Passive acoustic monitoring gives new insight into year-round duetting behaviour of a tropical songbird

Summary A total of 966 cichlids, Cichlasoma urophthalmus, was sampled from three karstic water bodies (cenotes) in the Yucatan Peninsula. Sex ratio was not different from 1. Specimens with ripe eggs were found during the dry and rainy seasons in the inland cenote and during the dry, rainy, and north winds seasons in the two wetland cenotes. With respect to relative fecundity, data show the C. urophthalmus inland population as two- to three-fold greater (53.1 ± 27.7) than the wetland populations (15.7 ± 5.1 and 18.2 ± 3.1). This is attributable to the different breeding strategies of C. urophthalmus populations inhabiting these two types of cenotes. In particular, the ichthyofauna from the two wetlands showed not only higher species richness (17 and 16 species) but also a higher number of potential predators (nine and eight species) as compared to the inland cenote (six species; two potential predators). It is hypothesized that C. urophthalmus adjusts its clutch size and extends its breeding periods as a response to riskier sites as compared to more secure ones; a higher competition for breeding sites and to increased fishing mortality.

The aim of this study was to compare testosterone concentration, body weight, scrotal circumference and age to penis detachment from days 30 to 240 in young Boer goat males (n = 22) born during the dry (n = 11) and the rainy (n = 11) seasons. In the dry season the parameters varied as follows: body weight from 3.7 ± 1.1 to 34.0 ± 4.7 kg, scrotal circumference from 7.9 ± 0.8 to 25.7 ± 2 cm, and testosterone concentration from 259.4 ± 172.4 to 4613.4 ± 2892 pc/mL. In the rainy season parameters varied as follows: body weight from 9.7 ± 2.3 to 28.1 ± 6.9 kg, scrotal circumference from 9.5 ± 1.5 to 22.0 ± 3.0 cm and testosterone from 521.9 ± 311.3 to 3417.9 ± 2021.8 pc/mL. At three months of age, 70% of animals born during the rainy season presented with penis detachment, compared to 67.6% of animals born during the dry season at five months of age. Penis detachment occurred in all males at four and seven months for animals born in the rainy and dry seasons, respectively. There was a positive correlation between testosterone concentration and body weight in the dry (r = 0.30) and rainy (r = 0.43) seasons, between testosterone and scrotal circumference in the dry (r = 0.42) and rainy (r = 0.52) seasons, and between body weight and scrotal circumference in the dry (r = 0.93) and rainy (r = 0.88) seasons. The animals born during the rainy season showed earlier development in all the evaluated parameters than animals born during the dry season. It was found that scrotal circumference is directly correlated to body weight and testosterone concentration. Keywords : Scrotal circumference, testosterone, young male goats, puberty, sexual maturity

Physicochemical parameters of surface water collected from six different points (P1 to P6) on River Sokoto were analysed during January (Dry Season) and August (Rainy Season), 2014 to determine its water quality using standard methods. The highest temperature of 25.6&#176C was recorded by P1 in dry season while P5 recorded the highest value of 29.2&#176C in rainy season. All the water samples were alkaline in dry season with the highest pH value of 8.50 in P5 and the least value of 8.02 in P6 whereas in rainy season, P1, P2 and P3 were slightly acidic while P5 and P6 were slightly neutral and P4 alkaline. The highest values of 510 μS/cm and 850.3 mg/l were recorded from P4 for electrical conductance and hardness respectively in the rainy season whereas in dry season, P5 and P4 had the highest values of 321 μS/cm and 282.8 mg/l respectively. The highest DO and BOD levels in dry season were 1.7 mg/l and 0.7 mg/l respectively in P1 and the least values were 0.7 mg/l and 0.2 mg/l respectively in P5. But in the rainy season, P6 recorded the highest DO value of 0.1 mg/l while P2 and P5 recorded the least value of 0.07 mg/l. For BOD, P5 had the highest value (2.13 mg/l) while P3 had the least value (0.20 mg/l). For COD, the highest value (230 mg/l) was found in P4 and P6 and the least value (30 mg/l) was found in P1 in dry season while in the rainy season, P2 had the highest COD value (1008 mg/l) and P4 had the least value of 32 mg/l. TDS and TSS values generally were higher in the rainy season than in the dry season due to higher amount of floating particles in the rainy season. While P1 and P6 recorded the highest values (800 mg/l and 700 mg/l respectively) in the rainy season, P4 recorded the least value of 100 mg/l in both seasons. The highest Chloride level was found in P4 in the dry (100 mg/l) and rainy (180 mg/l) seasons with the least level in P2 (35 mg/l) in dry season and in P1 and P2 with the least level of 60 mg/l in the rainy season. The highest concentration of Sulphate in P1 (220 mg/l) in dry season was far above the highest concentration (124 mg/l) in the rainy season whereas highest concentration of Nitrate in dry season in P1 (19.7 mg/l) was somehow below the highest concentration in rainy season in P4 (28.1 mg/l). Phosphate and Ammonia had the highest values of 1.77 mg/l and 0.84 mg/l respectively in P5 in dry season while in rainy season, P6 and P4 had the highest values of 0.22 mg/l and 1.20 mg/l respectively. There was significant seasonal variation in some physicochemical parameters and most of the parameters were within permissible limits, thus, making the water suitable for irrigation purposes.

