Posts Tagged 'South Atlantic'

Seasonal pH and carbondioxide level as indicator of vulnerability of fresh and marine aquatic systems to climate change in Nigeria

Rising atmospheric carbon dioxide (CO2) concentrations over the past two centuries have led to greater CO2 uptake by the oceans; raising concern over the current and future effects it may have on world climates. Certain changes are already evident but the impact of these changes on marine and coastal living resources is only poorly understood at this stage, particularly in sub-Saharan Africa. This study assessed seasonal dissolved carbon dioxide and pH of fresh and marine aquatic systems in Nigeria. Dissolved CO2 was non-significantly (p=0.07) higher in freshwater during the wet season (20±7ppm) compared to dry season (15 ± 1ppm), while in the marine system, dissolved CO2 level was significantly (p=0.02) higher (42±6ppm) during the dry season compared to the rainy season (31±5ppm). Mean pH values was significantly higher (p=0.003 and 0.05) in freshwater (6.8±0.8 and 6.9±0.2ppm) relative to marine (6.2±0.2 and 6.5±0.3ppm) during wet and dry seasons, respectively. The pH values were generally at the borderline of the acidic limit of the recommended pH values for aquaculture (6.5-9) during the two seasons. Rising atmospheric carbon dioxide (CO2) concentrations over the past two centuries have led to a greater CO2 uptake by the oceans, acidification and consequently, saturation, thereby affecting the ocean’s continued ability to store CO2. This study therefore provides preliminary information on seasonal changes in CO2 and pH of fresh and marine systems in Nigeria; and their potential impacts on global climate and aquatic ecosystems.

Continue reading ‘Seasonal pH and carbondioxide level as indicator of vulnerability of fresh and marine aquatic systems to climate change in Nigeria’

Assessment of the environmental impacts of ocean acidification (OA) and carbon capture and storage (CCS) leaks using the amphipod Hyale youngi

This study aims to ascertain the effects of CO2 induced water acidification and leaks from Carbon Capture and Storage activities on the South American amphipod Hyale youngi. A 10-day acute toxicity test was performed using sediments from two sites located inside the Santos Estuarine System. They were subjected to five pH treatments (8.1, 7.6, 7.0, 6.5, and 6.0). Metals (Cd, Cu, Cr, Pb, Ni and Zn) and the metalloid As were analyzed to determine the influence of their acidification-related mobility on the amphipods mortality. The results showed that mortality becomes significant when compared to control in pH 6.5 in the Canal de Piaçaguerasediment (contaminated) and at pH 6.0 in Ilha das Palmas sediment (reference).

Continue reading ‘Assessment of the environmental impacts of ocean acidification (OA) and carbon capture and storage (CCS) leaks using the amphipod Hyale youngi’

Time series pCO2 at a coastal mooring: internal consistency, seasonal cycles, and interannual variability

Marine carbonate system monitoring programs often consist of multiple observational methods that include underway cruise data, moored autonomous time series, and discrete water bottle samples. Monitored parameters include all, or some of the following: partial pressure of CO2 of the water (pCO2w) and air, dissolved inorganic carbon (DIC), total alkalinity (TA), and pH. Any combination of at least two of the aforementioned parameters can be used to calculate the others. In this study at the Gray’s Reef (GR) mooring in the South Atlantic Bight (SAB) we: examine the internal consistency of pCO2wfrom underway cruise, moored autonomous time series, and calculated from bottle samples (DIC-TA pairing); describe the seasonal to interannual pCO2w time series variability and air-sea flux (FCO2), as well as describe the potential sources of pCO2wvariability; and determine the source/sink for atmospheric pCO2. Over the ~8.5 years of GR mooring time series, mooring-underway and mooring-bottle calculated-pCO2wstrongly correlate with r-values > 0.90. pCO2w and FCO2 time series follow seasonal thermal patterns; however, seasonal non-thermal processes, such as terrestrial export, net biological production, and air-sea exchange also influence variability. The linear slope of time series pCO2w increases by 5.2±1.4 µatm y−1 with FCO2 increasing 51 to 70 mmol m−2 y−1. The net FCO2 sign can switch interannually with the magnitude varying greatly. Non-thermal pCO2w is also increasing over the time series, likely indicating that terrestrial export and net biological processes drive the long term pCO2w increase.

