Seabirds, excellent bioindicators of the health of marine ecosystems
Cristina G. Pedraz/DICYT A group of researchers of the Marine and Environmental Science Centre (MARE), a joint centre of six Portuguese universities including that of Coimbra, analyses the role of seabirds in marine resources with the ultimate aim of developing tools to help conserve the oceans. The group, which is run by Professor Jaime Ramos, uses seabirds as a model of study as access to these animals is relatively easy compared with others such as fish or whales.
The use of seabirds has many advantages both for validating theories and for immediate practical applications. To this end the group uses leading-edge technology such as GPS pagers and the analysis of stable isotopes to find out where these birds go and what they eat. This allows the monitoring of the health of ecosystems and the changes they undergo over time, owing for example to environmental factors such as climatic change or overfishing.
One of the researchers of the group, Filipe Rafael Ceia, explains that seabirds “are perhaps the most accessible higher marine predators, as they are not constantly in the water like fish and must needs return to land to breed, which makes their study so much easier”, and that moreover “they can cover large expanses of sea while foraging within a relatively short period of time and are excellent sampling tools”.
On the other hand, seabirds are considered to be "umbrella" species, i.e. to conserve these species it is also necessary to conserve the resources on which they depend, normally various species lower down the food chain such as fish, squid, or crustaceans on which man also depends to a large extent.
“Seabirds give us important clues to the health of the marine resources on which both they and we depend. As for the great challenges that we are facing today, such as climatic change and overfishing, seabirds can help to understand better what is happening in the oceans as it is they who are the first to feel the consequences”, he explains.
Filipe Ceia has been studying seabirds as bioindicators as part of his doctoral thesis since 2010. His work consists of investigating these birds at an individual level to determine individual indicators and the consequent specialisation in the exploiting of resources.
“By means of the study of feeding ecology we can understand better the effects of climatic change or overfishing and minimise their impact by good management. By means of GPS devices and the analysis of stable isotopes, we have analysed their behaviour and diet in detail, closely following the movements of the birds foraging at sea and finding out what they eat and in what proportions”, the researcher highlights.
During his doctoral thesis the researcher developed the theory of the existence of individual specialisation in various species of seabirds such as albatrosses, shearwaters, and gulls. According to this approach, individuals within a population may specialise in certain resources and have individual preferences both regarding diet and the places where they go to fish.
“The same thing happens with people; not all of us like fish and not all of us like meat, and while some people like to buy their food in shopping centres some of us prefer to use local shops. These results have strong implications in ocean conservation as they allow the improvement of management tools. For example, they help to monitor fish populations in a more sustainable way and to identify the areas with the greatest biodiversity which are therefore liable to become protected marine areas”, he concludes.
The research group is currently involved in a project in which seabirds are used as natural “samplers” of the ocean for the purpose of drawing up an isotopic map of the surface area of the Atlantic Ocean. The objective is that in the future this map will allow the following and locating of not only seabirds but also of all other marine animals from a single sample. In other words, “merely from the analysis of the stable isotopes of a sardine for example, it will be possible to find out the area where it was previously feeding and therefore to draw up migration routes and feeding areas so as to allow much more efficient management of marine resources”.
Ceia, F. R., Paiva, V. H., Ceia, R. S., Hervías, S., Garthe, S., Marques, J.C., Ramos, J. A. (2015) “Spatial foraging segregation by close neighbours of a highly mobile seabird species”. Oecologia, 177: 431-440.
Ceia, F. R., Paiva, V. H., Garthe, S., Marques, J. C., Ramos, J. A. (2014) “Can variations in the spatial distribution at sea and isotopic niche width be associated with consistency in the isotopic niche of a pelagic seabird species?” Marine Biology, 161: 1861-1872.
Ceia, F. R., Paiva, V. H., Fidalgo, V., Morais, L., Baeta, A., Crisóstomo, P., Mourato, E., Garthe, S., Marques, J. C., Ramos, J. A. (2014) “Annual and seasonal consistency in the feeding ecology of an opportunistic species, the yellow-legged gull (Larus michahellis)”. Marine Ecology Progress Series, 497: 273-284.