Acid sulfate soil is one of the most serious regional environmental problems after destruction of the peat layer over pyrite-containing sediment after agricultural land development and deforestation. Sulfuric acid discharged from acid sulfate soil causes acidification of river water. In pyrite distributing areas within the lower basin of the Sebangau and Kahayan rivers in Central Kalimantan, the water of the mainstream of the rivers as well as water discharged from canals into the mainstream in the rainy season show much higher acidity and a higher concentration of sulfate ions than in the dry season. The objective of the present study was to obtain information on utilization of natural water from local inhabitants in the basin with water pollution including sulfuric acid contamination. We held interviews with local inhabitants in sulfuric acid polluted areas in Paduran and Pangkoh as well as areas around Sigi village concerning the sources of water and evaluation of water quality in their habitat. Inhabitants around Sigi mostly depended on well water both in the rainy and dry seasons, whereas the sources of drinking water for inhabitants in Paduran and Pangkoh differed significantly between dry and rainy seasons. River water chemistry showed little difference between the dry season and the rainy season in the Sigi area, whereas river and canal water in the rainy season in Paduran and Pangkoh showed lower pH than in the dry season due to a high concentration of sulfuric acid in the rainy season. Accordingly, river and canal water in the rainy season in polluted areas was not available as drinking or cooking water and thus they avoided using river water for drinking or cooking in the rainy season. Although sulfuric acid concentration in river water both in Pangkoh and Paduran were higher in the rainy season than in the dry season, people in Pangkoh evaluated that water in the rainy season to be better than that in the dry season, whereas people in Paduran evaluated that water in the dry season to be better than that in the rainy season. Paduran people would evaluate water quality by SO42- concentration, whereas Pangkoh people would evaluate water quality by salt concentration because of the lower concentration of SO42- of water in Pangkoh in the rainy season than that in Paduran. Pangkoh people recognized that water contaminated with sulfuric acid was much preferable than water contaminated with sea salt, but they avoided using water contaminated with sulfuric acid in the rainy season. More than 70% of the Paduran people answered that river water presents a high risk for drinking and swimming, whereas only 11% or less of the Pangkoh people knew about the risk of sulfuric acid for human health. The Pangkoh people avoided using river water contaminated with sulfuric acid, but the knowledge about sulfuric acid’s effects on human health was not sufficient. Thus we concluded that although selectivity of water was similar for the local inhabitants of the two villages in polluted area, awareness about the risks of sulfuric acid pollution for human health proved to be quite different between the two villages.

