Introduced macroalgae in Denmark

When, where, how and

which effects?

Peter A. StæhrFreshwaterbiological Laboratory

Biological Institute, Univ. Copenhagen

Some ”basic” questions:

What is a macroalgae?

What characterizes an invasive macroalgae?

Which steps are involved in macroalgal invasions?

What are the likely impacts of an invasion?

Macroalgae?

Macroalgae?

Steneck & Dethier 1994

Invasive macroalgae?

Williams & Smith 2006

Invasive macroalgae?

Williams & Smith 2006

Num

ber

of in

trod

uctio

ns

Macroalgae in Danish waters

Ns = North SeaSk = SkagerrakK = KattegatLf = LimfjordenSa = Northern beltseaSb+Sm = Great beltLb = Little beltSu = OresoundBm+Bb = Baltic sea

Map of diving locations in the Danish marine monitoring program.

From 19892003: 9738 observations with 290 taxa, including 9 invasive

Which macroalgal NIS?

Red(159)

Bonnemaisonia hamifera Dasya baillouviana Gracilaria vermiculophyllaHeterosiphonia japonica= Dasysiphonia sp.

Neosiphonia harveyi

Polysiphonia elongella new!

Red(159)

Brown(126)

Bonnemaisonia hamifera Dasya baillouviana Gracilaria vermiculophyllaHeterosiphonia japonica= Dasysiphonia sp.

Neosiphonia harveyi

Colpomenia peregrina Sargassum muticum Fucus evanescensDictyota dichotoma

Which macroalgal NIS?

Red(159)

Brown(126)

Green(91)

Bonnemaisonia hamifera Dasya baillouviana Gracilaria vermiculophyllaHeterosiphonia japonica= Dasysiphonia sp.

Neosiphonia harveyi

Colpomenia peregrina Sargassum muticum Fucus evanescens

Codium fragile ssp. tomentosiodes / scandiavicum

Dictyota dichotoma

Which macroalgal NIS?

Class Species Origin Transport Year Europe Year DK

RedBonnemaisonia

hamiferaPacifics (Japan) Ship?

1890(England) 1900

RedDasya

baillouviana Mediterranean Ship?/oysters? Natural 1961

RedHeterosiphonia

japonica Pacifics Ship?/oysters?1994

(Holland) 2005

RedNeosiphonia

harveyi

Pacifics / NW Atlantics

Epiphytes?1908

(England?) 1986

RedGracilaria

vermiculophylla Pacifics Ship?/oysters?1935

(Norway?) 2003

BrownColpomenia

peregrina Pacifics Oysters?1905

(France) 1939

BrownFucus

evanescens North Atlantics Ship / natural Natural 1948

BrownSargassum

muticumPacifics(Japan) Oysters?

1960s (France?) 1984

BrownDictyota

dichotomaAtlantic Oysters /

natural? Natural 1939

Green

Codium fragile ssp.

tomentosoidesAtlantics (Japan) Ship/oysters?

1900 ca (Holland)

1919Green

Codium fragile ssp.

scandinavicumAtlantics

(Sibiria, Japan) Ship/oysters?1919

(Denmark)

Where from, how and when?

Where and how much?Regional distribution

Regioner

Ns K+Lf Sa Lb Sb+Sm Su Bw Bm+BbRel

ativ

dæ

knin

g (%

af s

amfu

nd)

0.001

0.01

0.1

1

10

Bonnemaisonia hamiferaCodium fragileColpomenia peregrinaDasya baillouvianaDictyota dichotomaFucus evanescensGracilaria vermiculophyllaNeosiphonia harveyiSargassum muticum

Regions

Re

lativ

e c

ove

r (%

of c

om

mun

ity)

Salty (34 ppm) Fresh (5-10ppm)

Dybdeinterval (m)

0-2

2-4

4-6

6-8

8-10

10-1

2

12-1

4

14-1

6

16-1

8

18-2

0

20-2

2

22-2

4

24-2

6

26-2

8Rel

ativ

dæ

knin

g (%

af s

amfu

nd)

0.001

0.01

0.1

1

10

Bonnemaisonia hamiferaCodium fragileColpomenia peregrinaDasya baillouvianaDictyota dichotomaFucus evanescensGracilaria vermiculophyllaNeosiphonia harveyiSargassum muticum

Re

lativ

e c

ove

r (%

of c

om

mun

ity)

Depth interval (m)

Where and how much?Depth distribution

Årstal

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

Rel

ativ

dæ

knin

g (%

af s

amfu

nd)

