Assessment of spawning and nursery habitats of hilsa in the Tetulia and Meghna river estuaries

In the south basin of Lake Biwa, Microcystis aeruginosa dominantly occurred and the water blooms were formed at the limit area in late summer of 1983, 1987, 1988, 1990, and 1994. The relationship between the dominant occurrence of M. aeruginosa and water quality and the meteorological condition in the south basin of Lake Biwa was examined, referring to data from Shiga Prefecture and the meteorological Agency.The changes of water quality in the south basin in early September of 1980-1994 showed a remarkable fluctuation of TP (total phosphorus), DIN (dissolved inorganic nitrogen), DIP (dissolved inorganic phosphorus), DIN:DIP, TN (total nitrogen):DIN, and TP:DIP ratios, and M. aeruginosa usually occurred in the water with comparatively low DIN:DIP ratio.The comparison of each average water quality with the dominant species of phytoplanktons in early September of 1980-1994 showed that M. aeruginosa dominantly occurred in the waters with low DIN, DIP, and DIN:DIP ratio and high TN: DIN and TP:DIP ratios. The species occurred in the years with the meteorological conditions of high air temperature, long sunshine time, and comparatively low rainfall (precipitation) during August. These features of M. aeruginosa were contrasted remarkably with those of Rhodomonas sp.

Natural and Anthropogenic Drivers of Water Quality in the Normanby Basin and Princess Charlotte Bay, Cape York Peninsula, Australia

Evaluation of organic pollution and eutrophication status of Kaohsiung Harbor, Taiwan

Nutrients were the key biogenic elements for the primary production in coastal water, and the increase of nutrient concentration led to eutrophication and frequent occurrence of harmful algal blooms. However, the seasonal nutrients variation, eutrophication pattern, and Chlorophyll a (Chl-a) response adjacent to Guangdong coastal water were still scarcely. In this study, to clarity the seasonal nutrients variation, eutrophication pattern, and Chl-a, response adjacent to coastal water, the spatiotemporal dissolved inorganic nitrogen (DIN) and phosphorus (DIP) patterns and Chl-a were explored by field observation using 52 stations in the coastal waters of Guangdong Province during the dry (April and May), wet (July and August) and normal (October and November) seasons in 2020. The results showed that the variability of Chl-a, DIN and DIP were significantly different in seasons (P<0.01), and the mean concentrations of Chl-a, DIN and DIP were 11.97 ± 28.12 μg/L, 25.84 ± 35.72 μmol/L and 0.59 ± 0.71 μmol/L.Among them, the mean value of Chl-a increased significantly from 9.99 ± 9.84 μg/L in the dry season to 18.28 ± 38.07 μg/L in the wet season, and then decreased significantly to 7.65 ± 27.64 μg/L in the normal season.The mean DIN value decreased significantly from 30.68 ± 43.58 μmol/L in the dry season to 21.91 ± 35.45 μmol/L in the wet season, and then increased to 24.91 ± 26.12 μmol/L in the normal season. the mean DIP value decreased from 0.58 ± 0.73 μmol/L in the dry season to 0.48 ± 0.65 μmol/L in the wet season and then increased significantly to 0.70 ± 0.73μmol/L in the normal season. In addition, the DIN and DIP concentrations at most monitoring stations met the Grade II national seawater quality standards, and only a few monitoring stations fail to meet the Grade IV national seawater quality standard. The DIN/DIP ratios ranged from 2.05 to 259.47, with an average of 43.77 ± 41.01, far exceeding the Redfield ratio, indicating the presence of P limitation in the nearshore waters of Guangdong Province. Besides, the EI values in the coastal waters of Guangdong Province are higher at 0.00 and 82.51, with an average of 4.16 ± 10.90. DIN and DIP were significantly and positively correlated with COD in each season (P<0.05). Moreover, DIN/DIP showed significantly positive correlations with Chl-a in all seasons (P<0.01), indicating that high Chl-a concentrations could be sustained by the nutrients supply in marine ecosystems. Therefore, it is necessary to strengthen the integrated management of land and sea and effectively mitigate regional estuarine and coastal water eutrophication and harmful algal blooms.

