Annual growth increments formed in bivalve shells are increasingly used as proxies of environmental variability and change in marine ecosystems, especially at higher latitudes. Here, we document that well-replicated and exactly dated chronologies can also be developed to capture oceanographic processes in temperate and semi-enclosed seas, such as the Mediterranean. A chronology is constructed for Glycymeris pilosa from a shallow embayment of the northern Adriatic and extends from 1979 to 2016. The chronology significantly (p < 0.05) and positively correlates to winter sea surface temperatures, but negatively correlates to summer temperatures, which suggests that extreme winter lows and extreme summer highs may be limiting to growth. However, the strongest and most consistent relationships are negative correlations with an index of the Adriatic-Ionian Bimodal Oscillating System (BiOS) for which positive values indicate the inflow of the ultraoligotrophic Eastern Mediterranean waters to the Adriatic. In contrast, the substantial freshwater flows that discharge into the Adriatic do not correlate to the bivalve chronology, emphasizing the importance of remote oceanographic processes to growth at this highly coastal site. Overall, this study underscores the potential of bivalve chronologies to capture biologically relevant, local- to regional-scale patterns of ocean circulation in mid-latitude, temperate systems.

The age and shell growth patterns in populations of Patella rustica of the Adriatic Sea were determined by analyzing the inner growth lines visible in shell sections. Marginal increment analysis showed annual periodicity with annual growth line being deposited in May. The growth analysis of 120 individual shells showed that 90.8 % of collected individuals were less than 4 years of age and only two individuals (1.6 %) were older than 6 years. Population structure was described and the generalized von Bertalanffy growth parameters were calculated: asymptotic length (L∞) was 38.22 mm and the growth constant (K) was 0.30 year-1. Growth performance index value of P. rustica (Ø’) was 2.64 and is among the lowest ranges reported for limpet species. Patella rustica shells were degraded to different degrees by microbial bioerosion. Microboring organisms identified were pseudofilamentous and filamentous cyanobacteria Hormathonema paulocellulare, Hyella caespitosa, Mastigocoleus testarum and Leptolyngbya sp. The overall intensity of infestation was relatively low, but increased in severity with shell length. The damage was most often restricted to the oldest parts of the shell, i.e. apex of the shell, posing difficulties in determining the exact position of the first growth line. The present study is first to introduce the use of inner growth lines in Patella rustica shell sections as a reliable method for age determination and it provides the first insight into the growth patterns of this keystone species while taking the interference of microbial shell bioerosion in consideration.

Cernuella virgata(Da Costa, 1778) (Mollusca: Hygromiidae), commonly known as the “vineyard snail,” is endemic species in Mediterranean and Western Europe including the British Isles, but in the Eastern USA and Australia it represents an introduced invasive species. The present work examines the genetic variability and phylogenetic relationships among the four populations of this land snail sampled along the east Adriatic region of Croatia using mitochondrial markers (partial 16S rDNA and COI gene) in addition to traditional methods of shell’s shape analysis. All the three molecular-phylogenetic approaches (median joining haplotype network analysis and Bayesian analysis, as well as maximum likelihood analysis) revealed two-three major subnetworks for both 16S rDNA and COI, with a clear distinction between south Adriatic haplotypes (Pisak) and north Adriatic haplotypes (Krk and Cres). The population from Karlobag was comprised of both north and south haplotypes, thus representing a putative contact zone between these two groups. The morphometric analysis showed that individuals from Cres island population were statistically significantly wider and higher than individuals from Pisak population. Analysis of the SW/SH ratio and the relationship between shell width and shell height showed no differences in shell growth between the two examined populations, indicating equal shell growth and shape, which gives the possibility that differences in size of individuals between those two populations could be influenced by biotic (physiological) or abiotic (environmental) factors. This study represents the first analysis of genetic variability and relatedness among native populations ofC. virgata.

In this study we present the results of a ten year survey of the aquatic macroinvertebrate fauna along four karst rivers: Jadro, Žrnovnica, Grab and Ruda, all of them situated in the Middle Dalmatia region of Croatia, in an attempt to construct the Iliric Biotic Index, which will be more applicable for the water quality analysis than the most frequently applied biotic index in Croatia, the Italian Modification of Extended Biotic Index. The rivers geologically belong to the Dinaric karst, unique geological phenomena in Europe. Benthic macroinvertebrates were collected along each river at 15 sites by standard methods of sampling along with several physicochemical parameters, including: temperature, dissolved oxygen, carbon dioxide, alkalinity, hardness and pH. Univariate and multivariate techniques revealed differences in the macroinvertebrate community structure as well as in physicochemical parameters between the Karst rivers and continental rivers. Based on those differences, the Iliric Biotic Index was proposed as the standard of karst river water quality in Croatia in accordance with the EU Water Framework Directive. Differences between the Iliric Biotic Index and the most commonly used biotic indices in the European Community and the USA (The Biological Monitoring Working Party (B.M.W.P.) scores, i.e. Extended Biotic Index, Indice Biotique, Family Biotic Index) suggest that karst rivers need a new biotic index.