Effects of limitation stress and of disruptive stress on induced antigrazing defense in the bladder wrack Fucus vesiculosus

Abstract

We assessed the effects of light limitation and temperature shift on palatability and induced antiherbivore defense in the brown alga Fucus vesiculosus L. Incubation for 2 wk at light intensities above the compensation point of photosynthesis and in the absence of grazers increased the palatability of F. vesiculosus and its subsequent consumption by the omnivorous isopod Idotea baltica Pallas. This effect correlated with an increased C:N ratio and mannitol content in the algal tissue, presumably due to increased photosynthetic carbon fixation. Mannitol, the primary product of photosynthesis in F. vesiculosus, proved to be a feeding cue for I. baltica, and depletion of the mannitol pool may therefore account for the reduced palatability during light limitation. At light intensities above the compensation point of photosynthesis, F. vesiculosus responded with decreasing palatability when it was exposed to I. baltica grazing. Irrespective of the preceding light regime, such defense induction was prevented during incubation under light limitation. Thus, under low light, defense induction is not only inhibited, but also less necessary due to the relative absence of feeding cues. Upward or downward shifts in water temperature by approximately 10°C also inhibited inducible defense in F. vesiculosus. However, such shifts did not affect algal growth and were therefore the consequence of an impairment of specific defense-related components rather than of resource limitation, unless compensatory growth was given priority over defense.

The responses of brown macroalgae to environmental change from local to global scales: direct versus ecologically mediated effects

“…2), reduced herbivore defences ("6" -> "8" in Fig. 2; Weinberger et al 2011), increased herbivore populations ("g" in Fig. 2; Hernandez et al 2010) and higher grazer diversity ("i", "f" in Fig.…”

Herbivore-induced defence response in the brown seaweedFucus vesiculosus(Phaeophyceae): temporal pattern and gene expression

“…Furthermore, a controlled shut-down of photosynthesis may minimize the oxidative damage that arises when photoautotrophic organisms are exposed to abiotic and/ or biotic stresses (Arora et al, 2002). Moreover, the primary CO 2 storage compound of photosynthesis in F. vesiculosus is mannitol, which was shown to be a feeding cue for the isopod I. baltica (Bidwell et al, 1972;Weinberger et al, 2011b). Strong down-regulation of photosynthesis may have resulted in reduced mannitol content and, thus, a reduced attractiveness of F. vesiculosus for isopods (Fig.…”

A non-native macroalga is less attractive for herbivores but more susceptible to light limitation and grazing stress than a comparable native species

“…However, the authors were not able to elicit whether energy shortage affected tissue quality, such as toughness, or whether chemical defences were impaired. Such an impairment under low light conditions was observed for the trophic interaction between the bladder wrack Fucus vesiculosus and the isopod Idotea baltica [8]. Here, during phases of light limitation, chemical defence induction was largely inhibited.…”

“…In this context, tolerance to adverse environmental conditions is viewed as an important pre-requisite for invasion success and it is a widely accepted notion that non-native species are more robust [4,5]. Several empirical studies that considered abiotic stressors such as temperature [6], wave action [7], light limitation [8], salinity fluctuations [9] and oxygen concentration [10] actually found that non-native organisms commonly have a higher tolerance than ecologically similar and/or taxonomically related native species. So far, most studies on the effects of environmental stress have focused on the physiological responses of single organisms to adverse conditions [11], but did not consider the consequences of stress for biotic interactions [12].…”