Light compensation points and the effects of grazing and light intensity on the consumption of the native Stypopodium zonale and the non-native Grateloupia imbricata by Paracentrotus lividus in laboratory experiment on Madeira Island in 2007

Experiments were conducted from 4 June to September 2007 inside laboratory facilities at the south coast of Madeira (32°38'N, 16°54'W). The organisms used for this study were the sea urchin Paracentrotus lividus collected at Doca do Cavacas (32° 38'06 N; 16° 56'52 W), the red seaweed Grateloupia imbricata collected from the marina of Funchal (32° 38'41 N; 16° 54'46 W) at 0.5 m water depth, and the brown seaweed Stypopodium zonale collected from boulders at Reis Magos, Caniço (32° 83'45 N; 16° 49'25 W) in water depths of 3-7 m.