2nd Climate Change Effects Symposium (Yeosu, 2012)

Jellyfish blooms as consequences of human perturbed environmental and ecosystems

Shin-ichi Uye (Hiroshima University, Japan)

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Bohai Sea Japan Sea

Yellow Sea

East China Area: 0.8 % of theSea total marinePacific area Ocean Fish catch: 11% of the world marine fish catch Human population: ca. 800 million Environmental hot spot: global warming, , harmful algal bloom, photochemical smog, yellow dust, bloom Recent jellyfish blooms in EAMS

© Asahi Shimbun Bloom of Aurelia aurita in coastal Bloom of Nemopilema nomurai over waters around EAMS entire EAMS

Increase in Aurelia aurita medusae in the Inland Sea of Japan (Seto Inland Sea)

Inland Sea of Japan

No data Pool of fishermen in 2002 No scientific Total respondents: 1,152 Experience: >20 years proof Question: “Did Aurelia aurita medusae increase in the last 20 years?” Respondents: 35%: “No, current medusa population level is the same as before 1982” 65%: “Yes, particularly in the last 10 years”

100

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e d

40

on

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0 <1982 1983-1987 1988-1992 1993-1997 1998-2002 Life cycle of Aurelia aurita Planula Planktonic Medusa stage Bethic (Spawning) stage Podocyst

Polyp

M & F colony Metephyra (Ecsystment)

(Repro- (Budding, duction) etc.)

Ephyra Strobila

(Strobilation) Effect of temperature and food supply on polyp reproduction rate Duration: 35 days Temperature ion cat phi tro Eu g in rm a W

Food supply Polyp’s main food: Microzooplankton

） 0.5 0.45 0.4 0.35 Favella spp. gC/ind/h) µg C/ind/h 0.3 ESD=55 m, 46 m

μ μ μ （ 0.25 0.2 0.15 Favella 0.1 Strombidinium Feeding rate ( Myrionecta 0.05 Curve fit

Ingestion rate Ingestion rate Strombidium sp. 0 ESD=38 m 0 500 1000 1500 μ FoodCiliate supply biomass （(μµggC/L) C/L） （fromT. Kamiyama) Microzooplankton increase: Eutrophication Myrionecta rubra Change in nutrient (N, P, Si) composition ESD=21 μm Dominance of microbial food chain

Polyp’s habitat: Artificial structures Polyps Ephyrae

48 m

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Installed on 9 April, 2010 20 Polyp density Strobilation (polyps cm-2) (% of polyps) 15 20 million ephyrae 10 released

5

0 JJASONDJFMAM 2010 2011 Ecosystem change in the Inland Sea of Japan Jellyfish-donimated Fish-donimated ecosystem ecosystem Warming QuickTimeý Dz TIFFÅiàèkǻǵÅj êLí£ÉvÉçÉOÉâÉÄ N/P ratio ǙDZÇÃÉsÉNÉ`ÉÉǾå©ÇÈǞǽDžÇÕïKóvÇ-ÇÅB

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Marine construction

50 Fish-donimated Jellyfish-donimated

tons) 40 4

30

20

10

Fish catch (x10 Fish catch 0 1960 1970 1980 1990 2000 2010 Transport of Nemopilema to Japanese waters

September

October

August

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November

CLSWM a C

m

hi s June u Ts BloomBloom ofof NemopilemaNemopilema inin thethe JapanJapan SeaSea 2002 05 07

1900 1920 19501958 1995 03 06 09 Causes: Environmental and ecosystem changes in Chinese coastal waters Global warming Eutrophication （1.7oC/25 years） (In Changjian Si river water）

Medusa

Ephyra DIP (Lin et al., 2005)

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100 Polyp 年間漁獲量（千トン） 50 Annual fish catch (10 fish Annual 0 Podocyst 1970 1975 1980 1985 1990 1995 2000 2005

