Posts Tagged 'laboratory'



Ocean warming drives decline in coral metabolism while acidification highlights species-specific responses

Ocean warming and acidification can have negative implications on coral reefs. This mechanistic study aims to evaluate the proximal causes of the observed negative response of Hawaiian corals to climate change scenarios. Net calcification (Gnet), gross photosynthesis, and dark respiration were measured in three species of Hawaiian corals across a range of temperature and acidification regimes using endpoint incubations. Calcification rates showed a curvilinear response with temperature, with the highest calcification rates observed at 26°C. Coral response to ocean acidification (OA) was species dependent and highly variable. OA enhanced calcification rates by 45% in the perforate coral, Montipora capitata, but had no short-term effect on the calcification or photosynthetic rates of imperforate corals, Pocillopora damicornis or Leptastrea purpurea. Further investigations revealed M. capitata to effectively dissipate protons (H+) while increasing uptake of bicarbonate (HCO−3), therefore maintaining high rates of Gnet under acute OA stress. This study demonstrates the first experimental evidence of the ability of a coral species to take advantage of increased dissolved inorganic carbon and overcome an increasing proton gradient in the boundary layer under OA conditions. These observed differences in coral metabolism may underlie the species-specific responses to climate change.

Continue reading ‘Ocean warming drives decline in coral metabolism while acidification highlights species-specific responses’

Variability of seawater chemistry in a kelp forest environment is linked to in situ transgenerational effects in the purple sea urchin, Strongylocentrotus purpuratus

While the value of giant kelp (Macrocystis pyrifera) as a habitat-forming foundation species is well-understood, it is unclear how they impact the oxygen concentration and pH of the surrounding seawater, and further, how such a dynamic abiotic environment will affect eco-evolutionary dynamics in a context of global change. Here, we profiled the nearshore kelp forest environment in Southern California to understand changes in dissolved oxygen (DO) and pH with high spatiotemporal resolution. We then examined transgenerational effects using sea urchins (Strongylocentrotus purpuratus) as our study organism. Using enclosures on the benthos, we conditioned adult sea urchins in situ at two locations – one inside the kelp forest and one outside the kelp forest. After a 11-week conditioning period timed to coincide with gametogenesis in the adults, the urchins were collected, spawned, and cultures of their progeny were raised in the laboratory in order to assess their performance to simulated ocean acidification. In terms of the physical observations, we observed significant changes in DO and pH not only when comparing sites inside and outside of the kelp forest, but also between surface and benthic sensors at the same site. DO and pH at the benthos differed in mean, the amplitude of the diel signal, and in the profile of background noise of the signal. Ultimately, these results indicated that both DO and pH were more predictably variable inside of the kelp forest environment. On the biological side, we found that adult sea urchins inside the kelp forest produced more protein-rich eggs that developed into more pH-resilient embryos. Overall, this study in a temperate kelp forest ecosystem is one of the first studies to not only observe biological response to highly characterized environmental variability in situ, but also to observe such changes in a transgenerational context.

Continue reading ‘Variability of seawater chemistry in a kelp forest environment is linked to in situ transgenerational effects in the purple sea urchin, Strongylocentrotus purpuratus’

Intertidal Mediterranean coralline algae habitat is expecting a shift toward a reduced growth and a simplified associated fauna under climate change

Coralline algae represent the most important bioconstructors in the Mediterranean Sea and are currently impaired by the effects of climate change (CC), particularly by global warming and ocean acidification (OA). We studied the effects of these two drivers on Ellisolandia elongata, an intertidal coralline algae that is known to host a rich biodiversity of associated fauna. We cultured turfs of E. elongata in experimental conditions of increased temperature and OA (using the values of the IPCC scenario RCP- 8.5 expected for 2100: actual mean temperature +3°C and pH = 7.78), and estimated alteration of algal linear growth and community structure, focusing especially on peracarid crustaceans and annelids. Our findings revealed a decrease in linear growth, yet with no significant changes on structural integrity, and a simplification of associated community, in particular for peracarids. Our study contributes to understand community-level response to CC drivers, highlighting the vulnerability of the fauna associated to an important Mediterranean marine habitat.

Continue reading ‘Intertidal Mediterranean coralline algae habitat is expecting a shift toward a reduced growth and a simplified associated fauna under climate change’

Contrasting responses of photosynthesis and photochemical efficiency to ocean acidification under different light environments in a calcifying alga

Ocean acidification (OA) is predicted to enhance photosynthesis in many marine taxa. However, photophysiology has multiple components that OA may affect differently, especially under different light environments, with potentially contrasting consequences for photosynthetic performance. Furthermore, because photosynthesis affects energetic budgets and internal acid-base dynamics, changes in it due to OA or light could mediate the sensitivity of other biological processes to OA (e.g. respiration and calcification). To better understand these effects, we conducted experiments on Porolithon onkodes, a common crustose coralline alga in Pacific coral reefs, crossing pCO2 and light treatments. Results indicate OA inhibited some aspects of photophysiology (maximum photochemical efficiency), facilitated others (α, the responsiveness of photosynthesis to sub-saturating light), and had no effect on others (maximum gross photosynthesis), with the first two effects depending on treatment light level. Light also exacerbated the increase in dark-adapted respiration under OA, but did not alter the decline in calcification. Light-adapted respiration did not respond to OA, potentially due to indirect effects of photosynthesis. Combined, results indicate OA will interact with light to alter energetic budgets and potentially resource allocation among photosynthetic processes in P. onkodes, likely shifting its light tolerance, and constraining it to a narrower range of light environments.

