unstable conditions probably unsuitable for human settlements.
In this paper, we synthesize recorded observations of moss, lichen and bird species in Bunger Hills, East Antarctica, and assess the role of environmental controls, including sediment, salinity, moisture and geology, on species' distributions. The distribution of snow petrels (Pagodroma nivea) appears to be associated with geology; they nest by preference in crevices in bedrock outcrops around the margins of the hills or wherever jointed cliffs are found. South polar skuas (Catharacta maccormicki) are seen throughout Bunger Hills, where they nest and prey on snow petrels. Mosses and lichens were most abundant around the ice margins where fresh snow and ice meltwater are abundant. In the central area of Bunger Hills, where the highest salt concentration in sediments is found and exposure to abrasion by wind-driven mineral sand grains and ice particles is greatest, mosses and lichens are reduced in abundance and diversity. Exposure of parts of Bunger Hills from the ice sheet throughout the Last Glacial Maximum, c. 20 ka bp, means that some land and lakes could have acted as regional refugia and as a locus of recolonization of other ice-free areas.
Quantifying the level of ecophysiological, biochemical, and agronomical fitness of herbicide-resistant (R) and herbicide-susceptible (S) weeds is useful for understanding the evolutionary development of herbicide resistance, but also for implementing herbicide-resistance management strategies. Although germination is a key fitness component in the life cycle of weeds, germinability of S and R weeds has rarely been evaluated under stressful conditions. Germinability traits of S and non–target site resistant subpopulations of blackgrass (Alopecurus myosuroides Huds.) sharing closely related genetic background were tested under salinity, drought stress, and accelerated seed-aging (i.e., exposed to 100% relative humidity at 45 C from 0 to 134 h) conditions. In addition, the activity of three antioxidant enzymes and protein concentration of accelerated aged seeds of the subpopulations were studied. There were no differences in maximum seed germination (Gmax) and time to 50% germination between the two subpopulations under optimum conditions. However, under salinity, drought stress, and accelerated aging conditions, there were differences between the subpopulations. The salinity, drought, and accelerated aging treatments reducing Gmax of the S subpopulation by 50% were 18 dS m−1, 0.75 MPa, and 90 h, respectively, while for the R subpopulation the corresponding values were 15 dS m−1, 0.66 MPa, and 67 h. No differences were found in the activity of the antioxidant enzymes and the content of protein between non-aged seeds of the subpopulations. The aging treatments reducing the activity of catalase and superoxide dismutase enzymes by 50% were 118 and 82 h for the S subpopulation, respectively, while they were 54 and 58 h for the R subpopulation. In contrast, there were no differences in the effect of the aging treatments on the peroxidase activity and protein content between subpopulations. The results provided clear evidence that the non–target site resistant loci of blackgrass is associated with fitness costs under environmental stress.
Capitulum mitella is a tropical/sub-tropical intertidal barnacle of high economic value. However, no studies have yet focused on the effects of the extrinsic and intrinsic factors that affect the metamorphosis of this species. The current study stored cyprids at room temperature (24–26°C) and low temperature (7°C) and then compared the effects of age and storage temperature on cyprid metamorphosis. The effects of salinity and temperature on cyprid metamorphosis and survival were examined. Results showed the following. (1) Young 0-day cyprids were not competent to metamorphose, and C. mitella cyprids had a pre-competent phase. (2) The cyprid metamorphosis percentage at different storage temperatures with the same age was higher at room temperature than at 7°C. Low temperature storage of cyprids appeared to be unsuitable for C. mitella. The ideal storage time at room temperature for cyprids was 3–5 days. (3) The cyprids could complete metamorphosis at a salinity range of 20–45 mg l−1, and the optimum salinity range for metamorphosis was 25–35 mg l−1. At 15 mg l−1 salinity, the cyprids could survive but failed to metamorphose. (4) The cyprids could survive and complete metamorphosis at 18–36°C, and the optimum temperature range for metamorphosis was 21–33°C. The metamorphosis of C. mitella cyprids can tolerate a wide spectrum of salinity and temperature, which is related to the distribution location, habitat environment and lifestyle. Results of this study may provide a basis for the settlement biology, recruitment ecology and aquaculture of this species.
