Marine Biology

, Volume 156, Issue 5, pp 969–981 | Cite as

The role of the amphipod Gammarus locusta as a grazer on macroalgae in Swedish seagrass meadows

  • Sandra Andersson
  • Malin Persson
  • Per-Olav Moksnes
  • Susanne BadenEmail author
Original Paper


Mesograzers are thought to play a critical role in seagrass beds by preventing overgrowth of ephemeral algae. On the Swedish west coast, eelgrass Zostera marina has decreased in recent decades as a result of eutrophication and increased growth of macroalgal mats (mainly filamentous Ulva spp. and Ectocarpales), with no indication of grazer control of the algae. The aim of this study was to investigate the ability of the amphipod Gammarus locusta to control algal blooms during nutrient-enriched and ambient conditions, using a combination of laboratory, field and model studies. Laboratory experiments demonstrated that juvenile and adult G. locusta could consume both Ulva spp. and Ectocarpales, but that consumption of Ulva spp. was significantly higher. Cannibalism was common in individual treatments involving multiple size-classes of G. locusta, but only large, male gammarids consumed smaller juveniles in the presence of Ulva spp. as an alternative food source. However, no negative effects of cannibalism were found on total grazing impact. A model using size-specific grazing rates and growth rates of G. locusta and of Ulva spp. suggests that approximately 62 young juvenile, or 27 adult G. locusta are needed per gram DW of Ulva spp. to control the algal growth during ambient nutrient conditions, and approximately 2.6 times as many gammarids during enhanced nutrient conditions. On the Swedish west coast, densities and mean sizes of G. locusta in eelgrass beds are below these critical values, suggesting that the gammarids will not be able to control the growth of the filamentous macroalgae. However, in the field cage experiment, immigration of juveniles and reproduction of encaged adult G. locusta resulted in unexpectedly high densities of G. locusta (>4,000 individual m−2), and very low biomass of Ulva spp. in both ambient and nutrient-enriched treatments. Although the high numbers of juveniles in all cages precluded any significant treatment effects, this suggests that in the absent of predators, the population of G. locusta can grow significantly and control the biomass of Ulva spp. Furthermore, low grazing of Ectocarpales in the laboratory and high biomass of these filamentous brown algae in the field indicate a preference for the more palatable green algae Ulva spp. This study indicates that the high grazing capacity of G. locusta, in combination with high reproduction and growth rates, would allow the amphipod to play a key role in Z. marina ecosystems by controlling destructive blooms of filamentous green algae. However, high predation pressure appears to prevent large populations of G. locusta in eelgrass beds on the Swedish west coast today.


Ulva Filamentous Alga Predator Treatment Swedish West Coast Macroalgal Bloom 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



We thank Carl Johan Svensson for helpful comments on the modelling part of the study, Kentaroo Tryman and Maj Persson for laboratory assistance and William Thorndyke for English language correction. This research was funded by grants from the Swedish Environmental protection Agency (SEPA contract no. 1-55-03 to S. Baden and 1-58-03 to P-O. Moksnes) within the national project Marine Biodiversity Patterns and Processes (MARBIPP), and from The Swedish Research Council for the Environment, Agricultural Sciences and Spatial Planning (FORMAS contract no. 21.5/2003-0213 to S. Baden). Funds were also provided from “Wåhlströms minnesfond för den Bohusländska havs- och insjömiljön”, and from the University of Gothenburg Marine Research Centre which are gratefully acknowledged.


