Seasonal group characteristics and occurrence patterns of Indo-Pacific humpback dolphins (Sousa chinensis) in Xiamen Bay, Fujian Province, China

2016 ◽  
Vol 97 (4) ◽  
pp. 1026-1032 ◽  
Author(s):  
Xianyan Wang ◽  
Fuxing Wu ◽  
Samuel T. Turvey ◽  
Massimiliano Rosso ◽  
Qian Zhu
Keyword(s):  
River Estuary ◽  
Wet Season ◽  
Jiulong River Estuary ◽  
Xiamen Bay ◽  
Encounter Rates ◽  
Dry Seasons ◽  
Sousa Chinensis ◽  
Peripheral Areas ◽  
Occurrence Patterns ◽  
Group Characteristics

Abstract Monthly field surveys were conducted between August 2010 and July 2015 to explore seasonal group characteristics and occurrence patterns of Indo-Pacific humpback dolphins (Sousa chinensis) in Xiamen Bay, China. Dolphins formed larger groups in winter and spring (dry seasons) than in summer and autumn (wet seasons; U = 1,564.00, P < 0.001). Sighting encounter rates were higher during the wet season than during the dry season (U = 181.00, P < 0.001), while individual encounter rates were not significantly different between seasons (F = 0.494, d.f. = 3, P = 0.688). Dolphin sightings and the foraging events were mainly found in inner harbors (Western Harbour and Tongan Bay) during the dry seasons and in peripheral areas (Jiulong River Estuary, Wuyu, and Dadeng-Xiaodeng) during the wet seasons. Seasonal occurrence patterns may be associated with the seasonal prey shifts between these different environments.

scholarly journals Seasonal and spatial controls on N2O concentrations and emissions in low-nitrogen estuaries: Evidence from three tropical systems

2019 ◽  
Author(s):  
Rachel Murray ◽  
Dirk Erler ◽  
Judith Rosentreter ◽  
Naomi Wells ◽  
Bradley Eyre
Keyword(s):  
Inorganic Nitrogen ◽  
River Estuary ◽  
The Other ◽  
Dissolved Inorganic Nitrogen ◽  
Wet Season ◽  
Tropical Estuaries ◽  
Dry Seasons ◽  
Low Nitrogen ◽  
Fitzroy River ◽  
Wet And Dry Seasons

AbstractEstuarine N2O emissions contribute to the atmospheric N2O budget, but little is known about estuary N2O fluxes under low dissolved inorganic nitrogen (DIN) conditions. We present high-resolution spatial surveys of N2O concentrations and water-air fluxes in three low-DIN (NO3−< 30µmol L−1) tropical estuaries in Queensland, Australia (Johnstone River, Fitzroy River, Constant Creek) during consecutive wet and dry seasons. Constant Creek had the lowest concentrations of dissolved inorganic nitrogen (DIN; 0.01 to 5.4µmol L−1of NO3−and 0.09 to 13.6µmol L−1of NH4+) and N2O (93–132% saturation), and associated lowest N2O emissions (– 1.4 to 8.4µmol m−2d−1) in both seasons. The other two estuaries exhibited higher DIN inputs and higher N2O emissions. The Johnstone River Estuary had the highest N2O concentrations (97–245% saturation) and emissions (– 0.03 to 25.7µmol m−2d−1), driven by groundwater inputs from upstream sources, with increased N2O input in the wet season. In the Fitzroy River Estuary, N2O concentrations (100–204% saturation) and emissions (0.03–19.5µmol m−2d−1) were associated with wastewater inputs, which had a larger effect during the dry season and were diluted during the wet season. Overall N2O emissions from the three tropical estuaries were low compared to previous studies, and at times water-air N2O fluxes were actually negative, indicating that N2O consumption occurred. Low water column NO3−concentration (i.e. < 5µmol L−1) appears to promote negative water-air N2O fluxes in estuary environments; considering the number of estuaries and mangrove creeks where DIN falls below this threshold, negative water-air N2O fluxes are likely common.

scholarly journals Mid-Level Riverine Outflow Matters: A Case of Microplastic Transport in the Jiulong River, China

2021 ◽  
Vol 8 ◽  
Author(s):  
Yifan Li ◽  
Siguang Liu ◽  
Mengyang Liu ◽  
Wei Huang ◽  
Kai Chen ◽  
...  
Keyword(s):  
River Estuary ◽  
Physical Factors ◽  
Coastal Environments ◽  
Small Particles ◽  
Jiulong River Estuary ◽  
Xiamen Bay ◽  
Jiulong River ◽  
Large Particles ◽  
The Status ◽  
Medium Level

