Posts Tagged 'South Pacific'

Variable response to warming and ocean acidification by bacterial processes in different plankton communities

Extracellular bacterial enzymes play an important role in the degradation of organic matter in the surface ocean but are sensitive to changes in pH and temperature. This study tested the individual and combined effects of lower pH (-0.3) and warming (+3°C) projected for the year 2100 on bacterial abundance, process rates and diversity in plankton communities of differing composition from 4 locations east of New Zealand. Variation was observed in magnitude and temporal response between the different communities during 5 to 6 day incubations. Leucine aminopeptidase activity showed the strongest response, with an increase in potential activity under low pH alone and in combination with elevated temperature in 3 of 4 incubations. Temperature had a greater effect on bacterial cell numbers and protein synthesis, with stronger responses in the elevated temperature and combined treatments. However, the most common interactive effect between temperature and pH was antagonistic, with lower bacterial secondary production in the combined treatment relative to elevated temperature, and lower leucine aminopeptidase activity in the combined treatment relative to low pH. These results highlight the variability of responses to and interactions of environmental drivers, and the importance of considering these in experimental studies and prognostic models of microbial responses to climate change.

Continue reading ‘Variable response to warming and ocean acidification by bacterial processes in different plankton communities’

Tropical coral reef coral patterns in Indonesian shallow water areas close to underwater volcanic vents at Minahasa Seashore, and Mahengetang and Gunung Api Islands

Coral community patterns on some Indonesian reefs influenced by CO2 from underwater volcanic vents and nutrients from eutrophication pressures were examined. The overall aim of the study was to provide an insight into the significance of future ocean acidification compared to eutrophication pressures on tropical coral communities. Coral cover and seawater characteristics at acidified sites (with varied levels of eutrophication), i.e., moderate acidification (pH: 7.87 ± 0.04), low acidification (pH: 8.01 ± 0.04) and reference (pH: 8.2 ± 0.02), were observed at reefs associated with Minahasa Seashore, and Mahengetang and Gunung Api Islands. Results showed that coral community patterns varied among locations and acidified sites, e.g., domination of families such as Alcyoniidae, Acroporidae, Poritidae and Heliporidae, and with different levels of abiotic cover. Surprisingly, pH was not detected as the major determining factor. This finding probably relates to tropical seawater temperatures being high enough to still allow for aragonite deposition even at pH values down to 7.8. Nutrients (phosphate and dissolved inorganic nitrogen) were shown to be the main determining factors that influenced community patterns on the observed coral reefs. Overall, the results indicate that tropical coral reef community patterns will continue to vary as pH decreases to the predicted oceanic value of pH 7.8 over the next 100 years, and bio-geo-ecological characteristics and anthropogenic pressures will be the major factors determining Indonesian tropical coral community structure, compared to pH.

Continue reading ‘Tropical coral reef coral patterns in Indonesian shallow water areas close to underwater volcanic vents at Minahasa Seashore, and Mahengetang and Gunung Api Islands’

Ocean acidification and warming impacts the nutritional properties of the predatory whelk, Dicathais orbita

Ocean warming and acidification have the potential to impact the quality of seafood with flow on effects for future food security and ecosystem stability. Here, we used a 35-day experiment to evaluate how ocean warming and acidification may impact the nutritional qualities and physiological health of Dicathais orbita, a predatory muricid whelk common on the east coast of Australia, and discuss the broader ecological implications. Using an orthogonal experimental design with four treatments (current conditions [~ 23 °C and ~ 380 ppm of pCO2], ocean warming treatment [~ 25 and ~ 380 ppm of pCO2], ocean acidification treatment [CO2 ~ 23 °C and ~ 750 ppm of pCO2], and ocean warming and acidification treatment [CO2, ~ 25 °C and ~ 750 ppm of pCO2]), we showed that changes in moisture and protein content were driven by significant interactions between ocean warming and acidification. Elevated ocean temperature significantly decreased protein in the whelk flesh and resulted in concurrent increases in moisture. Lipid, glycogen, potassium, sulfur, and phosphorus content also decreased under elevated temperature conditions, whereas sodium, boron and copper increased. Furthermore, elevated pCO2 significantly decreased lipid, protein and lead content. Whelks from control conditions had levels of lead in excess of that considered safe for human consumption, although lead uptake appears to be lowered under future ocean conditions and will be site specific. In conclusion, while D. orbita has received research attention as a potential food product with nutritious value, ocean climate change may compromise its nutritional qualities and reduce sustainable harvests in the future. Furthermore, ocean climate change may have deleterious impacts on the longevity and reproductive potential of this important rocky shore predator.

