Microbial Invasions in Aquatic Systems

Biological invasions are one of the leading causes of environmental change, resulting in biodiversity decline, disruption of ecosystem services and significant economic losses globally. Invasive micro-organisms have often been overlooked in the field of invasion biology and in resultant policy and legislation. This study aims to bridge some of the current knowledge and policy gaps regarding invasive microorganisms, focusing primarily on aquatic systems and bivalves specifically.
In this thesis I review the concept of the co-introduction of pathogens alongside invasive non-native species (INNS), and the potential implications on policy and legislation. I present a workflow to search literature on parasites and symbionts of the top 77 aquatic INNS to the UK, highlighting clear evidence of the knowledge gap within this field. I also address a potential future regulatory requirement for the UK water industry to mitigate the spread of invasive micro-organisms and present a risk analysis of pathogen spread via raw water transfers, highlighting freshwater diseases of importance to the UK and their potential for transmission.
Data from this thesis provide empirical evidence of novel parasite diversity associated with invasive bivalves, including novel parasitic associations between the newly established Asian date mussel Arcuatula senhousia in the Solent and pathogen groups of importance to aquaculture and biodiversity. A rare parasite, Haplosporidium raabei is recorded for the first time in UK waters from archival samples of the invasive zebra mussel, Dreissena polymorpha. Furthermore, I identified Haplosporidium raabei in multiple invasive bivalve species sampled from the River Thames, providing the first evidence this parasite may be capable of spillover to other bivalve species, as well as other novel haplosporidians associated with invasive bivalve tissue. I also formally describe a novel microsporidian parasite Morrittospora corbiculae n. gen. n. sp. associated with the invasive Asian clam, Corbicula fluminea from the Thames and evaluate its impact on native mussel species alongside examples of other microsporidians associated with aquatic INNS.