Short term effects of hypoxia and anoxia on sediment biogeochemistry

Hypoxia and anoxia alter the behaviour, diversity and habitat of the benthic communities and cause accumulation of organic matter and nutrients. Most studies have focused on the effect of anoxia on benthic organisms and little information is available on nutrient sediment-water fluxes and rates of key biogeochemical processes. This study aimed to evaluate the oxygen concentration at which harmful effects start to occur, the rates that the system responds to different levels of oxygen saturation in the overlying water and the recovery times of system processes when re-aeration are restored. Sampling was carried out at Breydon Water, Great Yarmouth in June, 2010 and key biogeochemical processes were monitored in sediment/artificial seawater mesocosms maintained at constant temperature in the laboratory. The experimental work assessed the short term effect of different levels of oxygen by manipulating oxygen into five different treatments; oxic (96% saturation in the overlying water), hypoxia (25% saturation), one day of anoxia (24 hours without oxygen followed by re-aeration of up to 6 days), four days of anoxia (4 days without oxygen and subsequent re-aeration for 3 days) and seven days of anoxia (0% saturation). The effect of these oxygen concentrations on different biogeochemical processes (solute transport, oxygen uptake, nutrient fluxes, porewater chemistry, and enzyme activities) was quantified. Bromide used in solute transport assessments were analysed using inductively coupled plasma mass spectrometry and oxygen was measured using an oxygen minielectrode. Nutrient analysis was carried out using the SKALAR autoanalyser and enzyme activities were measured using microplate based assays. With decreasing oxygen supply, ammonium and phosphate are rapidly released into the water column, and nitrate concentrations decrease, reflecting the reducing conditions. In oxic conditions, rapid transport of water and oxygen into the sediments occurs through irrigation fluxes. Slower transport was observed from the porewater of anoxic treatments, as only molecular diffusion occurs. Vertical profiles of alkaline phosphatase, cellobiohydrolase, β-glucosidase and chitinase activities in the sediment reflect organic matter inputs decreasing with depth. Urease activity was enhanced following anoxic incubations of 7 days, with an inverse relationship with porewater ammonium concentrations and increased total organic carbon input. The biogeochemical resilience of the system is dependent on the duration of anoxic events. The effect of 1 day anoxia is relatively reversible and the system recovers to normal conditions within the 7 days of treatment. However, hypoxia (25% oxygen saturation) or longer duration (4 days) anoxia followed by re-aeration are enough to cause negative effects on the biogeochemical functioning of the system. So, sediment biogeochemistry has some resilience towards short term anoxic events, but more prolonged hypoxia or anoxic events that are continued for only a few days can have major effects on ecosystem function

Tracing the carbon flow in tropical watershed using stable isotope technique

Research on catchment area have traditionally involved concentration and flux measurement to better understand weathering, transport and cycling of materials from land to sea. Potentially, modification of terrestrial environment can alter the carbon flow in a catchment. This research is to characterize dissolved inorganic carbon (DIC) in Sungai Kurau and Tasik Bukit Merah. A progressive depletion of (δ¹³C–DIC: -14.20 ± 0.47‰) towards downstream (δ¹³C–DIC: -24.44 ± 0.59‰) is observed. The trend indicates photosynthesis activity at the upper stream system where microbial respiration process is observed to occur at the Tasik Bukit Merah located at downstream area. The dynamic of carbon pathway is highly affected by allochthonous input and autochthonous process in the catchment system. Land use activities within the catchment can disturb the balance between biological and geological processes which control the carbon pool in Kurau catchment

Global patterns of nitrate isotope composition in rivers and adjacent aquifers reveal reactive nitrogen cascading

Remediation of nitrate pollution of Earth’s rivers and aquifers is hampered by cumulative biogeochemical processes and nitrogen sources. Isotopes (δ15N, δ18O) help unravel spatiotemporal nitrogen(N)-cycling of aquatic nitrate (NO3−). We synthesized nitrate isotope data (n = ~5200) for global rivers and shallow aquifers for common patterns and processes. Rivers had lower median NO3− (0.3 ± 0.2 mg L−1, n = 2902) compared to aquifers (5.5 ± 5.1 mg L−1, n = 2291) and slightly lower δ15N values (+7.1 ± 3.8‰, n = 2902 vs +7.7 ± 4.5‰, n = 2291), but were indistinguishable in δ18O (+2.3 ± 6.2‰, n = 2790 vs +2.3 ± 5.4‰, n = 2235). The isotope composition of NO3− was correlated with water temperature revealing enhanced N-cascading in warmer climates. Seasonal analyses revealed higher δ15N and δ18O values in wintertime, suggesting waste-related N-source signals are better preserved in the cold seasons. Isotopic assays of nitrate biogeochemical transformations are key to understanding nitrate pollution and to inform beneficial agricultural and land management strategies

Bats Diversity in Kolej Universiti Sains dan Teknologi Malaysia (KUSTEM)

The study of bats diversity was conducted in Kolej Universiti Sains dan Teknologi Malaysia (KUSTEM) from July until December 2004. The objective is to examine the diversity of bat species in KUSTEM area for conservation purpose. Ten mist nets were used as the capturing device. Species identification was based on the forearm measurement, weight, sex, maturity status and their reproduction. Bats were released after identification. A total of 99 individual bats were captured, comprising of two families and four species. Three species were frugivorous bats, Cynopterus brachyotis, Cynopterus horsfieldii and Eonycteris major from the family Pteropodidae. One insectivorous species, Kerivoulla papillosa was captured from the family Vespertillionidae. Cynopterus brachyotis is the highest captured individual and species, representing 70.97% of total capture. Shannon-Weiner index is 0.8569 and Simpson index is 0.4504. The bat diversity in KUSTEM is influenced by the capture device and duration of study

Household solid waste management practices and perceptions among residents in the East Coast of Malaysia

Background: Poor waste disposal practices hamper the progress towards an integrated solid waste management in households. Knowledge of current practices and perception of household solid waste management is necessary for accurate decision making in the move towards a more sustainable approach. This study investigates the household waste practices and perceptions about waste management in Panji, one of the sub-districts in Kota Bharu, Kelantan, Malaysia. Methods: A stratified random sampling technique using a cross-sectional survey questionnaire was used to collect data. A total of 338 households were interviewed in the survey and data were analyzed using SPSS. Chi-square goodness of fit test was used to determine the relationships between categorical variables, whereas Chi-square bivariate correlation test was performed to observe the correlation between the perceptions of waste segregation with socio-demographic background of the respondents. The correlation between perception of respondents with the locality, house type and waste type were also conducted. Principal component analysis was used to identify grouping of variables and to establish which factors were interrelated in any given construct. Results: The results of the study revealed that 74.3 % of households disposed of food debris as waste and 18.3% disposed of plastic materials as waste. The study also showed that 50.3% of the households segregate their waste while 49.7% did not. About 95.9% of the respondents were aware that improper waste management leads to disease; such as diarrhea and malaria. There were associations between locality, age and house type with waste segregation practices among respondents (Chi-square test, p<0.05). Principal Component Analysis showed that 17.94% of the variance has high positive loading (positive relationship) with age, marital status and, type of house. Conclusion: This study highlights the importance to design waste separation programs that suit the needs of targeted population as a boost towards sustainable solid waste management practices