ABSTRACTThe seasonal characterization and discrimination of savannahs in Brazil are still challenging due to the high spatial variability of the vegetation cover and the spectral similarity between some physiognomies. As a preparatory study for future hyperspectral missions that will operate with large swath width and better signal-to-noise ratio than the current orbital sensors, we evaluated six Hyperion images acquired over the Estação Ecológica de Águas Emendadas, a protected area in central Brazil. We studied the seasonal variations in spectral response of the savannah physiognomies and tested their discrimination in the rainy and dry seasons using distinct sets of hyperspectral metrics. Floristic and structural attributes were inventoried in the field. We considered three sets of metrics in the data analysis: the reflectance of 146 Hyperion bands, 22 narrowband vegetation indices (VIs), and 24 absorption band parameters. The VIs were selected to represent vegetation structure, biochemistry, and physiology. The depth, area, width, and asymmetry of the major absorption bands centred at 680 nm (chlorophyll), 980, and 1200 nm (leaf water) and 1700, 2100, and 2300 nm (lignin-cellulose) were calculated on a per-pixel basis using the continuum removal method. Using feature selection and multiple discriminant analysis (MDA), we tested the discriminatory capability of these metrics and of their combined use for vegetation discrimination in the rainy and dry seasons. The results showed that the spectral modifications with seasonality were stronger with the savannah woodland-grassland gradient represented by decreasing tree height, basal area, tree density and biomass and by increasing canopy openness. We observed a reflectance increase in the red, red edge, and shortwave (SWIR) intervals towards the dry season. In the near-infrared, the reflectance differences between the physiognomies were smaller in the dry season than in the rainy season. From the 22 VIs, the visible atmospherically resistant index (VARI), visible green index (VIg), and normalized difference infrared index (NDII) were the most sensitive indices to water stress and vegetation cover, presenting the largest rates of changes between the rainy (March) and dry (August) seasons in shrub and grassland areas. Absorption band parameters associated with the lignin-cellulose spectral features in the SWIR increased towards the dry season with great amounts of non-photosynthetic vegetation (NPV) in the herbaceous stratum. The opposite was observed for the 680 nm chlorophyll absorption band and the 980 and 1200 nm leaf water features. In general, the number of selected metrics necessary for vegetation discrimination was lower in the dry season than in the rainy season. The best MDA-classification accuracy was obtained in the dry season using nine VIs (79.5%). The combination of different hyperspectral metrics increased the classification accuracy to 81.4% in the rainy season and to 84.2% in the dry season. This combination added a gain higher than 10% for the classification of shrub savannah, open woodland savannah and wooded savannah.

Climate and detritus influence soil organic carbon (SOC) and labile SOC fractions by affecting soil microbial communities. However, it is not clear how, or to what extent, different detritus treatments affect soil microbial communities and SOC content in karst landscapes during different seasons. Plots in a karst landscape were treated with different detritus input regimes (control, no litter, no roots, no litter or roots, and double litter), and samples were collected during the dry and rainy seasons. We used Illumina sequencing of 16S rRNA to examine shifts in the diversity and composition of the associated soil microbial communities. Additionally, labile SOC fractions, including dissolved organic carbon (DOC) and microbial biomass carbon (MBC), along with soil physicochemical properties and C-degrading enzyme activities, were analyzed. The results revealed that the responses of soil properties and labile SOC fractions to detritus treatments were more pronounced during the rainy season than during the dry season, which mainly reflected that the levels of available potassium (AK), DOC, and MBC were significantly increased during the rainy season. Moreover, SOC and total nitrogen (TN) demonstrated significant changes with the double litter (DL) treatment during the rainy season. The responses of soil microbial communities to detritus treatments varied with the season, as reflected primarily in changes in the relative abundance of Ascomycota, unclassified_K_fungi, Proteobacteria, and Actinobacteriota. Climate, detritus treatments, and their interactions had significant effects on the species richness of soil bacterial communities, but did not influence fungal community diversity. Furthermore, structural equation modeling (SEM) revealed that the soil bacterial composition had the largest total effects on SOC, DOC, and MBC. In addition to directly influencing SOC, DOC, and MBC, soil properties (TN, AK, and pH) indirectly affected SOC, DOC, and MBC by altering C-degrading enzyme activity and the microbial community. We conclude that detritus treatments affect the soil microbial community and labile carbon fractions during both the rainy and dry seasons. Relationships among SOC, labile SOC fractions, enzyme activities, microbial communities, and function differed between seasons and among treatment types. This research advances our knowledge of how variation in detritus treatments affects biogeochemical cycling in karst soils during the rainy and dry seasons.

Differentiation analysis of VOCs in Kunming during rainy and dry seasons based on monitoring high temporal resolution

This study assessed sediment contamination by heavy metals and pesticide active ingredients linked to chemical inputs used in agricultural activities in the lower Ouémé. Pesticide residues from the organochlorine, pyrethroid and organophosphorus families were investigated by gas chromatography, and heavy metals (Cd, Pb, As, Ni, Zn, Fe, Mg, Cr and Hg) by atomic absorption spectrophotometry. The metallic pollution indices, the contamination factor (CF) and the ecological risk index were calculated. The results revealed 8 active ingredients in the rainy season and 9 in the dry season. Glyphosate was the active ingredient with the highest concentration at all stations, 9.65 ± 0.84 mg/kg recorded in the dry season at the Aguigadji station. All glyphosate values were above the EQS. DDT, Atrazine and Endosulfan also showed high concentrations in the dry and rainy seasons. Emamectin, Abamectin and Lambda Cyhalothrin also showed high concentrations in the dry season at Aguigadji, Ahlan and Sele. Only glyphosate was recorded at the control station (Toho), but in very low concentrations. Lead showed the highest concentrations at all the stations, 265.96 ± 21.02 mg/Kg in the rainy season and 255.38 ± 79.09 mg/Kg in the dry season, all detected at the Aguigadji station and above the EQS. Zn, Ni, Fe, Cu and Cr were all representative in both the dry and rainy seasons at the contaminated stations. Manganese showed high concentrations in the rainy season. Pb showed very high contamination (FC ≥ 6) at the Aguigadji and Ahlan stations and significant contamination (3 ≤ FC 6) at the Sele station in both the rainy and dry seasons. Ni, Hg and Cd, showed either moderate or significant contamination at the contaminated stations. The risk values showed a considerable ecological Ri (190 ≤ Ri

Seasonal parasitic contamination of vegetables marketed in Bori central market, Khana Local Government Area, Rivers State, Nigeria was investigated. A total of 80 vegetable samples, (40 samples each during the rainy and dry season respectively) were purchased from the Bori central market. The vegetable samples were examined in the laboratory for the presence of intestinal parasites using sedimentation techniques and microcopy. The results revealed that out of 80 vegetable samples (20 samples of each vegetable type and 40 samples each for rainy and dry seasons) examined, an overall prevalence of 41(51.3%) was recorded. Out of the 40 samples of vegetable each examined during the rainy and dry seasons, 23(57.5%) and18(45.0%) samples were positive for intestinal parasites during the rainy and dry seasons respectively. Across the two seasons, intestinal parasites belonging to four genera were identified. The genera were Ascaris, Giardia, Ancylostoma and Trichuris. A total of 23 intestinal parasites were identified during the rainy season (Ascaris 13/23(56.3%), Giardia 3/23(13.1%), Ancylostoma 4/23(17.4%) and Trichuris 3/23(13.1%) while a total of 18 parasites were extracted from the vegetables during the dry season (Ascaris 9/18(50%), Giardia 1/18(5.5%), Ancylostoma 3/18(16.7%) and Trichuris 5/18(27.8%). Carrot and tomatoes were the most statistically (P>0.05) contaminated vegetables in the rainy and dry seasons respectively. All species of parasites identified have a high relative abundance in the rainy season than in the dry season. Ascaris sp. (56.5%) was the most abundant species of parasite in the rainy season, followed by Ancylostoma sp. (10.0%), Giardia sp. (7.5%) and Trichuris sp. (7.5%). In the dry season, Ascaris sp. had the most relative abundance (50.0%), followed by Trichuris sp. (27.8%), Ancylostoma sp. (7.5%) and Giardia sp. (2.5%). There was a statistically significance difference (P<0.05) in the relative abundance of parasite species in the rainy and dry seasons. The high level of parasitic contamination of vegetables recorded in the study area is a public health concern and demands serious intervention especially in areas of health education on personal hygiene, sanitation and the danger of consumption of improperly washed vegetables, provision of sanitary facilities, mass deworming, open defecation and use of waste water for fertilizer.

Light influences many physiological processes in tea, as in all green plants. Tea production in the lowland area of Southern Nigeria is affected by Light Intensity (LI). Information on the response of tea to light intensity in the lowland is scanty. Therefore, the effect of LI on nutrient uptake and photosynthetic pigments contents of tea was investigated in Ibadan and Owena, southwest Nigeria. A field trial was conducted in the Research plots of Cocoa Research Institute of Nigeria Stations in Ibadan and Owena, Southwest Nigeria between 2016 and 2017 to evaluate the response of two tea cultivars, C143 and C318 to three LI which were achieved with sheds of different palm fronds layers (PFL): L1=[(2PFL-45% LI (4.57x104lux)]; L2=[(1PFL-65% LI (6.75x104lux)] and L3=100% LI (1.04x105lux) (control) under randomized complete block design with four replications. Data on Leaf nitrogen and magnesium uptake (mg/g) were obtained in the rainy season, and chlorophylls and carotenoids were obtained under rainy and dry seasons following standard procedures. Data were analysed with ANOVA and descriptive statistics at α0.05. L1 increased N and Mg by 149.78% and 155.10%, respectively, compared to L3 at Ibadan, and by 96.64% and 84.84%, respectively, at Owena. At Ibadan, 45% light increased chlorophyll by 69.62% and 147.78% compared to 65 and 100% lights, respectively in the dry season, and by 22.49% and 81.56%, respectively in the rainy season; whereas at Owena, L1 increased chlorophyll by 15.57% and 90.37% compared to L2 and L3, respectively in the dry season, and by 3.47% and 44.85%, respectively in the rainy season. At Ibadan, L1 enhanced the highest and lowest carotenoids in the rainy and dry seasons, respectively. The L2 caused the highest carotenoids, while L3 produced the least in the dry season at Owena. Therefore, for enhanced N, Mg, chlorophylls and carotenoids contents, reduced light intensities of 45 – 65% are recommended for growing tea in the dry and rainy seasons in Ibadan and Owena.

