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The marine prairies are paramount to the marine ecosystem playing a crucial role in various ways. Owing to the global atmospheric events inducing hydrospheric changes, marine seaweeds have been negatively affected and are vulnerable. Conventional methods (SCUBA), which were previously used to collect seagrasses, have become a destructive method for deriving unrecoverable damages for their stocks and have been replaced with remote sensing methods. Considering the advantages of the acoustic methods, two different in/ex-situ experiments were conducted to ground-truth the common seagrass, P. oceanica, in time and space of the Turkish Mediterranean water in 2011-2012 using a scientific echosounder with a split beam transducer operated at a frequency of 206 kHz. After the separation of the seagrass from spurious scatterers, the acoustic parameters (Sa: area backscattering strength, Sv: volume backscattering strength, and TS: Target Strength) were correlated and regressed with the biometric variables (Leaf Area Index, biomass, volume, length, width, diameter, or thickness) of different parts (leaf, rhizome, and sheath) of the seagrass. Estimation of biometrics by acoustic methods has been considered a challenge up to now. Statistical relationships between biometrics and acoustics were precisely examined for the species. The relationships were linearly established in the acoustic geometric region. There was a seasonal difference in the relationships. Their rhizomes and sheaths were considered unstable non-linear parts and remained unexplained for the acoustic response. Acoustic response to the leaf density (d, g cm-3), which was a distinguished component in the reflection, was found to be dependent on the seasonal biological activities of P. oceanica. Posidonia, which has a d greater than 1 g/cm3, produced the geometric region. The present study was the first attempt to establish the relationships of the seagrass under protection, and can decrease usage of destructive methods for future studies.

This Collective Article presents new information about the occurrence of 20 taxa that belong to six Phyla: one Cnidaria, one Ctenophora, two Annelida, four Mollusca, two Arthropoda, and ten Chordata. These records were reported from ten countries from the western to the eastern Mediterranean Sea as follows: Spain: early colonization signs of the Mar Menor lagoon by the cigar jellyfish Olindias muelleri; France: second record of the sea chub of the genus Kyphosus in French Mediterranean waters; Italy: first record of the marbled crab Pachygrapsus maurus in Sardinian waters; first records of the polychaetes Malmgrenia polypapillata and Levinsenia tribranchiata in the Tyrrhenian Sea; new record of the deep-sea squid Ancistrocheirus lesueurii in the Tyrrhenian Sea; first record of the pignosed arrowtooth eel Dysomma brevirostre in the Adriatic Sea; Tunisia: first documented record of the blue butterfish Stromateus fiatola and new record of the iconic great white shark Carcharodon carcharias in the Gulf of Gabes; Slovenia: first records of the sea slug Diaphorodoris alba and the sharpnose sevengill shark Heptranchias perlo; Montenegro: new record of the rare tope shark Galeorhinus galeus; Greece: new records of the rabbitfish Chimaera monstrosa and the electric ray Tetronarce nobiliana; first published record of the nuribranch Discodoris rosi; Turkey: first record of the ctenophore Hormiphora plumosa at country level; first records of the anomuran decapod Munida speciosa and the Mediterranean tripodfish, Bathypterois mediterraneus from the Levantine Sea; Cyprus: first documented record of the nuribranch Scyllaea pelagica; Lebanon: first record of the killer whale Orcinus orca from the Levantine Sea.

Overall and spatiotemporal total length-weight relationships (LWR) were studied for the 116 fish composing of 107 osseous and 9 cartilaginous fish species collected by otter trawl in the shelf and upper slope of Gulf of Antalya in 2014-2015. Of the 89 abundant bony species, 38 species had isometric growth, 24 species positive allometry, and 27 species negative allometry. Growth type was significantly affected with the sample size. LWRs of osseous fish species which had their body condition factor CF ��� 1 were significantly differentiated by factors region, season and depth, but none was for the fish having CF ��� 1. The factorial differences were found in relation with the CF. The b values for the osseous fish decreased slightly with bottom depth from lower shelf to middle shelf. The highest b values occurred for the ubiquitous fish on the entire shelf while the a values increased. At greater depths, the b values shifted the allometry from the isometry to the negative allometry. Average b value of osseous fish was 2.962 �� 0.048 (isometric), and median was 2.992. LWRs of body widthweight of batoid fish showed a b value ��� 3. Sexual dimorphism in the LWR occurred for 10 species.