Impact of Mining on Primary Producers. Dr Emily Roberts Scientific Officer Marine Ecologist Taranaki Regional Council

Transcription

1 Impact of Mining on Primary Producers Dr Emily Roberts Scientific Officer Marine Ecologist Taranaki Regional Council

2 Primary Producers Introduction Euphotic zone Benthic microalgae Phytoplankton Concerns Scale Nutrient versus light limitation Suggestions Scale of risk assessment Adaptive management Monitoring

3 Intro: Euphotic Zone Definition: Euphotic Zone Depth: light declined to 1% of surface value Compensation depth: o 24h mean photosynthesis = 24h mean respiration Pinkerton (2014) Predicting the effects of ironsand mining on optical properties of the STB

4 Intro: Euphotic Zone Pinkerton (2014) Predicting the effects of ironsand mining on optical properties of the STB

5 Intro: Euphotic Zone Natural Mining

6 Intro: Phytoplankton Relative average (2 year) light in water column: (% of surface?) Natural Compensation irradiance: ~1% Mining: Site A Pinkerton (2014) Mining: Site B

7 Intro: Benthic Microalgae Average (2 year) seabed: mol photons m -2 d -1 Natural Compensation irradiance: 0.4 mol photons m -2 d -1 Mining: Site A Pinkerton (2014) Mining: Site B

8 Intro: % Decrease over South Taranaki Bight Average Mining Site A Mining Site B Benthic microalgae: seabed 51% 59% Pinkerton (2014) Phytoplankton: Light in water column 8% 15% Phytoplankton primary production 4% 8% Total (B+P) primary production 5% 12% Energy flow to benthos 9% 16%

9 Concern 1: Scale STB: 12,500 km 2 Plume: ~800 km 2 Plume = <7% STB

10 Concern 1: Scale Consent Condition (April 2014): 9 (f) vii. No more than minor impact on STB phytoplankton abundance and distribution attributable to optical property changes arising from TTR s operations.

11 Concern 1: Scale Plume shifting Operations Water masses Seasonal Nutrient limitation High uncertainty More variable pulses of phytoplankton Require: Conditions minimize knock on food web effects

12 Concern 2: Nutrient vrs Light Discussion: Nutrient limitation, e.g.: McClary, Statement of Evidence, p33, Point 168 Pinkerton, Optical Properties Report, Point 14 Huber, Hearing Transcripts, p637 Venus, Hearing Transcripts, p1883 Clarify: Nutrient and light limitation of phytoplankton growth

13 Concern 2: Nutrient vrs Light Some of year: Phytoplankton growth N limited When phytoplankton N limited: decrease light without effecting growth Do not know: Extent: phytoplankton growth limited by N? Extent: phytoplankton rely on NH 4+? Point: growth switch from nutrient to light limitation? Area of plume: nutrient to light limitation?

14 Concern 2: Nutrient vrs Light N limitation of phytoplankton growth: important Current lack of info: Cannot use to imply plume minor impact on primary productivity Requires robust approach: assess impacts of plume: Risk assessment Consent conditions Adaptive management Monitoring

15 Suggestion 1: Scale of Risk Assessment Provide comparative estimates of primary productivity values over median footprint of plume: mining vrs non-mining Required: assess/manage potential foodweb impacts Values: inform monitoring effort & design

16 Suggestion 2: Adaptive Management Use adaptive management approach: manage potential impacts mining on PP Model: management tool Validated: appropriate monitoring Model output: development trigger values (SSC & optical) Spatial scale

17 Suggestion 3: Monitoring Develop robust monitoring programme: enable management risk in relation to primary producers Currently: plan proposed monitoring phytoplankton & benthic microalgae = limited: Benthic microalgae chlorophyll a: Condition 79 Primary productivity (incl. light) Conditions 83 & 131 (Venus, p1884: only light?) Joint Expert Reports Optical & Benthic 2 : Macrofauna: o Valuable: detecting when impact occurred o Limited: confirms impact in hindsight

18 Suggestion 3: Monitoring Develop predictive model: Forecast risk Inform implementation of appropriate trigger values Validated during baseline monitoring Monitoring: determine: o Effects of SSC on primary productivity o Switch nutrient to light limitation of phytoplankton growth Phytoplankton physiologist/modeller on TPRG

19 Thank You Dr Emily Roberts Scientific Officer Marine Ecologist Taranaki Regional Council