Research Outputs
Presence of the tunicate Asterocarpa humilis on ship hulls and aquaculture facilities in the coast of the Biobio Region, south central Chile
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_x000E_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_x000E_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.
Contrasting metatrochal behavior of mollusc and annelid larvae and the regulation of feeding while swimming
Molluscan veliger larvae and some annelid larvae capture particulate food between a preoral prototrochal band of long cilia that create a current for both swimming and feeding and a postoral metatrochal band of shorter cilia that beat toward the prototroch. Larvae encountering satiating or noxious particles must somehow swim without capturing particles or else reject large numbers of captured particles. Because high rates of particle capture are inferred to depend on the beat of both ciliary bands, arrest of the metatroch could be one way to swim while reducing captures. Larvae in eight families of annelids arrest metatrochal cilia frequently during prototrochal beat, often over a large part of the metatrochal band and with the arrested cilia aligned near the beginning of the effective stroke. In contrast, metatrochs of veligers of gastropods and bivalves rarely arrested while the prototroch beat, and those arrests were more localized and variable in position. This difference in metatrochal arrest was unexpected under hypotheses of either a single origin of this feeding mechanism or multiple origins within each phylum. Although different in metatrochal arrests, larvae of both phyla can separate swimming from feeding while both prototroch and metatroch beat. One hypothesis explaining low rates of capture per encounter, without metatrochal arrest, is a change in adhesion of prototrochal cilia with algae. In a few observations, part of the velar edge was retained within the veliger's shell so that exposed prototrochal cilia contributed to swimming while the adjacent metatroch and food groove were sequestered.
Tidal height and sand as potential drivers of the ecological interaction of the two intertidal mussels Perumytilus purpuratus and Semimytilus algosus
The mussels Perumytilus purpuratus and Semimytilus algosus are two dominant species of intertidal rocky shores of central Chile. These species have marked differences in their distribution patterns with P. purpuratus dominating the mid-intertidal zone and S. algosus dominating the lower intertidal zone usually in habitats influenced by sand. Although it has been suggested that differences in tolerance to environmental conditions, such as air exposure and presence of sand, can explain the distribution of these species, there are currently no experimental studies to support such hypotheses. Here, we evaluated the growth and survival rate in the field of both mussel species at four different tidal heights: 25, 75, 135, and 175 cm above the zero tide. In addition, filtration rates were estimated for both species in the presence and absence of sand in laboratory conditions. The results showed that shell and wet weight growth rates of P. purpuratus were highest in mid- and medium-high tidal heights, whereas the growth rate of S. algosus was highest in the medium-low level. Similar pattern was observed for survival percentage. Furthermore, small S. algosus individuals cultivated with sand in suspension had significantly higher filtration rates than P. purpuratus. In large individuals, no differences were observed between the two species nor between treatments (presence and absence of sand). These results indicate that the differences in the distribution patterns of P. purpuratus and S. algosus in the intertidal can be explained by differences in physiological tolerances to both air exposure and to the presence of sand.
A new case of poecilogony from South America and the implications of nurse eggs, capsule structure, and maternal brooding behavior on the development of different larval types
Poecilogony is the production of different larval types within the same species. Although rare, poecilogonous species are ideal systems for testing the evolutionary and ecological implication of different developmental modes in marine invertebrates. Here, we described a new case of poecilogony, the Southern Hemisphere spionid Boccardia wellingtonensis. We used a combination of common-garden experiments, video recordings, and in vitro manipulations of individuals from three sites to (1) document the type of poecilogony, the brooding behavior of the mother, and the hatching process; (2) experimentally measure the effect of nurse eggs on the growth and type of larvae produced; and (3) document variation in the length of the brooding period, number of capsules, larvae, and nurse eggs of mothers from three sites to explore the potential for plasticity in reproductive traits. These results were compared to the previously reported poecilogonous species B. proboscidea, which resembles B. wellingtonensis in size, morphology, ecology, and reproductive strategy but differs in capsule structure. We found that in contrast to B. proboscidea, B. wellingtonensis produced larvae that, in isolation and in the presence of nurse eggs, developed into a wide range of offspring sizes. Mothers brood and hatch the larvae with frequent partial hatching of the brood during the brooding period. Although larvae could not liberate themselves, larvae crossed to other capsules as interconnections between capsules broke during the developmental period, potentially affecting food availability, sibling competition for nurse eggs, and cannibalism. Variation in brooding time and number of capsules deposited among sites suggest local adaptations.
The influence of glacial melt and retreat on the nutritional condition of the bivalve Nuculana inaequisculpta (Protobranchia: Nuculanidae) in the West Antarctic Peninsula
Due to climate change, numerous ice bodies have been lost in the West Antarctic Peninsula (WAP). As a consequence, deglaciation is expected to impact the marine environment and its biota at physiological and ecosystem levels. Nuculana inaequisculpta is a marine bivalve widely distributed around Antarctica that plays an important role for ecosystem functioning. Considering that N. inaequisculpta inhabits coastal areas under effect of glacial melt and retreat, impacts on its nutritional condition are expected due to alterations on its physiology and food availability. To test this hypothesis, biochemical composition (lipids, proteins, and fatty acids) and energy content were measured in individuals of N. inaequisculpta collected in a fjord at different distances to the retreating glacier in the WAP. Oceanographic parameters of the top and bottom-water layers (temperature, salinity, dissolved oxygen, and chlorophyll-a) were measured to investigate how the environment changes along the fjord. Results showed that surface oceanographic parameters displayed a lower temperature and dissolved oxygen, but a higher salinity and chlorophyll-a content at nearest compared to farthest sites to the glacier. In contrast, a lower temperature and chlorophyll-a, and a higher salinity and dissolved oxygen was measured in the bottom-water layer toward the glacier. N. inaequisculpta had a higher amount of lipids (17.42 ± 3.24 vs. 12.16 ± 3.46%), protein (24.34 ± 6.12 vs. 21.05 ± 2.46%) and energy content (50.57 ± 6.97 J vs. 39.14 ± 5.80 J) in the farthest compared to the nearest site to the glacier. No differences were found in total fatty acids among all sites. It seems likely that lower individual fitness related to proximity to the glacier would not be related to nutritional quality of sediment food, but rather to food quantity.