Riverine outflow is one of the major pathways for microplastic transportation to coastal environments. Research on the output of microplastics in small- or medium-sized rivers will help accurately understand the status of their marine loads. In this study, we used both trawling and pumping methods to collect microplastics of different sizes in the Jiulong River Estuary and Xiamen Bay. We found that the abundance of small microplastics (44 μm–5.0 mm) was at least 20 times higher than the large particles (0.33–5.0 mm). The abundance of the large particles ranges from 4.96 to 16.3 particles/m3, and that of the small particles ranged from 82.8 to 918 particles/m3. Granule was the dominant shape (&gt;60%), and polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET) were the most common components. The riverine flux of small microplastics (44 μm–5 mm, 472 ± 230 t/y) was at a medium level and was eight times greater than that of large particles (0.33–5.0 mm, 61.2 ± 2.6 t/y). The behavior of the large microplastics was relatively conservative, whose abundance had a significant correlation with salinity (R2 = 0.927) and was mainly influenced by physical factors. In contrast, results of statistical analysis revealed that more complicated factors influenced the small microplastics.

scholarly journals Seasonal Estuarine Turbidity Maximum under Strong Tidal Dynamics: Three-Year Observations in the Changjiang River Estuary

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1854
Author(s):  
Xia Hua ◽  
Huiming Huang ◽  
Yigang Wang ◽  
Xiao Yu ◽  
Kun Zhao ◽  
...  
Keyword(s):  
Sediment Transport ◽  
River Discharge ◽  
River Estuary ◽  
Changjiang River ◽  
Changjiang River Estuary ◽  
Wet Season ◽  
Tidal Dynamics ◽  
The Changjiang River ◽  
The Changjiang River Estuary ◽  
Dry Seasons

The estuarine turbidity maximum (ETM) under strong tidal dynamics (during spring tides) was investigated along the Deepwater Navigation Channel (DNC) in the North Passage (NP) of the Changjiang River Estuary (CRE) in wet and dry seasons of 2016, 2017 and 2018. The observed water current, salinity, stratification and suspended sediment concentration (SSC) were illustrated and analyzed. Results show that the SSC was lower in wet seasons than dry seasons in 2016 and 2017 because of the weak influence of typhoons before observations in wet seasons. On the contrary, the SSC was higher in the wet season than the dry season in 2018 because of the strong influence of typhoons in the wet season. Our observations challenged the common perspective that SSC in the NP is higher in wet seasons than dry seasons, because the magnitudes of SSC were found to be easily influenced by strong winds before observations. The along-channel distribution of high SSC was determined by the location of salt wedge, and consequently, the ETM was further upstream in dry seasons than wet seasons. The observed SSC was more concentrated in lower water layers in wet seasons (“exponential” profile) than dry seasons (“linear” profile). This seasonal difference of vertical SSC was related to the flocculation setting velocity influenced by temperature rather than the weak stratification during spring tides. Moreover, on the basis of the net water/sediment transport and flux splitting, large river discharge and a low-SSC condition could reduce siltation in the middle DNC. The former vanished the convergence of water transport, and the latter reduced landward tidal pumping sediment transport. Sediment trapping and siltation in the dry seasons occurred in the seaward segment of the upper reach because of the decrease in the river discharge.

Prediction of suitable habitats for the Indo-Pacific humpback dolphin (Sousa chinensis) in the Beibu Gulf of China and Vietnam

2020 ◽  
Author(s):  
Caiwen Wu ◽  
Fan Zeng ◽  
Rui Liu ◽  
Xiuqing Hao ◽  
Xuyang Chen ◽  
...  
Keyword(s):  
Anthropogenic Activities ◽  
River Estuary ◽  
Line Transect ◽  
Suitable Habitat ◽  
Beibu Gulf ◽  
Wet Season ◽  
Protection Measures ◽  
Maximum Entropy Modeling ◽  
Sousa Chinensis ◽  
Suitable Habitats

