1. Ocean acidification and New Zealand coastal waters
Catriona Hurd,
Department of Botany,
University of Otago

2. 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
We are used to thinking about coral reefs. In New Zealand we have temperate reefs – equally diverse, productive and fragile as coral reefs.
Energy to support temperate reefs comes from algal photosynthesis – primary producers. Phytoplankton – that Cliff will/has talked about and seaweeds.
Secondary producers are animals that eat primary production – filter feeders or grazers
Top predators, include fish and carnivores such as star fish

3. 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
All algae will be affected. this is because the supply of CO2 will increase
Stanley (2008) Chem. Rev. 108; Hurd et al. J. Phycol. (2009 in press)

4. 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

5. 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
300% increase in CO2
Will increase photosynthesis of seaweeds that use only CO2
Could increase photosynthetic rates of all algae
9% increase in bicarbonate
Predict little effect on photosynthesis
Coralline seaweeds are dominant component of intertidal and subtidal
Hurd et al. (2009) J. Phycol. In press

6. Coralline seaweeds Global distribution
Paua larva
Global distribution
Invertebrate recruitment and settlement
Release chemicals that induce attachment and metamorphosis in e.g. paua
Vulnerable
Canaries in the coal mine?
Not only are they primary producers….
Paua larva newly settled
on coralline seaweed
Nelson (2009) Mar. Fresh. Res. 60

7. Calcifying invertebrates
A substantial proportion of marine invertebrates calcify
Keystone species
kina (sea urchins)
Commercial species
Mussels, oysters, paua (abalone)
Predators
starfish
Some have calcium carbonate skeletons, others use calcite to harden their chiton shells (e.g. crabs, crayfish)

8. 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

9. Molluscs – reduced Calcification at low pH
Ecosystem function – Bioturbators,
Food source & Habitat modifiers
C. gigas
Net calcification rate
umol CaCO3 g FW-1 h-1
M. edulis
Gazeau et al. 2007

10. Bivalves – reduced Calcification at low pH
Incubations at pH 7.3 (max pH decrease in business-as-usual climate change scenario by year 2300) (Caldeira and Wickett, 2003)
control
55 % growth reduction & 65% metabolic depression Diversion of energy to shell maintenance from growth & reproduction
Michailidis et al. (2004)

11. Economic importance Mussel farms Oyster farms
How will lower pH affect Greenlip Mussels, Paua and other NZ commercial species?
Mussel farms
green lipped mussels
898 farms, approx 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

12. Ecosystem responses Volcanic CO2-ventspH
Volcanic CO2-vents
Coralline seaweeds replaced by fleshy species at low pH
Decline in all calcareous invertebrates at low pH
Hall-Spencer et al. (2008) Nature 454

13. 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

14. 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