We have identified the feed offered to native pigs in a case study of smallholder in northern Thailand. We examined the types and fresh weights of pig feed over two 10-day periods in household A, in September 2006 (rainy season) and in December 2006 and January 2007 (dry season). The study results are as follows. (1) They offered 18 types of feed in total during the rainy and dry seasons, of which seven types were common to the rainy and dry seasons, five types were offered during the rainy season only, and six types during the dry season only. (2) They offered agricultural products as 34% of feed (rainy season) and 61% of feed (dry season), and natural plants used exclusively for pig feed as 66% of feed (rainy season) and 39% of feed (dry season). (3) The feed combinations at each feeding time differed 80% of the time during both the rainy and dry seasons. These results show not only that they offered diverse combinations of agricultural products and natural plants as pig feed, but also that they changed feed kinds in both the rainy and dry seasons.

Context In the tropics, there is a substantial demand for a broader understanding of the impact of supplementation strategies on animal growth. Aims The aim of this study was to evaluate the effects of different concantrate supplementation strategies during the dry, rainy, or both seasons on intake, digestibility, performance, and carcass weight of young Nellore bulls. Methods Twenty-eight young Nellore bulls with an initial average liveweight (LW) of 327 ± 4.2 kg of were used. Animals had ad libitum access to a Urochloa brizantha pasture and a mineral mixture sequentially in dry and rainy seasons. Treatments consisted of the following four concentrate supplementation strategies: (1) no concentrate supplementation (−/−); (2) 8 g/kg LW in rainy season (−/+); (3) 8 g/kg LW in dry season (+/−); and (4) 8 g/kg LW in both dry and rainy seasons (+/+). Key results Forage intake was lesser (P < 0.05) in cattle fed +/+ when contrasted against all other supplementation strategies. In the dry season, concentrate supplementation increased (P < 0.04) LW gain from 0.40 to 0.74 kg/animal.day. Considering performance in both the dry and rainy seasons, all supplementation strategies increased (P < 0.05) total LW gain, hot carcass weight, carcass fat and muscle when compared with the negative control treatment −/−. Bulls receiving +/+ had greater (P < 0.05) total LW gains and hot carcass weights than did −/+ and +/− treatments. Directly contrasting −/+ and +/−, supplementation in the rainy season tended (P < 0.10) to increase total LW gain and hot carcass weights. Conclusions Under the conditions of this experiment, concentrate supplementation decreased forage intake but increased LW gain, hot carcass weight and carcass quality. Concentrate supplementation in both the dry and rainy seasons provided greater LW gain and hot carcass weights than did concentrate supplementation during only the dry or rainy seasons. Concentrate supplementation only during the rainy season produced greater hot carcass weights and LW gains than did concentrate supplementation only during the dry season. Implications To achieve maximum LW gains and hot carcass weights, concentrate supplementation should be provided during both dry and rainy seasons. If supplementation costs are a limiting factor, concentrate supplementation during the rainy season is likely to provide greater LW gains and carcass weights than does concentrate supplementation only during the dry season. However, pasture nutritive value, carcass prices and supplement costs must be evaluated before selecting a supplementation strategy.