Research on the effects of environmental factors influenced by climate change on parasite transmissibility is an area garnering recent attention worldwide. However, there is still a lack of studies on the life cycle of Opisthorchis viverrini, a carcinogenic trematode found in countries of the Lower Mekong subregion of Lao PDR, Cambodia, Myanmar, Vietnam and Thailand. To evaluate the influences of environmental factors water temperature and salinity on the transmissibility of the liver fluke O. viverrini through cercarial stage, longevity of O. viverrini cercaria was examined at different experimental temperatures (22°C, 30°C and 38°C) and salinities (2.5 parts per thousand (PPT), 3.75 PPT and 5 PPT). The results reveal that different temperatures have statistically significant effects on cercarial longevity. The cercariae exhibited a thermostability zone ranging between 22°C and 30°C. Cercarial longevity was significantly shortened when water temperatures reached 38°C. Salinity also plays a key role in cercarial longevity, with cercarial survival significantly shorter at a salinity of 3.75 PPT than at 2.5 PPT and 5 PPT. A combined analysis of salinity and temperature revealed unique trends in cercarial longevity. At all experimental salinities, cercarial longevity was lowest when incubated in 38°C, but statistically significant from cercarial longevity at temperatures of 22°C and 30°C, and salinities of 2.5 PPT and 5 PPT. The results suggest that higher temperatures negatively impact parasite longevity. This reflects that O. viverrini transmission patterns may be impacted by changes in water temperature and salinity resulting from climate change.
Although numerous studies have investigated the individual effects of salinity, irrigation and fertilization on soil microbial communities, relatively less attention has been paid to their combined influences, especially using molecular techniques. Based on the field of orthogonal designed test and deoxyribonucleic acid sequencing technology, the effects of saline water irrigation amount, salinity level of irrigation water and nitrogen (N) fertilizer rate on soil bacterial community structure were investigated. The results showed that the irrigation amount was the most dominant factor in determining the bacterial richness and diversity, followed by the irrigation water salinity and N fertilizer rate. The values of Chao1 estimator, abundance-based coverage estimator and Shannon indices decreased with an increase in irrigation amount while increased and then decreased with an increase in irrigation water salinity and N fertilizer rate. The highest soil bacterial richness and diversity were obtained under the least irrigation amount (25 mm), medium irrigation water salinity (4.75 dS/m) and medium N fertilizer rate (350 kg/ha). However, different bacterial phyla were found to respond distinctively to these three factors: irrigation amount significantly affected the relative abundances of Proteobacteria and Chloroflexi; irrigation water salinity mostly affected the members of Actinobacteria, Gemmatimonadetes and Acidobacteria; and N fertilizer rate mainly influenced the Bacteroidetes' abundance. The results presented here revealed that the assessment of soil microbial processes under combined irrigation and fertilization treatments needed to be more careful as more variable consequences would be established by comparing with the influences based on an individual factor, such as irrigation amount or N fertilizer rate.
A new insular species of Paraethomys (Muridae, Rodentia) with medium-sized hypsodont teeth is described from the Zanclean of Mallorca (Balearic Islands, western Mediterranean). The m1 displays the most distinctive traits: hypsodonty, a high occurrence of an unusual anterior cingulum, a well-developed labial cingulum, high accessory labial cuspids resembling the Apodemus pattern and a funnel between c1 and the hypoconid. Paraethomys balearicus sp. nov. preserves traits close to those present in the earliest populations of Paraethomys meini from the upper Turolian, such as a developed posterior spur on t3 in the M1, a connection between t4 and t8 in the M1, a narrow connection between t6 and t9 in the M1 and the occasional presence of an individualized t9 and a t12 in some M2s. The relationship between the new taxon and its direct mainland ancestor gives additional support to a Messinian origin for the so-called Myotragus fauna, which became isolated after the refilling of the Mediterranean Sea 5.33 Ma ago. The absence of Paraethomys in other known younger Mallorcan sites suggests that its extinction most probably occurred at an indeterminate time during the Pliocene Epoch.