0.001

0.01

0.1

1

10

Bonnemaisonia hamiferaCodium fragileColpomenia peregrinaDasya baillouvianaDictyota dichotomaFucus evanescensGracilaria vermiculophyllaNeosiphonia harveyiSargassum muticum

Where and how much?Development in time

Year

Re

lativ

e c

ove

r (%

of c

om

mun

ity)

• 10-12 ”new” species out of 376 total• NIS species amount to 3.75% of total

cover • Most NIS in salty regions• Most at 2-4m (7%) and 20-22m (6%)• No obvious increase during recent years • Gracilaria is expected to spread fast• Lack of knowledge about NIS ecological

impact in Dk more research

Summary on Danish NIS

Donor population

Invasion of new populations

(2) Release and establisment

(1) Uptake, transport

(3) Spread (natural/associated)

(4) Impacts (large)

Invasion phases:

Time

E

ffec

t

1 2 43

Donor region

Recipient region

Physiological

Geographical

Life-history

Biotic resistance

Barriers of invasion:

Sargassum muticum in Denmark

– invasion and ecological effects

• Large (>2m) brown macroalgae (order Fucales)

• Related to Fucus vesiculosus and Halidrys siliquosa

• Floating vesicles

• Broad temperature (10-30 oC) and salinity (18-34 o/oo) tolerance

• Monoecious ~self fertilizing

• High regeneration ability

• Pseudo-perenial life-cycle

Sargassum muticum - phenology

2000?

Invasionhistory

• 60’ies – North America-> Oysters

• Origin – Asia (Japan)

• 70’ies – Europe (English Channel)-> oysters

• 1984 - Denmark-> oysters?-> sekundary spread (drifting)?

??

Ran

g no

.

% of total m

acroalgal cover

Temporal development in community structure

Relative change 1990– 97

Sargassum muticum

Halidrys siliquosa

No clustering

Epibionts on Sargassum (S) and Halidrys (H)

Species richness

Individual density

Biomass

0

500

1000

1500

2000

2500

Uroch

ordata

Crusta

cea

Echin

oder

mata

Moll

usca

Porife

ra

Polych

aeta

Cnidaria

mg

AF

DW

/ 1

00g

FW

alg

ae ±

SE

Sargassum muticum Halidrys siliquosa

Same epifauna but more on Sargassum

Large fluctuation in growth, production and loss

Loss to grazers = 1-2% 99% of production is accumulates as detritus

Even growht, production and loss

Sargassum

Halidrys

Seasonal variation in standing biomass

Fast decomposition

fast release

Impacts of S. muticum in Denmark

• Since the introduction in 1984, Sargassum muticum has become the most common macroalgae in Limfjorden

• The invasion has changed the macroalgal community structure with significant reductions in the cover of other large perennial browalgae

• The invasionen has not changed the epifaunal species composition, but has increased epifaunal abundance and seasonal variation

• The invasionen has resulted in a more unstabil and fluctuating biomass, with faster growth, turnover and nutrient release, similar to systems experiencing eutrophication

Litterature:• Wernberg-Møller, Thomsen & Stæhr (1998). Master thesis, RUC.

• Wernberg-Møller, Thomsen & Stæhr (1998). Urt 22:128-132.

• Stæhr, Pedersen, Thomsen, Wernberg & Krause-Jensen (2000). Mar Ecol-Prog Ser 207:79-88.

• Wernberg, Thomsen, Stæhr & Pedersen (2001). Botanica Marina 44:31-39.

• Wernberg, Thomsen, Stæhr & Pedersen (2004). Helgoland Marine Research 58:154-161.

• Pedersen, Stæhr, Wernberg & Thomsen (2005). Aquatic Botany 83:31-47.

•Thomsen M., Krause-Jensen D., Wernberg T., Stæhr P.A. og Nils Risgaard-Petersen. (2005) Fremmede tangarter i Danmark: Hvilke? Hvor udbredte? Hvornår? Urt 29: 110-115

• Thomsen, Wernberg, Stæhr & Pedersen (2006). Helgoland Marine Research 60:50-58.

•Thomsen MS, Wernberg T, Stæhr PA, Krause-Jensen D, Risgaard-Petersen N, Silliman BR. 2007. Alien macroalgae in Denmark - a national perspective. Marine Biology Research 3: 61-72

Further information (Mads Thomsen website on NIS):

http://cem.ecu.edu.au/coastal-marine/themes/reef-ecology/marine_invaders_bibliography.php