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It's too hot mum: baby abalone and sea urchins can't grow shells in warming ocean



15 February 2011

A 5-day-old juvenile sea urchin (Heliocidaris erythrogramma) reared in today's ocean conditions, showing normal spine formation (left) compared with a 5-day-old juvenile sea urchin reared in extreme conditions (high temperature and low pH), showing abnormal appearance and reduced spines (right).
A 5-day-old juvenile sea urchin (Heliocidaris erythrogramma) reared in today's ocean conditions, showing normal spine formation (left) compared with a 5-day-old juvenile sea urchin reared in extreme conditions (high temperature and low pH), showing abnormal appearance and reduced spines (right).

Marine abalone and sea urchins will not develop skeletons if the ocean continues to warm and acidify as predicted, says a new study published in Proceedings of the Royal Society B.

The results show that Sydney abalone and sea urchins reared in ocean conditions 100 years from now will be deformed, without shells or spines - suggesting that key sources of protein will be lost due to climate change in the future.

In the new study, lead author Professor Maria Byrne investigated how simultaneous exposure to increased temperature and acidity affects development - from fertilised egg to juvenile stages - of sea urchins and abalone, a first for any study.

Climate change is resulting in oceans that are simultaneously warming, acidifying and increasing in dissolved carbon dioxide (CO2).

"We wondered about the impact of climate change on shelled marine animals since ocean acidification reduces the amount of carbonate ions, which they need to make their calcium carbonate skeletons," says Professor Byrne from the School of Biological Sciences and School of Medical Sciences who collaborated with researchers from the University of Wollongong and Southern Cross University.

"For our study, we focussed on two ecologically and commercially important groups of marine invertebrates from South-Eastern Australia, which is a climate change hotspot where the ocean is warming several times faster than the global average. We collected them from Little Bay, an open ocean area near Sydney."

Abalone larva (Haliotis coccoradiata) at 21 hours, reared in today's ocean conditions, showing normal shell growth (left) compared with abalone larva at 21 hours, reared in mildly acidic conditions, showing absence of shell.
Abalone larva (Haliotis coccoradiata) at 21 hours, reared in today's ocean conditions, showing normal shell growth (left) compared with abalone larva at 21 hours, reared in mildly acidic conditions, showing absence of shell.

The researchers reared abalone and sea urchin embryos in ocean conditions projected for the years 2100 and beyond by the Intergovernmental Panel for Climate Change (IPCC). These included three temperature (current ambient, +2oC, +4oC) and three pH (current ambient, pH 7.8, pH 7.6) treatments, which were used in all combinations.

Abalone were particularly sensitive to change and did not do well in even slightly warmer and more acidic conditions (+2oC/pH 7.8). The sea urchins fared better and some offspring made it to the juvenile stage in these conditions and the interaction between the two stressors indicated that slight warming reduced the negative effect of lower pH. If the urchins were pushed to conditions projected beyond 2100 (+4oC) however, the juveniles produced were abnormal and had fewer spines.

According to Professor Byrne: "The embryos and larvae of certain marine shelled animals will have a difficult time surviving in tomorrow's oceans, which will be seriously detrimental to the persistence of those species. It is worrying to see how vulnerable abalone embryos are to near-future levels of warming and acidification, since this species has such commercial significance for fisheries. Similarly sea urchins are ecologically important as they function as grazers that structure habitats.

"Considering that the oceans are on a irreversible track of change for the foreseeable future and are a key source of food and prosperity for humans, it is important to consider how we are going to meet the needs of growing human population.  Marine invertebrates are a major food source - some species such as abalone are unlikely to adapt, while others such as some hardy oysters may persist."

Byrne et al (2010). Unshelled abalone and corrupted urchins: development of marine calcifiers in a changing ocean. Proceedings of the Royal Society B. DOI 10.1098/rspb.2010.2404. Abstract


Contact: Carla Avolio

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