Biodiversity consequences of Caulerpa prolifera takeover of a coastal lagoon

The genus Caulerpa has attracted much attention because many of its species were introduced into non-native regions and became notoriously invasive. This is the case of Caulerpa prolifera that has been rapidly expanding in Ria Formosa lagoon, taking over the deeper unvegetated soft bottoms and competing with seagrass meadows in the shallower areas. Here we address how C. prolifera invasion may affect the support of biodiversity, and specifically, the provision of habitat and nursery for commercial species by the native habitats of this coastal lagoon. Even though no significant differences in total species richness, diversity and evenness were found between C. prolifera and the native unvegetated habitat, the dissimilarity between these two habitats was highest, mostly driven by the extreme reduction of the gastropod Bittium reticulatum and of the tanaid Apseudopsis formosus. This may implicate changes in the trophic interactions of the ecosystem, for example decreasing the tanaid food source for seahorses, which are presently endangered in the lagoon. On the other hand, the fauna species richness, diversity and evenness were significantly higher in the native seagrass habitat than in C. prolifera. Juveniles of valuable flat and sparid fish were only observed in unvegetated sediments and seagrass meadows, respectively. The aggressive spread of C. prolifera in Ria Formosa may alter the structure of native faunal communities, with likely negative implications on fisheries. Nevertheless, the global biodiversity of the lagoon will not be likely drastically affected unless the seaweed takes over the seagrass meadows.FCT: PTDC/MAR-EST/3223/2014/ CCMAR/BI/011/2018/ DL 57/2016/CP1361/CT0004/ UIDB/04326/2020info:eu-repo/semantics/publishedVersio

Feeding ecology of the common dolphin (Delphinus delphis) in Western Iberian waters: has the decline in sardine (Sardina pilchardus) affected dolphin diet?

16 pages, 5 tables, 5 figuresPredator diet is expected to respond to changes in the abundance of important prey items. We investigated whether common dolphin diet has changed with changes in the pelagic fish community off the Iberian Peninsula in recent years, in particular with reference to the decline of sardine (Sardina pilchardus) and the increase of Atlantic chub mackerel (Scomber colias) and scads (Trachurus spp.), and estimated how much fish was removed by common dolphins in coastal waters of mainland Portugal. Based on analysis of stomach contents of stranded animals from 2010 to 2013 (n = 150), we related diet composition to sardine abundance, dolphin size and sex, season and region. Despite the decline in sardine stocks in recent years, sardines were the most important prey of common dolphins, as was previously reported in the 1990s, followed by chub mackerel and scads. However, small sardines have disappeared from the diet, consistent with recent poor recruitment to the stock. The relative importance of these pelagic species in the diet increased significantly with increasing dolphin length. The dietary importance of chub mackerel also varied regionally, with higher intake on the southern coast. Finally, we compared the estimated biomass of fish removed by dolphins with that taken by fisheries. We found that even with the severe quota restrictions on sardine catches, total biomass removed by fisheries was over five times greater than the estimated removal by common dolphins. Our results confirm the previously reported preference for energy-rich prey, especially sardine, suggesting that common dolphins in Portuguese waters specialise in feeding on this speciesThis work was funded by the projects SafeSea (EEA-Grants) and MarPro (European Commission Life Programme, NAT/PT/00038). This study received additional support from the Portuguese Foundation for Science and Technology (FCT) through grants SFRH/BPD/64889/2009 to A. Marçalo, SFRH/BD/51416/2011 to L. Nicolau, and SFRH/BD/30240/2006 to M. Ferreira. J. Giménez was supported by the Spanish Ministry of Economy and Competitiveness, through the Severo Ochoa Program for Centers of Excellence in R + D + I (SEV-2012-0262).Peer reviewe