Ocean acidification and its potential effect on abalone

Transcription

1 Ocean acidification and its potential effect on abalone Vonda Cummings NIWA Wellington

2 Fate of Anthropogenic CO 2 Emissions ( average) 8.6 ± 0.4 GtC/yr 92% 4.3±0.1 GtC/yr 45% 0.8 ± 0.5 GtC/yr 8% ± 0.5 GtC/yr 27% 2.6 ± 0.8 GtC/yr 27%

3 What is ocean acidification? Atmospheric CO 2 Dissolved CO 2 Carbonic Acid Hydrogen ions CO 2 + H 2 O H 2 CO 3 H + Decreases ph Bicarbonate ions HCO 3 - Carbonate ions CO 3 2- Calcification

4 What does this mean for marine organisms? Increased H+ (acidity): disrupts acid-base balance, internal processes (including calcification) Decreased carbonate availability (CO 3 2- ) affects shell/skeleton generation ability, may result in dissolution of existing structures More energy utilisation has potential effects on fitness: growth, reproduction, ability to cope with other stressors, population viability

5 How acidic is it? Average surface ocean ph is currently 8.1 (slightly basic) ph has declined by 0.1 since 1700/preindustrial The ph scale is logarithmic - so a ph change from 8.2 to 8.1 is a 30% increase in acidity

6 Changes in surface ocean ph IPCC business-as-usual scenario ph drop of 0.45 by 2100; i.e., to Each ph drop leads to a drop in CO 3 2- concentrations: at ph 7.75, the [CO 3 2- ] in the surface oceans will be half that of today Rate of change is 10x faster than any time in last 55M years Figure reference: Carol Turley, Plymouth Marine Lab

7 Ocean acidification experiments More and more in the past 10 years; Simple experiments; Majority manipulate only ph; Majority are laboratory experiments. Complexity of responses Variability between taxa groups, species, life history stages Within species, variable responses between locations No one ecosystem has the same community or environmental influences Very difficult to predict ecosystem responses

8 Molluscs % of studies which show negative effects of ocean acidification on one or more processes for each mollusc group: Parker et al Biology 2:

9 Experiments clearly show. Significant impacts on carbonate production, growth, development & survival Impacts on multiple life history stages Strongest effects on early life history stages (larvae and juveniles)

10 Abalone fertilisation Australian abalone, H. coccoradiata: fertilisation is robust to acidification (and warming) normal (>75%) rates at ph ( uatm, 20 o C) Byrne et al. 2010, Proc. Royal Soc B 278, Ezo abalone, H. discus hannai (Japan): fertilisation rates were reduced only at high pco 2 (>1650 uatm, 20 o C) Kimura et al. 2011, Fish. Oceanogr.

11 Larval development H. kamtschatkana after 8 days at reduced ph (ph 8.07, 12 o C, 800 ppm) Survival lower More shell abnormalities Normally developed larvae were smaller.

12 Larval development H. coccoradiata s y Control ph 8.2, 20 o C s y Warmed ph 8.2, 22 o C v y Acidified ph 7.8, 20 o C v s = shell v = velum y = yolk acidification (ph ) and warming (+2 to 4 O C) resulted in unshelled larvae and abnormal juveniles Modified from Fig 1, Byrne et al. 2010, Proc. Royal Soc B 278,

13 New Zealand paua Haliotis iris NIWA work on early life history stages Johnny Wright, Victoria University MSc Shaun Cunningham, University of Otago MSc Photo: Dave Allen, NIWA

14 Influence on juveniles Paua juveniles (14 months old, 24 mm SL)

15 ph (at 15 o C): 8.05, 7.95, 7.85, 7.75, 7.65 Temperature (ambient ph): 11, 13, 15, 19, 21 o C Temp/pH: Selected combinations 4 month long experiments Cummings et al (unpubl.), N.Z. Ministry for Primary Industries

16 Response variables measured: Survival Growth Physical condition (CI SW:SL ) Physiological condition (CI FW:SW ) Righting behaviour Respiration Shell weight loss (dead shell) Effect of acidification or warming alone Interactive effects of acidification and warming Relationship with carbonate availability (concentrations) Carbonate was only in short supply at 13 o C/7.65 Cummings et al (unpubl.), N.Z. Ministry for Primary Industries

17 Paua shell weight loss 7-25% greater in treatments with lower ph (or CO 2-3 ) (30-70 mg) Cummings et al (unpubl.), N.Z. Ministry for Primary Industries

18 Ambient ph, 13 o C ph 7.65, 13 o C Erosion of juvenile empty shells at lower ph Such extreme erosion was not observed in live juveniles Additional energetic cost of shell maintenance? we found effects on condition, growth and respiration rates of the juveniles which support this. Cummings et al (unpubl.), N.Z. Ministry for Primary Industries

19 Summary of paua responses ph gradient (acidification) Temperature gradient (warming) Growth; Physiological condition; Physical condition; Righting speed; Combined stressors Growth; Physiological condition; Physical condition; Righting speed; O 2 consumption shell wt loss shell wt loss shell wt loss No effect of ph alone Several variables influenced by temperature gradient Modelling indicated interactive effects of acidification and warming (red). Predicting impacts from single stressor studies may underestimate responses. Cummings et al (unpubl.), N.Z. Ministry for Primary Industries

20 Moving forward Methods needed to assess resilience and other early warning signals; Naturally variable system, better understanding required Multiple stressor system: salinity (FW input), season, location, sedimentation, competition, disease, food, etc Need strategies to mitigate other stressors that are more easily controlled

21 Kelly et al Science 332:

22 What can we do? monitor minimise additional stressors to help ameliorate threats coastal and riparian buffers, intact wetlands protect shell components of ecosystems monitor reduce CO 2 emissions

23 Future work Multiple stressor, in situ/in vivo experiments and observations; Experiments should incorporate natural variation in environmental parameters, community composition etc Paua fertilisation, development, physiology; reproductive success; detailed response of shell (mineralogy, composition and structure) Natural variation in ph and carbonate parameters (we lack NZ coastal data, monitoring badly needed!)

24 Thanks to... Judi Hewitt, Graeme Moss, Sarah Allen, Kim Currie, Neill Barr, Phil Heath, Claire Guy, Jane Halliday, Chazz Marriott Photo: Dave Allen, NIWA

25 Further reading/watching: NZ shellfish ocean acidification video: EPOCA website (including kids video); best practises guide to OA. These websites are also very useful for a basic explanation: