Marine Seals Research Articles

Desastres naturales en Canarias. La costa como espacio de riesgo en Tenerife

En el marco de los desastres naturales en Canarias, se analiza la importancia que adquieren los temporales marinos en la isla de Tenerife. Su litoral presenta un elevado grado de urbanización y, por ello, constituye un territorio de riesgo por los efectos negativos que dichos fenómenos pueden ocasionar. Con este motivo, se procede al estudio del comportamiento del oleaje y del viento, lo que permite identificar y caracterizar los episodios que entrañan peligro. El examen de una serie de eventos significativos posibilita establecer, además, cuáles son las situaciones atmosféricas que provocan los temporales marinos y determinar las modalidades dominantes en las costas según su orientación. Por último, se valoran las secuelas que, desde el punto de vista social, causan los episodios más representativos.

Demographic histories and genetic diversities of Fennoscandian marine and landlocked ringed seal subspecies.

Island populations are on average smaller, genetically less diverse, and at a higher risk to go extinct than mainland populations. Low genetic diversity may elevate extinction probability, but the genetic component of the risk can be affected by the mode of diversity loss, which, in turn, is connected to the demographic history of the population. Here, we examined the history of genetic erosion in three Fennoscandian ringed seal subspecies, of which one inhabits the Baltic Sea ‘mainland’ and two the ‘aquatic islands’ composed of Lake Saimaa in Finland and Lake Ladoga in Russia. Both lakes were colonized by marine seals after their formation c. 9500 years ago, but Lake Ladoga is larger and more contiguous than Lake Saimaa. All three populations suffered dramatic declines during the 20th century, but the bottleneck was particularly severe in Lake Saimaa. Data from 17 microsatellite loci and mitochondrial control-region sequences show that Saimaa ringed seals have lost most of the genetic diversity present in their Baltic ancestors, while the Ladoga population has experienced only minor reductions. Using Approximate Bayesian computing analyses, we show that the genetic uniformity of the Saimaa subspecies derives from an extended founder event and subsequent slow erosion, rather than from the recent bottleneck. This suggests that the population has persisted for nearly 10,000 years despite having low genetic variation. The relatively high diversity of the Ladoga population appears to result from a high number of initial colonizers and a high post-colonization population size, but possibly also by a shorter isolation period and/or occasional gene flow from the Baltic Sea.

Morbillivirus infections, with special emphasis on morbilliviruses of carnivores

Morbilliviruses infections cause significant mortality in human beings and animals. Measles virus is responsible for up to two million childhood deaths annually in the developing world, while rinderpest and peste des petits ruminants cause severe epizootics in domestic and wild ruminants in areas of the world where they remain endemic. Canine distemper virus (CDV) is a cause of fatal disease in many species of carnivores. Distemper is controlled by vaccination in domestic dogs and farmed mink, but it may be impossible to eradicate the virus because of its global distribution and wide variety of susceptible host species, which includes both freshwater and marine seals. Research is currently under way to develop new recombinant vaccines, since the currently available live attenuated vaccines for CDV are not safe for use for all species and many valuable zoo animals need to be protected from CDV. New morbilliviruses with potentially disastrous ecological consequences for marine mammals have been discovered in the past decade; phocid distemper virus (PDV) in seals and the cetacean morbillivirus (CMV) has been found in dolphins, whales and porpoises. Reverse transcription, coupled with the polymerase chain reaction (RT/PCR) and nucleic acid sequencing, has been used to characterise the morbilliviruses and has given insights into the evolution of this virus genus.

Vitamins A1 (Retinol), A2 (3,4-Didehydroretinol) and E (α-Tocopherol) in the Liver and Blubber of Lacustrine and Marine Ringed Seals (Phoca hispida sp.)

