Trophic versus structural effects of a marine foundation species, giant kelp (Macrocystis pyrifera)
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Foundation species create milieus in which ecosystems evolve, altering species abundances and distribution often to a dramatic degree. Although much descriptive work supports their importance, there remains little definitive information on the mechanisms by which foundation species alter their environment. These mechanisms fall into two basic categories: provision of food or other materials, and modification of the physical environment. Here, we manipulated the abundance of a marine foundation species, the giant kelp Macrocystis pyrifera, in 40 × 40-m plots at Mohawk Reef off Santa Barbara, California and found that its biomass had a strong positive effect on the abundance of bottom-dwelling sessile invertebrates. We examined the carbon (C) stable isotope values of seven species of sessile invertebrates in the treatment plots to test the hypothesis that this positive effect resulted from a nutritional supplement of small suspended particles of kelp detritus, as many studies have posited. We found no evidence from stable isotope analyses to support the hypothesis that kelp detritus is an important food source for sessile suspension-feeding invertebrates. The isotope composition of invertebrates varied with species and season, but was not affected by kelp biomass, with the exception of two species: the tunicate Styela montereyensis, which exhibited a slight enrichment in C stable isotope composition with increasing kelp biomass, and the hydroid Aglaophenia sp., which showed the opposite effect. These results suggest that modification of the physical habitat, rather than nutritional subsidy by kelp detritus, likely accounts for increased abundance of sessile invertebrates within giant kelp forests.
KeywordsEcosystem engineers Stable isotopes Detritus Sessile invertebrates Macroalgae
We thank S. Harrer, P. Laverty, C. Nelson, C. Santschi, N. Schooler, A. Wang, and K. Yager for field and laboratory assistance. The University of California Santa Barbara Marine Science Institute Analytical Laboratory analyzed samples for stable isotopes. This work was supported by the US National Science Foundation’s Long-Term Ecological Research Program and by NSF OCE 0962306 to H. M. P. and R. J. M.
Author contribution statement
R. J. M., H. M. P. and D. C. R. conceived and designed the experiments. R. J. M. and H. M. P. performed the experiments. R. J. M. analyzed the data. R. J. M., H. M. P. and D. C. R. wrote the manuscript.
- Bruno JF, Bertness MD (2001) Habitat modification and facilitation in benthic marine communities. In: Bertness MD, Hay ME, Gaines SD (eds) Marine community ecology. Sinauer, Sunderland, pp 201–218Google Scholar
- Carr MH, Reed DC Shallow rocky reefs and kelp forests. In: Mooney H, Zavaleta E (eds) Ecosystems of California. University of California Press, Berkeley (in press)Google Scholar
- Cohen J (2013) Statistical power analysis for the behavioral sciences. Routledge Academic, LondonGoogle Scholar
- Dayton PK (1972) Toward an understanding of community resilience and the potential effects of enrichments to the benthos at McMurdo Sound, Antarctica. In: Parker BC (ed) Proceedings of the Colloquium on Conservation Problems in Antarctica. Allen Press, LawrenceGoogle Scholar
- Dayton PK, Tegner MJ (1989) Bottoms beneath troubled waters: benthic impacts of the 1982–1984 El Nino in the temperate zone. In: Glynn PW (ed) Global ecological consequences of the 1982–83 El Nino-Southern Oscillation. Elsevier oceanography series no. 52. Elsevier, Amsterdam, pp 433–472 Google Scholar
- Ellison AM, Bank MS, Clinton BD, Colburn EA, Elliott K, Ford CR, Foster DR, Kloeppel BD, Knoepp JD, Lovett GM, Mohan J, Orwig DA, Rodenhouse NL, Sobczak WV, Stinson KA, Stone JK, Swan CM, Thompson J, Von Holle B, Webster JR (2005) Loss of foundation species: consequences for the structure and dynamics of forested ecosystems. Front Ecol Environ 3:479–486CrossRefGoogle Scholar
- Gerard VA 1976 Some aspects of material dynamics and energy flow in a kelp forest in Monterey Bay, California. Dissertation, University of California, Santa Cruz, CAGoogle Scholar
- Gili JM, Hughes RG, Alvà V (1996) A quantitative study of feeding by the hydroid Tubularia larynx Ellis and Solander, 1786. Sci Mar 60:43–54Google Scholar
- Graham MH, Vasquez JA, Buschmann AH (2007) Global ecology of the giant kelp Macrocystis: from ecotypes to ecosystems. Ocean Mar Biol 45:39–88Google Scholar
- Kendrick GA, Harvey E, Wernberg T, Harman N, Goldberg N (2004) The role of disturbance in maintaining diversity of benthic macroalgal assemblages in southwestern Australia. Jpn J Phycol 52:5–9Google Scholar
- Neter J, Kutner MH, Nachtsheim CJ, Wasserman W (1996) Applied linear statistical models, 4th edn. McGraw-Hill, New YorkGoogle Scholar
- Parnell PE, Miller EF, Lennert-Cody CE, Dayton PK, Carter ML, Stebbins TD (2010) The response of giant kelp (Macrocystis pyrifera) in southern California to low-frequency climate forcing. Limnol Oceanogr 55:2686–2702Google Scholar
- Pérez-Matus A, Ferry-Graham LA, Cea A, Vásquez JA (2008) Community structure of temperate reef fishes in kelp-dominated subtidal habitats of northern Chile. Mar Freshwater Res 58:069–1085Google Scholar
- Rosman JH, Koseff JR, Monismith SG, Grover J (2007) A field investigation into the effects of a kelp forest (Macrocystis pyrifera) on coastal hydrodynamics and transport. J Geophys Res-Oceans 112(C2):C02016Google Scholar
- Schiel DR, Foster MS (2015) The biology and ecology of giant kelp forests. University of California Press, BerkeleyGoogle Scholar
- Shepherd S, Edgar G (2013) Ecology of Australian temperate reefs: the unique south. CSIRO, CollingwoodGoogle Scholar