Project 3.3.1 - NESP Tropical Water Quality Hub

Bleaching and WQ – what is the connection?

EMatson@aims

AIMS: Australia’s tropical marine research agency.

Dr. Line K Bay Australian Institute of Marine Science

Impacts of extreme temperature on corals • Mass bleaching 1998, 2002, 2016 and 2017 Mortality: ~30% across GBR • No evidence in records going back 100 years


Mid-shelf Central Great Barrier Reef: Late February 2017


NESP 3.3.1:

Linkages between WQ and bleaching susceptibility and recovery •Mark Baird, Neal Cantin, Katharina Fabricius, Kate Quigley, Luke Correlations of WQ with bleaching and heat accumulation - What are the most important WQ parameters? Morris (PhD). Katherine Martin and Rachel Pears (GBRMPA) - Temperature range over which WQ matters ?

• Physiological and genetic mechanisms

Surveys

- Stress enzyme activity - Algal symbiont diversity and abundance

• End of river and reef based loads AIMS: Australia’s tropical marine research agency.

Physiology

eReefs model

Corals live in symbiosis with microbes Bacteria and archaea Virus and fungi

Coral host

• Types and relative

health • May be locally adapted


Health and performance

abundance essential for

Algal symbiont: Symbiodinium

Optimum

How does bleaching occur? Anti-oxidant and immunity responses

Genetic factors

C

D

A

9 Major Types

Cellular stress

Increased ROS + protein damage

Decrease of algal cells

Death AIMS: Australia’s tropical Bleaching marine research agency.

Recovery

Environmental perturbation: Heat, UV/light, contaminants, cold, salinity

How does WQ interact? • Nitrogen enrichment, then C and P limitation – N stimulates fast zooxanthellae growth leading to nutrient limitation and poor cellular health

Nitrogen

Zoox. growth

Nitrogen+Phosphorus

AIMS: Australia’s tropical marine research agency. Rosset et al. 2017

C+P limitation Nitrogen

Coral bleaching Phosphorus

Carbon enrichment • Sugars released by algae, organically enriched sediments etc • Stimulates growth of nitrogen fixing bacteria Sugar

Bacterial growth

Nitrogen release

No added sugar

Added sugar

Pogoreutz et al. 2017 AIMS: Australia’s tropical marine research agency.

Coral bleaching

Turbidity • Can affect light and variation in light • Can support food-webs that feed corals – Variation in growth and energetics

• Nitrogen-rich particles can lead to

High vs poor quality food

phosphorus limitation

Fabricius et al. 2013


Marine heat waves 2016 and 2017 • Annual maximum ocean heat accumulation • NOAA Degree Heating Weeks • DHW 4 (Bleach) and 8 (Mort). 2016 DHW 2 and 6 (Hughes et al 2017)

2016


2017

AIMS bleaching surveys • ~20 reefs across water quality gradients • Differential bleaching responses

2016 AIMS: Australia’s tropical marine research agency.

2017

Bleaching severity increases with heat stress

Severe bleaching and mortality (%)

Severe Bleaching & Mortality (%)

Accumulated heat exposure (NOAA DHW V3)


Minor Major Severe Mortality

Outstanding questions • Physiological stress and symbiosis in field bleached samples • Nutrient enrichment and stress experiments • Does response depend on native WQ regimes? • Correlations between bleaching level and WQ • WQ corrected thresholds • Further refine eReefs polyp model to predict bleaching AIMS: Australia’s tropical marine research agency.

eReefs model


Mid-shelf Central Great Barrier Reef: September 2017


Thank you [email protected]

Expert assistance from:

Frederieke Kroon, Eric Matson, Veronique Mocellin, Sam Noonan, and many others….


Bleaching scores NO BLEACHING

SEVERE: 95-100%

MINOR: 1 - 50%

RECENT MORTALITY


MAJOR: 50-95%

Particulate feeding (B, Z)

Light absorption by Chl a

Coral host synthesis recycling zooxanthellae Particulate organic matter (Dred) +

Translocation

Dissolved NO3, NH4, PO32-, CO2 , O2 AIMS: Australia’s tropical marine research agency.

pigment

Photon / energy pathways through the model photosystem

pigment synthesis photon absorption

RI

photon absorption Rubisco mediated carbon fixation

Chl a,c2 Per, bCaro

Xp

xanthophyll switching photon absorption

Energy passed to reaction centres in proportion to number and drive state change

produce Qred

Qox

Repair of reduced and inhibited reaction centres

Qred

produce Qin

Xh

Qin produce ROS

heat dissipation

Xanthophyll cycle AIMS: Australia’s tropical marine research agency.

Reaction centre dynamics

ROS

Example oxidative stress and symbiont loss during 2016.

Oxidative stress peaks in early March ~15 % symbiont loss followed by recover.

• Coral photosystem model performing intuitively well in GBR-wide 4 km configuration. • Next steps: use 1 km configuration and compare with field observations, run with pre-industrial catchment loads. AIMS: Australia’s tropical marine research agency.

20

Team 1.2: Overview • 11 Tasks, 1 pending, 1 finalised • Co-investment of 8/11 tasks, 1 pending • Summary of FTE • Summary of resources • Fine tuning of research, business and communication plan underway • New research proposals and targeted stakeholder engagement


Defence activities

Research & education

Traditional use of resources

Marine tourism

Shipping

Recreation (not incl. fishing)

Coastal development

Ports

Fishing (comm. & recreational)

Land-based run-off

Climate change

Impacts of human activities on the Reef

Very high impact High impact Low impact Very low impact

Modified from GBRMPA Outlook Report 2014 http://www.gbrmpa.gov.au/managing-the-reef/great-barrier-reef-outlook-report AIMS: Australia’s tropical marine research agency.

Long-term Reef condition 1985-2012 Cyclones & Storms: 48%

CoTS outbreaks: 42%

Coral bleaching: 10%


De’ath et al. 2012 10.1073/pnas.1208909109

% coral cover

Long-term Reef condition 1985-2017

• • •

The Reef is large- reefs differ between regions and from inshore –offshore Disturbances are mainly regional If left undisturbed damaged reefs recover over years to decades http://www.aims.gov.au/docs/research/monitoring/reef/latest-surveys.html


The oceans are changing (and will continue to do so…)

AIMS: Australia’s tropical marine research agency. Mass bleaching in early 2016