The Indo-Pacific humpback dolphin (Sousa chinensis) is a threatened coastal flagship species in Asian marine ecosystems, but the distribution of its suitable habitat remains unclear. In the present study, we characterized habitat relationships and predicted potential suitable habitats for humpback dolphins in the Beibu Gulf of China and Vietnam. Maximum entropy modeling identified six discontinuous areas in the Beibu Gulf, with a total area of 4396.8 km2, as suitable habitats for humpback dolphins. Of these, three suitable habitats covering 3948.8 km2 were known habitats, and three others covering an area of 448.1 km2 at the border of China and Vietnam or in Vietnamese waters (Beilun River Estuary, Qinghua, and Rongshi) were newly identified. Exploratory line-transect surveys are strongly recommended to determine whether dolphins are present in these three areas. The predicted suitable habitat showed seasonal variation, which increased slightly in the dry season compared with that in the wet season. Bathymetry is the most important predictor for habitat suitability, in line with the known coastal distribution of humpback dolphins. Our research predicted specific suitable habitat distributions, which can be used to develop practical protection measures, such as the establishment of marine protected areas for this species to monitor, mitigate, or prohibit harmful anthropogenic activities.

scholarly journals Spatial and temporal variations of hydrodynamics and sediment dynamics in Indus River Estuary,Pakistan

2021 ◽  
Keyword(s):  
Sediment Transport ◽  
River Discharge ◽  
Saltwater Intrusion ◽  
River Estuary ◽  
Dry Season ◽  
Water Levels ◽  
Spatial And Temporal Variation ◽  
Indus River ◽  
Wet Season ◽  
Dry Seasons

<p>Field investigations were conducted to study the seasonal variation of hydrodynamics and sediment transport in Indus River Estuary (IRE), Pakistan. The data of water levels, currents, salinity, and suspended sediment concentration (SSC) were collected hourly covering both wet and dry seasons. Tidal amplitudes were higher near the mouth than those at the middle and upper estuary. The ebb phase lasted longer than that of the flood during the wet season. The asymmetric tidal pattern with higher ebb velocity was observed during the wet season. A slight difference in current velocity was found during the dry season. The flood currents were higher at middle estuary than those in wet season. During the wet season, salinity variation within a tidal cycle slightly increased from the upper estuary to the mouth. Salinity was substantially higher during the dry season than the wet season at all three stations, with the absence of the flood-ebb variation, showing a strong saltwater intrusion. The SSC data revealed that the sediments were mainly brought into the estuary by freshwater discharge during the wet season. Sediment re-suspension process persists during the dry season, due to the tidal currents. A stronger saltwater intrusion occurred in the dry season due to weak river discharge. An estuarine turbidity maximum zone was formed near station-2 due to the combined effects of tides, river discharge and saltwater intrusion. Overall, field observations have shown a significant spatial and temporal variation in flood/ebb and wet/dry seasons for hydrodynamics and sediment transport in IRE.</p>

scholarly journals Contrasting capabilities of two ungulate species to cope with extremes of aridity

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Melinda Boyers ◽  
Francesca Parrini ◽  
Norman Owen-Smith ◽  
Barend F. N. Erasmus ◽  
Robyn S. Hetem
Keyword(s):  
Climate Change ◽  
High Water ◽  
Future Climate Change ◽  
Body Temperatures ◽  
Wet Season ◽  
Trade Off ◽  
Ambient Temperatures ◽  
Mammalian Herbivores ◽  
Dry Seasons ◽  
Connochaetes Taurinus

AbstractSouthern Africa is expected to experience increased frequency and intensity of droughts through climate change, which will adversely affect mammalian herbivores. Using bio-loggers, we tested the expectation that wildebeest (Connochaetes taurinus), a grazer with high water-dependence, would be more sensitive to drought conditions than the arid-adapted gemsbok (Oryx gazella gazella). The study, conducted in the Kalahari, encompassed two hot-dry seasons with similar ambient temperatures but differing rainfall patterns during the preceding wet season. In the drier year both ungulates selected similar cooler microclimates, but wildebeest travelled larger distances than gemsbok, presumably in search of water. Body temperatures in both species reached lower daily minimums and higher daily maximums in the drier season but daily fluctuations were wider in wildebeest than in gemsbok. Lower daily minimum body temperatures displayed by wildebeest suggest that wildebeest were under greater nutritional stress than gemsbok. Moving large distances when water is scarce may have compromised the energy balance of the water dependent wildebeest, a trade-off likely to be exacerbated with future climate change.

scholarly journals Fruiting phenology and consumption by birds in Ficus calyptroceras (Miq.) Miq. (Moraceae)

