Posts Tagged 'North Pacific'

Natural ocean acidification at Papagayo upwelling system (North Pacific Costa Rica): implications for reef development

Numerous experiments have shown that ocean acidification impedes coral calcification, but knowledge about in situ reef ecosystem response to ocean acidification is still scarce. Bahía Culebra, situated at the northern Pacific coast of Costa Rica, is a location naturally exposed to acidic conditions due to the Papagayo seasonal upwelling. We measured pH and pCO2 in situ during two non-upwelling seasons (June 2012, May–June 2013), with a high temporal resolution of every 15 and 30 min, respectively, using two Submersible Autonomous Moored Instruments (SAMI-pH, SAMI-CO2). These results were compared with published data from the upwelling season 2009. Findings revealed that the carbonate system in Bahía Culebra shows a high temporal variability. Incoming offshore waters drive inter- and intra-seasonal changes. Lowest pH (7.8) and highest pCO2 (658.3 µatm) values measured during a cold-water intrusion event in the non-upwelling season were similar to those minimum values reported from upwelling season (pH = 7.8, pCO2 = 643.5 µatm), unveiling that natural acidification occurs sporadically also in non-upwelling season. This affects the interaction of photosynthesis, respiration, calcification, and carbonate dissolution and the resulting diel cycle of pH and pCO2 in the reefs of Bahía Culebra. During non-upwelling season, the aragonite saturation state (Ωa) rises to values of > 3.3 and enhances calcification. Aragonite saturation state values during upwelling season falls below 2.5, hampering calcification and coral growth. Low reef accretion in Bahía Culebra indicates high erosion rates and that these reefs grow on the verge of their ecological tolerance. The Ωa threshold values for coral growth, derived from the correlation between Ωa and coral linear extension rates, suggest that future ocean acidification will threaten reefs in Bahía Culebra. These data contribute to build a better understanding of the carbonate system dynamics and coral reefs key response (e.g. coral growth) to natural low-pH conditions, in upwelling areas in the Eastern Tropical Pacific and beyond.

Continue reading ‘Natural ocean acidification at Papagayo upwelling system (North Pacific Costa Rica): implications for reef development’

Evaluating features of periphytic diatom communities as biomonitoring tools in fresh, brackish and marine waters

Highlights

• Diversity of periphytic diatoms from freshwater, brackish water and marine sites from the same biogeographical region was assessed.
• Taxonomical parameters (life-forms, cell density, biovolume, Shannon index, species richness and % relative abundance) effectively differentiate impacted sites from less-impacted one.
• Lipid bodies and deformities in diatoms show tremendous potential to be used as a rapid early warning system for assessing the ecological health of fluvial ecosystem.

Abstract

The aims of this study were to assess the biodiversity of periphytic diatom assemblages in fresh, brackish and marine waterbodies of Korea, and to assess the effect of environmental and anthropogenic factors on parameters such as the quantity and biovolume of lipid bodies and deformations of diatoms as early warning measures of anthropogenic impact. Diatom samples were collected from 31 sites (14 freshwater, 10 brackish and 7 marine), which included less impacted (upstream) and impacted (downstream) sites in each water type. Our results showed higher abundance and biodiversity of periphytic diatoms at the less impacted sites in terms of species richness, Shannon index, cell count and biovolume of the communities than at the impacted sites for freshwater and estuarine sites, but not for marine sites. 84 diatom species were noted in freshwater, 80 in brackish water and 40 in marine waters. In comparison to diatoms of the impacted sites, those of less impacted freshwater, brackish and marine sites had less lipid bodies (also less biovolume) and a lower percentage of teratological frustules, and showed more mobile forms in the community. Principal component analysis (PCA) also showed clear segregation of impacted from less impacted sites by the extent of the presence of lipid bodies (higher both in number and biovolume) and deformities in diatom frustules. Pearson correlation analysis revealed that lipid body induction and deformities were positively correlated with metals (Cd, Co, Cr, Cu, Fe, Pb and Zn) and nutrients (total phosphorus and total nitrogen), whereas they showed negative correlation with salinity, dissolved oxygen, suspended solutes and pH. Life-forms, lipid bodies and deformities in diatoms may be an effective biomonitoring tool for assessing biological effects of pollutants in non-marine aquatic ecosystems in Korea.