Continue reading ‘Ocean acidification and warming impacts the nutritional properties of the predatory whelk, Dicathais orbita’

Halocarbon emissions by selected tropical seaweeds: species-specific and compound-specific responses under changing pH

Five tropical seaweeds, Kappaphycus alvarezii (Doty) Doty ex P.C. Silva, Padina australis Hauck, Sargassum binderi Sonder ex J. Agardh (syn. S. aquifolium (Turner) C. Agardh), Sargassum siliquosum J. Agardh and Turbinaria conoides (J. Agardh) Kützing, were incubated in seawater of pH 8.0, 7.8 (ambient), 7.6, 7.4 and 7.2, to study the effects of changing seawater pH on halocarbon emissions. Eight halocarbon species known to be emitted by seaweeds were investigated: bromoform (CHBr3), dibro­momethane (CH2Br2), iodomethane (CH3I), diiodomethane (CH2I2), bromoiodomethane (CH2BrI), bromochlorometh­ane (CH2BrCl), bromodichloromethane (CHBrCl2), and dibro­mochloromethane (CHBr2Cl). These very short-lived halocarbon gases are believed to contribute to stratospheric halogen concentrations if released in the tropics. It was observed that the seaweeds emit all eight halocarbons assayed, with the exception of K. alvarezii and S. binderi for CH2I2 and CH3I respectively, which were not measurable at the achievable limit of detection. The effect of pH on halocarbon emission by the seaweeds was shown to be species-specific and compound specific. The highest percentage changes in emissions for the halocarbons of interest were observed at the lower pH levels of 7.2 and 7.4 especially in Padina australis and Sargassum spp., showing that lower seawater pH causes elevated emissions of some halocarbon compounds. In general the seaweed least affected by pH change in terms of types of halocarbon emission, was P. australis. The commercially farmed seaweed K. alvarezii was very sensitive to pH change as shown by the high increases in most of the compounds in all pH levels relative to ambient. In terms of percentage decrease in maximum quantum yield of photosynthesis (Fv∕Fm) prior to and after incubation, there were no significant correlations with the various pH levels tested for all seaweeds. The correlation between percentage decrease in the maximum quantum yield of photosynthesis (Fv∕Fm) and halocarbon emission rates, was significant only for CH2BrCl emission by P. australis (r = 0.47; p ≤ 0.04), implying that photosynthesis may not be closely linked to halocarbon emissions by the seaweeds studied. Bromine was the largest contributor to the total mass of halogen emitted for all the seaweeds at all pH. The highest total amount of bromine emitted by K. alvarezii (an average of 98% of total mass of halogens) and the increase in the total amount of chlorine with decreasing seawater pH fuels concern for the expanding seaweed farming activities in the ASEAN region.

Continue reading ‘Halocarbon emissions by selected tropical seaweeds: species-specific and compound-specific responses under changing pH’

Differential growth responses to water flow and reduced pH in tropical marine macroalgae

