Kelp rafts in the humboldt current: Interplay of abiotic and biotic factors limit their floating persistence and dispersal potential
Rothausler, E and Gomez, I and Hinojosa Toledo, IA and Karsten, U and Miranda, L and Tala, F and Thiel, M, Kelp rafts in the humboldt current: Interplay of abiotic and biotic factors limit their floating persistence and dispersal potential, Limnology and Oceanography, 56, (5) pp. 1751-1763. ISSN 0024-3590 (2011) [Refereed Article]
Copyright 2011 by the American Society of Limnology and Oceanography, Inc.
During summer 2009, we conducted a field experiment and a field survey at 30uS in the coastal Humboldt
Current to determine how floating time affects the physiological performance of kelp rafts. For the field
experiment kelp rafts were tethered in coastal waters and the field survey was specifically designed to collect freefloating
Macrocystis pyrifera across a latitudinal temperature gradient that reflects natural floating time.
Experimental kelps were kept under photosynthetic active radiation (PAR) and PAR + ultraviolet (UV; PAR +
UV) using filter foils, and tethered at the sea surface in their natural habitat. Ultraviolet radiation (UVR) did not
affect kelp physiology, but caused a decrease in kelp biomass. The field survey confirmed that sea-surface
temperature increased with distance from upstream source populations of M. pyrifera. Rafts sampled at
increasing distance from sources showed high epibiont cover and reduced blade lengths. Physiological
performance declined with increasing size of algal epibionts, which are indicators of floating time. Rafts that
were farthest from the southern source populations had lost their sporophylls, suggesting that dispersal potential
decreases with increasing floating time. The combined effects of abiotic (UVR and temperature) and biotic factors
accelerate degradation of M. pyrifera and, thus, can impede successful dispersal in the Humboldt Current at 30uS.
This suggests that floating macroalgae can be important dispersal vectors in areas with moderate environmental
stress (i.e., in temperate oceans).