Continue reading ‘Evaluating features of periphytic diatom communities as biomonitoring tools in fresh, brackish and marine waters’

Sponge reefs of the British Columbia, Canada Coast: impacts of climate change and ocean acidification

Sponge reefs living in deeper shelf waters on the western margin of North America are somewhat insulated from surface water effects of localized ocean warming but are susceptible to increasing hypoxia associated with ocean stratification and increasing upwelling. The largest reef complexes are projected to experience increasing upwelling and low-oxygen events in the future as part of the observed and projected changes in ocean ventilation accompanying increased atmospheric carbon dioxide concentrations. Inshore and shallow reefs are subjected to surface water warming in fiords. Surface water productivity is anticipated to change slightly likely having limited negative impact on the sponge reefs which are adapted to relatively low-nutrient situations. It is unknown the extent to which glass sponges might be resilient to lower oxygen conditions. While filtration is an energetically costly method of feeding, glass sponges appear to be adapted to reduce their energetic needs by using ambient flow to assist filtration. Populations that experience extreme hypoxia in some fiords may be extirpated by extreme anoxic events. Ocean acidification will not have as large an effect on the siliceous skeleton sponges as it will on corals and other carbonate-dependent organisms though it is possible changing pH will affect tissue functioning and homeostasis by compromising membrane pumps. Hexactinellid sponges and sponge reefs have been resilient to changing climate and ocean environments in the geologic past.

Continue reading ‘Sponge reefs of the British Columbia, Canada Coast: impacts of climate change and ocean acidification’

Elevated pCO2 affects tissue biomass composition, but not calcification, in a reef coral under two light regimes

Ocean acidification (OA) is predicted to reduce reef coral calcification rates and threaten the long-term growth of coral reefs under climate change. Reduced coral growth at elevated pCO2 may be buffered by sufficiently high irradiances; however, the interactive effects of OA and irradiance on other fundamental aspects of coral physiology, such as the composition and energetics of coral biomass, remain largely unexplored. This study tested the effects of two light treatments (7.5 versus 15.7 mol photons m−2 d−1) at ambient or elevated pCO2 (435 versus 957 µatm) on calcification, photopigment and symbiont densities, biomass reserves (lipids, carbohydrates, proteins), and biomass energy content (kJ) of the reef coral Pocillopora acuta from Kāne‘ohe Bay, Hawai‘i. While pCO2 and light had no effect on either area- or biomass-normalized calcification, tissue lipids gdw−1 and kJ gdw−1 were reduced 15% and 14% at high pCO2, and carbohydrate content increased 15% under high light. The combination of high light and high pCO2 reduced protein biomass (per unit area) by approximately 20%. Thus, under ecologically relevant irradiances, P. acuta in Kāne‘ohe Bay does not exhibit OA-driven reductions in calcification reported for other corals; however, reductions in tissue lipids, energy content and protein biomass suggest OA induced an energetic deficit and compensatory catabolism of tissue biomass. The null effects of OA on calcification at two irradiances support a growing body of work concluding some reef corals may be able to employ compensatory physiological mechanisms that maintain present-day levels of calcification under OA. However, negative effects of OA on P. acuta biomass composition and energy content may impact the long-term performance and scope for growth of this species in a high pCO2 world.

Continue reading ‘Elevated pCO2 affects tissue biomass composition, but not calcification, in a reef coral under two light regimes’

The fatty acid content of plankton is changing in subtropical coastal waters as a result of OA: results from a mesocosm study

Highlights

• First mesocosm experiment to investigate OA impacts on fatty acids profiles of plankton in subtropical coastal waters.
• Contents of total FA, PUFA, and MUFA of phytoplankton increased at late exponential phase under high pCO2 condition.
• Mesozooplankton grazing rate decreased, while DHA uptake rate increased under high pCO2 condition.

