Ascensão Ravara

Are organic falls bridging reduced environments in the deep sea? - results from colonization experiments in the Gulf of Cádiz.

Organic falls create localised patches of organic enrichment and disturbance where enhanced degradation is mediated by diversified microbial assemblages and specialized fauna. The view of organic falls as “stepping stones” for the colonization of deep-sea reducing environments has been often loosely used, but much remains to be proven concerning their capability to bridge dispersal among such environments. Aiming the clarification of this issue, we used an experimental approach to answer the following questions: Are relatively small organic falls in the deep sea capable of sustaining taxonomically and trophically diverse assemblages over demographically relevant temporal scales? Are there important depth- or site-related sources of variability for the composition and structure of these assemblages? Is the proximity of other reducing environments influential for their colonization? We analysed the taxonomical and trophic diversity patterns and partitioning (α- and β-diversity) of the macrofaunal assemblages recruited in small colonization devices with organic and inorganic substrata after 1-2 years of deployment on mud volcanoes of the Gulf of Cádiz. Our results show that small organic falls can sustain highly diverse and trophically coherent assemblages for time periods allowing growth to reproductive maturity, and successive generations of dominant species. The composition and structure of the assemblages showed variability consistent with their biogeographic and bathymetric contexts. However, the proximity of cold seeps had limited influence on the similarity between the assemblages of these two habitats and organic falls sustained a distinctive fauna with dominant substrate-specific taxa. We conclude that it is unlikely that small organic falls may regularly ensure population connectivity among cold seeps and vents. They may be a recurrent source of evolutionary candidates for the colonization of such ecosystems. However, there may be a critical size of organic fall to create the necessary intense and persistent reducing conditions for sustaining typical chemosymbiotic vent and seep organisms.

Starting a DNA barcode reference library for shallow water polychaetes from the southern European Atlantic coast

Annelid polychaetes have been seldom the focus of dedicated DNA barcoding studies, despite their ecological relevance and often dominance, particularly in soft‐bottom estuarine and coastal marine ecosystems. Here, we report the first assessment of the performance of DNA barcodes in the discrimination of shallow water polychaete species from the southern European Atlantic coast, focusing on specimens collected in estuaries and coastal ecosystems of Portugal. We analysed cytochrome oxidase I DNA barcodes (COI‐5P) from 164 specimens, which were assigned to 51 morphospecies. To our data set from Portugal, we added available published sequences selected from the same species, genus or family, to inspect for taxonomic congruence among studies and collection location. The final data set comprised 290 specimens and 79 morphospecies, which generated 99 Barcode Index Numbers (BINs) within Barcode of Life Data Systems (BOLD). Among these, 22 BINs were singletons, 47 other BINs were concordant, confirming the initial identification based on morphological characters, and 30 were discordant, most of which consisted on multiple BINs found for the same morphospecies. Some of the most prominent cases in the latter category include Hediste diversicolor (O.F. Müller, 1776) (7), Eulalia viridis (Linnaeus, 1767) (2) and Owenia fusiformis (delle Chiaje, 1844) (5), all of them reported from Portugal and frequently used in ecological studies as environmental quality indicators. Our results for these species showed discordance between molecular lineages and morphospecies, or added additional relatively divergent lineages. The potential inaccuracies in environmental assessments, where underpinning polychaete species diversity is poorly resolved or clarified, demand additional and extensive investigation of the DNA barcode diversity in this group, in parallel with alpha taxonomy efforts.

Phylogenetic relationships within Nephtyidae (Polychaeta, Annelida)

Ravara, A., Wiklund, H., Cunha, M. R. & Pleijel, F. (2010). Phylogenetic relationships within Nephtyidae (Polychaeta, Annelida). —Zoologica Scripta, 39, 394–405.