Continue reading ‘Time series pCO2 at a coastal mooring: internal consistency, seasonal cycles, and interannual variability’

Solar UVR sensitivity of phyto- and bacterioplankton communities from Patagonian coastal waters under increased nutrients and acidification

The effects of ultraviolet radiation (UVR) under future expected conditions of acidification and increase in nutrient inputs were studied on a post-bloom phytoplankton and bacterioplankton community of Patagonian coastal waters. We performed an experiment using microcosms where two environmental conditions were mimicked using a cluster approach: present (ambient nutrients and pH) and future (increased nutrients and acidification), and acclimating the samples for five days to two radiation treatments (full solar radiation [+UVR] and exclusion of UVR [–UVR]). We evaluated the short-term (hours) sensitivity of the community to solar UVR through chlorophyll afluorescence parameters (e.g. the effective photochemical quantum yield of PSII [ΦPSII]) at the beginning, at the mid-point and at the end of the acclimation period. Primary production and heterotrophic bacterial production (HBP) were determined, and biological weighting functions were calculated, at the beginning and at the end of the acclimation period. Mid-term effects (days) were evaluated as changes in taxonomic composition, growth rates and size structure of the community. Although the UVR-induced inhibition on ΦPSII decreased in both clusters, samples remained sensitive to UVR after the 5 days of acclimation. Also, under the future conditions, there was, in general, an increase in the phytoplankton carbon incorporation rates along the experiment as compared to the present conditions. Bacterioplankton sensitivity to UVR changed along the experiment from inhibition to enhancement of HBP, and future environmental conditions stimulated bacterial growth, probably due to indirect effects caused by phytoplankton. Those changes in the microbial loop functioning and structure under future global change conditions might have important consequences for the carbon pump and thus for the carbon sequestration and trophodynamics of Patagonian coastal waters.

Continue reading ‘Solar UVR sensitivity of phyto- and bacterioplankton communities from Patagonian coastal waters under increased nutrients and acidification’

Combined effects of sea water acidification and copper exposure on the symbiont-bearing foraminifer Amphistegina gibbosa

Coral reefs are threatened by global and local stressors such as ocean acidification and trace metal contamination. Reliable early warning monitoring tools are needed to assess and monitor coral reef health. Symbiont-bearing foraminifers (Amphistegina gibbosa) were kept under ambient conditions (no sea water acidification and no copper addition) or exposed to combinations of different levels of sea water pH (8.1, 7.8, 7.5 and 7.2) and environmentally relevant concentrations of dissolved copper (measured: 1.0, 1.6, 2.3 and 3.2 µg L−1) in a mesocosm system. After 10- and 25-d exposure, foraminifers were analyzed for holobiont Ca2+-ATPase activity, bleaching, growth and mortality. Enzyme activity was inhibited in foraminifers exposed to pH 7.2 and 3.2 µg L−1 Cu for 25 d. Bleaching frequency was also higher at pH 7.2 combined with copper addition. There was no significant effect of sea water acidification and copper addition on mortality. However, test size was smaller in foraminifers exposed to copper, with a positive interactive effect of sea water acidification. These findings can be explained by the higher availability of free copper ions at lower water pH. This condition would increase Cu competition with Ca2+ for the binding sites on the organism, thus inhibiting Ca2+-ATPase activity and affecting the organism’s overall fitness. Findings reported here suggest that key processes in A. gibbosa, such as calcification and photosynthesis, are affected by the combined effect of global (sea water acidification) and local (copper contamination) stressors. Considering the experimental conditions employed (mesocosm system, possible ocean acidification scenarios, low copper concentrations, biomarkers of ecological relevance and chronic exposure), our findings support the use of foraminifera and biomarkers analyzed in the present study as reliable tools to detect and monitor the ecological impacts of multiple stressors in coral reef environments.

