Picture: Tokashiki, Kerama Islands, Okinawa Japan

What can we do to conserve Coral Reefs under the threats

of global/local stresses?

150th Ocean Forum Mar 16 2018

Takashi NakamuraUniv. of the Ryukyustakasuke@sci.u-ryukyu.ac.jp

Coral Biology & Ecology

Coral colony

Coral branch

Plant or Animal ?

Coral reef

Polyp

Close up View

T. Kamiki 1001-3. The Coral –algal symbiosis

Photosynthetic algae

‘Zooxanthellae’1~3 million/㎠ tissue surface

Symbiosis

Amino acid, lipid, O2

Photosynthesis

Coral

CO2, NH4 +

Algae

Symbiosis w/ algae ~ A strategy to survive

1-4. The Coral –algal symbiosis

‘Zooxanthellae’

‘Coral’

provides up to 90 % of host energy requirements(Muscatine 1967, etc.)

Colonies to reef = habitats for others

Leaf-likeEncrusting

short-branching

Free living

Tabulate

BranchingMassive

1-5. Coral colonies and reef structure

Why corals are important?

2-1. The importance of coral reefs

of worlds’ coast lineof fish speciesof total fisheries catch

1/6

1/4

1/10

Where coral reefs are located?

UNEP (2006)

2-2. World map of Coral reefs

Ecological aspectsQ: Coral reef ~ less than ?% of the Ocean

Shelter / Reproduction / Nursery siteFood source

More than 25%Of Marine fish species

Spalding et. al. (2001)

Home to an estimated 2 million species in < 2% of the Ocean2-3. The importance of coral reefs I

Source: WRI, Reefs at risk revisited, 2011

Climate change as the threat to corals

“Coral bleaching”Greatest threat to coral reef ecosystem

induced by environmental stresses

Increase in Sea surface temperature “SST”

SSTs in the Pacific, Atlantic and Indian Ocean

Highest in the last 40,0000 years Hughes (2003)

Increased 0.4～0.7℃ in the last century

Trend in the Pacific Ocean

http://www.data.kishou.go.jp/kaiyou/db

Year by year difference 5 years average Long-term trend

Annu

al S

ST d

iffer

ence

(℃)

Year

Corals growing in a shallow reef area

NOW,What’s wrong with this picture?

Photograph by Loya Y .

Nearly dead coralsdue to environmental stress

Coral reefs are in trouble!!

3-1A. The definition of “Bleaching”

Bleaching as worldwide wake-up callReef Manager’s Guide to Coral Bleaching (2006)

3-3B. Impact of “Bleaching”

First world wide mass-scale bleaching events occurred in 1998 with strong El nino.

1998

Environmental stress induces “Bleaching”

Strong light Brown et al. (1994)

High water temperatureHoegh-Guldberg & Smith (1998)

Growth inhibition

MortalityCorals are

Highly sensitive toenvironmental change

Coral “Bleaching”3-2A. The causes of “Bleaching”

zooxanthellaeCoral Polyp

Baker et al. (2008) Estuarine, Coastal and Shelf Sciences

Documented bleaching events and regions

Mass scale Coral Bleaching:Timeline

Phuket, Thai June 2010

2010: Mass scale Bleaching in “Coral triangle (from Indian Ocean to Philippines)”; The worst case since 1998 (CNN Oct.21)

2014-2017 Mass bleaching events

2014: Guam ~ Northern Marianas, Marshalls, Florida keys

2015: PNG, Fiji, Samoa, Maldives, Indonesia, Caribbean, Panama, Kiribati, Hawaii

2016: French Polynesia, New Caledonia, Fiji, GBR, Japan

2017: Indian Ocean, Kenya, Florida keys

“The worst case” mass bleaching (Source: NOAA bleaching watch 2016)

Bleaching as worldwide threatReef Manager’s Guide to Coral Bleaching (2006)

3-3B. Impact of “Bleaching”

The incidence and severity of mass coral bleaching events has increased continuously over the last two decades.

1998

Bleaching as worldwide threat

3-3B. Impact of “Bleaching”

The incidence and severity of mass coral bleaching events has increased continuously over the last two decades.

Reef Manager’s Guide to Coral Bleaching (2006)

2006

Bleaching as worldwide threat

The incidence and severity of mass coral bleaching events has increased continuously over the last two decades.

Reef Manager’s Guide to Coral Bleaching (2006) and isolated reports from 2018 to 2017

2017

2014: Guam ~ Northern Marianas, Marshalls, Florida keys

2015: PNG, Fiji, Samoa, Maldives, Indonesia, Caribbean, Panama, Kiribati, Hawaii

2016: French Polynesia, New Caledonia, Fiji, GBR, Japan

2017: Indian Ocean, Kenya, Florida keys

2014-2017 Mass bleaching events

Sekisei lagoon, Okinawa Japan

Yaeyama IslandsPopulation: 54,000, Area: 592 km2

Example from Okinawa mass bleaching 2016 (Sekisei lagoon)

>95% bleached at 35 sites for 10 species out of 11 sampled.

