Archive for March, 2013

Some microscopic marine organisms could adapt to climate change

Certain tiny, ocean-dwelling creatures called foraminifera can survive in conditions similar to those caused by ocean acidification, say scientists.

The researchers, from Plymouth University and the National Autonomous University of Mexico, found the first evidence that some foraminifera can handle very low-pH conditions near seafloor vents in the Gulf of California. Carbon dioxide bubbles up through these vents, lowering the pH of the surrounding seawater and mimicking conditions of ocean acidification.

Continue reading ‘Some microscopic marine organisms could adapt to climate change’

How climate change threatens the seas (text and videos)

Special report: USA TODAY will explore how climate change is affecting Americans in a series of stories this year.

OYSTER BAY, Wash. — The tide rolls out on a chilly March evening, and the oystermen roll in, steel rakes in hand, hip boots crunching on the gravel beneath a starry, velvet sky.

As they prepare to harvest some of the sweetest shellfish on the planet, a danger lurks beyond the shore that will eventually threaten clams, mussels, everything with a shell or that eats something with a shell. The entire food chain could be affected. That means fish, fishermen and, perhaps, you.

Continue reading ‘How climate change threatens the seas (text and videos)’

Rising CO2 interacts with growth light and growth rate to alter photosystem II photoinactivation of the coastal diatom Thalassiosira pseudonana

We studied the interactive effects of pCO2 and growth light on the coastal marine diatom Thalassiosira pseudonana CCMP 1335 growing under ambient and expected end-of-the-century pCO2 (750 ppmv), and a range of growth light from 30 to 380 µmol photons·m−2·s−1. Elevated pCO2 significantly stimulated the growth of T. pseudonana under sub-saturating growth light, but not under saturating to super-saturating growth light. Under ambient pCO2 susceptibility to photoinactivation of photosystem II (σi) increased with increasing growth rate, but cells growing under elevated pCO2 showed no dependence between growth rate and σi, so under high growth light cells under elevated pCO2 were less susceptible to photoinactivation of photosystem II, and thus incurred a lower running cost to maintain photosystem II function. Growth light altered the contents of RbcL (RUBISCO) and PsaC (PSI) protein subunits, and the ratios among the subunits, but there were only limited effects on these and other protein pools between cells grown under ambient and elevated pCO2.

Continue reading ‘Rising CO2 interacts with growth light and growth rate to alter photosystem II photoinactivation of the coastal diatom Thalassiosira pseudonana’

Growth and development of larval bay scallops (Argopecten irradians) in response to early exposure to high CO2

Coastal and estuarine environments experience large variability and rapid shifts in pCO2 levels. Elevated pCO2, or ocean acidification, often negatively affects early life stages of calcifying marine invertebrates, including bivalves, but it is unclear which developmental stage is most sensitive. I hypothesized that initial calcification is a critical stage during which high pCO2 exposure has severe effects on larval growth and development of bay scallop (Argopecten irradians). Using five experiments varying the timing of exposure of embryonic and larval bay scallops to high CO2, this thesis identifies two distinct stages of development during which exposure to high CO2/low pH causes different effects on bay scallop larvae. I show that any exposure to high CO2 consistently reduces survival of bay scallop larvae. I also show that high CO2 exposure during initial calcification (12-24 h post-fertilization) results in significantly smaller shells, relative to ambient conditions, and this size decrease persists through the first week of development. High CO2 exposure at 2-12 h post-­ fertilization (pre-calcification), does not impact shell size, suggesting that the CO2 impact on size is a consequence of water chemistry during calcification. However, high CO2 exposure prior to shell formation (2-12 h post-fertilization) causes a high incidence of larval shell deformity, regardless of CO2 conditions during initial calcification. This impact does not occur in response to high CO2 exposure after the 2-12 h period. The observations of two critical stages in early development has implications for both field and hatchery populations. If field populations were able to time their spawning to occur during the night, larvae would undergo initial calcification during the daytime, when CO2 conditions are more favorable, resulting in larger veliger larvae. Hatcheries could invest minimal resources to monitor and modify water chemistry only during the first day of development to ensure larva are exposed to favorable conditions during that critical period.