Difference of Dissolved Inorganic Nitrogen (DIN) and Dissolved Inorganic Phosphorus (DIP) budgets in the Bohai Sea between 1980s and 1990s related the decrease of the Yellow River discharge is discussed on the basis of observed data. The estuarine circulation in the Bohai Sea had been weakened from 80s to 90s due to the decrease of the Yellow River discharge and the average residence time of fresh water had become longer. DIN concentration increased but DIP concentrations decreased from 80s to 90s in the Bohai Sea. Primary production was regulated mainly by water temperature and DIN concentration in 80s but it was regulated mainly by DIP concentration in 90s. Primary production was larger than decomposition plus bottom release and nitrogen fixation was larger than denitrification in 90s. However, decomposition plus bottom release was larger than primary production and denitrification was larger than nitrogen fixation in 90s in the Bohai Sea.

Relationships of the summer nutrient concentrations in the East China Sea with the Changjiang diluted water, upwellings and Kuroshio intrusion, from an interannual perspective.

Vertical distributions of atmospheric black carbon in dry and wet seasons observed at a 356-m meteorological tower in Shenzhen, South China

This study was conducted to evaluate the impact of seasonal variations (wet and dry season) on the reproductive and productive performance and to do an economic evaluation of hair sheep under Halaieb rangeland conditions and determine which season is the best in grazing areas. A total of 64 multiparous Abou-Delik ewes were bred in two different seasons. During the first season (dry season), a total of 35 ewes, 2-4years of age and 32.02 0.52 kg weight, were bred during May and June, while lambing and lactation took place in the months of November, December and January. On the other hand, during the wet season, 29 ewes, 2-4years age and 31.06 0.57 kg weight, were bred during November and December, whereas lambing and lactation took place in the months of May, June and July. Sheep grazed 8 h daily in the same pastures during the study and then moved back to the barns to receive a sorghum vulgare supplement with a dosage of 250 g per head per day. The results revealed that there were no significant effects of breeding season on conception, lambing and abortion rates. However, the wet season had higher ( ) prolificacy, mortality rates, lambs' weight and lambs born to ewes serviced. Contrariwise, dry-season lambs had a higher ( ) weaning weight. Also, milk yield (mL d ) and number of lambs weaned per lambs born (LW/LB) increased ( ) in the dry season compared to the wet season. No significant differences between the two seasons regarding the biological criteria studied were observed. On the other hand, the flock bred in the dry season generated a higher gross margin than that bred in the wet season. In this context, variable costs of the wet breeding season flock were recorded to be close to the value of the dry breeding season. Hence, it is concluded that the reproductive and productive performance of hair sheep raised in grazing areas in the Halaieb triangle is affected when lambs are born during the dry season because of the higher lamb mortality rate during this period which eliminates any comparative advantage for the good reproductive performance of ewes during the period of feed availability in the wet season. The high lamb mortality rates and low weaning weights in the wet breeding season lessen the economical merits of higher reproductive performance during the seasonal availability of feed in the wet season.

Spatio–temporal variation in Chlorophyll, Nutrients and Primary Productivity of some selected sampling stations in Lagos lagoon were investigated using conventional method from November 2019 to July 2020, in order to compare the result with data from satellite image using MODIS Aqua. Global Positioning Receiver was used to capture the geographic coordinates of the sampling stations. Water sampling was carried out monthly using standard methods during wet and dry seasons. The observed data were subjected to statistical analysis using Microsoft Excel and SPSS version 20. In wet season, the highest mean value for Chlorophyll a (1.15±0.02 µg/L) was recorded in Ofin while the lowest values (0.06±0.01 µg/L) was observed in Okobaba. During the dry season, the highest mean value (0.75±0.10 µg/L) was in Ofin while the lowest mean value (0.27±0.0.08 µg/L) was recorded in Ibeshe. The MODIS satellite variation in chlorophyll-a showed that the highest value of highest recorded value (1.37±0.00 µg/L) was in wet season (Ijede) while the lowest value (0.12±0.01 µg/L) was observed in dry season (Okobaba). The highest transparency value (0.97±0.01 mg/L) was recorded in dry season (Ofin) while the lowest value (0.35±0.25 mg/L) was recorded in wet season (Oworonsoki). The highest mean value of Surface Sea temperature was recorded in the dry season of Apapa (30.28±1.15oC) while the lowest mean value (26.41±1.15oC) was observed in Okobaba in the wet season. The chlorophyll-a concentration analyzed using standard method and MODIS satellite, in both dry and wet seasons in the sampled stations differ greatly from one another in terms of the mean concentration. The primary productivity of Lagos Lagoon was relatively low, with no significant spatial variations between sampling stations. The results of sea surface temperature, transparency and chlorophyll ‘a’ estimation from the MODIS revealed that the values were positively correlated with laboratory result with r2-value of 0.67, 0.80 and 0.77. This indicates that MODIS data and laboratory results generated for Lagos Lagoon were positively related.

