Toxicological risks on the human health of populations living around the Mediterranean Sea linked to the invasion of non-indigenous marine species from the Red Sea: A review

The Mediterranean region is, by far, a prime travel destination, having hosted more than 330 million tourists in 2016, mostly for seaside holidays. A greatly increased influx of thermophilic Red Sea species, introduced through the Suez Canal in a process referred to as Lessepsian invasion (in honor of Ferdinand de Lesseps who instigated the building of the Suez Canal), have raised awareness among scientists, medical personnel, and the public, of health risks caused by some venomous and poisonous marine species. The main species of concern are the poisonous Lagocephalus sceleratus, and the venomous Plotosus lineatus, Siganus luridus, Siganus rivulatus, Pterois miles, Synancea verrucosa, Rhopilema nomadica, Macrorhynchia philippina and Diadema setosum. Recognizing that the main factors that drive the introduction and dispersal of Red Sea biota in the Mediterranean, i.e., Suez Canal enlargements and warming seawater, are set to increase, and international tourist arrivals are forecasted to increase as well, to 500 million in 2030, an increase in intoxications and envenomations by alien marine species is to be expected and prepared for.

Patterns of invasive ctenophore Mnemiopsis leidyi distribution and variability in different recipient environments of the Eurasian seas: A review

Harmful invader ctenophore Mnemiopsis leidyi's expansions in the Eurasian Seas, its spatio-temporal population dynamics depending on environmental conditions in recipient habitats have been synthesized. M. leidyi found suitable temperature, salinity and productivity conditions in the temperate and subtropical environments of the semi-enclosed seas, in the coastal areas of open basins and in closed water bodies, where it created autonomous populations. M. leidyi changes its phenology depending on seasonal temperature regime in different environments. We assessed ranges of sea surface temperature, sea surface salinity and sea surface chlorophyll values, sufficient for M. leidyi general occurrence and reproduction based on comprehensive long-term datasets, contributed by co-authors. This assessment revealed that there are at least two eco-types (Southern and Northern) in the recipient seas of Eurasia with features specific for their donor areas. The range of thresholds for M. leidyi establishment, occurrence and life cycle in both eco-types depends on variability of environmental parameters in their native habitats.

Twenty two years of sewage sludge marine disposal monitoring in the Eastern Mediterranean Sea: Impact on sediment quality and infauna and the response to load reduction

Effects of sewage sludge disposal on sediments and infauna are presented in a unique long-term (22years) data set from the Eastern Mediterranean. While organic carbon (Corg) and metals affected sediment quality in an area which size varied seasonally, the infauna exhibited seasonal "boom and bust" cycle. Metal concentrations declined following load reduction. However, Corg did not decrease and infaunal abundance, closely related to Corg, varied with changes in environmental forcing. Mild winters affected the infaunal populations at the heavily impacted stations, due to anoxic conditions. Planned cessation of disposal is estimated to reduce Corg and metal concentrations to pre-discharge levels. Yet the resettling biota is expected to differ significantly from the pre-discharge one and consist in large part of Erythraean non indigenous species.

Distribution and population structure of the alien Indo-Pacific Randall's threadfin bream Nemipterus randalli in the eastern Mediterranean Sea

As part of a comprehensive study of trawl fishery catch off Israel (Ashdod) and Turkey (Iskenderun and Antalya) conducted during 2008-2011, the population explosion of Nemipterus randalli, first recorded in the Mediterranean Sea in the beginning of 2005, was documented. The smallest individuals occurred on deeper bottoms (120 m), significantly more individuals were collected at night, and juvenile recruitment to the commercial fishery occurred during November and December at 40 m depth.

