Juan Moreira is a professor at the Autonomous University of Madrid, but 20 years ago he carried out his doctoral thesis at the University of Vigo, a study on the fauna of the Bay of Baiona. Jesús Souza Troncoso, currently director of ECIMAT, developed his doctoral thesis at the University of Santiago 30 years ago on the fauna of the Ares estuary. Now, 20 and 30 years later respectively, both have launched a pioneering initiative, repeating their studies to compare the results and thus verify the health of these two places in order to detect possible changes in the marine fauna.
In the case of researcher Juan Moreira, the sampling and studies of his doctoral thesis, launched in 1995 in the Baiona estuary, will be repeated. At that time, the current director of ECIMAT started a project at the University of Vigo to study the distribution of invertebrates in that same estuary. Moreira got involved in this project and was in charge of the species identification part, resulting in the discovery of seven new species of marine invertebrates from the Baiona cove. “It was a surprise,” Moreira acknowledges, “because we tend to think that in coastal areas we have everything catalogued, and that is not the case, there are things that escape us, either because they are cryptic or because they resemble known species.” The researcher explains that now, with the current analyses, he does not expect to obtain similar results, “since 20 years ago, this area was scarcely studied.” In this new stage, the same sampling points, the same methodology and the same researchers participate, although Moreira and Troncoso are joined by researchers Marcos Rubal and Puri Veiga.
Sampling in the Ría de Baiona began in July of this year. Now the laboratory work begins to analyze the substrates (sand, mud, etc.) and carry out the analyses that have to do with the physical component (grain size, amount of organic matter, temperature or salinity, etc.) in order to analyze the faunal composition of the different substrates. Moreira is waiting for the extraction phase to finish in spring to begin the process of identifying the fauna. In this way, in two years they would have the necessary data to begin comparing the data with those from 20 years ago. This time, the researchers are betting on the starting hypothesis that the results will be similar, which would indicate that no significant environmental change has occurred. In the event that the results show differences, Moreira explains that “they will have to be identified and the causes sought”. However, they are focusing on a factor that could be the cause of changes: the installation shortly after the first study of several rafts on the northern bank of the inlet. For now, the most preliminary results do not show major changes in the studied area of the estuary but, as the researcher recalls, “there is still much to analyze, since at each sampling point (19 in total) there may be 70-80 species of invertebrates from different biological groups and different ways of life”. Another piece of data extracted from the first analyses is the presence of a gastropod associated with oyster farming (Crepidula fornicata) of which only two individuals were found 20 years ago. “Now we have confirmed the presence of juvenile specimens, which implies a good health of the population that reproduces”. The fact that it is more common than it was 20 years ago is, for the researchers, an indication of possible changes that they will have to study in order to assess its real impact.
In the case of the Ría de Ares, studied by Souza Troncoso 30 years ago, the study will have fewer sampling points (15 compared to 61) and will use different analysis techniques. His thesis focused on the bionomic cartography of molluscs from the Ría de Ares and Betanzos. At that time, they worked with live animals that in this case had been collected by dredging with trawls, so the samples were qualitative, not quantitative. Currently, the techniques are different, as the collection methods are more intensive, since the samples can be preserved, and the statistical techniques are more powerful, so the approach will be different from that of the 1980s. The idea of the director of Ecimat is to compare, on the one hand, the quantitative data of the new study with the results obtained 30 years ago in a study carried out by the USC in which a box corer dredge was used (which allows surface sediment to be recovered from the seabed) and, on the other hand, the results relating to molluscs with the data extracted from his thesis. The objective is to check if there are changes in both the fauna and the substrates and to study the physical parameters (sediment, salinity, temperature, etc.) that may affect the distribution of the fauna.
The initial study allowed for the first time to map the distribution of fauna in the Ares estuary. The studies resulted in several works, new citations and new distributions of the intertidal fauna. “We published the distribution of organisms in the estuary related to the sediment parameters and we also worked, as in Moreira’s thesis, to make the vertical distribution inside the sediment”. This study 30 years later qualifies as “very important, because it is one of the first approaches that they do after so many years for soft substrates and applying the same methodology and we believe that the results will be spectacular”.
The researchers do not expect to find substantial changes in the Ares and Betanzos estuaries, since the sediments seem a priori very similar to those analyzed 30 years ago. However, explains Souza Troncoso “we want to detect changes in the faunal and sediment composition by comparing the three parts of the estuary (inner, middle and outer), for which we already have a priori data”. The main point of interest is the outer port of Ferrol, since several studies have confirmed its impact on the Ferrol estuary, causing siltation of the seabed. The researchers will now seek to verify whether the sea currents have dragged this mud towards Ares.
