Helena Adão

Population Biology of the Red Swamp Crayfish Procambarus Clarkii (Girard, 1852) in Southern Portugal

Population structure and recruitment of Procambarus clarkii were studied from 1989 to 1991 in a freshwater reservoir in southern Portugal. Two distinct recruitment periods were observed, the main one from October to February and a less significant one during spring and summer. With regard to population structure, juveniles were clearly dominant in January and February. The present results suggest that more than one generation per year may occur under favourable climatic conditions.

Sample acidification effects on carbon and nitrogen stable isotope ratios of macrofauna from a Zostera noltii bed

Acidificationtreatmenthasbeenusedinmoststableisotopestudiestoeliminateinorganicnon-dietarycarbon, allowing d 13 C measurement of organic carbon needed for trophic studies. Because only limited information about the acidification effects on isotopic ratios exists in the literature, we provide an assessment of such effects for a wide range of benthic macroinvertebrates from estuarine intertidal sediments with sparseZostera noltiiHornem. vegetation. Our results revealed only few significantd 13 C shifts for macrobenthos; however,d 13 C decrease after acidification was substantial for several species. We conclude that acidification is not necessary for removing calcium carbonate in a majority of macrobenthos, but we alsosuggest preliminary testing before deciding it can be omitted.The magnitude of thed 15 N shifts was substantial for some species and variability in d 15 N values of replicate acidified samples exceeded that of non- acidified samples. Therefore, sample acidification should be avoided for d 15 N determination. Moreover, acidification effects vary considerably among species belonging to a single class, rendering generalisations from single-species information potentially spurious. Additional keywords: decarbonation, inorganic carbon, macrobenthos, sample treatment, seagrass.

DNA Barcoding and Morphological Identification of Benthic Nematodes Assemblages of Estuarine Intertidal Sediments: Advances in Molecular Tools for Biodiversity Assessment

Concerns regarding the status of marine ecosystems have increased in part due to traditional and emerging human activities in marine waters, driving a demand for approaches with high sample throughput capability to improve ecosystem monitoring. Nematodes are already used as indicator species in biodiversity assessments and biomonitoring of terrestrial and marine systems, with molecular approaches offering the opportunity to utilize these organisms further in large scale ecological surveys and environmental assessments. Based on an available nematode dataset for estuarine sediments of the Mira estuary (SW coast, Portugal), we evaluated the diversity of the nematode community of this system, using the molecular markers 18S rRNA and COI genes. These approaches were compared to voucher specimens from a morphological characterization of the same samples allowing validation and comparison between nematode communities. The spatial and temporal variability of the density and diversity of the nematode assemblages was analyzed based on morphological characterization to allow the validation and efficiency of the genetic characterization. A PCO ordination plot showed a distinct separation of the assemblages between sampling occasions confirmed by PERMANOVA analysis, which showed significant differences, although no significant differences were detected between sampling sites. The morphological characterization identified 50 genera of which only 26 and 25 distinct 18S rRNA and COI DNA barcodes, respectively, were obtained. 90.2% of the morphologically identified specimens representing eleven different genera, successfully generated DNA barcodes for both 18S rRNA and COI genes. This study confirmed that the success of the 18S rRNA gene PCR amplification is higher than of COI gene with 43 species amplified against 34. The study highlights a limitation of available sequences for both targets in databases when compared to the known diversity of marine nematodes. The gene sequences of this study enriched the databases, contributing gene sequences from 7 and 16 new genera for the 18S rRNA and COI genes, respectively. A robust database of gene sequences is a prerequisite for the development of robust high sample throughput techniques to be applied in marine assessing and monitoring programs.

Structural and Functional Composition of Benthic Nematode Assemblages During a Natural Recovery Process of Zostera noltii Seagrass Beds

In 2008, the stable seagrass beds of the Mira estuary (SW Portugal) disappeared completely; however, during 2009, they have begun to present early symptoms of natural recovery, characterised by a strongly heterogeneous distribution. This study was designed to investigate the spatial and temporal variability patterns of species composition, densities and trophic composition of the benthic nematode assemblages in this early recovery process, at two sampling sites with three stations each and at five sampling occasions. Because of the erratic and highly patchy seagrass recovery and the high environmental similarity of the two sampling sites, we expected within-site variability in nematode assemblages to exceed between-site variability. However, contrary to that expectation, whilst nematode genus composition was broadly similar between sites, nematode densities differed significantly between sites, and this between-site variability exceeded within-site variability. This may be linked to differences in the Zostera recovery patterns between both sites. In addition, no clear temporal patterns of nematode density, trophic composition and diversity were evident. Nematode assemblages generally resembled those of other estuarine muddy intertidal areas, which have a high tolerance of stress conditions.

Benthic nematode biodiversity of the Abzu, Tiamat and Michael Ivanov mud volcanoes located along the SWIM fracture zone (Gulf of Cadiz)

Studies that focus on meiofaunal assemblages of deep-sea mud volcanoes show an unpredictable abundance and diversity in a clear response to the different environmental conditions of the seeped sediment. The mud volcanoes Abzu, Tiamat and M. Ivanov (ATI), are located along the SWIM1 fracture zone, in front of the accretionary wedge of the Gulf of Cadiz (AWGC). The geological setting and the fluid geochemical characteristics of the ATI mud volcanoes are different from those located within the AWGC. The main aim of this study is to describe and compare the spatial and vertical distributions of the meiofauna and nematode assemblages from the ATI mud volcanoes, the Porto mud volcano located in the AWGC, and a non-seep site (Site 2) as reference. The pore-water on the uppermost sediment layers has compositions close to the near-bottom seawater. The meiofauna abundances were generally lower and the vertical distribution of the assemblages showed a typical pattern, gradually decreasing towards depth. The lack of spatial patterns of the standing stocks contrasts with the spatial variability of diversity and biomass, related to the differences in the nematode assemblages that are distinct between ATI, Site 2 and the Porto mud volcano. The ATI and Site 2 assemblages are similar to deep-sea non-seep habitats, and are clearly coupled with the environmental conditions of the bottom seawater. No evidence of seep conditions favouring the development of specialised fauna were found. The lower diversity and the presence of higher dominance species could be driven by distinct seepage conditions of the Porto mud volcano.