Vulnerability of Antarctic marine benthos to increased temperatures and ocean acidification associated with climate change - parent record

Brief description

Metadata record for data from AAS (ASAC) project 3134.

Data from this project will be available via the child records.

Public
Ocean acidification and warming are global phenomena that will impact marine biota through the 21st century. This project will provide urgently needed predictive information on the likely survivorship of benthic invertebrates in near shore Antarctic environments that is crucial for risk assessment of potential future changes to oceans. As oceans acidify carbonate saturation decreases, reducing the material required to produce marine skeletons. By examining the effects of increased ocean temperature and acidification on planktonic and benthic life stages of both calcifying and non-calcifying ecologically important organisms, predictions can be made on the potential vulnerability of marine biota to climatic change.

Project Objectives:
This project aims to deliver one of the first assessments of the impacts that ocean warming and acidification through rising CO2 levels will have on Antarctic benthic marine invertebrates and of the adaptive capacity of common Antarctic biota to climate change. The developmental success of species that have a skeleton will be compared to those that do not under controlled conditions of increased sea water temperature and CO2. A comparison of the responses and sensitivity of developmental stages of calcifiers (echinoids, bivalves) and non-calcifiers (asteroids) to elevated CO2 and temperature will generate much needed empirical data for assessment of risk and adaptive capacity of Antarctica's marine biota and will enable predictions of how benthic invertebrates will fare with respect to climate change scenarios.

The specific aims of the project are to:
1 - examine the impacts of predicted future elevated ocean temperatures and CO2 on fertilisation success, embryonic and larval development of Antarctic molluscs and echinoderms
2 - document skeletal calcification and morphology and growth in larvae under controlled conditions of increased sea water temperature and CO2.
3 - compare the dynamics of biomineralisation with respect to the elemental composition in response to increased temperature and CO2 in species with aragonite and calcite exoskeletons (bivalves) and porous high magnesium calcite endoskeletons (echinoids) to assess the potential for an in-built adaptive response in calcification
4 - used as a biomarker measure of stress and impaired calcification.
5 - compare biomineralisation and elemental signatures in skeletons in larvae of Antarctic molluscs and echinoderms under climate change scenarios with that determined for related species at lower latitudes to assess the relative sensitivity and vulnerability of Antarctic biota.

Taken from the 2009-2010 Progress Report:
Progress against objectives:
1. Unsuccessful as target species, Sterechinus neumayeri had already passed its spawning period, and attempts to spawn and fertilise the Antarctic bivalve, Laternula ellipticaskeleta failed.
2. Skeletal calcification and morphology of juveniles of Abatus nimrodi were successfully documented under controlled conditions of ocean warming and acidification.
3. Juveniles of A. nimrodi were preserved and returned to Australia in order to compare the dynamics of biomineralisation and skeletal mineralogy.
4. No heat shock protein experiments were carried out.
5. Air-dried tests of S. neumayeri and A. nimrodi were RTA'd in order to compare the dynamics of biomineralisation and skeletal mineralogy.

Taken from some project abstracts written by two students working on the project:

Impacts of ocean acidification and increasing seawater temperature on the early life history of the Antarctic echinoderm Sterechinus neumayeri.

Simultaneous effects of ocean acidification and temperature change in Antarctic environments warrant investigation as little is known about the synergistic consequences of these parameters on Antarctic benthic species.
Fertilisation success, embryo cleavage, blastulation and gastrulation were documented in the sea urchin Sterechinus neumayeri, reared for up to 12 days under experimental pCO2 and elevated temperature scenarios predicted by the IPCC (2007) over the next century. Experimental treatments included controls (-1 degrees C, pH 8.0), elevated temperature (1 degrees C, 3 degrees C) and decreased pH (7.8, 7.6) in all combinations in a multi-factorial design. Preliminary results suggest that fertilisation and development up to the gastrula stages are robust to increases in pCO2 and temperature predicted by the year 2100. Percentages of normally developing blastula and gastrula were also slightly higher in temperatures 2 degrees C above ambient.

