ISSN / EISSN : 0078-3234 / 2300-7370
Published by: Elsevier BV (10.1016)
Total articles ≅ 614
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This study gives updated information on the isolation of ulvan from green alga Ulva fasciata Delile in Egypt through isolation and chemically characterization of sulfate polysaccharides by two sequential extraction steps using different solvents; distilled water, HCl and Na2EDTA forming fraction I (F-I). Fraction II (F-II) was obtained from remaining seaweeds using NaOH to give FDWNaOH, FHClNaOH, and FEDTANaOH. All products obtained were tested for their biological activities. The highest polysaccharides total extraction yield was 11.8% for water extract (F-I& F-II). The highest protein content was found in FEDTANaOH (2.44%). The highest sulfate content was recorded for F-I (HCl) (21.38%). Total carbohydrates range was (11.99–63.90%) for F-I and (15.06–76.65%) for F-II. Monosaccharides; galactose, rhamnose, and uronic acid were detected at all fractions, with concentrations varying from 0.11 to 1.34%, from 0.61 to 1.81% and from 11.06 to 19.30%, respectively. H1 NMR of (F-II) demonstrated the signals of ring and methyl protons of polysaccharide. The appearance of the stretching bands of the sulfate ester (C-O-S) and sulfate groups (S=O) in the FT-IR spectrum of FHClNaOH confirmed the presence of sulfated polysaccharides, typical of ulvan. The microbial species Vibrio damsela was the most susceptible to FDWNaOH, followed by Aeromonas hydrophila and Vibrio fluvialis with inhibition zones of 30, 22, 22 mm at 150 mg/ml, respectively. FDWNaOH was the most effective fraction having antifouling property. The highest antioxidant activity was observed for F-IHCl followed by FDWNaOH. At concentrations 25 and 50 mg/l,FEDTANaOH displayed the highest anti-inflammatory activity (94.0 and 91.40%, respectively).
Tropical cyclone Amphan is the first super cyclone that happened in the north Indian Ocean in the last 20 years. In this work, multi-platform datasets were used to investigate the responses of the upper ocean to cyclone Amphan. The most striking response was the cold wake left by the cyclone spanning the entire Bay of Bengal with an amplitude up to ∼4°C. Satellite salinity observations revealed that the maximum increase in surface salinity was ∼1.5 PSU on the right side of the track of Amphan. Surface circulation was also observed to be modulated with the passage of a cyclone with a rightward bias in the change in its speed and direction. The currents observed from a moored buoy showed strong inertial oscillations. Argo observations showed that changes induced by the cyclone occurred up to 150 m depth of the cyclone and ocean heat content in the upper 150 m depth decreased due to the passage of the cyclone. There was an enhancement of surface chlorophyll concentration (∼1.5 mg/m3) after the passage of the cyclone, which was centred along the track of the cyclone where the winds were the highest. Mixed layer heat and salinity budget analysis showed that the sea surface cooling and increase in salinity was primarily driven by vertical mixing processes, though horizontal advection contributed meagrely. This study also brings forward the fact that regional differences exist in the responses of the ocean to the forcing of cyclones.
Mabahiss Bay and Safaga Bay are two important ports along the Red Sea coast of Egypt. The present study is the first to monitor halogen concentrations in these two ports. Certain halogens (F, Cl, Br and I) in coastal waters and sediments exhibited different behaviors. Fluoride (1.92–8.31 mg/L and 0.34–1.24 mg/g), chloride (20.76–22.68 g/L and 0.38–8.31 mg/g), bromide (95.90–151.84 mg/l and 6.66–50.61 mg/g), and iodide (2.77–39.19 μg/L and 1.71–3.76 μg/g) appeared in the seawater and sediments of Mabahiss Bay, respectively. In Safaga Bay, F, Cl, Br and I yielded ranges of (1.80–10.15 mg/L and 0.14–0.74 mg/g), (21.47–22.57 g/L and 0.68–1.42 mg/g), (15.98–146.51 mg/L and 6.13–74.59 mg/g) in seawater and sediments, respectively. In Mabashis Bay exclusively, the bromide and iodide levels in seawater increased significantly, and the sediments were vice versa. The average fluoride value in the two ports' seawater was higher than that in the unpolluted Mediterranean Sea. In contrast, the average bromide content in Mabahiss Bay seawater exceeded the Mediterranean Sea level. The seawater chloride content of the two ports was within the Mediterranean seawater's value, but the iodide concentration was lower than that of the unpolluted seawater. The application of different multivariate statistical techniques showed that halogen's distribution and halogen's geochemical characteristics control interaction in each region, ground flux, and proximity to human sources.
This study investigates the inhibitory effects of thalli and their extracts of the macroalga Turbinaria ornata on the germination of dinoflagellate cysts, previously isolated from Red Sea surface sediments. The experiments were conducted on cysts of five harmful dinoflagellate species including Alexandrium catenella, Cochlodinium polykrikos, Dinophysis accuminata, Prorocentrum cordatum and Scrippsiella trochoidea. The results showed neither macroalgal thalli nor their extracts had direct impact on the cyst germination of all species. Instead, these macroalgal materials remarkably affected the germling viability and culturability of progeny cells of these cysts. Dry macroalgal thalli exhibited stronger inhibitory effects on germling viability and cell culturability (IC50= 0.235-–0.543, 0.385–1.43 mg mL−1, respectively) than fresh thalli (IC50=2.201-–4.716, 2.17–7.18 mg mL−1, respectively). The macroalgal ethanol extract was approximately 2-5 times more effective (IC50 = 0.012–0.047 and 0.024–0.089 mg mL−1, respectively) than aqueous extract (IC50 = 0.04–0.1 and 0.054–0.207 mg mL−1, respectively) against the germling viability and vegetative progeny cells of all cyst species. Among different species, A. catenella and C. polykrikos germlings were more sensitive to macroalgal thalli and their extracts than those of S. trochoidea, P. cordatum and D. acuminata. Meanwhile, progeny cells of A. catenella exhibited the highest sensitivity to all macroalgal materials. Our results suggest that the use of T. ornata may be a promising strategy for inhibiting the division of progeny cells of dinoflagellate cysts and impairing the recurrence of HABs in confined coastal areas.
