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Introduced macroalgae in Denmark

Introduced macroalgae in Denmark. Peter A. Stæhr Freshwaterbiological Laboratory Biological Institute, Univ. Copenhagen. When, where, how and which effects?. Some ”basic” questions:. What is a macroalgae? What characterizes an invasive macroalgae?

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Introduced macroalgae in Denmark

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  1. Introduced macroalgae in Denmark Peter A. Stæhr Freshwaterbiological Laboratory Biological Institute, Univ. Copenhagen When, where, how and which effects?

  2. 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?

  3. Macroalgae?

  4. Macroalgae? Steneck & Dethier 1994

  5. Invasive macroalgae? Williams & Smith 2006

  6. Invasive macroalgae? Number of introductions Williams & Smith 2006

  7. Macroalgae in Danish waters Ns = North Sea Sk = Skagerrak K = Kattegat Lf = Limfjorden Sa = Northern beltsea Sb+Sm = Great belt Lb = Little belt Su = Oresound Bm+Bb = Baltic sea Map of diving locations in the Danish marine monitoring program. From 19892003: 9738 observations with 290 taxa, including 9 invasive

  8. Which macroalgal NIS? Red (159) Heterosiphonia japonica = Dasysiphonia sp. Bonnemaisonia hamifera Dasya baillouviana Gracilaria vermiculophylla Neosiphonia harveyi Polysiphonia elongella new!

  9. Which macroalgal NIS? Red (159) Heterosiphonia japonica = Dasysiphonia sp. Bonnemaisonia hamifera Dasya baillouviana Gracilaria vermiculophylla Neosiphonia harveyi Brown (126) Colpomenia peregrina Sargassum muticum Fucus evanescens Dictyota dichotoma

  10. Which macroalgal NIS? Red (159) Heterosiphonia japonica = Dasysiphonia sp. Bonnemaisonia hamifera Dasya baillouviana Gracilaria vermiculophylla Neosiphonia harveyi Brown (126) Colpomenia peregrina Sargassum muticum Fucus evanescens Dictyota dichotoma Green (91) Codium fragile ssp. tomentosiodes / scandiavicum

  11. Where from, how and when?

  12. Where and how much?Regional distribution Relative cover (% of community) Regions Salty (34 ppm) Fresh (5-10ppm)

  13. Where and how much?Depth distribution Relative cover (% of community) Depth interval (m)

  14. Where and how much?Development in time Relative cover (% of community) Year

  15. Summary on Danish NIS • 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

  16. Effect 4 1 2 3 Time Invasion phases: Donor population (1) Uptake, transport (2) Release and establisment (3) Spread (natural/associated) (4) Impacts (large) Invasion of new populations

  17. Barriers of invasion: Donor region Geographical Physiological Life-history Biotic resistance Recipient region

  18. Sargassum muticum in Denmark – invasion and ecological effects

  19. Sargassum muticum - phenology • 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

  20. Invasion history ? ? • Origin – Asia (Japan) • 60’ies – North America • -> Oysters • 70’ies – Europe • (English Channel) • -> oysters • 1984 - Denmark • -> oysters? • -> sekundary spread • (drifting)? 2000?

  21. Rang no. % of total macroalgal cover

  22. Temporal development in community structure Relative change 1990– 97

  23. Sargassum muticum Halidrys siliquosa

  24. Epibionts on Sargassum (S) and Halidrys (H) No clustering

  25. Species richness Individual density Biomass

  26. Same epifauna but more on Sargassum

  27. Seasonal variation in standing biomass Sargassum Large fluctuation in growth, production and loss Loss to grazers = 1-2%  99% of production is accumulates as detritus Halidrys Even growht, production and loss

  28. Fast decomposition  fast release

  29. 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 Impacts of S. muticum in Denmark

  30. 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

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