Immune suppression of the echinoderm Asterias rubens (L.) following long-term ocean acidification

We compared effects of exposure to predicted near-future (2100) ocean acidification (OA; pH 7.7) and normal seawater (Control; pH 8.1) on immune and stress responses in the adult sea star Asterias rubens. Analyses were made after one week and after six months of continuous exposure. Following one week exposure to acidified water, the pH of coelomic fluid was significantly reduced. Levels of the chaperon Hsp70 were elevated while key cellular players in immunity, coelomocytes, were reduced by approximately 50%. Following long-term exposure (six months) levels of Hsp70 returned to control values, whereas immunity was further impaired, evidenced by the reduced phagocytic capacity of coelomocytes and inhibited activation of p38 MAP-kinase. Such impacts of reduced seawater pH may have serious consequences for resistance to pathogens in a future acidified ocean.

The ocean acid test

How will marine life respond to ocean waters that are growing ever more acidic? In a remote Norwegian fjord, scientists are finding out by simulating the corrosive seas of the future.

Photo by Nick Cobbing

Rising ocean temperatures will be devastating for sea urchins and abalone

Marine abalone and sea urchins in Sydney Harbour will not develop normal skeletons if the ocean continues to warm and acidify as predicted, a study has found.

Such impaired development could have a dramatic effect on the survival of these economically and ecologically important sea creatures.

A group of Australian marine biologists reared abalone and sea urchins in present ocean conditions and compared them with young raised in warmer, more acidic environments that scientists predict will become reality for the world’s oceans within the next 100 years.
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While abalone larvae raised in control conditions had a well-developed shell after 21 hours of life, most larvae reared in water with a pH of 7.6 – a 0.4 drop in pH level compared with today – were dead or severely abnormal after the same time frame. An increase in temperature of just two degrees had a negative effect on baby abalone development and only 20 per cent of young raised in water four degrees warmer than today survived.

The study found developing abalone had only a limited ability to cope with changes in temperature and acidity, and larvae could not recover and grow shells when they were placed in normal conditions.

Dr Murray Roberts: Chilling threat being posed to our deep-sea wonders

Scotland’s cold water corals are one of the world’s great natural treasures, says Dr Murray Roberts

Cold-water corals provide a rich habitat for other forms of marine life, and archive thousands of years’ worth of information on climate change, but they’re under threat from fishing, mining and, ironically, climate change itself.

Think of corals and what springs to mind? Island paradises in clear blue waters? Palm trees, sandy beaches and luxurious holidays in the Caribbean? All true, but corals aren’t only found in the tropics. In fact, there are more coral species in deep, cold-water waters than on shallow, tropical reefs. And it’s these cold-water corals in the North Atlantic that my research team at Heriot-Watt University studies. It’s fascinating and frustrating work. With almost every survey comes evidence that human activities have damaged deep-sea habitats and the spectres of global warming and ocean acidification may completely alter the present balance of ocean ecosystems, with huge implications for marine life and the people it supports.

Effect of ocean acidification on otolith development in larvae of a tropical marine fish

Calcification in many invertebrate species is predicted to decline due to ocean acidification. The potential effects of elevated pCO₂ and reduced carbonate saturation state on other species, such as fish, are less well understood. Fish otoliths (earbones) are composed of aragonite, and thus, might be susceptible to either the reduced availability of carbonate ions in seawater at low pH, or to changes in extracellular concentrations of bicarbonate and carbonate ions caused by acid-base regulation in fish exposed to high pCO₂. We reared larvae of the clownfish Amphiprion percula from hatching to settlement at three pH_NBS and pCO₂ levels (control: pH 8.15 and 404 μatm CO₂; intermediate: pH 7.8 and 1050 μatm CO₂; extreme: pH 7.6 and 1721 μatm CO₂) to test the possible effects of ocean acidification on otolith development. There was no effect of the intermediate treatment (pH 7.8 and 1050 μatm CO₂) on otolith size, shape, symmetry between left and right otoliths, or otolith elemental chemistry, compared with controls. However, in the more extreme treatment (pH 7.6 and 1721 μatm CO₂) otolith area and maximum length were larger than controls, although no other traits were affected. Our results support the hypothesis that pH regulation in the otolith endolymph of fish exposed to elevated pCO₂ can lead to increased precipitation of CaCO₃ in otoliths of larval fish, as proposed by an earlier study, however, our results also show that sensitivity varies considerably among species. Importantly, our results suggest that otolith development in clownfishes is robust to even the more pessimistic changes in ocean chemistry predicted to occur by 2100.

Changing Planet: Ocean acidification – The chemistry is less than basic!

Summary: Students will use a pH indicator solution to detect the presence of carbon dioxide and changes in acidity, and to model ocean-atmosphere interactions.

Source: Adapted by NESTA/Windows to the Universe team members Missy Holzer, Jennifer Bergman, and Roberta Johnson from the Carbon Dioxide Sources and Sinks activity on Windows to the Universe.

Time: This activity requires careful preparation including some set-up the previous day. It is recommended that the directions be read carefully before beginning this activity.

• Materials preparation: 40 minutes
• Class time: 40 minutes
• Discussion and review: 30 minutes

Student Learning Outcomes:

• Students will be able to explain the concept of ‘sources’ and ‘sinks’ as they relate to carbon dioxide.
• Students will understand the use of an indicator solution (BTB) to reveal the presence of carbon dioxide as well as levels of acidity.
• Students explain the cause and effect relationship between lower pH levels of seawater and carbonate ion availability for shell formation in marine organisms.