Trace element concentrations in the Mediterranean monk seal (Monachus monachus) in the eastern Mediterranean Sea

Mediterranean Marine Mammals: Possible Future Trends and Threats Due to Mercury Contamination and Interaction with Other Environmental Stressors

Despite decreasing anthropogenic mercury (Hg) emissions in Europe and the banning and restriction of many persistent organic pollutants (POPs) under the Stockholm Convention, Mediterranean marine mammals still have one of the highest body burdens of persistent pollutants in the world. Moreover, the Mediterranean basin is one of the most sensitive to climate change, with likely changes in the biogeochemical cycle and bioavailability of Hg, primary productivity, and the length and composition of pelagic food webs. The availability of food resources for marine mammals is also affected by widespread overfishing and the increasing number of alien species colonizing the basin. After reporting the most recent findings on the biogeochemical cycle of Hg in the Mediterranean Sea and the physico-chemical and bio-ecological factors determining its exceptional bioaccumulation in odontocetes, this review discusses possible future changes in the bioavailability of the metal. Recent ocean-atmosphere-land models predict that in mid-latitude seas, water warming (which in the Mediterranean is 20% faster than the global average) is likely to decrease the solubility of Hg and favor the escape of the metal to the atmosphere. However, the basin has been affected for thousands of years by natural and anthropogenic inputs of metals and climate change with sea level rise (3.6 ± 0.3 mm year-1 in the last two decades), and the frequency of extreme weather events will likely remobilize a large amount of legacy Hg from soils, riverine, and coastal sediments. Moreover, possible changes in pelagic food webs and food availability could determine dietary shifts and lower growth rates in Mediterranean cetaceans, increasing their Hg body burden. Although, in adulthood, many marine mammals have evolved the ability to detoxify monomethylmercury (MMHg) and store the metal in the liver and other organs as insoluble HgSe crystals, in Mediterranean populations more exposed to the metal, this process can deplete the biological pool of Se, increasing their susceptibility to infectious diseases and autoimmune disorders. Mediterranean mammals are also among the most exposed in the world to legacy POPs, micro- and nanoplastics, and contaminants of emerging interest. Concomitant exposure to these synthetic chemicals may pose a much more serious threat than the Se depletion. Unfortunately, as shown by the literature data summarized in this review, the most exposed populations are those living in the NW basin, the main feeding and reproductive area for most Mediterranean cetaceans, declared a sanctuary for their protection since 2002. Thus, while emphasizing the adoption of all available approaches to mitigate anthropogenic pressure with fishing and maritime traffic, it is recommended to direct future research efforts towards the assessment of possible biological effects, at the individual and population levels, of chronic and simultaneous exposure to Hg, legacy POPs, contaminants of emerging interest, and microplastics.

Trace Elements and Contaminants Concentrations in Tissues of Caspian Seals (Pusa caspica) along the Iranian Coast

The Caspian seal (Pusa caspica) is an endangered species that only lives in the Caspian Sea. Little information is available on its exposure to contaminants, and no data exists for Southern sub-populations. From 2011 to 2016, tissues samples were collected from 20 Caspian seals to (i) Define the concentration of trace elements in five different matrices and the concentration of 30 pesticides in their blubber; (ii) Determine whether differences in contaminant concentrations are age- or sex-related; (iii) Evaluate if detected concentrations can represent a risk to the species. Age- and sex-related variations were detected for Zn and Hg in the blubber and Fe in the kidney by age only. Exceptionally high Hg concentrations and low levels of hepatic Zn were detected, raising some concern about the reproductive health of seals. Similarly, the DDTs levels detected were in the range of adverse reproductive effects in marine mammals. Based on these results, potentially adverse effects on the immune and endocrine systems of the Caspian seal cannot be ruled out. Therefore, it is of the utmost importance that pollutant monitoring becomes an integral component of conservation strategies for the Caspian seal.

First Report of the Parasitic Nematode Pseudoterranova spp. Found in Mediterranean Monk Seal (Monachus monachus) in Greece: Conservation Implications

The Mediterranean monk seal (Monachus monachus) is classified as an endangered species by the IUCN, with a global population that does not exceed 800 individuals. There is limited understanding around the biology and health status of the species, rendering possible parasitic infections grave for its conservation efforts. The aim of the current study was the molecular identification of a parasitic nematode found in the digestive system of a sub-adult Mediterranean monk seal individual, that was found stranded in the area of Pagasitikos Gulf, Greece in 2019. Analysis of the stomach contents revealed the presence of two intact female nematode individuals. Standard protocols were followed as DNA extraction of the parasites was conducted and PCR amplification of the cytochrome oxidase subunit I (COI) mitochondrial gene was implemented. Sequencing analysis of a 585 bp-amplified product displayed a 96% similarity of the screened nematodes to the Pseudoterranova bulbosa species. Bayesian inference was implemented for the subsequent tree reconstruction. The phylogenetic tree revealed a clear genetic similarity between our parasitic nematode individuals named as Pseudoterranova spp. and Pseudoterranova bulbosa (bootstrap value: 82%), which is indicated for the first and only time as such, to be found in the waters of the Mediterranean Sea and also in the stomach of a Mediterranean monk seal.

A GIS-based multi-criteria model for offshore wind energy power plants site selection in both sides of the Aegean Sea

Location selection for offshore wind farms is a major challenge for renewable energy policy, marine spatial planning, and environmental conservation. This selection constitutes a multi-criteria decision-making problem, through which parameters like wind velocity, water depth, shorelines, fishing areas, shipping routes, environmental protection areas, transportation, and military zones should be jointly investigated. The aim of the present study was thus to develop an integrated methodology for assessing the siting of bottom-fixed offshore wind farms in two different countries (with different legal, political, and socio/economic characteristics). Our methodology combined multi-criteria decision-making methods and geographical information systems and was implemented in Cyclades (Greece) and in the sea area of İzmir region (Turkey). Experts used fuzzy sets and linguistic terms to achieve more consistent and independent rankings and results. In the Turkish region, the results showed that 519 km² (10.23%) of the study area is suitable for offshore wind farms, while in the Greek region, only 289 km² (3.22%) of the study area was found to be suitable. This spatial suitability analysis may contribute to provide some useful recommendations for the spatial marine planning at the regional scale, as well as for the preliminary assessment of new offshore wind farms in both countries.

As, Cr, Hg, Pb, and Cd Concentrations and Bioaccumulation in the Dugong Dugong dugon and Manatee Trichechus manatus: A Review of Body Burdens and Distribution

The death of dozens of manatees Trichechus manatus recently in Tabasco, Mexico, has captured international attention. Speculation about possible causes include water and food contamination by metals. Although federal authorities have ruled out water chemical pollution, the cause of these deaths is still awaiting conclusive laboratory results. Present work seeks to summarize information currently available on non-essential metals and those of great toxicological relevance in Sirenia (dugongs and manatees), highlighting its body distribution, presence in blood, and its relationship with their geographical distribution, gender and age, whenever possible. This paper focuses on the five elements: As, Cr, Hg, Pb and Cd, which are commonly considered as threats for marine mammals and reported in Sirenia. Some of these metals (Cr and Cd) were thought to be related to the recent deaths in Tabasco. All five elements are accumulated by Sirenia at different levels. Metal presence is associated to their diet but does not necessarily imply adverse effects for dugongs and manatees. Toxicological aspects and the human consumption risk in case of any illegal or traditional consumption in some cultures are discussed. Important toxicological research areas that need to be addressed are highlighted.