SAMS news room

28 Nov 2013, Oban -- Alien species in our coastal waters are on the increase. Many more are likely to come. Some will expand their range. Some can cause environmental and economic impact and some are plain revolting.

Over the past few decades there has been an exponential increase in the spread of non-native species around the world. This trend has been seen around Britain and Ireland, and although increasing species numbers and species abundance may partly reflect more frequent and more intense monitoring, it is believed to be real.

Non-native species (NNS) are species that have been intentionally or unintentionally introduced to regions outside their usual, natural range and dispersal potential. Higher numbers of introductions are linked to snowballing human mobility and the growth of fast, efficient modes of transport, particularly international shipping, which help high levels of survival.

If a newly introduced species becomes established and begins to threaten biodiversity, cause economic damage or both, they are called "invasive". Biological invasions are one of the greatest threats to marine biodiversity and can be economically and ecologically devastating.

There are now more than 90 NNS species known to live in British marine and brackish waters. Of these over 60 are established and several are considered to be high impact –environmentally, economically or both—and some of them continue to expand their range.

Already in Britain, NNS are estimated to cost the economy £1.7 billion a year, with the annual cost to marine-based industries, like shipping and aquaculture, estimated at £39.9 million, which is probably an underestimate because little distinction is made between native and non-native species during pest control operations.

Improved knowledge and understanding of taxonomy, biogeography, and invasion biology has exposed the origin of many species now in British waters, and DNA marker techniques have provided more precise methods of tracking alien species.

The two main areas of origin are the North Pacific and North-west Atlantic. Introductions from regions with similar environmental conditions are more likely to become established and widespread. There are, however, species like the zebra mussel Dreissena polymorpha from the Ponto-Caspian region, and the tubeworm Ficopomatus enigmaticus from the Indo-Pacific, that tolerate a lot of conditions and have successfully established in British waters.

Most alien species here were initially reported in the English Channel and have then expanded their range from ‘hubs’, using a selection of dispersal methods to spread northwards to the North or Celtic Seas.

Trade is mainly responsible for their introduction, bringing them in ships’ ballast waters and sediments, on fouled hulls (and other hard structures) and in imported consignments of cultured species. Port and marina developments, increased leisure use of boats, and aquaculture all pose risks too.

Conditions created by climate change and extreme weather have also led to the introduction and establishment of some NNS in the North Atlantic and in poleward dispersal, northwards in to the Celtic and North Seas. Climate change can influence every stage of the invasion process, but because of a lack of biological and physiological data, it is often difficult to attribute, for example, shifts in distribution or increased reproductive success, directly to climate change.

Rising seawater temperatures have resulted in the recruitment of some species, like the Pacific oyster Crassostrea gigas, at more northerly locations in UK and Europe. They may have also led to others, including the bryozoan Bugula neritina, becoming established beyond the warm water areas created by power station outflows.

Regional climate models predict the current trend of warming will continue throughout the 21st century. If the environmental and economic impacts of NNS are to be mitigated, it is critical to understand how the indirect consequences of climate change –including changes in seawater temperature, increased atmospheric CO2, increased rainfall, heat waves, frequency of storm events, and ocean acidification— will influence the establishment of alien species and the range that they may occupy in the introduced environment.

The skills of national and international taxonomists have been essential to understand current NNS distributions around Britain and Ireland. Yet, marine taxonomists are in decline and the work done so far has concentrated on near shore marine and brackish water species because of the ease of sampling. This means there has been less offshore benthic and pelagic sampling. With the rapid development of offshore marine renewable energy, this is an area that requires urgent attention.

Despite, since the last MCCIP report card on non-natives (2010), the production of more biological data and the publication (Minchin et al, 2013) of a full list of NNS in British marine and brackish waters, there continues to be a lack of long-term data and in-depth biological information. Although there are a number of groups (SAMS, ERI, NAFC, MBA) trying to fill knowledge gaps, the overall intermittence of monitoring programmes and detailed surveys needs to change.

Links

For more on Liz's research click here

For the MCCIP's 2013 report card click here