Assessment of Physico-Chemical Properties of the Pasur River Estuarine Water

This study aimed to investigate physico-chemical properties of the Pasur River Estuarine (PRE) water connected to the Sundarbans mangrove ecosystem during the dry season for examining the ecosystem health. In-situ measurement and water sample collection were performed to assess physico-chemical properties at fifteen sampling stations along the main axis of the estuary in March 2018, April 2018, January 2019 and March 2019. Surface water temperature ranged from 20.7 to 33.7°C, pH from 7.1 to 7.9, and salinity from 8.5 to 16.2 PSU (practical salinity unit). Dissolved Oxygen (DO) concentration varied from 5.9 to 8.4 mg/L. Ammonium-nitrogen (NH4 +) was the dominant nitrogenous compound among the dissolved inorganic nitrogenous (NH4 + +NO3 -+NO2 -) compounds, and ranged from 0.11 to 2.11 mg/L. Higher NH4 + concentration in water column was largely attributed to release by tidal wash-out of the interstitial waters of the surficial mangrove sediments. In contrast, phosphate concentration varied from 0.07 to 5.8 mg/L. The Pearson correlation coefficient was calculated to elucidate the correlation among physico-chemical properties during the dry season. Temperature showed a significant positive correlation with salinity and total dissolved solids (TDS), and negative correlation with DO. Similarly, salinity showed a significant positive correlation with TDS and negative correlation with DO. According to the Redfield ratio, the PRE is a nitrogen-limited estuarine system during the dry season. Ann. Bangladesh Agric. (2020) 24(1) : 1-16

Climate change overtakes coastal engineering as the dominant driver of hydrological change in a large shallow lagoon

Ecosystems in shallow micro-tidal lagoons are particularly sensitive to hydrologic changes. Lagoons are complex transitional ecosystems between land and sea, and the signals of direct human disturbance can be confounded by variability of the climate system, but from an effective estuary management perspective, the effects of climate versus direct human engineering interventions need to be identified separately. This study developed a 3D finite-volume hydrodynamic model to assess changes in hydrodynamics of the Peel–Harvey Estuary, a large shallow lagoon with restricted connection with ocean; this was done by considering how attributes such as water retention time, salinity and stratification have responded to a range of factors, focusing on the drying climate trend and the opening of a large artificial channel over the period from 1970 to 2016, and how they will evolve under current climate projections. The results show that the introduction of the artificial channel has fundamentally modified the flushing and mixing within the lagoon, and the drying climate has changed the hydrology by comparable magnitudes to that of the opening of the artificial channel. The results also highlight the complexity of their interacting impacts. Firstly, the artificial channel successfully improved the estuary flushing by reducing average water ages by 20–110 d, while in contrast the reduced precipitation and catchment inflow had a gradual opposite effect on the water ages; during the wet season this has almost counteracted the reduction brought about by the channel. Secondly, the drying climate caused an increase in the salinity of the lagoon by 10–30 PSU (Practical Salinity Unit); whilst the artificial channel increased the salinity during the wet season, it has reduced the likelihood of hypersalinity (>40 PSU) during the dry season in some areas. The opening of the artificial channel was also shown to increase the seawater fluxes and salinity stratification, while the drying climate acted to reduce the salinity stratification in the main body of the estuary. The impacts also varied spatially in this large lagoon. The southern estuary, which has the least connection with the ocean through the natural channel, is the most sensitive to climate change and the opening of the artificial channel. The projected future drying climate is shown to slightly increase the retention time and salinity in the lagoon and increase the hypersalinity risk in the rivers. The significance of these changes for nutrient retention and estuary ecology are discussed, highlighting the importance of these factors when setting up monitoring programmes, environmental flow strategies and nutrient load reduction targets.

A Data-Independent-Acquisition-based proteomic approach towards understanding the acclimation strategy of Microchloropsis gaditana CCMP526 in hypersaline conditions

Salinity is one of the significant factors that affect growth and cellular metabolism, including photosynthesis and lipid accumulation, in microalgae and higher plants. Microchloropsis gaditana CCMP526 can acclimatize to different salinity levels by accumulating compatible solutes, carbohydrates, and lipids as an energy storage molecule. We used proteomics to understand the molecular basis for acclimation of M. gaditana to increased salinity levels (55 and 100 PSU (Practical Salinity Unit). Correspondence analysis (CA) was used for the identification of salinity-responsive proteins (SRPs). The highest number of altered proteins was observed in 100 PSU. Gene Ontology (GO) enrichment analysis revealed a separate path of acclimation for cells exposed to 55 and 100 PSU. Osmolyte and lipid biosynthesis was up-regulated in high saline conditions. However, concomitantly lipid oxidation pathways were also up-regulated at high saline conditions, providing acetyl-CoA for energy metabolism through the TCA cycle. Carbon fixation and photosynthesis were tightly regulated, while chlorophyll biosynthesis was affected under high salinity conditions. Importantly, temporal proteome analysis of salinity-challenged M. gaditana revealed vital salinity-responsive proteins which could be used for strain engineering for improved salinity resistance.

