Biology and ecology of the siphonophore Muggiaea atlantica in the northeast Atlantic

• Main Author: Blackett, Michael
• Format: Thesis
• Language: English
• Published: 2015
• Subjects: Northeast Atlantic
• Online Access: https://eprints.soton.ac.uk/391095/; https://eprints.soton.ac.uk/391095/1/Blackett%252C%2520M_Thesis_final_Mar_16.pdf

In many regions of the world the abundance and distribution of jellyfish is increasing. These changes have important consequences for marine ecosystems and the services that they provide to humans. It is a fundamental goal of marine ecologists to develop understanding of how jellyfish populations respond to environmental change. Two key processes are involved in the regulation of jellyfish populations: local demographics (i.e. production and mortality) and dispersal (i.e. immigration and emigration). A failure to discriminate between the contributions of these two fundamental processes can obscure the specific environmental factors that drive changes in jellyfish populations, impeding understanding. This thesis aims (1) to assess recent changes in the abundance and distribution of Muggiaea atlantica in the coastal waters of the United Kingdom; and to (2) investigate the influence of environmental variability on both the biological (i.e. demography) and physical (i.e. dispersal) processes that drive these changes. This study utilised data collected from a network of coastal monitoring stations, together with data on a range of local and regional hydroclimatic environmental factors. I show that since the late 1960s, there has been a progressive northward extension of this species’ distribution from its centre of population in the Bay of Biscay and Iberian Coast region. These changes involved the establishment of a resident population in the Western English Channel (WEC) and the subsequent development of transient seasonal populations on the east and west coasts of Scotland. In the WEC the M. atlantica population was capable of overwintering, sustaining a resident population irrespective of immigration. This population was modulated primarily by the availability of suitable local environmental conditions that influenced demography (temperature and food availability) and secondarily by changes to water circulation patterns that influenced its dispersal. In contrast, in Scotland M. atlantica was incapable of ...