The increase in long distance transport of commercial goods has greatly accelerated the previously minor geographical dispersion of organisms. The extent to which an organism can invade a new environment may be limited by the difficulty of the local conditions or the complexity of the local ecosystem. The likelihood of invasion may increase if the new ecosystem is undergoing change, either by directly improving conditions for the guest organism or worsening conditions for preexisting species. Nevertheless, every ecosystem has its peculiarities. For the GRACCIE project, we are interested in tackling two issues related to the aforementioned phenomena, for which our local surroundings are particularly amenable. The first is the atmospheric dispersion of microorganisms, and the second is the entry of invader marine species into the western Mediterranean.

The microbial component of atmospheric aerosols was discovered in the 19^th century, however it has only been in the past decade that it has gathered significant attention (Hanna, 2001). Recent studies indicate that fungi, bacteria and perhaps viruses can survive journeys of thousands of km in the high atmosphere, suspended in dust particles from African desserts and propelled by the wind (Griffin et al. 2002). The interaction between local/regional pollutants and dust has been reported as a major reaction pathways to increase the levels of aerosols and to change the atmospheric behaviour (nucleation of clouds and chemistry of deposition) of the original dust emissions (Levin et al., 1994; Alastuey et al., 2004).The magnitude of this phenomenon and its consequences for ecosystems and humans remains poorly understood. There have been reports of plagues and sicknesses in flora and fauna of aquatic ecosystems in the USA that have failed to adapt to colonizing microbes (Kellogg and Griffin 2003). Analogous events in Europe have yet to be studied. Atmospheric aerosols also include pollen and spores that have a large impact on human respiratory allergies. In this context, the Iberian Peninsula serves as an ideal laboratory for researching the atmospheric transport of biological aerosols and Saharan dust, and for evaluating potential relationships of these phenomena to climate change.

Introduction of new species into the ecosystems is most likely the second leading cause of loss of planetary biodiversity; the first being the destruction of natural habitats (Kaiser and Gallagher, 1997). Marine environments are equally susceptible to this phenomenon, especially in costal regions, where humans have the greatest impact (Carlton and Geller, 1993). The Mediterranean is particularly vulnerable to fouling species; it was the cradle of many ancient civilizations, it has a densely populated littoral, it is linked by an artificial canal (the Suez) to a completely unrelated sea, and is a heavy transit zone. The total number of algae species introduced into the Mediterranean has doubled every twenty years since the beginning of the 20^th century (Ribera and Boudouresque, 1995), meaning that of the ca. 80 foreign algae species that will arise in the next twenty years, five to ten will be invaders (Boudouresque and Verlaque, 2002). The introduction of invader macroalgae into Spanish coastal zones of the Mediterranean follows similar trends and is most worrisome for the Balearic archipelago. During the last ten years, numerous invader species have arisen in the area: Caulerpa taxifolia (1993), Acrothamnion preissii (1994), Asparagopsis taxiformis (1996), Womersleyella setacea (1997), Lophocladia lallemandii (1998) and Caulerpa racemosa (1999). The GRACCIE project aims to elucidate why have invader species have made such a dramatic entrance in the past ten years. We believe that transport is not the sole cause; there exists some connection to climate and environmental changes. Possible clues may be found by studying the similarities of the imputed species. In addition, we hope to determine whether the dynamics of the aforementioned occupations can lead to radical changes in littoral benthonic communities.