Continue reading ‘Growth and development of larval bay scallops (Argopecten irradians) in response to early exposure to high CO2’

Evolutionary responses of a coccolithophorid Gephyrocapsa oceanica to ocean acidification

The ongoing ocean acidification associated with a changing carbonate system may impose profound effects on marine planktonic calcifiers. Here, we show that a coccolithophore, Gephyrocapsa oceanica, evolved in response to an elevated CO2 concentration of 1000 μatm (pH reduced to 7.8) in a long term (∼ 670 generations) selection experiment. The high CO2 selected cells showed increases in photosynthetic carbon fixation, growth rate, cellular particulate organic carbon (POC) or nitrogen (PON) production and a decrease in C:N elemental ratio, indicating a greater up-regulation of PON than of POC production under the ocean acidification condition. Cells from the low CO2 selection process shifted to high CO2 exposure showed an enhanced cellular POC and PON production rates. Our data suggest that the coccolithophorid could adapt to ocean acidification with enhanced assimilations of carbon and nitrogen but decreased C:N ratios.

Continue reading ‘Evolutionary responses of a coccolithophorid Gephyrocapsa oceanica to ocean acidification’

Threatened Puget Sound marine life shows global threat of ocean acidification

Chemistry is not always easy to learn or communicate about, but it is at the very root of the problem our oceans face today. The chemistry of the world’s oceans and inland marine waters, such as Puget Sound, is changing significantly and with unprecedented speed. The most serious of these radical changes is ocean acidification. We must pay attention to this problem and act to reduce the threat it poses.

The ocean is 30 percent more acidic than it was before the industrial revolution began 250 years ago. If current trends continue, the increase may reach 100 percent by mid-century. The primary cause is carbon dioxide emissions from burning fossil fuels – coal, gas, and oil. The oceans absorb roughly 30 percent of those emissions from the atmosphere. When carbon dioxide mixes with seawater, it forms carbonic acid, and the chemical building blocks needed for the shells or skeletons of species such as mollusks, crustaceans and corals (called calcifiers) are reduced, making it difficult for these creatures to develop.

Continue reading ‘Threatened Puget Sound marine life shows global threat of ocean acidification’

Sex in murky waters : anthropogenic disturbance of sexual selection in pipefish

Animals experience variation in their environment because of natural changes. However, due to anthropogenic disturbance, the speed and severity of these changes have recently increased. This thesis investigates how reproductive behaviours may be affected by human induced environmental change. In specific, I investigate how visual and chemical changes in the aquatic environment, caused by eutrophication, affect mating systems and sexual selection in fish. Broad-nosed- and straight-nosed pipefish, which both have been studied in detail for a long period, were used as model organisms. These two species are particularly suitable model organisms since they perform complex courtship behaviours, including the advertisement of ornaments and a nuptial dance. Further, two distinct populations were studied, one on the Swedish west coast and one in the Baltic Sea, as these two locations vary in the degree and extent of environmental disturbance, in particular turbidity. I found that changes in the visual environment had no impact on the development of female sexual ornaments in these sex-role reversed pipefishes, but it hampered adaptive mate choice. Turbidity also had a negative effect on reproductive success in the Baltic Sea population. Changes in the chemical environment in the form of increased pH reduced the probability to mate, while hypoxia did not alter mating propensity. However, hypoxic water delayed the onset of both courting and mating. Hence, human induced change in aquatic environments may alter the processes of sexual selection and population dynamics.