Abstract

Ocean Acidification (OA) effects on marine plankton are most often considered in terms of inorganic carbon chemistry, but decreasing pH may influence other aspects of cellular metabolism. Here we present the effects of OA on the fatty acid (FA) content and composition of an artificial phytoplankton community (Phaeodactylum tricornutum, Thalassiosira weissflogii, and Emiliania huxleyi) in a fully replicated, ∼4 m3 mesocosm study in subtropical coastal waters (Wuyuan Bay, China, 24.52°N, 117.18°E) at present day (400 μatm) and elevated (1000 μatm) pCO2 concentrations. Phytoplankton growth occurred in three phases during the 33-day experiment: an initial exponential growth leading to senescence and a subsequent decline phase. Phytoplankton sampled from these mesocosms were fed to mesozooplankton collected by net haul from Wuyuan Bay. Concentrations of saturated fatty acids (SFA) in both phytoplankton and mesozooplankton remained high under acidified and non-acidified conditions. However, polyunsaturated fatty acids (PUFA) and monounsaturated fatty acids (MUFA) increased significantly more under elevated pCO2 during the late exponential phase (Day 13), indicating increased nutritional value for zooplankton and higher trophic levels. Indeed, uptake rates of the essential FA docosahexaenoic acid (C20:5n3, DHA) increased in mesozooplankton under acidified conditions. However, mesozooplankton grazing rates decreased overall with elevated pCO2. Our findings show that these selected phytoplankton species have a relatively high tolerance to acidification in terms of FA production, and local mesozooplankton in these subtropical coastal waters can maintain their FA composition under end of century ocean acidification conditions.

Continue reading ‘The fatty acid content of plankton is changing in subtropical coastal waters as a result of OA: results from a mesocosm study’

Effects of the interaction of ocean acidification, solar radiation, and warming on biogenic dimethylated sulfur compounds cycling in the Changjiang River Estuary

Ocean acidification (OA) affects marine primary productivity and community structure, and therefore may influence the biogeochemical cycles of volatile biogenic dimethyl sulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) and photochemical oxidation product dimethyl sulfoxide (DMSO). A 23-day incubation experiment on board was conducted to investigate the short-term response of biogenic sulfur compounds production and cycling to OA in the Changjiang River Estuary and further understand its effects on biogenic sulfur compounds. Result showed that phytoplankton abundance and species presented remarkable differences under three different pH levels in the late stage of the experiment. A significant reduction in chlorophyll a (Chl-a), DMS, particulate DMSP (DMSPp), and dissolved DMSO (DMSOd) concentrations was identified under high CO2 levels. Moreover, minimal change was observed in the production of dissolved DMSP (DMSPd) and particulate DMSO (DMSOp) among treatments. The ratios of DMS, total DMSP (DMSPt), and total DMSO (DMSOt) to Chl-a were also not affected by a change in pH. In addition, DMS and DMSOd were highly related to mean bacterial abundance under three pH levels. Additional incubation experiments on light and temperature showed that the influence of pH on productions of dimethylated sulfur compounds also depended on solar radiation and temperature conditions. DMS photodegradation rate increased with decreasing pH under full-spectrum natural light and UVB light. Thus, OA may lead to decreasing DMS concentrations in the surface seawater. Light and temperature conditions also play an important role in the production and cycling of biogenic sulfur compounds.

Continue reading ‘Effects of the interaction of ocean acidification, solar radiation, and warming on biogenic dimethylated sulfur compounds cycling in the Changjiang River Estuary’

Submarine groundwater discharge drives biogeochemistry in two Hawaiian reefs

Groundwater inputs are typically overlooked as drivers of environmental change in coastal reef studies. To assess the impact of groundwater discharge on reef biogeochemistry, we examined two fringing reef environments, located in Maunalua Bay on the south shore of O‘ahu, Hawai‘i, that receive large inputs of submarine groundwater discharge. We supplemented 25- and 30-d time series measurements of salinity, water temperature, pH, dissolved oxygen, and 222Rn with high-resolution 24-h nutrient, dissolved inorganic carbon (DIC), total alkalinity (TA), and δ13C–DIC measurements to evaluate both groundwater-induced and biologically-driven changes in coastal carbonate chemistry across salinity gradients. Submarine groundwater discharge at these two locations was characterized by low pHT (7.36–7.62), and variable DIC (1734–3046 μM) and TA (1716–2958 μM) content relative to ambient seawater. Groundwater-driven variability in coastal carbonate system parameters was generally on the same order of magnitude as biologically-driven variability in carbonate system parameters at our study locations. Further, our data revealed a shift in reef metabolism from net dissolution to net calcification across this groundwater-driven physicochemical gradient. At sites with high levels of groundwater exposure, net community production and calcification rates were reduced. Our findings shed light on the importance of considering groundwater inputs when examining coastal carbonate chemistry.

Continue reading ‘Submarine groundwater discharge drives biogeochemistry in two Hawaiian reefs’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

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