2002 ◽  
Vol 62 (2) ◽  
pp. 339-346 ◽  
Author(s):  
J. RAGUSA-NETTO
Keyword(s):  
Food Resource ◽  
Bird Species ◽  
Dry Season ◽  
Dry Forest ◽  
Wet Season ◽  
Frugivorous Birds ◽  
Fruiting Phenology ◽  
Dry Seasons ◽  
Seed Dispersers ◽  
Wet And Dry Seasons

Figs are a remarkable food resource to frugivores, mainly in periods of general fruit scarcity. Ficus calyptroceras Miq. (Moraceae) is the only fig species in a type of dry forest in western Brazil. In this study I examined the fruiting pattern as well as fig consumption by birds in F. calyptroceras. Although rainfall was highly seasonal, fruiting was aseasonal, since the monthly proportion of fruiting trees ranged from 4% to 14% (N = 50 trees). I recorded 22 bird species feeding on figs. In the wet season 20 bird species ate figs, while in the dry season 13 did. Parrots were the most important consumers. This group removed 72% and 40% of the figs consumed in the wet and dry seasons, respectively. No bird species increases fig consumption from dry to wet season. However, a group of bird species assumed as seed dispersers largely increases fig consumption from wet to dry season, suggesting the importance of this resource in the period of fruit scarcity. The results of this study points out the remarkable role that F. calyptroceras plays to frugivorous birds, in such a dry forest, since its fruits were widely consumed and were available all year round.

Effects of Phosphorus and Carbofuran on the Growth and Nitrogen Fixation of Azolla pinnata and the Yield of Rice

1988 ◽  
Vol 24 (2) ◽  
pp. 183-189 ◽  
Author(s):  
D. P. Singh ◽  
P. K. Singh
Keyword(s):  
Grain Yield ◽  
Nitrogen Uptake ◽  
Dry Season ◽  
Rice Grain ◽  
Azolla Pinnata ◽  
Wet Season ◽  
Area Index ◽  
Nitrogen Yield ◽  
Matter Production ◽  
Dry Seasons

SUMMARYThe effects of phosphorus fertilizer and the insecticide carbofuran on the growth and N2-fixation of Azolla pinnata and on the growth, grain yield and nitrogen uptake of intercropped rice were examined in a wet and a dry season. Treatment with phosphorus or carbofuran increased the biomass of Azolla and the amount of nitrogen fixed (nitrogen yield) in both seasons, but the response was much better in the dry season. Azolla inoculation at 1.0 t ha−1 resulted in a greater bio mass and nitrogen yield than inoculation at 0.5 t ha−1. In the dry season, a combination of phosphorus and carbofuran enhanced the growth and N2-fixation of Azolla more than either treatment alone. Carbofuran treatment slowed the rate of decomposition of Azolla, particularly in the dry season. The plant height, leaf area index and dry matter production of rice at flowering time were increased in the plots treated with phosphorus or carbofuran in the wet season and these treatments increased rice grain yield and nitrogen uptake in both the wet and dry seasons.

scholarly journals Shifts of Bacterioplankton Metabolic Profiles along the Salinity Gradient in a Subtropical Estuary

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Hidetoshi Urakawa ◽  
Jaffar Ali ◽  
Rheannon D. J. Ketover ◽  
Spencer D. Talmage ◽  
Juan C. Garcia ◽  
...  
Keyword(s):  
Salinity Gradient ◽  
Water Discharge ◽  
River Estuary ◽  
Metabolic Profiles ◽  
Wet Season ◽  
Biolog Ecoplates ◽  
Utilization Patterns ◽  
Subtropical Estuary ◽  
Discharge Patterns ◽  
Bacterioplankton Communities

Understanding the biodegradation potential of river bacterioplankton communities is crucial for watershed management. We investigated the shifts in bacterioplankton metabolic profiles along the salinity gradient of the Caloosahatchee River Estuary, Florida. The carbon source utilization patterns of river bacterioplankton communities were determined by using Biolog EcoPlates. The number of utilized substrates was generally high in the upstream freshwater dominated zone and low in the downstream zone, suggesting a shift in metabolic profiles among bacterioplankton assemblages along the estuarine gradient. The prokaryotic cell numbers also decreased along the estuarine salinity gradient. Seasonal and site-specific differences were found in the numbers of utilized substrates, which were similar in summer and fall (wet season) and winter and spring (dry season). Bacterioplankton assemblages in summer and fall showed more versatile substrate utilization patterns than those of winter and spring communities. Therefore, our data suggest that microbial metabolic patterns in the subtropical estuary are likely influenced by the water discharge patterns created by dry and wet seasons along the salinity gradient.

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