Recent studies have shown that anguillid eel populations in habitats spanning the marine–freshwater ecotone can display extreme plasticity in the range of catadromy expressed by individual fish. The apparent use of marine and freshwater habitats by the European eel Anguilla anguilla was examined by analysing the strontium (Sr) and calcium (Ca) concentrations in otoliths of eels collected from a tidal Atlantic lake system in Ireland. Variations of the Sr:Ca ratio in the otoliths indicated that a variety of environmental salinities had been experienced in the habitats that were occupied during the growth phase of these individuals in the tidal Atlantic lake system. The otolith microchemistry of these eels indicated that most of the eels had entered each salinity environment (freshwater (FW); brackish water (BW); marine-dominated water (MW) and full seawater (SW)) from fresh water to full seawater just after recruitment and had stayed in each environment until maturation without movement to other salinity environments. Only 2 of 93 (2%) eels had shifted their habitat once in their lives. This result suggests that each individual might have an environmental habitat preference, although each individual could move along a short (<2 km) salinity gradient.
To compare the growth and biosynthetic ability of long-chain PUFA (LC-PUFA) of the genetically improved farmed tilapia (GIFT) (Oreochromis niloticus) in different water salinities, an 8-week feeding trial was conducted on the GIFT juveniles at 0, 12 and 24 ‰ (parts per thousand; ppt), respectively, with three isonitrogenous (32 %) and isolipidic (8 %) diets (D1–D3). Diet D1 with fish oils (rich in LC-PUFA) as lipid source was used as the control, while D2 and D3 with vegetable oil (free LC-PUFA) blends as lipid source contained different ratios of linoleic acid (LA, 18 : 2n-6) and α-linolenic acid (ALA, 18 : 3n-3) at 4·04 (D2) and 0·54 (D3), respectively. At the end of feeding trial, the growth performance of D2 and D3 groups under all salinity treatments was as good as that of D1 group, which indicates that the GIFT juveniles may convert dietary LA and ALA into LC-PUFA to meet the requirement of essential fatty acids for normal growth and physiology. When fed the same diets, GIFT at 12 ppt had a better growth performance coupled with a higher liver and muscle arachidonic acid content than those in freshwater. Furthermore, brackish water (24 ppt) significantly promoted the mRNA levels of elongase 5 of very long-chain fatty acids (elovl5) and peroxisome proliferator-activated receptor α (pparα) in liver, when compared with freshwater. These results suggest that the GIFT may display better growth performance together with a relatively higher endogenous LC-PUFA biosynthetic ability under brackish water (12 and 24 ppt), probably through improving the expression of elovl5 and pparα in liver.
