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Posted May 2009

Climate change and invasive species are major drivers of change in marine environments, implicated in the decline and even collapse of several ecosystems.

In her review of marine invasions and climate change, Anna Occhipinti-Ambrogi, from the Universita` degli Studi di Pavia, highlights examples from the Mediterranean, where warming is regarded as particularly important in the establishment of alien species.

Nearly half the fish catches along the Israeli coast are of non-native species that have invaded through the Suez Canal, and the introduced micro-algae Ostreopsis armata has recently bloomed repeatedly in the Ligurian Sea, causing respiratory diseases among tourists to the region. Increased temperatures are thought to have increased the dominance of these non-native species from warmer waters.

However, Occhipinti-Ambrogi says most studies linking climate change with the spread of marine invaders are failing to consider the effects of increased rates of introductions (‘propagule pressure’) by ships, aquaculture, the aquarium trade, and the opening of navigable canals.

She stresses the importance of accounting for changes induced by propagule pressure, and also disentangling the effects of biotic factors (constraints or facilitation of invasion by resident species) and abiotic factors (such as climate change).

Occhipinti-Ambrogi also notes that a 2005 study contradicts the widely held view that the primary effect of ocean warming will be a shift of species towards the poles and the replacement of cold water species by warm water species.

Analysing marine communities colonising coastal habitat warmed by the outfall of a power station, Schiel and colleagues found that the responses of marine communities to warming were mostly unpredictable and “strongly coupled to direct effects of temperature on key taxa and to indirect effects operating through ecological interactions”.

Occhipinti-Ambrogi says knowledge of marine communities is limited, resulting in marine invasions going unrecorded.

References
Occhipinti-Ambrogi A. 2007. Global change and marine communities: Alien species and climate change. Marine Pollution Bulletin 55: 342-352.