RESUMO

The Southern Ocean and the Antarctic Circumpolar Current create environmental conditions that serve as an efficient barrier to prevent the colonization of non-native species (NNS) in the marine ecosystems of Antarctica. However, warming of the Southern Ocean and the increasing number of transport opportunities are reducing the physiological and physical barriers, increasing the chances of NNS arriving. The aim of this study was to determine the limits of survival of the juvenile mussels, M. chilensis, under current Antarctic conditions and those projected under climate change. These assessments were used to define the mussels potential for establishment in the Antarctic region. Experimental mussels were exposed to four treatments: -1.5 °C (Antarctic winter), 2 °C (Antarctic summer), 4 °C (Antarctic projected) and 8 °C (control) for 80 days and a combination of physiological and transcriptomics approaches were used to investigate mussel response. The molecular responses of mussels were congruent with the physiological results, revealing tolerance to Antarctic winter temperatures. However, a higher number of regulated differentially expressed gene (DEGs) were reported in mussels exposed to Antarctic winter temperatures (-1.5 °C). This tolerance was associated with the activation of the biological processes associated with apoptosis (up regulated) and both cell division and cilium assembly (down regulated). The reduced feeding rate and the negative scope for growth, for a large part of the exposure period at -1.5 °C, suggests that Antarctic winter temperatures represents an environmental barrier to M. chilensis from the Magellanic region settling in the Antarctic. Although M. chilensis are not robust to current Antarctica thermal conditions, future warming scenarios are likely to weaken these physiological barriers. These results strongly suggest that the West Antarctic Peninsula could become part of Mytilus distributional range, especially with dispersal aided by increasing maritime transport activity across the Southern Ocean.

Assuntos

RESUMO

Among anthropogenic habitats built in the marine environment, floating and non-floating structures can be colonized by distinct assemblages. However, there is little knowledge whether these differences are also reflected in the functional structure. This study compared the functional diversity of sessile and mobile invertebrate assemblages that settle over three months on floating vs. non-floating artificial habitats, in two Chilean ports. Using morphological, trophic, behavioral, and life history traits, we found differences between mobile and sessile assemblages regarding the effect of the type of habitat on the functional diversity. Compared to sessile assemblages, a greater functional similarity was observed for mobile assemblages, which suggests that their dispersal capacity enables them to balance the reduced connectivity between settlement structures. No traits, prevailing or selected in one or the other habitat type, was however clearly identified; a result warranting for further studies focusing on more advanced stages of community development.

Assuntos

RESUMO

Examining the effects of disturbances within marine urban communities can shed light on their assembly rules and invasion processes. The effects of physical disturbance, through the removal of dominant native habitat-builders, were investigated in the recolonization of disturbed patches and colonization of plates on pier pilings, in a Chilean port. On pilings, disturbance substantially affected community structure after 3 months, although it slowly converged across treatments after 10 months. On plates, cryptogenic and non-indigenous species richness increased with removal severity, which was not observed in natives. Opportunistic taxa took advantage of colonizing at an early successional stage, illustrating a competition-colonization trade-off, although indirect effects might be at play (e.g. trophic competition or selective predation). Recovery of the habitat-builders then occurred at the expense of cryptogenic and non-indigenous taxa. Whether natives could continue winning against increasing propagule and colonization pressures in marine urban habitats deserves further attention. The interactions between disturbance and biological invasions herein experimentally shown in situ contribute to our understanding of multiple changes imposed by marine urbanization in a growing propagule transport network.

Assuntos

RESUMO

Global biodiversity is both declining and being redistributed in response to multiple drivers characterizing the Anthropocene, including synergies between biological invasions and climate change. The Antarctic marine benthos may constitute the last biogeographic realm where barriers (oceanographic currents, climatic gradients) have not yet been broken. Here we report the successful settlement of a cohort of Mytilus cf. platensis in a shallow subtidal habitat of the South Shetland Islands in 2019, which demonstrates the ability of this species to complete its early life stages in this extreme environment. Genetic analyses and shipping records show that this observation is consistent with the dominant vectors and pathways linking southern Patagonia with the Antarctic Peninsula and demonstrates the potential for impending invasions of Antarctic ecosystems.

Assuntos

RESUMO

Growing coastal urbanization together with the intensification of maritime traffic are major processes explaining the increasing rate of biological introductions in marine environments. To investigate the link between international maritime traffic and the establishment of non-indigenous species (NIS) in coastal areas, biofouling communities in three international and three nearby local ports along 100 km of coastline in south-central Chile were compared using settlement panels and rapid assessment surveys. A larger number of NIS was observed in international ports, as expected in these 'invasion hubs'. However, despite a few environmental differences between international and local ports, the two port categories did not display significant differences regarding NIS establishment and contribution to community structure over the studied period (1.5 years). In international ports, the free space could be a limiting factor for NIS establishment. The results also suggest that local ports should be considered in NIS surveillance programs in Chile.

Assuntos

RESUMO

Non-native ascidians are important members of the fouling community associated with artificial substrata and man-made structures. Being efficient fouling species, they are easily spread by human-mediated transports (e.g., with aquaculture trade and maritime transports). This is exemplified by the ascidian Asterocarpa humilis which displays a wide distribution in the Southern Hemisphere and has been recently reported in the Northern Hemisphere (NW Europe). In continental Chile, its first report dates back from 2000 for the locality of Antofagasta (23°S). Although there was no evidence about the vectors of introduction and spread, nor the source, some authors suggested maritime transport by ship hulls and aquaculture devices as putative introduction pathways and vectors. In the present study, we report for the first time the presence of A. humilis on the hull of an international ship in a commercial port in Concepción bay (36°S), south central Chile. We also found one individual associated to a seashell farm, 70 km far from Concepción bay. Further individuals were subsequently identified within Concepción bay: one juvenile settled upon international harbor pilings and a dozen individuals along aquaculture seashell longlines. For the first specimens sampled, species identification was ascertained using both morphological criteria and molecular barcoding, using the mitochondrial gene cytochrome c oxidase subunit I (COI) and a nuclear gene (ribosomal RNA 18S). The nuclear 18S gene and the mitochondrial gene COI clearly assigned the specimens to A. humilis, confirming our morphological identification. Two haplotypes were obtained with COI corresponding to haplotypes previously obtained with European and Northern Chilean specimens. The present study thus reports for the first time the presence of A. humilis in the Araucanian ecoregion, documenting the apparent expansion of this non-native tunicate in Chile over 2,000 km, spanning over three ecoregions. In addition we reveal the potential implication of the international maritime transport as a vector of spread of this species along the Eastern Pacific coast, and the putative role of aquaculture facilities in promoting local establishments of non-native tunicates.