>80% mortality in mid Oct.*Worst bleaching impactrecord since 1998

Example: Tabular coral 98.4% bleached Acropora hyacinthus

Tokyo Kyuei ©

Non-bleached

Early bleaching

Half bleached

Fully bleached

Dead

Diving site “Milky Way”in Sekisei lagoon

Sept.11, 2015

Sept.6, 2016

May 6, 2017

This year… survey on these damaged reefs

Fecundity of survived colonies:Recruitment density on natural substrate:

<20 % of 2016…

Recovery potentials of Sekisei coral community are severely impaired

Increasing trend of coral bleaching events is recognized as “clear and present problem” due to climate change

Other than climate change…

Impacts of Bleaching can be minimized by reducing locally induced stresses such as sedimentation, land reclamation, over harvesting, sewage/pollution etc.

However, we still have no sufficient way to reverse the climate change trends and it’s impact to reefs yet.

Local threats:Lower resilience

Post-bleaching- Algae increased in Sekisei lagoonLive coral cover (%) Turf algae cover (%) Macro algae (%)

*** *** N/S

Live coral cover (%)

Turf algae cover (%)

Kojima 2018 MSc. thesis

Most corals can’t compete with them especially in nutrient-rich environment

Macro/micro algae dominationinhibits coral recovery

How long will it last?

Yoron IslandKagoshima PrefecturePopulation: 5,400Area: 20 km2

20 years after 1998 Mass bleaching event

Kyuden

TerasakiTerasaki-kurohana inner

Minata

Minata inner

Akasaki Coral heads

AkasakiKyanion

Tomori

Pricia

Sea-man’s inner

Sea-man’s

Ohganeku coast

Sites (14 total)

Fu-sha East

Outer reef: High coral cover in 2016 CoralsSoft corals

Macro algae

Turf algae

Lime stone

Sand

K. Kojima （Msc. Thesis）

1960’s

1980’s

Inner reef: very low coral cover

CoralsSoft corals

Macro algae

Turf algae

Lime stone

Sand

K. Kojima （Msc. Thesis）

1980’s (Photo: Kiyomi Kaneko)

2017(Photo: Kana Kojima)

20 years without recovery

Why ??

Not much hope for lagoon

Density of coral recruits (juveniles) as “indicator for coral community recovery”

1 year old Acroporid recruitment

・Density per a Quadrat (1 m x 1 m x 10 ／site)

1 year old colony on settlement tile

12.3㎜ in diameter

Acroporid recruitment density at each site（1 year +2 years）

Too low to recover !!

Outer reefs （9 sites） Inner reefs （5 sites）

Not much hope for inner reefs…

What we should worry?

“What we might overlooked in the field?”

Fertilizer for sugarcane fieldRaw sewage of stock raising

Porous limestone substrate ⇒ Sub-ground water seeps into lagoon

Chronic input of: Nitrogen & Phosphate to semi-enclosed lagoon system

Geo-social characteristics of Yoron Is.

Major industry: Agriculture/farming, tourism and fisheries.

Nutrient rich treatments Lower settlement & survival of coral babies

n=60

10

20

30

40

50

Settl

emen

t & su

rviv

al(%

)

Exposure to combined （N）

and（P）

Treatment

Exposure to （N）and（P）

separately

Kojima 2018 MSc. thesis

How larvae settlement & survival suppressed?

Normal polyp (in control seawater)500 µm

500 µm

Kojima 2018 MSc. thesis

NASA GISS: Global temp anomaly report 2016

We know temperature will continue to rise

World temperature deviation in Sept. (baseline: 1951-1980)

Tem

pera

ture

dev

iatio

n

Global warming…

Possible solutions ?

Possible solutions ?

Looking for tolerant/robust colonies (host coral/zooxanthellae)

“Super-coral” projects (US, Australia, Japan etc.)

Transplantation to natural coral reefs

to form robust community

Limited species, locations…

Permeable substrate (carbonate limestone)

Corals

Thermalexchangers

Underground water (cooler saltwater) conditioning Project

Impermeable layer

PermeableFormation(Limestone)

Heat PumpUnderground

seawater (cooler !!)

Possible solutions ?Geo-engineering approach

Corals Corals

What we can do? Local stress reduction is importantClimate change impacts are likely amplified by local stresses

Soil erosion and sedimentation

Chemical pollutionFertilizers, Herbicides,

Detergents etc.

Overexploitation of herbivorous species

In case of “Coral reef Islands” conservation,

1. Realize the uniqueness & history of each island/reefs (local)

2. Understand the current status (global and local)3. Recognize problems (global and local)4. Share information & solutions by networking5. Cooperate to tackle these problems together

Acknowledgements:

Part of these studies have been supported by Japanese Ministry of Environment, JSPS Research fund “Kakenhi A” (leader: S. Harii ) and “Kakenhi B (leader:T. Shinbo) and Collaborative research supported by JST/JICA SATREPS (leader: T. Nakamura).

Thank you

Thank you for your attention

1960 in Kitakyushu 2010

Importance of environment was realized during the 1960s’ due to severe pollution–related health disasters

In 1960’s

Source: Kitakyushu city office

Human disturbances to coastal ecosystems in mainland Japan