Concentrations of vitamins A1 (retinol), A2 (3,4-didehydroretinol) and E (α-tocopherol) in the liver and blubber of ringed seals from Lake Saimaa (Phoca hispida saimensis), Lake Ladoga (P. h. ladogensis), the Baltic Sea (P. h. botnica) and Spitsbergen (P. h. hispida) were determined by high-performance liquid chromatography. The freshwater seals had much lower levels of vitamin A1 but higher levels of vitamin A2 than the marine seals. The concentrations of vitamin E in the livers of the subspecies studied were high compared with earlier reports of seals, but the ranges were large. The livers of the marine seals contained more vitamin E than the livers of the freshwater seals, but the levels in the blubber were uniform in all populations, except in old specimens from the Baltic. The differences between the freshwater and marine seals are suggested to be due mainly to diet. The ratios of A1 to A2 in the liver and blubber and in the fish diet were similar for the marine seals and for the freshwater seals (but differed in the marine and freshwater populations), which suggests no great differences in the absorption, transport and metabolism of the two analogues. Blubber was an important storage site for the vitamins studied, and age-dependent increases were detected, especially for vitamin E. In the 2-month to 2-year-old ringed seals of Lake Saimaa, however, the vitamin E concentration in the blubber was not affected by age.

Presence of airborne contaminants in the wildife of northern Que´bec

As part of the environmental impact studies of the Great Whale and the Nottaway-Broadback-Rupert (NBR) hydroelectric projects, Hydro-Que´bec collected data on the occurrence and levels of several contaminants present in wildlife from both regions between 1989 and 1991. The analyses performed included metals (mercury, arsenic, selenium, cadmium, lead, nickel and copper), polychlorinated biphenyls (PCBs as arochlors or the sum of 20–40 congeners) and organochlorine pesticides such as hexachlorobenzene (HCB), DDT, DDE, hexachlorocyclohexane (HCH), chlordane, mirex and dieldrin. Species sampled included fish (freshwater and marine), birds (waterfowl, gull and ptarmigan), terrestrial mammals (marten, mink and hare) and marine mammals (freshwater and marine seals, belugas). Most laboratory analyses were carried out on both muscle and liver tissues, but some were conducted on other tissues as well: feathers, eggs and blubber. The results indicate that numerous airborne contaminants were present in the wildlife of both the Great Whale and the NBR study areas and that their level of contamination was similar to that of other northern environments. Total mercury in muscle was high in piscivorous fish, birds and mammals (terrestrial and marine). We observed significant levels of cadmium and lead in the livers of some herbivorous terrestrial animals, such as mearmigans and hares. Among the organochlorine contaminants analyzed, levels of PCBs and DDE in piscivorous birds (mergansers and loons) and in marine mammals (seals and belugas) were high. For some contaminants, such as mercury, cadmium, lead, PCBs and DDE, the levels observed in some species or tissues could be considered worrisome with regard to public health, if those species or tissues constitute an important part of traditional native diets.

Mercury and major essential elements in seals, penguins, and other representative fauna of the Antarctic.

Concentrations of total Hg and major essential elements, Ca, Mg, Na, and K, were measured in the muscle, liver, and kidney of three species of seals, crabeater seal (Lobodon carcinophagus), leopard seal (Hydrurga leptonyx), and Weddell seal (Leptonychotes weddelli) collected in the Antarctic. The muscle and liver of three species of penguins, i.e., gentoo penguin (Pygoscelis papua), Adelie penguin (P. adeliae), chinstrap penguin (P. antarctica), and other representative fauna were also analyzed for the elements. Distinct inter-tissue differences in the metal concentration were observed; liver had the greatest concentrations of Hg, kidney showed maximum concentration of Ca and Na, while muscle was characterized by the greatest content of Mg and K. Inter-specimen differentiation of concentrations among the same species was distinctly visualized for Hg but not for the major essential elements. The Hg concentration in the seals analyzed are in keeping with those reported previously by other authors. Such comparison for Ca, Mg, Na, and K was impossible because of the lack of available literature data for their concentrations in marine seals. Numerous significant correlations were observed between concentrations of the several metals analyzed. There was no correlation between Hg, which is a non-essential element and both Zn and Cd which are essential and non-essential elements, respectively in the liver or kidney of seals. However, there were significant correlations between concentration of Zn and the sum of molar concentrations of Hg+Cd in kidney (r = 0.82) and liver (r = 0.76). The results suggest that several control mechanisms operate to maintain physiologically required levels that decreases any effect of heavy metal toxicants such as Hg and Cd.