Robustness in life history of the brown seaweed Ascophyllum nodosum (Fucales, Phaeophyceae) across large scales: effects of spatially and temporally induced variability on population growth
- 244 Downloads
Understanding the demography and function of biotope-forming seaweed species is of great importance for the conservation of the target species itself, as well as its associated organisms. The brown seaweed Ascophyllum nodosum is fundamental for the functioning of coastal marine ecosystems in the North Atlantic. In this study, we use a data-based size-classified matrix model to investigate the temporal and spatial variability in demography, and the environment-specific stochastic sensitivity and elasticity, of two A. nodosum populations, one in western Sweden and one on the Isle of Man in the Irish Sea. A significant difference between the two populations was that the Swedish population had comparably low and more variable stochastic population growth rate (λs). This pattern was partly explained by the relatively high and varying mortality rates during extreme ice-years in Sweden, and by the lower survival of small individuals during all years. There were also fewer large individuals in Sweden due to lower transitions to the larger size-classes and higher probability of shrinkage. Sensitivities were analogous in the two populations, and showed a high selection pressure for increased individual growth. Elasticities were also similar, with the exception that survival of the smallest individuals (i.e., transition a1,1), had a higher elasticity on the Isle of Man. Overall, the stochastic growth rate (λs) was most sensitive to proportional changes in loop- (i.e., survival within size-class) and, to some extent, growth-transitions in both study areas. These results show that structurally and demographically diverging A. nodosum populations may be similarly sensitive to changes in vital rates. This, in turn, indicates a plastic life history of A. nodosum that may cope with large environmental variability. The results further suggest that environmental change affecting the survival or growth of the larger, reproductive A. nodosum individuals could have severe and regional effects on the abundance and biomass of this species, with potential negative effects on the biodiversity of the associated communities.
KeywordsVital Rate Primary Shoot Ascophyllum Nodosum Swedish West Coast Stochastic Sensitivity
We are grateful to the staff and students at Port Erin Marine Laboratory and Tjärnö Marine Biological Laboratory for their help and hospitality. This study was supported by the Swedish Natural Science Research Council through contract B-BU 9949-302, by the Swedish Research Council through contract 621-2007-5779, by Formas through contract 21.0/2004-0550, and by the Swedish Environmental Protection Agency through the project MARBIPP (Marine Biodiversity Patterns and Processes). MARICE (an interdisciplinary research platform at the Faculty of Sciences, University of Gothenburg), the Royal Swedish Academy of Science, through the foundation of Hierta-Retzius, and the foundations of Helge Ax:son Johnson, Knut and Alice Wallenberg, Wilhelm and Martina Lundgren and Kapten Carl Stenholm provided additional support.
- Austin GE, Rehfisch HA, Viles HA, Berry PM (2001) Impacts on coastal environments. In: Harrison PA, Berry PM, Dawson TE (eds) Climate change and nature conservation in Britain and Ireland: modelling natural resource responses to climate change (the MONARCH Project). UK Climate Impact Programme, Oxford, pp 177–228Google Scholar
- Baardseth E (1970) Synopsis of biological data on knobbed wrack Ascophyllum nodosum (Linnaeus) Le Jolis. FAO Fish Synop 38:1–38Google Scholar
- Brown JH, Lomolino MV (eds) (1998) Biogeography. Sinauer associates, SunderlandGoogle Scholar
- Caswell H (2001) Matrix population models. Sinauer Associates Incorporated, SunderlandGoogle Scholar
- Dixon P, Friday N, Ang P, Heppel S, Kshatriya M (1996) Sensitivity analysis of structured-population models for management and conservation. In: Tuljapurkar S, Caswell H (eds) Structured-population models in marine, terrestrial, and freshwater systems. Chapman and Hall, New York, pp 471–514Google Scholar
- Hawkins SJ, Hartnoll RG, Kain JM, Norton TA (1992) Plant-animal interactions on hard substrata in the north-east Atlantic. In: John DM, Hawkins SJ, Price JH (eds) Plant-animal interactions in the marine benthos, vol 46. Clarendon Press, Oxford, pp 1–32Google Scholar
- Jonsson PR, Granhag L, Moschella PS, Åberg P, Hawkins SJ, Thompson RC (2006) Interactions between wave action and grazing control the distribution of intertidal macroalgae. Ecology 87:1169–1178. doi: https://doi.org/10.1890/0012-9658(2006)87[1169:IBWAAG]2.0.CO;2 CrossRefGoogle Scholar
- Schiel DR, Foster MS (2007) The population biology of large brown seaweeds: ecological consequences of multiphase life histories in dynamic coastal environments. Annu Rev Ecol Evol Syst 37:343–372. doi: https://doi.org/10.1146/annurev.ecolsys.37.091305.110251 CrossRefGoogle Scholar
- Thompson RC, Roberts MF, Norton TA, Hawkins SJ (2000) Feast or famine for intertidal grazing molluscs: a mis-match between seasonal variations in grazing intensity and the abundance of microbial resources. Hydrobiologia 440:357–367. doi: https://doi.org/10.1023/A:1004116505004 CrossRefGoogle Scholar
- Weaver AJ, Eby M, Wiebe EC, Bitz CM, Duffy PB, Ewen TL, Fanning AF, Holland MM, MacFadyen A, Matthews HD, Meissner KJ, Saenko O, Schmittner A, Wang HX, Yoshimori M (2001) The UVic system model: model description, climatology, and appplications to past, present and future climates. Atmos Ocean 39:361–428CrossRefGoogle Scholar