  1. Baden SP, Boström C (2001) The leaf canopy of seagrass beds: faunal community structure and function in a salinity gradient along the Swedish coast. Ecol Stud 151:213–236CrossRefGoogle Scholar
  2. Baden S, Pihl L (1984) Abundance, biomass and production of mobile epibenthic fauna in Zostera marina (1) meadows, western Sweden. Ophelia 23(1):65–90CrossRefGoogle Scholar
  3. Baden S, Gullström M, Lundén B, Pihl L, Rosenberg R (2003) Vanishing seagrass (Zostera marina, L.) in Swedish coastal waters. Ambio 32(5):374–377. doi:[0374:VSZMLI]2.0.CO;2 CrossRefGoogle Scholar
  4. Boström C, Baden S, Krause-Jensen D (2003) The seagrass of Scandinavia and the Baltic Sea. In: Green EP, Short FT (eds) World atlas of seagrasses. University of California Press, Berkeley, pp 27–37Google Scholar
  5. Christie H, Kraufvelin P (2004) Mechanisms regulating amphipod population density within macroalgal communities with low predator impact. Sci Mar 68:189–198. doi: CrossRefGoogle Scholar
  6. Costanza R, d’Arge R, de Groot R, Farber S, Grasso M, Hannon B, Naeem S, Limburg K, Paruelo J, O’Neill RV, Raskin R, Sutton P, van den Belt M (1997) The value of the world’s ecosystem services and natural capital. Nature 387:253–260. doi: CrossRefGoogle Scholar
  7. Cruz-Rivera E, Hay ME (2000a) Can quantity replace quality? Food choice, compensatory feeding, and fitness of marine mesograzers. Ecology 81:201–219CrossRefGoogle Scholar
  8. Cruz-Rivera E, Hay ME (2000b) The effects of diet mixing on consumer fitness: macroalgae, epiphytes, and animal matter as food for marine amphipods. Oecologia 123:252–264. doi: CrossRefGoogle Scholar
  9. Duarte CM, Fourqurean JW, Krause-Jensen D, Olesen B (2006) Dynamics of seagrass stability and change. In: Larkum AWD, Orth RJ, Duarte CM (eds) Seagrasses: biology, ecology and conservation. Springer, Berlin, pp 271–294Google Scholar
  10. Duffy JE, Harvilicz AM (2001) Species-specific impacts of grazing amphipods in an eelgrass-bed community. Mar Ecol Prog Ser 223:201–211. doi: CrossRefGoogle Scholar
  11. Duffy JE, Hay ME (2000) Strong impacts of grazing amphipods on the organization of a benthic community. Ecol Monogr 70:237–263CrossRefGoogle Scholar
  12. Edgar GJ (1990) The use of size structure of benthic macrofaunal communities to estimate faunal biomass and secondary production. J Mar Biol Ecol 137:195–214. doi: CrossRefGoogle Scholar
  13. Edgar GJ (1993) Measurement of the carrying capacity of benthic habitats using a metabolic-rate based index. Oecologia 95:115–121CrossRefGoogle Scholar
  14. Edgar GJ, Klumpp DW (2003) Consistencies over regional scales in assemblages of mobile epifauna associated with natural and artificial plants of different shape. Aquat Bot 75:275–291. doi: CrossRefGoogle Scholar
  15. Eriksson BK, Johansson G, Snoeijs P (2002) Long-term changes in the macroalgal vegetation of the inner Gullmar fjord, Swedish Skagerrak coast. J Phycol 38:284–296. doi: CrossRefGoogle Scholar
  16. Fredriksen S, Christie H, Sæthre BA (2005) Species richness in macroalgae and macrofauna assemlages on Fucus serratus L. (Phaeophyceae) and Zostera marina L. (Angiospermae) in Skagerrak, Norway. Mar Biol Res 1:2–19. doi: CrossRefGoogle Scholar
  17. Fromentin J-M, Gjøsæter J, Bjørnstad ON, Stenseth NC (2000) Biological processes and environmental factors regulating the dynamics of the Norwegian Skagerrak cod populations since 1919. J Mar Sci 57:330–338Google Scholar
  18. Green EP, Short FT (2003) World atlas of seagrasses. University of California Press, BerkeleyGoogle Scholar
  19. Hauxwell J, Cebriàn J, Furlong C, Valiela I (2001) Macroalgal canopies contribute to eelgrass (Zostera marina) decline in temperate estuarine ecosystems. Ecology 82(4):1007–1022CrossRefGoogle Scholar
  20. Hay ML, Fenical W (1988) Marine plant-herbivore interactions: The ecology of chemical defence. Annu Rev Ecol Syst 19:111–145. doi: CrossRefGoogle Scholar
  21. Holmer M, Bondgaard EJ (2001) Photosynthetic and growth response of eelgrass to low oxygen and high sulfide concentrations during hypoxic events. Aquat Bot 70:29–38. doi: CrossRefGoogle Scholar
  22. Hughes AR, Bando KJ, Rodriguez LF, Williams SL (2004) Relative effects of grazers and nutrients on seagrasses: a meta-analysis approach. Mar Ecol Prog Ser 282:87–99. doi: CrossRefGoogle Scholar
  23. Jephson T, Nyström P, Moksnes P-O, Baden S (2008) Trophic interactions within Zostera marina beds along the Swedish coast. Mar Ecol Prog Ser 369:63–76. doi: CrossRefGoogle Scholar
