ocean acidification and new zealand coastal waters catriona hurd, department of botany, university...
TRANSCRIPT
Ocean acidification and New Zealand coastal waters
Catriona Hurd,
Department of Botany,
University of Otago
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
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)
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
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
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
Calcifying invertebrates
• A substantial proportion of marine invertebrates calcify
• Keystone species– kina (sea urchins)
• Commercial species– Mussels, oysters,
paua (abalone)
• Predators– starfish
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
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
55 % growth reduction & 65% metabolic depression
Diversion of energy to shell maintenance from growth & reproduction
0 20 40 60 80 10012
14
16
18
20
22
24
26
28
30
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)
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?
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
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
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