Comparing siphonophores in Bantry Bay and the Western English Channel (Plymouth Marine Laboratory's L4 station) indicates both regions share a similar pattern of inter-annual occurrence and provides novel information on the seasonality and occurrence of siphonophores in Irish coastal waters. Muggiaea atlantica displayed a distinct seasonality, whereas the physonect species were sporadic in occurrence. Muggiaea atlantica was the most abundant species (250 colonies m−3), with densities an order of magnitude higher than either physonect. In total, three siphonophore species were found, the calycophoran Muggiaea atlantica, and the physonects, Nanomia bijuga and Agalma elegans. To address this lack of knowledge, plankton samples were collected during two periods (March 2009-March 2011 and April 2014-November 2015) from a coastal embayment in the southwest of Ireland. In temperate coastal regions, comparatively less is known about the diversity and abundance of siphonophores, where periodic blooms can restructure the plankton communities and have been correlated with high mortalities in the salmon aquaculture industry. In the latter regard it is worth noting that the total life span of planulae of benthic species is generally less (3-4 days) than that of species with medusae (2-10 days) (Sommer, 1992) both life cycles seemingly limit dispersal. Historically, siphonophores have been under-sampled and of the studies conducted there has been a bias towards oceanic oligotrophic waters where they are considered to be more important. Using this phylogeny, we reconstruct the evolutionary history of characters central to the unique biology of siphonophores, including zooid type, life. Morphological changes throughout their life cycle, phenotypic plasticity and. Most jellyfish in these groups have a bottom-living stage in their life cycle that restricts them to the shelves around most continents. Siphonophores are at times amongst the most abundant invertebrate zooplankton predators in the oceans. During a survey of the siphonophore community in the Kuroshio Extension.