First account on the diversity of Ophryotrocha (Annelida, Dorvilleidae) from a mammal-fall in the deep-Atlantic Ocean with the description of three new species

Annelids of the genus Ophryotrocha are globally distributed in a wide variety of organically enriched habitats. Although mostly known from shallow water, the expansion of deep-sea research revealed several new Ophryotrocha species mainly associated with organic-falls, in particular with cetacean carcasses, or whale-falls. Despite the great deal of interest that fauna associated with whale-falls have attracted, very little is known about this fauna in the deep-Atlantic Ocean. Hereby we analyse, for the first time, the Ophryotrocha assemblage associated with a mammal-fall in this region of the worlds ocean. Specimens were collected from the bones of degrading cow carcasses deployed in the Setúbal canyon at approximately 1000 m depth. Using morphological characters and phylogenetic analyses based on the nuclear gene H3 performed on 31 Ophryotrocha species, we report the presence of five different species, we describe three new species and extend the distribution of O. scutella. Ophryotrocha scutella was previously known from a shallow-water whale-fall and organically enriched sediments beneath a fish farm off Scandinavia and is the first species to be reported from organic-falls in both shallow and deep waters. The presence of five congeners emphasize the importance of the genus Ophryotrocha in the degradation of organic matter in the deep-sea. Our results substantially increase the number of deep Atlantic species in the genus Ophryotrocha and highlight the remarkable unknown diversity and biogeographic patterns hidden behind unstudied deep-sea habitats. http://zoobank.org/urn:lsid:zoobank.org:pub:A12699DA-E580-4782-941A-48D7B31E4DAE

Polychaeta (Annelida) from the continental shelf off Aveiro (NW Portugal): Species composition and community structure

The present study provides a checklist of the polychaete fauna collected on the continental shelf off Aveiro (NW Portugal), within an area located between latitudes 40°30’N and 40°50’N and longitudes 8°40’W and 9°20’W, and a depth range of 8 to 185 m. The list includes 136 species, belonging to 37 families, from which 19 are new records for the Portuguese coast ( Isolda pulchella , Mesochaetopterus sagittarius , Aphelochaeta multibranchis , Chaetozone cf. vivipara , Diplocirrus hirsutus , Goniadella gracilis , Gyptis mediterranea , Lumbrinerides crassicephala , Eumida bahusiensis , Eumida ockelmanni , Nereiphylla paretti , Phyllodoce rosea , Glyphohesione klatti , Malmgreniella arenicolae , Prionospio aluta , Pseudopolydora paucibranchisata , Pseudopolydora pulchra , Scolelepis mesnili , Polycirrus cf. medusa ). The shelf off Aveiro presents a well- defined pattern of sediment distribution, with finer sand on the inner (8–22 m depth) and the outer (94–184 m depth) parts of the shelf and coarser sediments on the mid-shelf. The distribution of polychaete assemblages follows closely the aforementioned sedimentary pattern, showing different specific composition and structure in each of the three areas. Depth was also found to play an important role in the distribution of some polychaete species.

Mesochaetopterus sagittarius: an example of a biogeography discrepancy between larval and adult boundaries: implication for recruitment studies

A geographic discrepancy between the distribution boundaries for larvae and adults of the chaetopterid Mesochaetopterus sagittarius was recorded. The most northerly position where benthic individuals, probably not reproductive, have been collected in the Atlantic corresponds to the latitude of Aveiro (Portugal). The most northerly position for larvae corresponds to that of Arcachon (France). The larvae found off Arcachon constitute an influx of subtropical origin. They rarely succeed in passing the fixation stage, and when they do, the benthic stage is not capable of reproduction. The occupation of a very large zone by planktonic larvae spread over 4° of latitude (500 km), eventually resulting in sterile benthic populations, confirms that environmental constraints are less severe on larvae than on adults. This work emphasizes, through the integration of different oceanographic disciplines, the importance of knowing the structure of the spatial distribution of adults when seeking to achieve a better understanding of local recruitment.

Two new species of scale worms (Polychaeta: Aphroditiformia) from deep-sea habitats in the Gulf of Cadiz (NE Atlantic)

Two new species of scale worms are described from the Gulf of Cadiz (NE Atlantic), at depths between 1100 and 2230 m. Australaugeneria iberica sp. nov. (Polynoidae) was obtained from an alcyonarian colony collected at the flank of Carlos Ribeiro mud volcano; it is characterized by the presence of neuropodial hooks only on segment two and by having the first parapodia not enlarged. This is the first report of the genus for the deep sea. The diagnosis of Australaugeneria is emended and a table comparing all species of the genus is provided. Pholoe petersenae sp. nov. (Pholoidae) was collected from the crater of three mud volcanoes (Darwin, Captain Arutyunov and Carlos Ribeiro) in areas of active seepage. This species is characterized by the presence of prostomial peaks and parapodia stylodes and the absence of eyes.