Marine construction (Wang, 2006) Ecosystem shift in Jellyfish dominated Chinese costal waters ecosystem Human forcing 1) global warming 2) eutrophication 3) overfishing 4) marine Jellyfish construction 5) others spiral Fish dominated ecosystem Favorable conditions conducive to recurrent jellyfish blooms have already prevailed in Chinese coastal waters Annual fish catch (x104 tons) Recurrent 10 15 20 10 15 20 0 5 0 5

1969 1971 1973 Nemopilama bloomsvsfishstocks 1975 1977 1979 1981 1983 1985 1987 1989 1991 Japan Sea East Chine Sea 1993 1995

1997 Bloom years 1999 2001 2003 2005 2007 2009 Environmental factors cannot explain year-to-year difference in the occurrence of Nemopilema

No bloom in Bloom in 2009 2008 (as of Oct. 29) (2010, 2011) Podocyst production and excystment Colonized polyps and podocysts Podocysts

Dormant for at QuickTimeý Dz ÉtÉHÉg - JPEG êLí£ÉvÉçÉOÉâÉÄ Ç™Ç±ÇÃÉsÉNÉ`ÉÉǾå©ÇÈÇ…ÇÕïKóvÇ-ÇÅB least 5.5 years

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Excystment Polyp walks!

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4 months old

5 years old

Even after dormancy of 5 years, no significant change occurred in the structure and nutrient reserves of podocysts Induction of podocyst excystment Temperature (oC) Salinity Excystment (%) for 80 days 31 33 39 High temp. 27 33 55 23 33 4 19 (control) 33 1 15-5 33 0

19 24 7 19 16 20 Low salinities 19 8 19

19 () 33 13 Deoxygenation 19 (in mud) 33 25

Excystment is induced when the podocysts are exposed to some extreme environmental conditions

HypotheticalHypothetical schemescheme toto causecause NemopilemaNemopilema toto bloombloom oror nonnon--bloombloom Non‐bloom year Bloom year

MassiveMassive bloombloom

Spawning

Ephyra Ephyra release release

Strobiration Strobiration

Asexual reproduction Mass Excystment Low salinity Podocyst accumulation Hypoxia Forecast of Nemopilema bloom intensity by ferry-on-deck sighting survey

Tianjin

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Qingdao

Shimonoseki

Taicang

Shanghai Ferry survey during 6-10 June, 2009 Ferry survey during 4-8 July, 2009 Simulated transport process of Nemopilema in the Japan Sea Assumptions and conditions for the model 1) Initial position: Three (A, B and C) zones in the Tsushima Strait 2) Start of particle release: 25 June in A (blue), 30 June in B (green), 7 July in C (red) 3) Stop of particle release: 13 July 4) Calculation period: from 25 June to 15 September 5) Vertical movement: diel vertical migration

A Tsushima B Strait C

(from Watanabe et al.) Abundance and biomass of Nemopilema in July, 2009 In July In the Yellow and East China Seas Total abundance: 23 billion medusae Average wet weight：1.8 kg Total biomass：41.3 million ton WW

Yellow Sea

Avg density： 68,700 km-2 13 billion medusae Avg density： 38,100 km-2 East China Sea Abundance and biomass of Nemopilema in September, 2009 In September

Japan Sea

Avg density： 25,000 km-2 (219 mg C m-2)

In the Japan Sea Total abundance: 13 billion medusae Average wet weight：15.9 kg Total biomass：20.8 million ton WW Fish catch in 2009: 0.42 million ton WW Annual change in average density of Nemopilema medusae in the Yellow Sea in July

?

Bloom years Warning

Non-bloom years

2012 Conclusion 1) Former productive and fish-dominated ecosystem in East Asian Marginal Seas may have sifted to jellyfish-dominated one, largely by human-induced perturbation in the region. 2) In the giant jellyfish blooms, which show a remarkable year-to-year difference in the intensity, some biological factors (e.g. podocyst dormancy and excystment) may also be important. 3) The year-to-year bloom intensity of the giant jellyfish can be forecasted by ferry sighting survey in early summer. These forecasts enable fishermen to prepare well in advance for possible jellyfish attacks. 4) Fishermen need modifications of fishing nets to cope with current jellyfish-dominated seas.