Carr LA and Bruno JF (2013), Warming increases the top-down effects and meta...

ECB-ART-42970

PeerJ 2013 Jan 01;1:e109. doi: 10.7717/peerj.109.

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Warming increases the top-down effects and metabolism of a subtidal herbivore.

Carr LA , Bruno JF .

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Ecological theory and experiments indicate that warming can increase the relative strength of top-down effects via alterations to metabolic rates in several different systems, thereby resulting in decreased plant biomass at higher temperatures. However, the general influence of increased environmental temperature on top-down effects is not well understood in systems where organisms experience relatively large variation in temperature. Rapid ocean temperature changes are pervasive throughout the Galápagos Islands due to upwelling and downwelling of internal waves, ENSO events and seasonality. We measured the effect of large, but not uncommon, water temperature variation on the metabolism and grazing rate of a common subtidal herbivore and on photosynthesis of their algal prey in the Galápagos Islands in July 2012. We found that green urchin consumption and metabolism were greater at the higher temperature treatment (28°C), resulting in significantly less algal biomass. Our result that warming increased green urchin metabolic rates, even in a highly dynamic system, provides further support for a mechanistic link between environmental temperature and feeding rates. And further, our findings suggest individual response to temperature results in changes in top-down effects. And if this response is maintained over longer-time scales of days to weeks, this could translate to alterations of larger-scale ecological patterns, such as primary producer community composition and structure.

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Genes referenced: LOC115923516 LOC115925415

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References [+] :

Barber, Biological consequences of el nino. 1983, Pubmed

	Figure 1. Map of Galápagos Archipelago and the surrounding currents.Colored triangles relate to curves in Fig. 2. Map courtesy of A. Valdivia and modified from Schaeffer et al. (2008).

	Figure 3. Mesocosm temperature values during both experiments.Temperature in each mesocosm (n = 20 per temperature) was recorded every 5 min. with an iButton Thermochron datalogger (Dallas Semiconductor, Dallas, Texas, USA). The box corresponds to the 25th and 75th percentiles and the dark line inside the box represents the median consumption value. Error bars are the minimum and maximum.
	Figure 4. Temperature effects on urchin grazing rates, metabolism and algal photosynthesis.Temperature effects on (A) urchin consumption of Ulva, (B) urchin oxygen consumption, and (C) on Ulva net photosynthesis. Values are means ± SE; n = 10.