In the Rio de la Plata salinity, temperature, chlorophyll a (chl a), and densities (ind. m−3) of the copepods Acartia tonsa and Paracalanus parvus were measured from January to November in 2003 by following a nested weekly and monthly design. Such sampling yielded two separate datasets: (i) Yearly Dataset (YD) which consists of data of one sampling effort per month for 11 consecutive months, and (ii) Seasonal Weekly Datasets (SWD) which consists of data of one sampling effort per week of any four consecutive weeks within each season. YD was assumed as a medium-term low-resolution (MTLR) dataset, and SWD as a short-term high-resolution (STHR) dataset. The hypothesis was, the SWD would always capture (shorter scales generally captures more noise in data) more detail variability of copepod populations (quantified through the regression relationships between temporal changes of salinity, temperature, chl a and copepod densities) than the YD. Analysis of both YD and SWD found that A. tonsa density was neither affected by seasonal cycles, nor temporal variability of salinity, temperature and chl a. Thus, compared to STHR sampling, MTLR sampling did not yield any further information of the variability of population densities of the perennial copepod A. tonsa. Analysis of SWD found that during summer and autumn the population densities of P. parvus had a significant positive relationship to salinity but their density was limited by higher chl a concentration; analysis of YD could not yield such detailed ecological information. That hints the effectiveness of STHR sampling over MTLR sampling in capturing details of the variability of population densities of a seasonal copepod species. Considering the institutional resource limitations (e.g. lack of long-term funding, manpower and infrastructure) and the present hypothesis under consideration, the authors suggest that a STHR sampling may provide useful complementary information to interpret results of longer-term natural changes occurring in estuaries.
Prairie groundcherry [Physalis hederifolia (A. Gray) var. fendleri (A. Gray) Cronquist] is an invasive perennial weed with the potential to become a significant summer weed across 409 million hectares in Australia. Current management practices do not provide effective control of established populations. A better understanding of the seed biology is needed to effectively manage this weed. A series of field and laboratory studies were conducted to determine plant fecundity, soil seedbank longevity, and the factors that affect seed germination. Physalis hederifolia has the capacity to produce 66 to 86 berries plant−1, 51 to 74 seeds berry−1, and approximately 4,500 seeds plant−1, with the seeds potentially able to persist in the soil seedbank for 20 yr if buried in an intact dry berry pod. The bare-seed component of the soil seedbank can be virtually exhausted within 3 yr if cultivation is minimized to avoid burial of seed. Optimal temperature for germination is diurnal fluctuations of 15 C within the temperature range of 10 and 30 C. Increasing osmotic stress levels reduced the germination under all temperature regimes, with less than 6% germination occurring at −0.96 MPa. Physalis hederifolia seed germination was not significantly affected by substrate pH 4 to 10 or salt levels less than 160 mM, while the germination was significantly reduced at NaCl concentrations above 160 mM. These results suggest that P. hederifolia can adapt to a range of substrate conditions. Stopping seed set, avoiding grazing plants with viable seeds, and minimizing seed burial in the soil are some effective strategies to control this weed.
Soil salinity is a major limitation to legume production in many areas of the world. Identification of the genetic source of salt tolerance is critical in soybean breeding for improving soybean production in salt-affected regions. Vietnam has unique sources of soybean germplasm and varieties are grown in the area where exposure to salinity is frequent. However, there is little research on the identification of salt tolerant sources in the Vietnamese gene pool. The present study compared 18 Vietnamese soybean cultivars for their differences in salt tolerance. Under a range of NaCl stress from 0 to 200 mM NaCl, there was a large variation in salt tolerance among the 18 soybean lines evaluated. The soybean accession PI 675847 A (Vietnamese variety DT2008), was identified as a useful source of salt tolerance. During vegetative growth, PI 675847 A had lower leaf scorch scores, higher cell membrane stability, better photosynthesis and biomass accumulation under NaCl stress than the other 17 strains evaluated. In addition, PI 675847 A maintained better growth and seed yield in salt-affected soils compared with the sensitive lines. Analyses of ion contents in plant leaves under saline conditions showed that PI 675847 A was able to limit uptake and transport of Na+ and Cl−. Because of its higher productivity under saline conditions, PI 675847 A will be a useful germplasm source in soybean improvement programs for salt tolerance.
