The First Recorded Occurrences and the Distribution of Physalia physalis (Hydrozoa: Physaliidae) in Algerian Waters

Recently, there have been recorded findings of the pleustonic siphonophore Physalia physalis Linnæus, 1758, in different regions of Algeria. Several colonies washed ashore during March and May 2021 along the Algerian coast. Thirty colonies were observed on surface water and stranded on the beach between March and May from Beni Saf (35.30182° N;-1.40293° W) to Skikda (36.916557° N;7.162915° E). The highest number of such strandings of this species was recorded in Tipaza and Algiers. This is the first record of P. physalis in Algeria, extending the previously known distributions from the tropical and sub-tropical latitudes of Atlantic, Pacific and Indian oceans and may represent a danger to human health and the coastal economy. Strandings of P. physalis were notably associated with sea surface current and wind forces pushing P. physalis to become stranded on beaches. Our findings highlight the need for a monitoring program to be developed to understand more about trends associated with changes in the distribution and impact of this species. This work provides an update on the spatial distribution of P. physalis in the Mediterranean Sea.