Continue reading ‘Combined effects of sea water acidification and copper exposure on the symbiont-bearing foraminifer Amphistegina gibbosa’

Conservation of Brazilian coral reefs in the Southwest Atlantic Ocean: a change of approach

Brazil has the most extensive and richest areas of coral reefs in the South Atlantic Ocean, with its fauna characterized by high endemism and adaptations related to its growth and morphology, to its coral building fauna and to the depositional environment that differ from other coral reefs around the world. In spite of the effects from changes in the global environmental, the main stress factors for Brazilian reefs are local level threats, such as pollution and overfishing. The effects from these threats reduce biodiversity and result in decreasing stocks at different trophic levels. The trend that currently exists, regarding marine resource use, implies that reassessing the conservation strategies is urgently necessary if the degradation of these environments is to be reversed. It is necessary that the practices used in adjacent watersheds be improved, combined with actions to protect and recover native vegetation, along with planning for developing coastal areas, which will ensure that sedimentation rates be controlled and pollution sources are drastically reduced. Brazil should have to adopt a multidisciplinary approach to lead an evolution from traditional threat management in individual portions of ecosystems to large-scale management strategies in complex socio-economic and natural systems.

Continue reading ‘Conservation of Brazilian coral reefs in the Southwest Atlantic Ocean: a change of approach’

The influence of environmental variability on the biogeography of coccolithophores and diatoms in the Great Calcite Belt

The Great Calcite Belt (GCB) of the Southern Ocean is a region of elevated summertime upper ocean calcite concentration derived from coccolithophores, despite the region being known for its diatom predominance. The overlap of two major phytoplankton groups, coccolithophores and diatoms, in the dynamic frontal systems characteristic of this region, provides an ideal setting to study environmental influences on the distribution of different species within these taxonomic groups. Water samples for phytoplankton enumeration were collected from the upper 30 m during two cruises, the first to the South Atlantic sector (Jan–Feb 2011; 60 °W–15 °E and 36–60 °S) and the second in the South Indian sector (Feb–Mar 2012; 40–120 °E and 36–60 °S). The species composition of coccolithophores and diatoms was examined using scanning electron microscopy at 27 stations across the Sub-Tropical, Polar, and Sub-Antarctic Fronts. The influence of environmental parameters, such as sea-surface temperature (SST), salinity, carbonate chemistry (i.e., pH, partial pressure of CO2 (pCO2), alkalinity, dissolved inorganic carbon), macro-nutrients (i.e., nitrate + nitrite, phosphate, silicic acid, ammonia), and mixed layer average irradiance, on species composition across the GCB, was assessed statistically. Nanophytoplankton (cells 2–20 μm) were the numerically abundant size group of biomineralizing phytoplankton across the GCB, the coccolithophore Emiliania huxleyi and the diatoms Fragilariopsis nana, F. pseudonana and Pseudonitzschia sp. were the most dominant and widely distributed species. A combination of SST, macro-nutrient concentrations and pCO2 were the best statistical descriptors of biogeographic variability of biomineralizing species composition between stations. Emiliania huxleyi occurred in the silicic acid-depleted waters between the Sub-Antarctic Front and the Polar Front, indicating a favorable environment for this coccolithophore in the GCB after spring diatom blooms remove silicic acid to limiting levels. After full consideration of variability in carbonate chemistry and temperature on the distribution of nanoplankton in the GCB, we find that temperature remains the dominant driver of biogeography in a large proportion of the modern Southern Ocean.

Continue reading ‘The influence of environmental variability on the biogeography of coccolithophores and diatoms in the Great Calcite Belt’


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Ocean acidification in the IPCC AR5 WG II

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