The Arabian Gulf is a very significant ocean body, which hosts more than 55% of the oil reserves of the world and produces about 30% of the total production, and thus, it is likely to face high risk and adverse problems by the intensified environmental stressors and severe climatic changes. Therefore, understanding the hydrography of the Gulf is very essential to identify various marine environmental issues and subsequently, developing marine protection and management plans. In this study, hydrography data collected at 11 stations along 3 linear transects in the early summer of 2016 were analyzed. The physicochemical parameters exhibited apparent variations along each transect, both laterally and vertically, connected to stratification, formation of different water masses and excessive heating. The temperature and salinity decreased laterally from nearshore to offshore, while layered density structures were identified in the offshore regions. The pH, dissolved oxygen (DO) and chlorophyll fluorescence (Fo) exhibited distinct horizontal and vertical variations. The observed pH is within the normal ranges, indicating that seawater acidification may not be a threat. The highest DO (6.13–8.37 mg/l) was observed in a layer of 24-36 m water depth in the deeper regions of the central transect.
We report a considerable range expansion of four Ponto-Caspian amphipod species in transitional waters along the southeastern Baltic Sea coast. Chaetogammarus warpachowskyi and Dikerogammarus haemobaphes were found for the first time in Latvia, the former being common along the coast, while the latter was encountered only in the port of Riga. This indicates a coastal expansion of 400 to 600 km, assuming an origin from the Curonian or Vistula lagoons. We also officially document an expansion for Chelicorophium curvispinum in Latvia of ca. 300 km until Riga, confirming recent unpublished records. Moreover, we document a second invasion route of Pontogammarus robustoides into Estonia from nearby Latvian waters by uncovering a population at the port of Pärnu. This species was previously known in Estonia only from the Gulf of Finland (>500 km from Pärnu). With the exception of D. haemobaphes, all newly recorded species were represented by various life-stages and ovigerous females, indicating viable populations. Overall, our findings reveal that Ponto-Caspian amphipods are much more widespread in the Baltic area than previously known and highlight the need for more stringent monitoring.
Coastal lagoons have been providing ecological, economic and cultural benefits for many centuries. Despite their importance, the monitoring of coastal lagoons poses numerous challenges related to their complex environmental processes, their large variability in size and their remote location, inhibiting effective management programmes. This study demonstrates the effectiveness of Sentinel-2 satellites to map highly dynamic morphological and hydrological changes in the Louro lagoon, a small choked lagoon located on the Galician coast (NW Spain). For this purpose, a simple methodology using the Normalised Difference Water Index (NDWI) has been evaluated, which allows to monitor the sand barrier changes and the inlet formation. The results show that the sand barrier's opening and closing might take only a very short period, and the recovery of the lagoon to its full water level can happen in less than a month. Sentinel-2 images also reveal drastic changes in the water level once the sand barrier is broken. A water surface area of 0.24 km2 was estimated on 04/11/ 2019, while this surface was reduced to 0.10 km2 on 04/12/ 2019. Monitoring these changes is critical to understand the different processes ongoing in these valuable environments and making informed decisions for their management and protection.
Oceanologia, Volume 63; https://doi.org/10.1016/s0078-3234(21)00070-1
Sea level trends and their forcing over the eastern Mediterranean basin are investigated by using 27 years (1993–2019) of gridded sea level anomalies (SLA) derived from satellite altimetry and 9 tide gauge stations, along with sea surface temperature (SST) and temperature and salinity profiles. The contributions of atmospheric (wind and pressure) and steric components to the interannual variability of total SLA were evaluated. The thermosteric component represents the major contributor to the linear trend and was positive over most of the eastern Mediterranean, with a spatially averaged trend of 2.13±0.41 mm/year, accounting for 69 % of the total sea level trend (3.1±0.61 mm/year). In contrast, the halosteric effect has a negative contribution to the steric SLA, with a mean trend of -0.75±0.19 mm/year. The atmospheric component trend was much lower at 0.32±0.24 mm/year. The interannual variability of SLA accounts for about 36% of overall sea level variability. Steric and atmospheric contributions to the interannual variability of sea level in the eastern Mediterranean account for about 52% and 18%, respectively. The strongest interannual variability and trends in SLA were observed over the basin's main recurrent gyres, with the maximum positive trend obtained over the Mersa–Matruh and Cyprus gyres, as well as the North Shikmona eddy, and maximum negative trend over the Ierapetra gyre. Over the study period, all tide gauges showed a positive and statistically significant trend, ranging from 1.47±0.77 to 5.79±1.32 mm/year after applying glacial isostatic adjustment and atmospheric correction, and were in good agreement with reconstructed steric sea level data.
In a series of ad-hoc surveys at different academic institutions in the Baltic Sea region, students and young scholars were asked about their views about the environmental issues of the Baltic Sea, and who would be responsible for the management of the Baltic Sea. Overfishing, climate change and waste were considered the most significant issues, while tourism and constructions (of bridges, etc.) were less often recognized as severe. The responsibility for the management of the Baltic Sea was mostly attributed to the European Union or to the respective national governments.