The physical environment plays a key role in facilitating the transfer of nutrients and dissolved gases to marine organisms and can alter the rate of delivery of dissolved inorganic carbon. For non-calcifying macroalgae, water motion can influence the physiological and ecological responses to various environmental changes such as ocean acidification (OA). We tested the effects of lowered pH under three different flow speeds on three dominant non-calcifying macroalgal species differing in their carbon-use and are commonly found in the back reefs of Moorea, French Polynesia. Relative growth rates (RGR) of two phaeophytes, Dictyota bartayresiana and Lobophora variegata (HCO3− users), and a rhodophyte, Amansia rhodantha (CO2 user) were measured to examine how the combined effects of OA and flow can affect algal growth. Growth rates were affected independently by pCO2 and flow treatments but there was no significant interactive effect. Additionally, growth rates among species varied within the different flow regimes. Of the three species, L. variegata had the overall greatest increase in RGR across all three flow speeds while A. rhodantha exhibited the greatest negative impact under elevated pCO2 at 0.1 cm·s− 1. These differential responses among algal species demonstrate the importance of flow when examining responses to a changing environment, and if the responses of macroalgae differ based on their carbon-use strategies, it may provide advantages to some macroalgal species in a future, more acidic ocean.

Continue reading ‘Differential growth responses to water flow and reduced pH in tropical marine macroalgae’

Biodiversity of gastropoda in the coastal waters of Ambon Island, Indonesia

Gastropods belonging to the mollusk phylum are widespread in various ecosystems. Ecologically, the spread of gastropoda is influenced by environmental factors, such as temperature, salinity, pH and dissolved oxygen. This research was conducted to determine the correlation between the factors of physico-chemical environment and the diversity of gastropoda in coastal water of Ambon Island, Indonesia. This research was conducted at two research stations, namely Station 1 at Ujung Tanjung Latuhalat Beach and Station 2 at coastal water of Waitatiri Passo. The results of a survey revealed that the average temperature on station 1 was 31.14°C while the average temperature of station 2 was 29.90°C. The average salinity at Station 1 was 32.02%o whereas the salinity average at Station 2 was 30.31%o. The average pH in station 1 and 2 was 7.03, while the dissolved oxygen at station 1 was 7.68 ppm which was not far different from that in station 2 with the dissolved oxygen of 7.63 ppm. The total number of species found in both research stations was 65 species, with the types of gastropoda were found scattered in 48 genera, 19 families and 7 orders. The most commonly found gastropods were from the genus of Nerita and Conus. 40 species were found in station 1 and 40 species were found in station 2. The results of the analysis showed the diversity value was very high with the diversity average of gastropoda in station 1 as much as 3.64 and in station 2 as much as 3.60 and classified into moderate category. In addition, the results of the correlation analysis showed that there was a significantly positive correlation between physical-chemical environmental factors (temperature, salinity, pH and dissolved oxygen) and the diversity of gastropoda in Coastal Waters of Ambon Island.

Continue reading ‘Biodiversity of gastropoda in the coastal waters of Ambon Island, Indonesia’

Environmental controls on the growth, photosynthetic and calcification rates of a Southern Hemisphere strain of the coccolithophore Emiliania huxleyi

We conducted a series of diagnostic fitness response experiments on the coccolithophore, Emiliania huxleyi, isolated from the Subtropical Convergence east of New Zealand. Dose response curves (i.e., physiological rate vs. environmental driver) were constructed for growth, photosynthetic, and calcification rates of E. huxleyi relative to each of five environmental drivers (nitrate concentration, phosphate concentration, irradiance, temperature, and pCO2). The relative importance of each environmental driver on E. huxleyi rate processes was then ranked using a semi-quantitative approach by comparing the percentage change caused by each environmental driver on the measured physiological metrics under the projected conditions for the year 2100, relative to those for the present day, in the Subtropical Convergence. The results reveal that the projected future decrease in nitrate concentration (33%) played the most important role in controlling the growth, photosynthetic and calcification rates of E. huxleyi, whereas raising pCO2 to 75 Pa (750 ppm) decreased the calcification : photosynthesis ratios to the greatest degree. These findings reveal that other environmental drivers may be equally or more influential than CO2 in regulating the physiological responses of E. huxleyi, and provide new diagnostic information to better understand how this ecologically important species will respond to the projected future changes to multiple environmental drivers.

Continue reading ‘Environmental controls on the growth, photosynthetic and calcification rates of a Southern Hemisphere strain of the coccolithophore Emiliania huxleyi’

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Ocean acidification in the IPCC AR5 WG II

OUP book