The impact of acidification on marine ecosystems has become a topic of priority research, following realization of unabated ocean acidification (OA), derived from globally-rising atmospheric CO2. Many coastal and estuarine ecosystems have historically been acidified through various processes, and it is possible that we can learn and make predictions about OA impacts from the ways estuarine species and communities adapt and respond to acidified water. Studying estuarine acidification, nonetheless, aids understanding of the processes that affect ecological structure and functioning, important for coastal conservation and management. A broad-based research programme was implemented at UBD between 2011 and 2015, to investigate how variation in acidity and salinity affected assemblages and species in the Brunei Estuarine System (BES), an ecologically and economically important natural system in the region. This review summarizes studies that investigated for the BES, (i) the physical habitats and water physicochemistry, (ii) responses of planktonic and benthic microbial and faunal assemblages to exposure to variable and potentially highly acidic water, (iii) effects of acidification on ecological processes, such as barnacle dispersal and recruitment, (iv) behavioural and physiological mechanisms of organisms to cope with highly fluctuating and extreme pH water, with special reference to the gastropod, Indothais gradata, and (v) contaminant uptake by Indothais gradata under acidified conditions. The significance of the findings to the ecology of the BES, gaps that need addressing, and how estuarine acidification may contribute to predicting responses to OA are evaluated and discussed.
SUMMARY Harmful algal bloom (HAB) is a proliferation of algae, which naturally produce biotoxins and cause harmful effects to humans, the environment and organisms associated with it. Paralytic shellfish poisoning (PSP) was reported for the first time in Kuantan Port, Pahang, Malaysia, in November 2013, followed by a second episode in August 2014. The toxicity level reported during the second event was as high as 3500 μg of STX equiv./100 g shellfish. Ten people were hospitalized with PSP symptoms after consuming contaminated shellfish. This study was conducted at Kuantan Port to identify the organisms responsible for these events. Water samples were collected monthly for a period of 12 months beginning in September 2014. HAB species were identified based on their morphology using light and fluorescence microscopes, and their classification was supported by molecular evidence based on internal transcribed spacer (ITS) sequences. Monthly cell abundance of Alexandrium tamiyavanichii was measured at four sampling stations. Toxin production by three strains isolated from the area was determined using HPLC. Our results revealed the presence of several HAB species, including the PSP‐producing species A. tamiyavanichii. The highest cell density of A. tamiyavanichii was 840 cells L−1. The presence of GTX components was detected in these strains. However, other toxin components could not be determined. This study reported, for the first time, the presence of PSP‐producing A. tamiyavanichii on the Pahang coast of east Peninsular Malaysia and confirmed that the PSP events in Kuantan Port were attributable to this species. The presence of this species further indicates that several safety measures need to be considered to safeguard public health, particularly in Pahang coastal waters.
Dinoflagellate is the second largest group of phytoplankton in the marine environment and many of the species have been recognized as toxic species. The high abundance of this species can cause a lot of problems to human health, marine organisms especially caged fish and to the natural environment. In Malaysia, several species of Alexandrium have been reported to cause human intoxication after consumption of contaminated shellfish. During the event, shellfish was banned and lead to economic lost especially to the local fishermen. Therefore, this study was conducted to find alternative way to mitigate the blooms of harmful algae particularly Alexandrium tamiyavanichii using ornamental plant, Sanseviera trifasciata or known as mother-in-law tongue. The extraction of this plant was done in distilled water using dried and fresh plants. Different concentrations of crude extracts (0.001, 0.01, 0.1, 0.5, 1, 1.5, 2 and 2.5 mg/mL) were tested on A. tamiyavanichii within 24 hours. The removal efficiencies (RE) were determined for each concentration tested. The extracts were also tested on brine shrimp to see the possible harmful effect. Results indicate that both extraction methods yielded positive results on A. tamiyavanichii whereby the crude extracts managed to mitigate the species. The LC50 of brine shrimp recorded were 30 mg/ml for fresh plant extract and 70 mg/mL for dried plant extracts. This indicates the possibility of the extractions to be used to mitigate harmful algal bloom (HAB) particularly Alexandrium and provide an alternative way to the relevant agencies to minimize the impact of HAB
After the recognition of fossil zygospores of Holocene age as those of Debarya glvptosperma (De Bary) Wittr., a representative of a family of filamentous algae, the Zygnemataceae, the ecological amplitude of this manifestly rare species could be assessed indirectly by means of a paleoecological approach.
Margalefidinium polykrikoides blooms resulted in massive fish mortality in many countries around the world. The prevalence of booms is believed to be associated with the eutrophication of the coastal area. Therefore, this study aims to determine the effects of different nitrogen (N) and phosphorus (P) concentrations on the growth of M. polykrikoides. Experiments were conducted on M. polykrikoides isolated from the affected area by exposing the cell to various N and P ratio: seawater without the addition of N and P (SW), equal N:P ratio (NP), trial ratio of N and P (TR), F/2 medium (+NP), deficient N (–N), and deficient P (–P). The experiments were carried out in triplicates for 20 d in similar environmental conditions with the determination of density, specific growth rate, and cell size during the study period. Furthermore, nutrient concentrations nitrite+nitrate (NO2 –+NO3 –), phosphate (PO4 3–), and ammonia (NH4 +) were measured initially in the medium and both nutrients and chlorophyll were determined at the end of the experiment. The results revealed that M. polykrikoides grew in all the experiments, but the growth patterns differed between the treatments. The highest specific growth rate (0.1901 ± 0.017 d–1) with the highest cell density (1709 ± 68.21 cells mL–1) with a long chain of cells was observed in TR during the exponential phase. However, cell size was significantly smaller in SW compared to other nutrient conditions during the exponential phase. This study shows that M. polykrikoides a flexible species in nutrient uptake, thus allowing the species to survive in different nutrient conditions. The understanding of this bloom mechanism is important in monitoring and management of this harmful species, particularly in Sabah coastal waters.
Blooms of toxic Alexandrium tamiyavnichii have been recorded in several parts of the world including Malaysia. This Harmful algal bloom (HAB) has led to human illness and loss to fishery industries. In order to control the bloom and minimize the effects, the growth of the species needs to be inhibited using a mitigation agent, preferably environment friendly agent. In this study, an ornamental plant, Sansevieria trifasciata will be used to inhibit the growth of A. tamiyavanichii. The plants were fractionated to obtain fractions (dichloromethane (DCM) and methanol) from ethanol fresh and dried plants extracts. Eight concentrations (0.001, 0.01, 0.1, 0.5, 1.0, 1.5, 2.0 and 2.5 mg/mL) of these fractions were tested on the algae for 24 hours and removal efficiencies (RE) were determined. Toxicity test was conducted on Artemia using 10, 50, 100 and 500 mg/mL concentrations of active fractions for 24 hours. Phytochemical compounds were detected using standard procedures. Results obtained showed that the growth of A. tamiyavanichii was inhibited by all concentration tested. Active fractions from DCM using both fresh and dried plants showed good results with more that 80% RE values at 5 mg/mL within 2.5 to 5 hours. During the experiments, DCM used did not change the pH of the culture medium compared to methanol fraction. For phytochemical screening tests, compounds detected in all fractions were alkaloids, tannins, glycosides, reducing sugars and terpenoids. These compounds might cause the inhibition of targeted algae, however further study is needed to determine the bioactivity and its specific effect on HAB species. To conclude, fractions of DCM from fresh and dried S. trifasciata have the potential in the mitigation of A. tamiyavanichii. This could help to minimize the impact of this species on human health and reduce the loss to fishery industries.
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