Roma, Joana, Schertenleib, Katrin, Ramalhosa, Patrício, Gestoso, Ignacio, Canning-Clode, João and Lenz, Mark (2021) Moderately elevated temperatures increase macroalgal food consumption in two sea urchin species from coastal waters of Madeira. Journal of Experimental Marine Biology and Ecology, 542-543 . Art.Nr. 151603. DOI 10.1016/j.jembe.2021.151603.

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Abstract

Highlights:
• Sea urchin food consumption and gonad index followed thermal performance curves.
• Body size and sex interacted with temperature and influenced food consumption rates.
• Only body size, not sex, in addition to temperature influenced gonad indices.
• Larger sea urchins were impacted to a greater extent by warmer temperatures.

Rising sea surface temperatures affect the feeding behaviour and reproductive success of many coastal benthic invertebrates. This experimental study investigated the effects of ocean warming on macroalgal food consumption rates in the sea urchins Arbacia lixula and Paracentrotus lividus from Madeira Island to assess how the feeding pressure they exert may change under warmer ocean conditions. Additionally, in A. lixula, the relationship between temperature and the gonad index was examined to estimate potential future reproductive output. Over the course of 25 days, 180 individuals of each species were exposed to temperatures between 22 degrees C and 31 degrees C. After 20 days, consumption rates were assessed in 48-h feeding trials. Gonad indices of A. lixula were determined on the last day of the experiment. In the thermal range investigated, both traits were found to be unimodal functions of temperature. In addition to temperature, consumption rates in both species and the gonad indices in A. lixula were influenced by body size, while feeding in A. lixula also varied between sexes. Maximum food consumption rates (A. lixula and P. lividus) as well as maximum gonad indices (only A. lixula) were observed between 25 degrees C and 26 degrees C. These values are at the upper end of the temperature range that currently prevails around Madeira, and may become average summer temperatures by the year 2100. Consequently, both sea urchin species may thrive during future warm summers and may enhance their top-down control on local macroalgal populations.

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