Observadores del Mar - Seawatchers is an internet platform aimed at connecting citizens and scientists to investigate together the current state of our seas and oceans. Citizens can participate by contributing with their observations and experience. We wish to understand the effects of global warming, pollution, biodiversity changes, invasions of alien species and overfishing in marine ecosystems. To this end, we collect observations and sightings on the distribution and abundance of marine species, the emergence of rare or invasive marine species or the signs of change in ecosystems (mortality of organisms, amassing of surface and bottom pollution).This platform of projects, linked to ongoing research is coordinated by the Institute of Marine Sciences of Barcelona (ICM-CSIC) and relies on the collaboration among citizens scientists from different national and international centers. The main challenges we have are: (1) to detect global warming impacts in biology and distribution of species; (2) to inform about the appearance and expansion of introduced or invasive species; (3) to inform about the presence of warning species such as jellyfish or pufferfish; (4) to expand the knowledge about biology, habitat and distribution of native species; (5) to report the pollution of coasts and sea bottoms and its impact in marine life and ecosystems

Decapod crustaceans (crabs, shrimps, prawns, lobsters, spiny lobsters, hermit crabs,? are a very diverse and still poorly known faunal group, especially so for the wide public. Compared with fish, which are much more evident and easier to watch underwater, crustaceans are much more difficult to obtain reliable information from, since many of them have nocturnal habits, and stay under rocks, buried in the sand or in crevices during most of daytime. Notwithstanding, there is a reasonable number of species that we can be able to see if we watch attentively in the correct habitats, such as crevices or small caves in rocky shores. We aim to obtain data and information on the occurrence not only of the scarce species but also of the common ones. Species that today are common may not be so in a few years time, and inversely, species that today are scarce, or not yet here, may be common tomorrow. Collaboration is necessary and very valuable.