Experimental and survey-based evidences for effective biotic resistance by predators in ports
Of the suite of species interactions involved in biotic resistance to species invasions, predation can have complex outcomes according to the theoretical and empirical framework of community ecology. In this study, we aimed to determine the likelihood of consumptive biotic resistance within fouling communities in four ports of central Chile. Notably, we examined the influence of micro- (> 1–2 mm, < 1–2 cm) and macro- (> 1–2 cm) predators, with a particular focus on their effects on non-indigenous species (NIS). Experimental and observational approaches were combined. An exclusion experiment was carried out over 4 months to examine predator effect on the early establishment of new assemblages on settlement panels. Later successional stages upon panels were examined over a total of 26 months and supported by rapid assessment surveys in the surrounding habitats. Community structure was significantly influenced by the exclusion treatments. Macropredators reduced the fouling biomass and abundance, although conflicting patterns emerged from the exclusion of both categories of predators. Altogether, predators reduced the abundance of most NIS and cryptogenic species, some of them being only observed when the two categories of predators were excluded—a pattern generally sustained over the long-term dynamics in community development. Our results show an effective consumptive biotic resistance, furthermore possibly dependent on predator size. Further work is however needed to determine the influence of the functional diversity of natural enemies on the efficiency of biotic resistance and its interplay with other biotic interactions (competition or mutualism). A comprehensive understanding of these processes should in turn help defining management strategies in a context of habitat modification and species loss.
Non-indigenous species contribute equally to biofouling communities in international vs local ports in the Biobío region, Chile
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.
Greater functional similarity in mobile compared to sessile assemblages colonizing artificial coastal habitats
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 as-semblages 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.
Genetic population structure of lane snapper Lutjanus synagris (Linnaeus, 1758) in Western Atlantic: Implications for conservation
Genetic structure and connectivity information can be used to identify biological corridors and prioritize the conservation of areas that help maintain ecosystem integrity. Some marine fish, especially those of commercial interest, have been proposed as suitable indicators to identify potential marine biological corridors due to their high mobility among habitats and socioeconomic importance. In this study, we assessed the genetic structure of lane snapper populations in the Honduran Caribbean to evaluate connectivity and identify potential environmental barriers. Furthermore, we evaluated the genetic characteristics of the lane snapper on a larger spatial scale, including populations across the rest of its distribution range in the western Atlantic, using mtDNA and nuDNA markers. Our results demonstrate a significant genetic diversity of lane snappers in the Honduran Caribbean. Furthermore, despite their high dispersal potential, we observed genetic structuring in lane snapper populations on a larger spatial scale, resulting in the formation of two distinct groups throughout their distribution range: group 1 from Florida, the Gulf of Mexico, Honduras, and Colombia and group 2 from Puerto Rico and Brazil. This genetic differentiation can be attributed to oceanographic barriers such as river plumes and marine currents. These findings have the potential to significantly impact marine conservation and management efforts in the region, both at local and regional scales. It is anticipated that they will not only inform but also elicit a response, driving further action towards effective conservation measures. At a local scale, we recommend that conservation efforts focus on protecting critical habitats. At a regional scale, lane snappers should be included in the management plans of existing marine protected areas necessary to ensure the long-term sustainability of the species and the marine ecosystems in which it resides.
Structural attributes and macrofaunal assemblages associated with rose gorgonian gardens (Leptogorgia sp. nov.) in Central Chile: Opening the door for conservation actions
Gorgonians (like corals) are important habitat-forming organisms that support a diversity of macrofauna. This study explored structural attributes of gorgonian gardens formed by rose gorgonians (Leptogorgia sp. nov.) and associated macrofaunal assemblages in Caleta Pichicuy (Central Chile). Hierarchical sampling was conducted at 20 m depth (maximum colony abundances) in order to assess spatial variability in abundance and colony attributes at two spatial scales (among sites and rocky walls). The abundance and composition of the associated vagile and sessile macrofauna were also examined using univariant (Taxa richness and Shannon index (H’e)) and multivariant approaches and were compared with adjacent bare rocky habitats. Our results showed a high abundance of gorgonians (ca. 28.9–36.5 colonies m−2) compared to other gorgonian gardens in the world. For structural attributes, our results showed smaller colonies with thicker holdfasts in more exposed sites, suggesting the influence of hydrodynamic forces on the colony morphology. Taxa richness and H’e of vagile fauna showed threefold and twofold, respectively, higher values in gorgonian gardens compared to bare walls, but no differences were observed for sessile fauna. In addition, PCoA and PERMANOVA evidenced a distinctive assemblages’ composition between habitats for both vagile and sessile fauna. Correlation analyzes and dbRDA showed, however, little association between structural attributes and associated faunal assemblages (R2 = 0.06, and ca. 3–9.4% of the total variation explained, respectively). Our results constitute the first assessment of structural habitat complexity and accompanying fauna in these gorgonian gardens and establish the baseline for understanding possible future changes associated to human activities.