Siphonophores are colonial hydrozoans that feed on zooplankton including fish larvae, and occur throughout the world's oceans from surface waters to ocean depths. Here we describe the composition of hyponeustonic siphonophores (0–3 m depth) from the tropical Colombian Pacific Ocean based on 131 plankton samples collected between June–October from 2001–2004. Samples were dominated by species of Calycophorae, with only three species of Physonectae identified, consistent with their deeper depth distribution. Muggiaea atlantica, Chelophyes contorta, Diphyes dispar, and Eudoxoides mitra were the most common of the 21 species identified. We found moderate structuring of the siphonophore community by the salinity gradient from inshore to offshore, and greater richness during the night because of diel vertical migration. Temperature did not play a significant role in structuring siphonophore communities, perhaps because of the narrow temperature range observed (3.5 °C). We extend the known temperature and salinity range of several species, including M. atlantica up to temperatures of 28.6 °C and salinities down to 24.7. Interestingly, only polygastric stages of M. atlantica were found, suggesting the reproductive stage of M. atlantica in tropical waters might be found in deeper waters. Chelophyes appendiculata was rare in our study and C. contorta was common, providing evidence they have a potential allopatric relationship, with C. contorta replacing C. appendiculata in warm water. Finally, we found siphonophore abundance was positively related to the abundance of copepods and fish eggs, with the top 13 most abundant species all having positive correlations, suggesting siphonophore abundances are tightly controlled by their food.
Much of the agricultural area in California’s southwestern San Joaquin Valley (SJV) is prone to moisture stress and high soil-salinity conditions. Increased prevalence of glyphosate-resistant (GR) biotypes of junglerice [Echinochloa colona (L.) Link] in these environments and their ecological implications need to be further explored. Studies were conducted on GR and glyphosate-susceptible (GS) biotypes of E. colona to compare the effects of moisture and salinity stress on seed germination and salinity stress alone on growth and seed production. Intraspecific competition between the GR and GS plants was also assessed in a replacement series design experiment. With respect to germination, both biotypes were tolerant to moisture and salinity stress at germination; however, the GR biotype was more tolerant than the GS biotype. Water potential and electrical conductivity (EC) levels that reduced germination by 50% were estimated as −1.5 and −2.3 MPa and 8.5 and 12 dS m−1 for the GS and GR biotypes, respectively. The EC levels that reduced aboveground biomass by 50% were estimated as 9 and 11.5 dS m−1 for the GS and GR biotypes, respectively. Seed production was generally greater in the GR than the GS plants below 10 dS m−1. All plants produced up to 140 seeds plant−1, even at 20 dS m−1. The GR plants were more competitive and produced more aboveground dry biomass and seeds than the GS plants when grown together or alone. In conclusion, differences between these particular GR and GS biotypes to environmental stresses and intraspecific competition were noted that could have ecological implications for their prevalence in the southwestern SJV. The results also suggested that there could be high genetic variability and phenotypic plasticity in E. colona populations in the SJV and further population shifts could occur due to selection pressure from glyphosate.
Progressive salinization of water and soil will be increasingly severe in low-lying coastal areas as climate change proceeds. Thus, understanding the economic impacts of salinity intrusion will be essential for effective adaptation planning. This paper uses econometric analysis to predict the impact of climate-induced increases in soil salinity on high-yielding-variety rice production in coastal Bangladesh. Findings indicate an output decline of 15.6 percent in nine subdistricts where soil salinity will exceed 4 deciSiemens per meter before 2050. Without new adaptation strategies, the predicted changes will result in 7.7 and 5.6 percent losses in the Barisal and Chittagong regions, respectively.
One of the future challenges to produce food in a Mars environment will be the optimization of resources through the potential use of the Martian substratum for growing crops as a part of bioregenerative food systems. In vitro plantlets from 65 potato genotypes were rooted in peat-pellets substratum and transplanted in pots filled with Mars-like soil from La Joya desert in Southern Peru. The Mars-like soil was characterized by extreme salinity (an electric conductivity of 19.3 and 52.6 dS m−1 under 1 : 1 and saturation extract of the soil solution, respectively) and plants grown in it were under sub-optimum physiological status indicated by average maximum stomatal conductance <50 mmol H2O m−2 s−1 even after irrigation. 40% of the genotypes survived and yielded (0.3–5.2 g tuber plant−1) where CIP.397099.4, CIP.396311.1 and CIP.390478.9 were targeted as promising materials with 9.3, 8.9 and 5.8% of fresh tuber yield in relation to the control conditions. A combination of appropriate genotypes and soil management will be crucial to withstand extreme salinity, a problem also important in agriculture on Earth that requires more detailed follow-up studies.