In order to evaluate the effect of cutting height (9, 12, and 15 cm) and frequency (3, 4, and 5 wk -rainy season- and 5, 6 and 7 wk -dry and windy seasons) a randomized block design with a 3x3 factorial arrangement and three replicates was used to study Brachiaria humidicola attributes: herbage accumulation, growth rate (GR), leaf mass (LM), tiller weight (TW) and tiller density (TD). No interaction effect was observed between cutting height and frequency for studied variables (P>0.05). Herbage mass distribution was 79, 13, and 8% for the Rainy, Windy and Dry seasons, respectively, with an average annual herbage yield of 11,154 kg DM ha-1. The highest GR (100 kg DM ha-1 d-1) was observed in August, and the lowest (5 kg DM ha-1 d-1) on May. Seasonal LM was 85, 99 and 100 % for the Rainy, Windy and Dry seasons, respectively, in the Rainy Season the highest (P<0.05) leaf percentage (90 %) was observed in the three weeks cutting frequency at 9 and 12 cm cutting height, and no differences were detected between treatments in the Windy and Dry seasons. The highest TW was recorded on September (747 mg tiller-1) and the lowest (80 mg tiller-1) on May. The greatest TD was observed on March and April in the 5 and 6 wk cutting frequencies at 15 cm cutting height (6088 to 6400 tillers m-2). It can be concluded that the highest herbage yield, GR, and TW were observed in the Rainy Season at 5 wk cutting frequency and 15 cm cutting height.

The aim of the present study was to assess the impacts of the dry and rainy seasons on the physiological and behavior aspects of crossbreed dairy cows of Amazon biome of Costa Marques, Rondônia, Brazil. The study was conducted during the rainy and dry seasons and evaluated crossbred cows (n=17). The data were subjected to normality test, analysis of variance by the F test, mean comparison of means at a 5% significance level, and Pearson's correlation. During the rainy season, cows had significantly higher ketone body levels (p=0.0334), milk production (p=0.0229), and rectal temperature (p=0.0025). The respiratory rate increased significantly (p=0.0105) in the dry season compared to the rainy season. The behavior results showed longer times for milking (p=0.0325), grazing in full sunlight (p=0.0071), and water intake (p=0.001) during the rainy season. Water intake time, milking time, and milk production were positively correlated. The rainy and dry seasons did significantly affect ketone body level, milk production, rectal temperature, respiratory rate, times for milking, grazing in full sunlight, and water intake in crossbred dairy cows Amazon biome of Costa Marques, Rondônia, Brazil.

Investigations were carried out during the rainy and dry seasons of 2023–2024 in the Ha Long bay to evaluate composition of the carbonate buffer as well as the air-sea CO2 flux. The results showed that in the dry season, pH, temperature and salinity was higher than in rainy season. pH were from 7.68–8.33, average 8.25 in the dry season, 8.10 in the rainy season. Temperature were from 17.6–34.6oC, average 20.1oC in the dry season, 32.12oC in the rainy season. Sanility were from 15–31‰, average 30.7‰ in the dry season, 25 ‰ in the rainy season. DIC were from 41.91–58.77 mg/kg. TA were from 868.29–1,148.9 µmol/kg, average 1,105.98 µmol/kg in the dry season, 966.42 µmol/kg in the rainy season. The carbonate buffer in rainy season composed of HCO3- occupied from 87.42 to 88.02%, CO32- occupied from 11.67 to 12.20 %, CO2 occupied from 0.31 to 0.38%, and in dry season HCO3- occupied from 85.97 to 88.02%, CO32- occupied from 11.67 to 13.77 %, CO2 occupied from 0.26 to 0.31%. The partial pressure of CO2 (pCO2) in water in dry season were lower and less fluctuation in the rainy season. In dry season, pCO2 were from 81.75 to 169.84 µatm, average 99.16 µatm at day-night site and average 113.30 µatm at spatial sites. In rainy season, pCO2 were from 60.47 to 430.96 µatm, average 164.78 µatm at day-night site and average 134.28 µatm at spatial sites. The flux of CO2 exchange through the sea surface-air ranged from -13.0 to -7.4 mmol/m2/day, average -10.2 ± 1.0 mmol/m2/day at day-night site, average -11.6 ± 0.9 mmol/m2/day at spatial sites in rainy season; from -13.7 to -11.1 mmol/m2/day, average -12.9 ± 0.8 mmol/m2/day at day-night site and average 12.6 ± 0.6 mmol/m2/day at spatial sites in dry season. Thus, in the rainy season and dry season, Ha Long Bay acted as a sink for atmosphere CO2 and the CO2 flow rate in the dry season was higher than the rainy season.