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Deep-water kelps are little-known large brown algae occurring close to the lower limit of photosynthetic life in the sea. This study compares historical and recent records of the deep-water Mediterranean kelp Laminaria rodriguezii in the Adriatic Sea. Historical records include data from herbarium collections and trawling fishery expeditions in the mid-twentieth century, while recent data comprise records of the last 17 years from MEDITS expeditions, ROV surveys of historical kelp locations, benthic surveys and records by fishermen. Altogether, these findings demonstrate that the Adriatic population of L. rodriguezii has suffered a decline of more than 85 % of its historical range and is now present only around the small offshore island of Palagruža. Bottom trawling activities are presumably responsible for the disappearance elsewhere. We propose to classify L. rodriguezii as “Endangered” in the Adriatic Sea under IUCN criteria B1ab(i,iii,iv), ver 3.1. Oceanographic characteristics of the habitat suggest that besides high water transparency, presence of North Adriatic Dense Water with both strong currents and stable low temperatures of around 14 °C are essential oceanographic factors for the development of L. rodriguezii in the Central Adriatic. The origin of cold water thus differs from that at upwelling sites permitting populations of tropical deep-water kelps. The phylogenetic position of L. rodriguezii is so far unknown. DNA sequences from nuclear and cytoplasmic markers of two thalli from Croatia and the western Mediterranean confirmed that L. rodriguezii is a member of the Laminariaceae and most closely related to L. ochroleuca, L. pallida and the Brazilian deep-water kelp L. abyssalis. © 2016, The Author(s).

A new geographic record of the oomycete Olpidiopsis feldmanni infecting the tetrasporophytic stage of the red alga Asparagopsis sp. from the Adriatic Sea, confirmed through morphological identification, allowed us to expand previous observations of this organism. Ultrastructural investigations of environmental material showed a large central vacuole and a cell wall thicker than previously reported from other basal oomycete pathogens of algae. Phylogenetic analysis closely associates O. feldmanni to O. bostrychiae concurrent with structural observations. This constitutes the first genetic characterisation of an Olpidiopsis species that was initially described before 1960, adding to the genetic data of 3 other marine Olpidiopsis species established and genetically characterised in the last 2 decades. The paper discusses concurrences of the ultrastructural observations made here and in previous studies of the marine Olpidiopsis species with those made on the freshwater species. © The authors 2015.

The projekt "Biodiversity in the Preservation in the Adriaic Sea" is created to promote apecial protection of selected areas. The network of specially protected areas (marine parks, fish reserves, special reserves etc.) in the Croatian part of the Adriatic Sea with strictly defined management regulation has an aim to preserve and to protect the biodiversity and to allow the natural renewal of bioresources, especially of economically important species. In the present preliminary research, the following main characteristics of the narine area of the island of Palgruža have been determinated: dimension and bathymetry ; physical paremeters: temperature, salinity, density, transparency and colour ; chemical parameters: concentration of nutrients, pH and oxygen concentration ; benthic bionomy: distribution and composition of benthic communities, and composition of coastal populations of fish, cephalopods and crustaceans. The proper protocol for systematic protection includes a thorough inventory species, conditions and environmental impacts, the collection of monitoring data to track change and ongoing research into the dynamics of underwater communities. Priority concerning research and inclusion into specially protected areas should be extended to the open sea islands. The elaboration and implementation concepts of projects are thus highly compatible with the development - policy guidelines of national scientific-research programme nad National Island Development Strategy.

The aim of this paper is to evaluate the colonization of the green alga Caulerpa racemosa var. cylindracea thirteen years after it was signalled in the Mediterranean Sea. The alga has been recorded along the coasts of 11 nations, developing on all kind of substrata, both in polluted and in unpolluted areas, between 0 and 70 m depth. The length of coastline affected by the invasion of C. racemosa var. cylindracea in Spain, France, Italy and Croatia ranged from 700 to 750 km at the end of 2003. The main aspects of the ecology of the species in the Mediterranean Sea and the effects of the invasion on human activities in coastal areas are also discussed

Coralline red algae are significant components of sea bottom and up to now considered as exclusively marine species. Here we present the first coralline alga from a freshwater environment, found in the Cetina River (Adriatic Sea watershed). The alga is fully adapted to freshwater, as attested by reproductive structures, sporelings and an inability to survive brackish conditions. Morphological and molecular phylogenetic analyses reveal the species belongs to Pneophyllum and is described as P. cetinaensis sp. nov. The marine-freshwater transition most probably occurred during the last glaciation. The brackish-water ancestor was preadapted to osmotic stress and rapid changes in water salinity and temperature. The particular characteristics of the karst Cetina River, such as hard water enriched with dissolved calcium carbonate and a pH similar to the marine environment, favoured colonization of the river by a marine species. The upstream advance and dispersal is facilitated by exceptionally pronounced zoochory by freshwater gastropods. Pneophyllum cetinaensis defies the paradigm of Corallinales as an exclusively marine group.