Ocean acidification and New Zealand coastal waters
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Transcript of Ocean acidification and New Zealand coastal waters
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Ocean acidification and New Zealand coastal waters
Catriona Hurd,
Department of Botany,
University of Otago
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NZ’s coastal ecosystems
• Temperate reefs• Primary producers:
– seaweeds and phytoplankton
• Secondary producers– Filter feeders: mussels,
oysters, barnacles– Grazers: kina, paua,
limpets
• Predators– Starfish– Fish
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Which species will OA affect directly?
• All algae – fleshy and calcifying
• Calcifying invertebrates:– Mollusks: paua (abalone),
oysters, mussels – Crustaceans: barnacles,
crabs, crayfish– Echinoderms: kina,
(urchins), starfish– Sponges – Corals – Bryozoans – Serpulid worms
Stanley (2008) Chem. Rev. 108; Hurd et al. J. Phycol. (2009 in press)
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Seaweed-based ecosystems
• Ecosystem engineers– Provide habitat
complexity and shelter for animals
• Supply 50% of energy to coastal food webs– Some seaweeds are
grazed– Most provide food
particles - ‘kelp flakes’
• Globally unique ~800 seaweed species~30% found only in NZ
Hurd et al. (2004) Phycol. Res. 52
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Predictions on how seaweed productivity will be affected
• Increase in growth and productivity of fleshy seaweeds– Seaweeds reliant on
only CO2 will have greatest increase
• Decline in growth of calcifying (coralline) seaweeds– 80% cover of subtidal
habitats around Otago
Hurd et al. (2009) J. Phycol. In press
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Coralline seaweeds
• Global distribution• Invertebrate
recruitment and settlement– Release chemicals
that induce attachment and metamorphosis in e.g. paua
• Vulnerable• Canaries in the coal
mine?
Nelson (2009) Mar. Fresh. Res. 60
Paua larva
Paua larva newly settledon coralline seaweed
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Calcifying invertebrates
• A substantial proportion of marine invertebrates calcify
• Keystone species– kina (sea urchins)
• Commercial species– Mussels, oysters,
paua (abalone)
• Predators– starfish
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Impacts of high CO2 (low pH)- Echinoderms
•Keystone species controlling kelp distributions
•Fished extensively worldwide
•Production of outer test affected during larval settlement stage at high pCO2
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Net calcification rateumol CaCO3 g FW-1 h-1
Molluscs – reduced Calcification at low pH
M. edulis
C. gigas
Ecosystem function – Bioturbators, Food source & Habitat modifiers
Gazeau et al. 2007
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55 % growth reduction & 65% metabolic depression
Diversion of energy to shell maintenance from growth & reproduction
0 20 40 60 80 10012
14
16
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Time (days)
Mea
n sh
ell l
engt
h (m
m)
Incubations at pH 7.3 (max pH decrease in business-as-usual climate change scenario by year 2300) (Caldeira and Wickett, 2003)
controlcontrol
Bivalves – reduced Calcification at low pH
Michailidis et al. (2004)
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Economic importance
Mussel farms
• green lipped mussels
• 898 farms, approx. 6535 ha
• total revenue $181,400,000
Oyster farms • pacific oysters, North Island
• 236 farms, approx. 928 ha
• total revenue $26,000,000
Photos and data from www.fish.govt.nz
How will lower pH affect Greenlip Mussels, Paua and other NZ commercial species?
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Ecosystemresponses
Hall-Spencer et al. (2008) Nature 454
pH
•Volcanic CO2-vents
•Coralline seaweeds replaced by fleshy species at low pH
•Decline in all calcareous invertebrates at low pH
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Seaweeds engineer their own environment
• Photosynthesis raises the pH of seawater
• Calcification rates of coralline seaweeds enhanced in this seagrass meadow
Semesi et al. (2009) Mar. Ecol. Prog. Ser. 382
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New Zealand coastal waters:What do we need to know?
• Species-specific responses to OA– Select ‘model’ seaweed and animal species – Controlled laboratory experiments– Acclimation and adaptation
• Ecosystem responses– What knowledge do we have of NZ coastal
ecosystems? – Near-shore observatories– Food-web studies