International arrivals: widespread bioinvasions in European Seas

The European Union lacks a comprehensive framework to address the threats posed by the introduction and spread of marine non-indigenous species (NIS). Current efforts are fragmented and suffer substantial gaps in coverage. In this paper we identify and discuss issues relating to the assessment of spatial and temporal patterns of introductions in European Seas (ES), based on a scientifically validated information system of aquatic non-indigenous and cryptogenic species, AquaNIS. While recognizing the limitations of the existing data, we extract information that can be used to assess the relative risk of introductions for different taxonomic groups, geographic regions and likely vectors. The dataset comprises 879 multicellular NIS. We applied a country-based approach to assess patterns of NIS richness in ES, and identify the principal introduction routes and vectors, the most widespread NIS and their spatial and temporal spread patterns. Between 1970 and 2013, the number of recorded NIS has grown by 86, 173 and 204% in the Baltic, Western European margin and the Mediterranean, respectively; 52 of the 879 NIS were recorded in 10 or more countries, and 25 NIS first recorded in European seas since 1990 have since been reported in five or more countries. Our results highlight the ever-rising role of shipping (commercial and recreational) as a vector for the widespread and recently spread NIS. The Suez Canal, a corridor unique to the Mediterranean, is responsible for the increased introduction of new thermophilic NIS into this warming sea. The 2020 goal of the EU Biodiversity Strategy concerning marine Invasive Alien Species may not be fully attainable. The setting of a new target date should be accompanied by scientifically robust, sensible and pragmatic plans to minimize introductions of marine NIS and to study those present.

Sewage sludge impact on sediment quality and benthic assemblages off the Mediterranean coast of Israel-a long-term study

The distributions of benthic assemblages, heavy metals and organic carbon (Corg) in sediments were examined during a long-term study at a sewage sludge disposal site off the Mediterranean coast of Israel. The disposal of sewage sludge has a marked but localized, seasonally dependent, impact on the benthic assemblages and sediment quality. Elevated concentrations of Corg, Hg, Cd, Cu, Zn, Pb, and to a lesser degree Ni in the sediments were detected mostly northward of the sewage outfall, in the direction of the prevalent longshore current. High concentrations of Corg and metals were reflected by elevated populations of tolerant and opportunistic polychaetes in spring and by an azoic zone in fall. The impacted area extended mainly towards the north (up to ca. 4 km) and to a lesser extent south of the outfall (up to ca. 2.5 km). No evidence of increased accumulation of sewage sludge with time was found, nor of pollutants associated with it. Principal component analysis (PCA) grouped the anthropogenic metals and Corg with infaunal abundance for the spring surveys, while biotic diversity was negatively correlated with the pollutants. In the PCA of fall surveys, abundance was negatively correlated with the pollutants, decreasing with increased concentration of Corg and anthropogenic metals. We suggest that the seasonal pattern shown by infaunal abundance, anthropogenic metals and Corg is due to the stratification of the water column from spring to fall on one-hand and winter storms on the other. Winter storms resuspend and disperse the fine organic particles, sweeping the site clean of sludge; accumulation of sludge takes place throughout the quiescent periods of the year, when stratification is reestablished. The disposal site is dispersive and the spatial extent of the impacted area varies seasonally and interannually. This monitoring study, in addition to addressing specific questions about sewage sludge impact, represents an unusually large and unique set of long-term measurements that will serve as a basis to evaluate the site recovery following the cessation of disposal.

The effects of freshwater flushing on marine heterotrophic protists--implications for ballast water management

Survivorship of ballast-entrained marine heterotrophic protists was examined following freshwater flushing. The recovered taxa, including typical marine rhizopods such as Platyamoeba murchelanoi, Labyrinthula spp, Pontifex maximus, Thecamoeba orbis, and the ciliate Condylostoma arenarium, were reared in waters of various salinities. After 2 months, the original salinity subsample retained five protist taxa, the freshwater six, including the amoeba Cochliopodium bilimbosum, the brackish water 22 taxa, and the seawater 19 taxa. Since protists form a major component of marine microbial food webs, their survival may be instrumental in supporting complex ballast-entrained food webs. Our study raises questions as to the reliability of open-ocean exchange (OOE) or freshwater flushing as effective control measures.

Pathological alterations typical of human Tay-Sachs disease, in the retina of a deep-sea fish

Micrographs of retinas from the deep-sea fish Cataetyx laticeps revealed visual cells containing membranous whorls in the ellipsoids of the inner segments resulting from stretching and modifications of the mitochondria membranes and their cristae. These pathological structures seem to be homologous to the whorls observed in retinas of human carriers of Tay-Sachs disease. This disease, a genetic disorder, is found in humans and some mammals. Our findings in fish suggest that the gene responsible can be found throughout the vertebrate evolutionary tree, possibly dormant in most taxa.