Quantitative PCR enumeration of vcgC and 16S rRNA type A and B genes as virulence indicators for environmental and clinical strains of Vibrio vulnificus in Galveston Bay oysters

Oysters from a reef in Galveston Bay, Texas, USA, were screened for more virulent clinical strains versus less virulent environmental strains of Vibrio vulnificus using a combination of quantitative PCR assays for the virulence correlating gene (clinical variant, vcgC) and 16S rRNA types A and B (type A = environmental, type B = clinical). The combination of vcgC and 16S rRNA type B loci to determine clinical type strains was suitable, as indicated by the strong correlation (R2 = 0.98; p < 0.001) between these gene counts over time and their relative proportion (up to 93.8% and 94.3%, respectively) to vvhA genes used to quantify all strains of V. vulnificus. A strong seasonal shift of V. vulnificus strain types was observed. Environmental strains (16S rRNA type A) predominated from April to mid-June as salinities increased from 22 to 27 PSU (practical salinity unit) and temperatures rose 20 to 28 °C, with peak gene quantities of 16 812 ± 56 CFU/g. As temperatures increased to ≥30 °C from mid-June to September and salinities rose above 27 PSU, clinical strains (16S rRNA type B; vcgC) predominated with peak quantities 31 868 ± 287 and 32 360 ± 178 CFU/g, respectively.

Effects of salinity and sea salt type on egg activation, fertilization, buoyancy and early embryology of European eel, Anguilla anguilla

SummaryImproper activation and swelling of in vitro produced eggs of European eel, Anguilla anguilla, has been shown to negatively affect embryonic development and hatching. We investigated this phenomenon by examining the effects of salinity and sea salt type on egg dimensions, cell cleavage patterns and egg buoyancy. Egg diameter after activation, using natural seawater adjusted to different salinities, varied among female eels, but no consistent pattern emerged. Activation salinities between 30–40 practical salinity unit (psu) produced higher quality eggs and generally larger egg diameters. Chorion diameters reached maximal values of 1642 ± 8 μm at 35 psu. A positive relationship was found between egg neutral buoyancy and activation salinity. Nine salt types were investigated as activation and incubation media. Five of these types induced a substantial perivitelline space (PVS), leading to large egg sizes, while the remaining four salt types resulted in smaller eggs. All salt types except NaCl treatments led to high fertilization rates and had no effect on fertilization success as well as egg neutral buoyancies at 7 h post-fertilization. The study points to the importance of considering ionic composition of the media when rearing fish eggs and further studies are encouraged.

<i>Sanyuania cuneata</i> Zhao & Whatley, 1992 (Ostracoda, Cytheroidea, Cytherideidae) from Japan: morphology, distribution and environmental significance

Sanyuania cuneata Zhao &amp; Whatley, 1992 was reported initially from Late Pleistocene core samples from the northern part of the Yellow Sea and Recent sediments collected from supra tidal pools (17 practical salinity unit (psu)) in Xiangshangang Bay, East China Sea (Zhao &amp; Whatley, 1992). Later, specimens were discovered, but not identified, in Lake Nakaumi, Shimane Prefecture, SW Japan (Fig. 1) (as Cytheridae gen. et. sp. indet. by Tanaka et al. (1998) and Sanyuania sp. by Seto et al. (1999)). Further examination of these Japanese specimens has clarified that they are conspecific with the Chinese specimens. This has provided an opportunity to review the distribution (Fig. 1) and potential environmental significance of Sanyuania cuneata and, for the first time, to describe its appendages (Fig. 2).Specimens figured herein were recovered from Lake Nakaumi (35°26′ 50″ N, 133°07′50″ E) at a depth of 0.3–6.0 m and salinity of 8–17 psu on 9 September 1998. The surface of the sediment was covered by the byssus of the mussel Musculista senhousia (Benson, 1842).Sanyuania cuneata is probably endemic to the East China Sea and the southwestern part of the Sea of Japan and is a potentially useful palaeoenvironmental indicator of brackish (steno-haline) environments in the area. By using the oxygen isotopic data from planktonic foraminifers and the estimated value of salinity flowing into the Japan Sea, Matsui et al. (1998) approximated that the salinity of the surface water of Japan Sea declined to about 20 psu during the Last Glacial Maximum . . .