Continue reading ‘Contrasting responses of photosynthesis and photochemical efficiency to ocean acidification under different light environments in a calcifying alga’

Insensitivities of a subtropical productive coastal plankton community and trophic transfer to ocean acidification: results from a microcosm study

Highlights
• Lower apparent growth was observed under elevated CO2 of 1000 μatm.

• Primary production and trophic transfer were unaffected by high CO2.

• Fatty acid profiles of phyto-/zooplankton were unaffected by ocean acidification.

Abstract
Ocean acidification (OA) has potential to affect marine phytoplankton in ways that are partly understood, but there is less knowledge about how it may alter the coupling to secondary producers. We investigated the effects of OA on phytoplankton primary production, and its trophic transfer to zooplankton in a subtropical eutrophic water (Wuyuan Bay, China) under present day (400 μatm) and projected end-of-century (1000 μatm) pCO2 levels. Net primary production was unaffected, although OA did lead to small decreases in growth rates. OA had no measurable effect on micro-/mesozooplankton grazing rates. Elevated pCO2 had no effect on phytoplankton fatty acid (FA) concentrations during exponential phase, but saturated FAs increased relative to the control during declining phase. FA profiles of mesozooplankton were unaffected. Our findings show that short-term exposure of plankton communities in eutrophic subtropical waters to projected end-of-century OA conditions has little effect on primary productivity and trophic linkage to mesozooplankton.

Continue reading ‘Insensitivities of a subtropical productive coastal plankton community and trophic transfer to ocean acidification: results from a microcosm study’

Ocean acidification increases the accumulation of titanium dioxide nanoparticles (nTiO2) in edible bivalve mollusks and poses a potential threat to seafood safety

Large amounts of anthropogenic CO2 in the atmosphere are taken up by the ocean, which leads to ‘ocean acidification’ (OA). In addition, the increasing application of nanoparticles inevitably leads to their increased release into the aquatic environment. However, the impact of OA on the bioaccumulation of nanoparticles in marine organisms still remains unknown. This study investigated the effects of OA on the bioaccumulation of a model nanoparticle, titanium dioxide nanoparticles (nTiO2), in three edible bivalves. All species tested accumulated significantly greater amount of nTiO2 in pCO2-acidified seawater. Furthermore, the potential health threats of realistic nTiO2 quantities accumulated in bivalves under future OA scenarios were evaluated with a mouse assay, which revealed evident organ edema and alterations in hematologic indices and blood chemistry values under future OA scenario (pH at 7.4). Overall, this study suggests that OA would enhance the accumulation of nTiO2 in edible bivalves and may therefore increase the health risk for seafood consumers.

Continue reading ‘Ocean acidification increases the accumulation of titanium dioxide nanoparticles (nTiO2) in edible bivalve mollusks and poses a potential threat to seafood safety’

A new mesocosm system to study the effects of environmental variability on marine species and communities

Climate change will shift mean environmental conditions and also increase the frequency and intensity of extreme events, exerting additional stress on ecosystems. While field observations on extremes are emerging, experimental evidence of their biological consequences is rare. Here, we introduce a mesocosm system that was developed to study the effects of environmental variability of multiple drivers (temperature, salinity, pH, light) on single species and communities at various temporal scales (diurnal ‐ seasonal): the Kiel Indoor Benthocosms (KIBs). Both, real‐time offsets from field measurements or various dynamic regimes of environmental scenarios, can be implemented, including sinusoidal curve functions at any chosen amplitude or frequency, stochastic regimes matching in situ dynamics of previous years and modeled extreme events. With temperature as the driver in focus, we highlight the strengths and discuss limitations of the system. In addition, we examined the effects of different sinusoidal temperature fluctuation frequencies on mytilid mussel performance. High‐frequency fluctuations around a warming mean (+2°C warming, ± 2°C fluctuations, wavelength = 1.5 d) increased mussel growth as did a constant warming of 2°C. Fluctuations at a lower frequency (+2 and ± 2°C, wavelength = 4.5 d), however, reduced the mussels’ growth. This shows that environmental fluctuations, and importantly their associated characteristics (such as frequency), can mediate the strength of global change impacts on a key marine species. The here presented mesocosm system can help to overcome a major short‐coming of marine experimental ecology and will provide more robust data for the prediction of shifts in ecosystem structure and services in a changing and fluctuating world.

Continue reading ‘A new mesocosm system to study the effects of environmental variability on marine species and communities’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book