No abstract

This study investigated the effects of sudden weaning of angel fish larvae (Pteraphylum scalari) from Artemia nauplii to commercial larval feed. Four days post hatch (DPH) larvae were reared in four different weaning protocols (TR1-TR4) with triplicates in a complete randomize design. Larvae in TR1 and TR4 were exclusively fed Artemia nauplii and dry feed respectively. In TR2 and TR3, larvae were initially fed Artemia nauplii and suddenly wean to formulated feed on 14 DPH and 7 DPH respectively. The experiment was lasted for 28 days. At the end of the experiment, final mean weight (FW), total length (FL), height (FH), Daily Weight Gain (DWG), Specific Growth Rate (SGR), survival and stress index were compared. Significantly highest (P < 0.05) FW, DWG and SGR were observed in TR1 and TR2 while former values of TR3 were not significantly different from TR1. Highest FL observed in TR1 and TR2 while FL of TR2 was statistically similar to that of TR3. The poorest growth was observed in larvae solely fed formulated feed. Survival and the stress index were independent from weaning methods. Although sudden weaning is possible on 7 DPH, larvae showed comparatively higher growth when switch off to formulate feed on 14 DPH.

The present study evaluated the impact of cesium ((133)Cs) at four concentrations (0, 0.001, 0.01, and 0.1 mg L(-1)) on growth, concentrations of chlorophyll and carotenoid pigments, and oxidative stress responses in the charophyte, Nitella pseudoflabellata, over 30 days. Oxidative stress was quantified by measuring anti-oxidant enzyme activities and H2O2 content. When compared with the control, significantly elevated activity levels of the anti-oxidative enzymes ascorbic peroxidase, catalase and guaiacol peroxidase were observed at 0.1 mg L(-1) (all p < 0.05), even though the H2O2 level was not significantly elevated. Carotenoid and chlorophyll a and b pigment levels were significantly reduced (all p < 0.05) at Cs exposures of 0.01 and 0.1 mg L(-1). Photosynthetic efficiency (i.e., Fv/Fm) was significantly reduced (p < 0.05) at Cs concentrations ≥0.001 mg L(-1). Significant reduction (p < 0.05) of plant growth (i.e., shoot length) was also observed after 1 week of exposure at Cs concentrations ≥0.001 mg L(-1). Our results suggested that Cs exposure reduced plant growth and affected plant functioning via activating the defense mechanism against oxidative stress in Nitella.

Atapaththu K.S.S., Asaeda T., Yamamuro M., Kamiya H.: Effects of water turbulence on plant, sediment and water quality in reed (Phragmites australis) community. Ekológia (Bratislava), Vol. 36, No. 1, p. 1-9, 2017. Even though the interaction between water movements and aquatic plant is crucial for the aquatic ecosystem management, the importance of water turbulence in this regard is not well documented. To add to our knowledge on the interaction between aquatic plant communities and water turbulence, this study examined turbulence, plant, sediment and water quality at the reed community (Phragmites australis) in the Lake Shinji, Japan. Observations were conducted along transects perpendicular to the shoreline. For each transect, reed communities were observed at land ward side, centre, water ward and the outside of the reed community. An elevated level of turbulence was observed outside compared to inside reed community, where the magnitude of turbulence decreased with distance into the community interior. A significant positive correlation was observed for turbulence and surface-dissolved oxygen where the latter was negatively correlated to reed density. Sediment composition was affected by water turbulence where the content of coarse particles positively correlated to turbulence. Accumulation of organic matter in anoxic sediments together with fine particles was observed under low turbulence. Our findings can offer insight into understanding the interactions between turbulence and aquatic plant communities.