Impacts of ocean acidification and increasing seawater temperature on juveniles of two Antarctic heart urchins, Abatus ingens and Abatus shackletoni.

Simultaneous effects of ocean acidification and temperature change in Antarctic environments warrant investigation as little is known about the synergistic consequences of these factors on Antarctic benthic species. Juvenile Abatus ingens and Abatus shackletoni were incubated under experimental pCO2 and elevated temperature scenarios reflective of those predicted by the IPCC (2007). Direct development from embryos to juveniles occurs in these species without a pelagic larval phase and the developing young are lecithotrophic for an extended period. Adult urchins were collected near Davis Station during the Austral summer season (January-February 2011). Juveniles were extracted from the parental brood pouch and reared in flow-through experimental treatments for 4 weeks. CO2-enriched air was supplied to seawater in which pCO2 was regulated at the target levels of 448 plus or minus 6.51 (pH 8.01 plus or minus 0.005), 846 plus or minus 6.58 (pH 7.83 plus or minus 0.005) and 1371 plus or minus 7.34 (pH 7.63 plus or minus 0.007) ppm and seawater temperature was set at -1 plus or minus 0.03 degrees C (Control) and 1 plus or minus 0.32 degrees C. Preliminary results from this investigation showed significant increases in spine growth in juveniles of both A.ingens and A. shackletoni over the experimental period. However, juveniles reared in 1 degrees C significantly exhibited more incidences of epithelial separation in the spines compared to those reared in -1 degrees C. This suggests that, although there is an inherent capacity for tolerance of varying levels of pH in seawater in the absence of the protection afforded by the maternal brood pouch, these juveniles are still at risk from increasing temperatures.

Lineage

Progress Code: completed

Statement: The values provided in temporal and spatial coverage are approximate only.

Taken from the 2009-2010 Progress Report:
Variations to work plan or objectives:
The main focus of experiments were changed from fertilisation and larval development of invertebrates to calcification of juvenile echinoderms with existing skeleton under predicted ocean warming and acidification scenarios. This occurred because adults of S. neumayeri collected around Davis had already passed their spawning period by the time the aquarium field module was set-up and running. Eight trials on L. elliptica were conducted to see if they were a good substitute species, but all attempts were unsuccessful.

Field work:
Initial collection of S. neumayeri were carried out around Davis station, mostly through snorkelling around Ellis Fjord. A. nimrodi were collected for us by the divers and were mostly taken from the mouth of Heidemann Bay. L. elliptica were also collected by the divers, however they were obtained from a variety of locations. Animals were collected as and when we needed them.

Laboratory activity/analysis:
Animals were dissected no later than a couple of days after they were brought in by divers.

For experiments involving A. nimrodi, juveniles were collected from the brood pouch of the parent and separated into two classes (early and late) of juveniles. They were then photographed individually and placed into our treatments in batches of 10. Experiments were run for 4 weeks in order to see a stronger effect of ocean warming and acidification on calcification. After 4 weeks, juveniles were taken out and photographed again to document any changes, then they were preserved in trace amounts of 2.5% glutaraldehyde and returned to Australia for further analysis. A total of 2 trials were conducted.

For L. elliptica, animals were dissected and strip-spawned to obtain gametes. These gametes were fertilised under different sperm concentrations in order to discover the optimal sperm concentration needed for this species for a successful fertilisation. Eggs which were mixed with sperm were stored in controlled temperature cabinets for 48 hours to see if fertilisation had occurred. However, 8 trials were conducted and none were successful.

Difficulties affecting project:
There were initial difficulties with the setting-up of the field aquarium module as parts needed were not available. However, these have all been solved, and we do not expect it to interfere with the experimental design. However, further work involving A. nimrodi might not be possible for future seasons as these animals can only be collected through diving, and there might not be a dive team present on station for the following season.