This study constitutes a first attempt to investigate sex differences in osmoregulatory capacity and metabolic responses in relation to hyper- and hypo-osmoregulation in the intertidal euryhaline crab Uca tangeri. Adult male and female specimens from Cadiz Bay, Spain (36°23′–37′N 6°8′–15′W), were acclimated to three different environmental salinities (12, 33 and 55 psu) during 7 days, and several parameters were assessed in haemolymph (osmolality, glucose, amino acids, triglycerides and lactate) as well as in metabolic key organs (hepatopancreas, anterior and posterior gills: glycogen, free glucose, amino acids and triglycerides). Specimens from both sex exhibited high and similar hyper- and hypo-osmoregulatory capacities. However, metabolite levels were differentially affected upon acclimation to low and high salinity in several metabolic organs and haemolymph of male and females: (i) glycogen in gills, (ii) free glucose in gills and hepatopancreas, (iii) amino acids in hepatopancreas, (iv) triglycerides in haemolymph, hepatopancreas and posterior gills, and (v) lactate in haemolymph. The results suggest the occurrence of differential metabolic adjustments upon hyper- and hypo-osmoregulation related to sex in the intertidal euryhaline crab U. tangeri.
The Vera Basin is one of a series of interconnected Neogene–Quaternary-age basins located within the Betic Cordillera in SE Spain. The initial marine phase in the basin is represented by the sedimentary succession of the Abad Member (Tortonian–Messinian) and comprises mainly marls with varying amounts of intercalated siliciclastic–calcareous turbidites. The succession contains a rich ichnofauna comprising 12 ichnogenera (21 ichnospecies), which can be subdivided into a number of distinct ichnoassemblages. Detailed analysis of the distribution of these ichnoassemblages reveals that deposition occurred within the Nereites ichnofacies, more specifically, the Paleodictyon sub-ichnofacies, presumably in a lobe-type setting, and at epi- to mesobathyal depths (i.e. 200–1000 m). Changes within the ichnofacies suggest that there is a clear deep-through-to-shallow trend within the succession extending from the older (i.e. Almocáizar Corridor) to the younger (i.e. centre of the Vera Basin) parts of the succession. These changes coincide with the onset of the Messinian Salinity Crisis (MSC) across the region, and correlate well with the pre-MSC through to Lago Mare deposits.
Micropaleontological studies of the Black Sea, including ostracod records, have suggested that early Holocene salinity values were between ~5 and 10 practical salinity units (psu), contrasting with present values of 18–22 psu. However, more precise paleoenvironmental reconstructions based on ostracod assemblages require additional information related to their modern ecological affinities. This study uses modern species information collected from samples with living fauna to interpret the fossil Holocene assemblages of two sediment cores, Ak-2575 and Ak-521, collected from the northeastern outer shelf of the Black Sea. A total of 37 ostracod species are recorded in the fossil assemblages, with 2 related to freshwater/oligohaline environments, 23 from Caspian-type environments, and 12 from environments similar to the Mediterranean. Three distinct assemblage zones are identified from the Caspian type dominating in the early Holocene up to 7.4 cal ka BP, a mixed assemblage of Caspian type and Mediterranean type from 7.4 to 6.8 cal ka BP, and a progressive dominance of Mediterranean species from 6.8 cal ka BP. It is very likely that the dominant control of ostracod species occurrence during the period up to ~6.8 cal ka BP is salinity. A range of factors including temperature, biotope, and sedimentation rates influenced the species distribution over the last 6.8 cal ka BP.