Local population disappearance follows (20 yr after) cycle collapse in a pivotal ecological species

Populations of the echinoid Paracentrotus lividus have undergone spectacular population fluctuations over the last 40 yr at Lough Hyne, SW Ireland. Censuses in 2000 and 2001, reported here, show no individuals present in the South Basin of Lough Hyne, for what is believed to be, the first time since observations began in the late 1920s. As with many echinoids, P. lividus was considered to have a pivotal role in benthic ecology through control of algae by grazing. The discontinuation of P. lividus in South Basin of Lough Hyne is significant for 3 reasons. First, the database was 1 of the longest running censuses of a discrete echinoid population anywhere. Second, some corresponding environmental and population size structure data had been recorded over several decades. Third, P. lividus was very important in structuring the shallow benthic community of the oldest marine reserve in Europe.