Aquatic plants in agricultural landscapes play a vital role in maintaining the ecological integrity within the aquatic systems while facing an array of disturbances. Among them, information on herbicide exposure on non-target aquatic plants is scarce. The present study was designed to fill this information gap by detecting the impacts of 2-methyl-4-chlorophenoxyacetic acid (MCPA) on Hydrilla verticillata using morpho-anatomical and physiological biomarkers and assessing the environmental risk of MCPA to the non-target environment. H. verticillata was exposed to different MCPA concentrations (10, 100, 500, 1000 μg/L) and control (0 μg/L) for 7 days. At the end of the experiment, plant growth, pigments, HO content, peroxidase activity (POD) and plant anatomy were compared. The environmental risk was assessed using predicted environmental concentration/predicted no effect concentration (PEC:PNEC) ratio, hazard quotient (HQ) and hazard index (HI). Control plants exhibited the highest growth, and a growth decline was noted in parallel to MCPA exposure, where a similar trend was detected for the plant pigment contents. MCPA induced chlorosis and oxidative stress in H. verticillata. Risk analysis detected high values for PEC:PNEC ratios (3-9), HQ (1.92-5.79) and HI (28.15). MCPA-exposed H. verticillata could recover once those plants received natural conditions. Overall, present findings showed the negative impacts of MCPA on non-target aquatic plant H. verticillata. These findings will be useful to clarify the interaction between agrochemicals and non-target aquatic plants. Such information would benefit to decide the criteria in aquatic ecosystem management.

The interactions between macrophytes and water movement are not yet fully understood, and the causes responsible for the metabolic and ultrastructural variations in plant cells as a consequence of turbulence are largely unknown. In the present study, growth, metabolism and ultrastructural changes were evaluated in the aquatic macrophyte Elodea nuttallii, after exposure to turbulence for 30 days. The turbulence was generated with a vertically oscillating horizontal grid. The turbulence reduced plant growth, plasmolysed leaf cells and strengthened cell walls, and plants exposed to turbulence accumulated starch granules in stem chloroplasts. The size of the starch granules increased with the magnitude of the turbulence. Using capillary electrophoresis-mass spectrometry (CE-MS), analysis of the metabolome found metabolite accumulation in response to the turbulence. Asparagine was the dominant amino acid that was concentrated in stressed plants, and organic acids such as citrate, ascorbate, oxalate and γ-amino butyric acid (GABA) also accumulated in response to turbulence. These results indicate that turbulence caused severe stress that affected plant growth, cell ultrastructure and some metabolic functions of E. nuttallii. Our findings offer insights to explain the effects of water movement on the functions of aquatic plants.

No abstract

Microcystins (MCs) and cylindrospermopsin (CYN) are the most abundant toxins produced by cyanobacteria in tropical freshwaters. We studied the spatial distribution of MC and CYN in two multipurpose reservoirs, Mahakanadarawa and Nachchaduwa in Anuradhapura district in Sri Lanka in September 2020. Fourteen water quality parameters, phytoplankton composition, chlorophyll-a, MC and CYN concentrations were analyzed in triplicate in 25 sampling sites from each reservoir. Both reservoirs were at hypereutrophic status. Microcystis was the dominant cyanobacteria with 0-3.75 x 10 3 cell/mL in Mahakanadarawa and 1-7 x 10 3 cell/mL in Nachchaduwa. Besides Microcystis, no other potential MCproducing cyanobacteria were observed. In Mahakanadarawa, MC was detected in the range of 0.11-1.63 µg/L which was above the WHO permissible level (1.0 µg/L) for drinking water. Although comparatively high Microcystis cell density was present in Nachchaduwa, its MC concentration was low (0.06-0.17 µg/L). The CYN concentration in Nachchaduwa was above the WHO permissible level (0.7 µg/L) for drinking water. It was 0.20-1.02 µg/L in Nachchaduwa and 0.03-0.08 µg/L in Mahakanadarawa. We did not observe any potential CYN-producing cyanobacteria in either of the reservoirs. There was no relationship between the spatial distribution pattern of MC and Microcystis cell density in both reservoirs. Although the majority of physico-chemical properties of water indicated suitability for drinking, co-occurrence of high concentrations of MC and CYN indicated their unsuitability for drinking. Hence, this study highlights the necessity for routing detection of cyanotoxins in both reservoirs. Further, our findings alarm potential health risks for the local community that relies on Mahakanadarawa and Nachchaduwa reservoirs for drinking, irrigation and fisheries.