Continue reading ‘Sex in murky waters : anthropogenic disturbance of sexual selection in pipefish’

Climate change and intertidal wetlands

Intertidal wetlands are recognised for the provision of a range of valued ecosystem services. The two major categories of intertidal wetlands discussed in this contribution are saltmarshes and mangrove forests. Intertidal wetlands are under threat from a range of anthropogenic causes, some site-specific, others acting globally. Globally acting factors include climate change and its driving cause—the increasing atmospheric concentrations of greenhouse gases. One direct consequence of climate change will be global sea level rise due to thermal expansion of the oceans, and, in the longer term, the melting of ice caps and glaciers. The relative sea level rise experienced at any one locality will be affected by a range of factors, as will the response of intertidal wetlands to the change in sea level. If relative sea level is rising and sedimentation within intertidal wetlands does not keep pace, then there will be loss of intertidal wetlands from the seaward edge, with survival of the ecosystems only possible if they can retreat inland. When retreat is not possible, the wetland area will decline in response to the “squeeze” experienced. Any changes to intertidal wetland vegetation, as a consequence of climate change, will have flow on effects to biota, while changes to biota will affect intertidal vegetation. Wetland biota may respond to climate change by shifting in distribution and abundance landward, evolving or becoming extinct. In addition, impacts from ocean acidification and warming are predicted to affect the fertilisation, larval development, growth and survival of intertidal wetland biota including macroinvertebrates, such as molluscs and crabs, and vertebrates such as fish and potentially birds. The capacity of organisms to move and adapt will depend on their life history characteristics, phenotypic plasticity, genetic variability, inheritability of adaptive characteristics, and the predicted rates of environmental change.

Continue reading ‘Climate change and intertidal wetlands’

Dissecting the impact of CO2 and pH on the mechanisms of photosynthesis and calcification in the coccolithophore Emiliania huxleyi

Summary

  • Coccolithophores are important calcifying phytoplankton predicted to be impacted by changes in ocean carbonate chemistry caused by the absorption of anthropogenic CO2. However, it is difficult to disentangle the effects of the simultaneously changing carbonate system parameters (CO2, bicarbonate, carbonate and protons) on the physiological responses to elevated CO2.
  • Here, we adopted a multifactorial approach at constant pH or CO2 whilst varying dissolved inorganic carbon (DIC) to determine physiological and transcriptional responses to individual carbonate system parameters.
  • We show that Emiliania huxleyi is sensitive to low CO2 (growth and photosynthesis) and low bicarbonate (calcification) as well as low pH beyond a limited tolerance range, but is much less sensitive to elevated CO2 and bicarbonate. Multiple up-regulated genes at low DIC bear the hallmarks of a carbon-concentrating mechanism (CCM) that is responsive to CO2 and bicarbonate but not to pH.
  • Emiliania huxleyi appears to have evolved mechanisms to respond to limiting rather than elevated CO2. Calcification does not function as a CCM, but is inhibited at low DIC to allow the redistribution of DIC from calcification to photosynthesis. The presented data provides a significant step in understanding how E. huxleyi will respond to changing carbonate chemistry at a cellular level.

Continue reading ‘Dissecting the impact of CO2 and pH on the mechanisms of photosynthesis and calcification in the coccolithophore Emiliania huxleyi’

Spatial community shift from hard to soft corals in acidified water

Anthropogenic increases in the partial pressure of CO2 (pCO2) cause ocean acidification, declining calcium carbonate saturation states, reduced coral reef calcification and changes in the compositions of marine communities1. Most projected community changes due to ocean acidification describe transitions from hard coral to non-calcifying macroalgal communities2; other organisms have received less attention, despite the biotic diversity of coral reef communities. We show that the spatial distributions of both hard and soft coral communities in volcanically acidified, semi-enclosed waters off Iwotorishima Island, Japan, are related to pCO2 levels. Hard corals are restricted to non-acidified low- pCO2 (225 μatm) zones, dense populations of the soft coral Sarcophyton elegans dominate medium- pCO2 (831 μatm) zones, and both hard and soft corals are absent from the highest- pCO2 (1,465 μatm) zone. In CO2-enriched culture experiments, high- pCO2 conditions benefited Sarcophyton elegans by enhancing photosynthesis rates and did not affect light calcification, but dark decalcification (negative net calcification) increased with increasing pCO2. These results suggest that reef communities may shift from reef-building hard corals to non-reef-building soft corals under pCO2 levels (550–970 μatm) predicted by the end of this century3, and that higher pCO2 levels would challenge the survival of some reef organisms.

Continue reading ‘Spatial community shift from hard to soft corals in acidified water’


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