The spatial rhythm and periodic pattern of fish species was studied in lower and upper streams in Eniong River, Southeastern Nigeria for 12 consecutive months (April, 2019- March, 2020) using standard methods and procedures. A total of 178 individuals of fish species belonging to 14 families and 25 species were recorded in the study. The results revealed species abundance in favour of the lower stream with only two species: Clarias macromystax (Clariidae) and Malapterurus electricus (Malapteruridae) not found in the lower stream. Populations were generally bigger in lower stream 122 (69.32%) than their counterparts in upper stream with 56 (30.68%) samples. The family Cichilidae dominates the lower stream while Clariidae dominates the upper stream. The result of Jaccard Index Similarity of the number of species found between the upper stream and lower stream revealed the value of 0.461˂50%. The overall range of fish sampled falls within (9.7-25.5cmTL) with size structure generally bigger in the wet season than in the dry season. Species had seasonal abundance in the wet season than the dry season. In the wet season, Oreochromis niloticus and Clarias macromystax were the most abundant species in June and September (wet season) while Malapterurus electricus and Citharinus citharus were not found in the wet season. In the dry season, twelve (12) species were completely absent-Hepsetus akawo, Ctenopoma nebulosum, pollimyrus asperses, Marcusens senegaleusis, Ccoptodon zelli, Cclarias gariepinus, Cclarias macromystax, Synodontis obesus, Schilbe mystus, Schilbe uranoscopus and Protopterus annectens and Hemichromis fasciatus. The most abundant species found in both dry and wet seasons were Oreochromis niloticus, Chrysichthys nigrodigitatus and Hemichromis fasciatus. The fish diversity ranges from typical freshwater fishes to brackish species. The greatest dissimilarity between the wet and dry seasons’ samples was generated by Oreochromis niloticus. The study recorded the highest species richness (Margaleaf) and diversity (Shanno-Wiener) in the wet season with 23 species while the lowest with the smallest abundance was observed in the dry season with 13 species. The study recommends low exploitation in the upper stream and in the dry season to enhance species productivity and sustainability in Eniong River, Southeastern Nigeria.

Large amorphous particles (Nuta) observed in coastal areas after phytoplankton blooms and red tide outbreaks were collected by Nuta traps. These particles are always thickly attached to mooring ropes and/or fishing nets. From the decomposition experiments of Nuta and the sinking particles, dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) regenerations were active in Nuta, but were not active in sinking particles. In Nuta, regeneration abundances during 10 days were 567 µg-N/mg of initial particulate organic nitrogen (PON), and 583 µg-P/mg of initial particulate phosphorus (PP), respectively. Thus DIP was more regenerated from Nuta than DIN. Ten days integral regeneration abundances of DIN and DIP from Nuta were estimated to be 36% and 79% of in situ DIN and DIP standing stocks, respectively. Nuta contributes an important role of nutrient regeneration particularly DIN, in coastal water. Carbon and nitrogen stable isotope ratios of suspended particles, sinking particles and Nuta indicated that these three different type of particles were almost the same origin, and thus Nuta in the coastal water should be made from phytoplankton debris.

The main seasonal characteristics in the tropics include both spatial patterns and temporal parameters of onset, cessation, duration, and the number of wet and dry seasons. Previous studies showed that wet seasons shortened and dry seasons extended with global warming, but the changes in spatial distribution and the number of wet and dry seasons are still unclear. Here, we analyze the climatic characteristics of once wet and dry season a year (annual regime) and twice wet and dry seasons a year (biannual regime), and find that regimes of wet and dry seasons have changed from 1935 to 2014. Across the equator and the Tropic of Cancer and Capricorn, some regions where there used to be an annual regime have become a biannual regime; instead, other regions have shifted from a biannual regime into an annual regime. With seasonal regimes shifting, areas of the biannual regime have expanded at a rate of 31 000 km2/decade. Meanwhile, in annual regime regions, wet seasons have been shortened in 60.3% of regions, with an average of 7 d; the onset dates of wet seasons have been delayed in 64.8%, with an average of 6 d. Besides, wet seasons have become wetter in 51.1% of regions, and dry seasons have become drier in 59.9%. In biannual regime regions, the shortened wet seasons have occurred in 83.7% of regions, with an average shortening of 8 d, and precipitation has decreased in both wet and dry seasons. Moreover, the shorter wet seasons will amplify further by the end of the 21st century. The continuous seasonal changes will threaten agricultural, ecological security, and even human well-being.

