Project Update: December 2005
The aim of this project was to understand the role of mussel beds in the maintenance of local biodiversity and to evaluate mussels as ecosystem engineers. For this, several localities from the estuarine to the oceanic zone were sampled. Species richness (invertebrates and algae) was measured as the number of species present in each locality. In all cases the final richness was evaluated from a cumulative species-sampling effort curve. Mussel net abundance was measured at each site and correlated with the species richness. Two main results were found:
1. Species richness (S) increased significantly with mussel abundance. The proportion of the variance accounted was for 39%. This suggests an important role for mussel beds in the creation of habitats for benthic species.
2. The estuarine zone was dominated by the blue mussel Mytiuls edulis platensis while the oceanic zone was dominated by Brachidontes rodriguezii. In this sense, a mussel-replacement pattern could be identified. This replacement has been associated with the salinity gradient.
Mussel beds provide a structural habitat for other benthic species in the low intertidal zone. In this way the complex structure generated by each mussel species enhances the associated diversity. A positive interaction among sessile macrobenthos (mussel beds) and mobile fauna is suggested. From east to west, a mussel replacement was observed.
So, in order to protect and conserve the biodiversity harbored in the rocky intertidal zone of Uruguay it is necessary to take into account the three regions pointed in the figure below (results from the first project) but also the dominant cover of mussel beds in each region must be taken into account.
|Regions identifiable as targets for conservation
The description of the spatial variability of species richness and composition of the rocky intertidal systems of Uruguay will allow for identification of areas of high conservation priority. Furthermore, coastal areas with environmental risks could be detected and environmental impacts could be evaluated due to the existence of baseline data herein provided. The results will be of great utility for the development of conservation and management plans for marine coastal ecosystems. In Uruguay, baseline data on benthic biodiversity is scarce or lacking, making selection of areas or habitats to protect very difficult.
So, the results of this work could be of outmost importance to local biodiversity conservation. The Uruguayan committee of the IUCN has started working in local meetings about marine issues. In this context, the main objective of the IUCN is "to contribute to the design, creation and management of Protected Areas in Uruguay." The high priority areas identified in this and the previous project funded through the Small Grants Program will be of great relevance for the IUCN initiative.
A manuscript has been submitted to the journal Acta Oecologica, which includes the findings of this project. The divulgation of this project has also been driven through local meetings and presentations in regional or local congresses, which seem to be a powerful tool for involving the local population in conservation issues. During the field work, a lot of the locals asked about our work. We explained the importance of conserving the biodiversity of our coast, and realized that most people were surprised about the great number of animals living in these environments and especially the enormous number of invertebrates that live within mussel beds.
Figure 1. One of the sites sampled in this work, called Cabo Polonio. It is a rocky cape on the east coast of Uruguay affected by semidiurnal, low-amplitude tides (range < 0.5 m) that are largely controlled by wind conditions (direction and speed).
Figure 2. Two typical species found it along the Uruguayan coast. On the left, an anemone present in the mussel-engineered patches, while on the right, a species of limpet, Lottia subrrugosa, reported mainly in the non-engineered patches.