Rade Garić

Bacterial Diversity in the South Adriatic Sea during a Strong, Deep Winter Convection Year

ABSTRACT The South Adriatic Sea is the deepest part of the Adriatic Sea and represents a key area for both the Adriatic Sea and the deep eastern Mediterranean. It has a role in dense water formation for the eastern Mediterranean deep circulation cell, and it represents an entry point for water masses originating from the Ionian Sea. The biodiversity and seasonality of bacterial picoplankton before, during, and after deep winter convection in the oligotrophic South Adriatic waters were assessed by combining comparative 16S rRNA sequence analysis and catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH). The picoplankton communities reached their maximum abundance in the spring euphotic zone when the maximum value of the chlorophyll a in response to deep winter convection was recorded. The communities were dominated by Bacteria, while Archaea were a minor constituent. A seasonality of bacterial richness and diversity was observed, with minimum values occurring during the winter convection and spring postconvection periods and maximum values occurring under summer stratified conditions. The SAR11 clade was the main constituent of the bacterial communities and reached the maximum abundance in the euphotic zone in spring after the convection episode. Cyanobacteria were the second most abundant group, and their abundance strongly depended on the convection event, when minimal cyanobacterial abundance was observed. In spring and autumn, the euphotic zone was characterized by Bacteroidetes and Gammaproteobacteria. Bacteroidetes clades NS2b, NS4, and NS5 and the gammaproteobacterial SAR86 clade were detected to co-occur with phytoplankton blooms. The SAR324, SAR202, and SAR406 clades were present in the deep layer, exhibiting different seasonal variations in abundance. Overall, our data demonstrate that the abundances of particular bacterial clades and the overall bacterial richness and diversity are greatly impacted by strong winter convection.

Comparative analysis of specialized metabolites and antioxidant capacity in vitro of different natural populations of Globularia spp.

Abstract Total phenolic, flavonoid, condensed tannin and iridoid content, as well as antioxidant capacity in vitro, were determined spectrophotometrically in methanolic extracts of different plant parts of the Mediterranean medicinal plant Globularia alypum L. and three widespread European species of the same genus: G. cordifolia L., G. meridionalis (Podp.) O. Schwarz and G. punctata Lapeyr. In order to consider possible environmental influences on the production of specialized metabolites, each species, except G. alypum, was collected from three different natural populations. Great variations in the amounts of specialized metabolites were observed among different plant parts and species. For example, total phenolic content ranged from 10.13 (G. punctata, flowers) to 44.90 (G. cordifolia, flower stems) mg gallic acid equivalent g−1 dry weight. Moreover, great differences, attributed to location-specific environmental factors, were observed among different populations of the same species. For example, a strong positive correlation was observed among mean monthly temperatures and total phenolic contents in the leaves of studied Globularia spp. (r = 0.75, p = 0.019). However, despite these differences, all species were rich in bioactive substances when compared to G. alypum, especially in their aerial parts. A very good positive correlation was observed between total phenolic content and DPPH radical scavenging capacity (r = 0.86, p < 0.001)/ABTS radical scavenging capacity (r = 0.83, p < 0.001). The results obtained show that G. cordifolia, G. meridionalis and G. punctata are rich in bioactive substances, providing support for their pharmaceutical utilization. Further investigations are needed to verify the possibility of their medicinal use.

Ecology and population structure of the hyperbenthic copepod Mesaiokeras hurei Kršinić, 2003 (Calanoida: Mesaiokeratidae) from an isolated marine lake (Mljet island, Southern Adriatic Sea, Croatia)

The monogeneric family Mesaiokeratidae (Copepoda: Calanoida) is exclusively bentho-pelagic and comprises nine small hyperbenthic species. Previous knowledge of these species has been limited to the description of their morphology and habitat. We provide new information about the ecology of Mesaiokeras hurei Krsinic, 2003, one of the small-size species of the family and found only in an isolated marine lake on the southern Adriatic island of Mljet (Croatia). Genetic markers were used to investigate its phylogenetic relationships with other copepods. The abundance of M. hurei abundance was highly variable over the years and seasons sampled. Densities were higher in spring and autumn. It was particularly abundant in 2011, averaging 629 ± 800 individuals/m3, and with a maximum of 1971 individuals m−3 in November, but averaged 74 ± 71 individuals/m3 and 66 ± 71 individuals/m3 in 2001 and 2008, respectively. Specimens were found in a range of temperatures, from 10.5°C to 18.3°C, but a majority of individuals (67%) was found in the 12-14°C layer. In addition to temperature, oxygen was a significant predictor ( p < 0 . 001 ) of the vertical micro-distribution of M. hurei. The DNA barcode sequence for the species is reported here for the first time. Analysis of the nuclear small subunit rRNA gene fragment (18S) showed a genetic similarity with representatives of the superfamily Clausocalanoidea.

Fritillaria ragusina sp. nov., a new species of Appendicularia (Tunicata) from the Adriatic Sea

A new species of appendicularian, Fritillaria ragusina, is described from specimens collected between the surface and 300 m depth at three stations in the open south Adriatic Sea (north-eastern Mediterranean). Fritillaria ragusina is characterized by a broad trunk–tail connection created by a wide tail fin in the initial part of the tail, sloping shoulders of the tail fin, broad tail musculature, multiple fusiform amphichordal cells along the edge of the tail musculature and small size at sexual maturity (maximum recorded trunk length of 445 mm and maximum recorded tail length of 960 mm). Maximum abundance, 2.4 ind m-3, was found within the 0–50 m layer.