Poyang Lake is the largest freshwater lake connecting the Yangtze River in China. It undergoes dramatic dynamics from the wet to the dry seasons. A comparison of the hydrological changes between the wet and dry seasons may be useful for understanding the water flows between Poyang Lake and Yangtze River or the river system in the watershed. Gauged measurements and remote sensing datasets were combined to reveal lake area, level and volume changes during 2000–2020, and water exchanges between Poyang Lake and Yangtze River were presented based on the water balance equation. The results showed that in the wet seasons, the lake was usually around 1301.85–3840.24 km2, with an average value of 2800.79 km2. In the dry seasons, the area was around 618.82–2498.70 km2, with an average value of 1242.03 km2. The inundations in the wet seasons were approximately quadruple those in the dry seasons. In summer months, the lake surface tended to be flat, while in winter months, it was inclined, with the angles at around 10′′–16′′. The mean water levels of the wet and dry seasons were separately 13.51 m and 9.06 m, with respective deviations of around 0–2.38 m and 0.38–2.15 m. Monthly lake volume changes were about 7.5–22.64 km3 and 1–5.80 km3 in the wet and dry seasons, respectively. In the wet seasons, the overall contributions of ground runoff, precipitation on the lake surface and lake evaporation were less than the volume flowing into Yangtze River. In the dry seasons, the three contributions decreased by 50%, 50% and 65.75%, respectively. Therefore, lake storages presented a decrease (−7.42 km3/yr) in the wet seasons and an increase (9.39 km3/yr) in the dry seasons. The monthly exchanges between Poyang Lake and Yangtze River were at around −14.22–32.86 km3. Water all flowed from the lake to the river in the wet seasons, and the chance of water flowing from Yangtze River in the dry seasons was only 5.26%.

The impact of seasonal variation on anemia and nutritional status with associated factors in 6–12 years Ghanaian school age children in peri-urban communities

Leafhoppers constitute one of the largest groups of pests causing damage to crops worldwide. Edge grasses, which are border crops (also known as border grasses), contain diverse plant species and maintain large populations of leafhoppers during the tropical dry and wet seasons. However, little is known about the diversity of leafhoppers on these grasses. The objective of this study was to characterize the diversity of leafhoppers on maize and on surrounding border grasses during the dry and wet seasons. Leafhopper adults were collected with a sweep net from border grasses during the dry season, when maize is absent. During the wet, maize-growing season, leafhoppers were collected in both the maize fields and their surrounding edge grasses. A highly diverse (H' = 1.97 ± 2.03) leafhopper population was seen on the edge grasses during the dry season, and during the wet season, leafhopper diversity was higher in the edge grasses (H'= 1.79 ± 1.72) than in the maize fields themselves (H'= 1.67 ± 1.12). Throughout the wet season, the most abundant leafhopper species in border grasses were Stirellus bicolor (Van Duzee) (Hemiptera: Cicadellidae), Graminella sonora (Ball) (Hemiptera: Cicadellidae), and Balclutha incisa (Matsumura) (Hemiptera: Cicadellidae), whereas Dalbulus maidis (DeLong) (Hemiptera: Cicadellidae) was the most abundant species in maize fields. All of these species were from the subfamily Deltocephalinae. Canonical Component Analysis showed that leafhopper abundance of Sibovia compta (Fowler) (Hemiptera: Cicadellidae), Graphocephala aurolineata (Fowler) (Hemiptera: Cicadellidae), D. maidis, and S. bicolor was associated with abiotic factors such as relative humidity, soil moisture, temperature, and pluvial precipitation. Nevertheless, for most leafhopper species, abundances were not significantly correlated with the abiotic variables measured.