  24. Jernakoff P, Brearley A, Nielsen J (1996) Factors affecting grazer-epiphyte interactions in temperate seagrass meadows. Oceanogr Mar Biol Annu Rev 34:109–162Google Scholar
  25. Kraufvelin P, Salvoius S, Christie H, Moy F, Karez R, Pedersen M (2006) Eutrophication-induced changes in benthic algae affect the behaviour and fitness of the marine amphipod Gammarus locusta. Aquat Bot 84:199–209. doi: CrossRefGoogle Scholar
  26. Lamare MD, Wing SR (2001) Caloric content of New Zealand marine macrophytes. N Z J Mar Freshw Res 35:335–341CrossRefGoogle Scholar
  27. Lotze HK, Schramm W, Schories D, Worm B (1999) Control of macroalgal blooms at early developmental stages: Pilayella littoralis versus Enteromorpha spp. Oecologia 119:46–54CrossRefGoogle Scholar
  28. Lotze HK, Worm B (2000) Variable and complementary effects of herbivores on different life stages of bloom-forming macroalgae. Mar Ecol Prog Ser 200:167–175. doi: CrossRefGoogle Scholar
  29. Lotze HK, Worm B, Sommer U (2000) Propagule banks, herbivory and nutrients supply control population development and dominance patterns in macroalgal blooms. Oikos 89:46–58. doi: CrossRefGoogle Scholar
  30. Lotze HK, Worm B, Sommer U (2001) Strong bottom-up and top-down control of early life stages of macroalgae. Limnol Oceanogr 46:749–757CrossRefGoogle Scholar
  31. MacNeil C, Dick JTA, Elwood RW (1999) The dynamics of predation on Gammarus spp. (Crustacea: Amphipoda). Biol Rev Camb Philos Soc 74:375–395. doi: CrossRefGoogle Scholar
  32. McGlathery KJ (1995) Nutrient and grazing influences on a subtropical seagrass community. Mar Ecol Prog Ser 122:239–252. doi: CrossRefGoogle Scholar
  33. Moksnes P-O, Gullström M, Tryman K, Baden S (2008) Bottom-up and top-down control of epiphytes and grazers in Zostera marina communities in Sweden. Oikos 117:763–777. doi: CrossRefGoogle Scholar
  34. Oldevig H (1933) Sveriges amphipoder (The Swedish amphipods). Göteborgs Kungl. Vetenskaps Vitterhets-Samhälles Handlingar Ser B 3(4). Elanders, GothenburgGoogle Scholar
  35. Orth RJ, Carruthers TJB, Dennison WC, Duarte CM, Fourqurean JW, Heck KL, Hughes AR Jr, Kendrick GA, Kenworthy WJ, Olyarnik S, Short FT, Waycott M, Williams SL (2006) A global crisis for seagrass ecosystems. Bioscience 56(12):987–996. doi:[987:AGCFSE]2.0.CO;2 CrossRefGoogle Scholar
  36. Persson M, Andersson S, Baden S, Moksnes P-O (2008) Trophic role of the omnivorous grass shrimp Palaemon elegans (Rathke) in a Swedish eelgrass system. Mar Ecol Prog Ser 371:203–212. doi: CrossRefGoogle Scholar
  37. Pihl L, Svensson A, Moksnes P-O, Wennhage H (1999) Distribution of green algal mats throughout shallow soft bottoms of the Swedish Skagerrak archipelago in relation to nutrient sources and wave exposure. J Sea Res 41:281–294. doi: CrossRefGoogle Scholar
  38. Pihl L, Baden S, Kautsky N, Rönnbäck P, Söderqvist T, Troell M, Wennhage H (2006) Shift in fish assemblage structure due to loss of seagrass Zostera marina habitats in Sweden. Estuar Coast Shelf Sci 67:123–132. doi: CrossRefGoogle Scholar
  39. Rumohr H, Brey T, Ankar S (1987) A compilation of biometric conversion factors for benthic invertebrates of the Baltic Sea. Baltic Mar Biologists 9:56Google Scholar
  40. Short FT, Wyllie-Echeverria S (1996) Natural and human-induced disturbance of seagrasses. Environ Conserv 23:17–27CrossRefGoogle Scholar
  41. Sokal RR, Rohlf FJ (1981) Biometry. WH Freeman, New YorkGoogle Scholar
  42. Underwood AJ (1981) Techniques of analysis of variance in experimental marine biology and ecology. Oceanogr Mar Biol Annu Rev 19:513–605Google Scholar
  43. Valentine J, Duffy JE (2006) The central role of grazing in seagrass ecology. In: Larkum AWD, Orth RJ, Duarte CM (eds) Seagrasses: biology, ecology and conservation. Springer, Berlin, pp 463–501Google Scholar
  44. Valiela I, McClelland J, Hauxwell J, Behr PJ, Hersh D, Foreman K (1997) Macroalgal blooms in shallow estuaries: controls and ecophysiological and ecosystem consequences. Limnol Oceanogr 42:1105–1118CrossRefGoogle Scholar
  45. Worm B, Lotze HK, Sommer U (2000) Coastal food web structure, carbon storage, and nitrogen retention regulated by consumer pressure and nutrient loading. Limnol Oceanogr 45:339–349CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Sandra Andersson
    • 1
  • Malin Persson
    • 2
  • Per-Olav Moksnes
    • 2
  • Susanne Baden
    • 1
    Email author
  1. 1.Department of Marine EcologyUniversity of Gothenburg-KristinebergFiskebäckskilSweden
  2. 2.Department of Marine EcologyUniversity of GothenburgGöteburgSweden

Personalised recommendations