• Climate change can affect every stage of the introduction, colonization, establishment and invasion of alien species; this report examines the evidence for marine species in the UK and Ireland.
• The introduced Pacific oyster (Crassostrea gigas) spread from oyster farms in the early 1990s, becoming established in southern England. Similarly, new self-sustaining populations are now established in Northern Ireland with recruitment occurring in favourable years. Current sea temperature projections are thought likely to result in certain species such as Crassostrea gigas recruiting every year in Northern Ireland, Wales and south-west England by 2040.
• Rising water temperatures may have contributed to the expansion in range of a number of species such as the bryozoan Bugula neritina, previously restricted to warm water areas such as power station outlets, and the red seaweed Caulacanthus ustulatus which was introduced from Asia and spread rapidly to Devon in 2004, Cornwall in 2005 and Kent in 2009.
• The invasive gastropod, the slipper limpet Crepidula fornicata, which can build up enormous populations in southern England, seems to be expanding in range, possibly in association with rising temperatures, although its spread may be more related to aquaculture activities.
• Recent outbreaks of a viral disease of Crassostrea gigas oysters may be associated with climate change, and transport of oysters from France is spreading the virus.
• Changes in ocean physics and chemistry could favour some non-native species over native species.

What is already happening: Medium

Climate driven changes may affect directly native species performance, modifying population dynamics which can ultimately result in distributional shifts and changes in the composition and diversity of coastal communities (e.g. Ling, 2008) as well as coastal habitat loss. Similarly, other global stressors like marine invasions have profound and often irreversible consequences on the ecology and economics of marine systems (Grosholz, 2002). Despite the mounting research effort dedicated to the study of climate change and IAS in the marine realm, empirical studies linking both these global stressors are limited and mostly observational (e.g. Harris & Tyrrell, 2001; Diederich et al., 2005). Interactions between climate changes and biological invasions may have widespread and unexpected effects on coastal ecosystem dynamics (Harley et al., 2006).

What could happen: Low

The level of confidence has been decreased since the 2007-08 MCCIP ARC. This may be because the previous report focused on the arrival and spread of new aliens rather than their biology and impacts, which are more poorly understood.

The top priority knowledge gaps that need to be addressed in the short term to provide better advice to be given to policy makers are:

1. Relevant biological information on invasive species (e.g. molecular data indicating origins; population genetics; and physiological tolerances) is still lacking for the great majority of species, meaning that confident predictions of the future trajectory of existing invasions cannot be made for many aliens.
2. There is very little information on the ecological effects of alien species interacting with native species for all but a few species in a few locations (Arenas et al., 2006b), so that even if we knew what the species would do, we would not be able to predict its effects on native species.
3. The lack of integration concerning knowledge gaps (1) and (2) means that potential effects of climate change on native species are still very poorly understood - results to date are often conflicting, counter-intuitive, and strongly confounded by other anthropogenic factors.

We believe there is a strong consensus about these knowledge gaps.

Oyster disease:

IFREMER is believed to be researching this outbreak. It has already had serious impacts on European oyster cultivation and these could become more widespread.

Crepidula

The spread of Crepidula to Northern Ireland has stopped Mytilus relaying and export www.bbc.co.uk/newsline/content/articles/2009/05/26/invasive_species_feature.shtml

Further spread will have effects on the aquaculture industry. Northern Ireland Environment Agency are commissioning research on this species.

Maggs, C., Mineur, F., Bishop J. and McCollin, T. (2010) Non-Natives in MCCIP Annual Report Card 2010-11, MCCIP Science Review, 12pp. www.mccip.org.uk/arc