Ion concentrations in seagrass: A comparison of results from field and controlled-environment studies

Osmoregulation is essential for the survival of seagrasses in marine and hypersaline environments. The aim of this study was to examine ion concentrations of four seagrass species (Posidonia australis, P. sinuosa, Amphibolis antarctica and A. griffithii) after exposure to salinity changes. Plant fragments were placed in a series of aquaria at marine salinity (35) and, after one week of acclimation, exposed for 7 days to salinities between 20 and 70. Cl−, Na+ and total ion concentration increased with salinity in leaf tissue of the four seagrasses species. These results were compared with those of P. australis and A. antarctica samples collected at three locations at Shark Bay, Western Australia where higher salinities occurred, ranging from 46 to 51. Concentrations of K+ and Ca+2 were higher in seagrass tissues from Shark Bay than in those in aquarium trials. Cl−, Na+ and total ions in P. australis and A. antarctica from Shark Bay were lowest at the highest salinity location. The K+/Na+ ratio in the aquarium trials (under ambient conditions) was in the following order: A. antarctica = A. griffithii > P. australis > P. sinuosa and Ca+2/Na+ ratio was: A. antarctica = A. griffithii > P. sinuosa > P. australis. This species order indicates a physiological capacity to tolerate variation in salinity. Furthermore, these ratios were higher in the locality with highest salinity in Shark Bay, indicating acclimation and adaptation of ion concentrations to the salinity regime in the environment.A.G. was supported by an FPI grant from Universidad de Alicante

Short-term impacts of salinity pulses on ionic ratios of the seagrasses Thalassia testudinum and Halodule wrightii

We examined the effects of short-term salinity pulses on ion accumulation in the seagrasses Thalassia testudinum and Halodule wrightii. Plant fragments were exposed for approximately 1 week to 10, 23 (ambient salinity), 30, 40, 50 and 70 psu. The concentrations of total ions, Cl− and Na+ increased with higher salinity in leaves and rhizomes of both seagrass species. In contrast, the concentrations of K+ and Ca2+ generally decreased with higher salinity, although the decrease was relatively small and only observed at extreme salinities. Our results indicate the concentrations of Cl− and Na+ were higher in rhizomes than in leaves, possibly reflecting effective ion exclusion mechanisms in leaves. Under ambient (control) salinity the ratios K+/Na+ and Ca2+/Na+ were 38% and 46% higher in H. wrightii than in T. testudinum leaves, which support the notion that H. wrightii is more tolerant of salinity increases than T. testudinum. In concert, our results show novel observations of ion osmolyte concentrations in these seagrass species that point to adaptive responses to salinity pulses. Despite these adaptive responses, pulses of extremely high salinity (>50 psu) lasting approximately 1 week are detrimental to these seagrass species.This research was financed by a grant of University of Alicante

Elysia timida (Risso, 1818) tres décadas de investigación

During the last 30 years, studies on Elysia timida (Risso, 1818) have addressed various aspects related to food sources, photosynthetic efficiency of kleptoplasts, population genetics, chemical ecology and reproductive biology, both in the Mediterranean Sea and in the Mar Menor coastal lagoon. E. timida shows a strong specific interaction with Acetabularia acetabulum, retaining functional chloroplasts for at least 45 days and obtaining extra energy in periods when food resources are scarce. It shows control of parapodia, avoiding pigment photodestruction under oversaturated light conditions. The chemical ecological relationships established between E. timida and its potential predator fish, Thalassoma pavo, have also been evaluated, and it has been found that that the extracts of the mollusc contain repellent and unpalatable polypropionate compounds. Population genetics has demonstrated the genetic divergence between populations showing high and significant values of FST and genetic distances, and at least six privative alleles that are not shared with Mediterranean populations have been detected in lagoon populations. This sacoglossan is a poecilogonic species, and its lagoon populations show a greater reproductive output than Mediterranean populations; they produce a greater number of egg masses and embyros per individual, and the capsules have a wider diameter.Durante los últimos 30 años los estudios sobre Elysia timida (Risso 1818) han abordado diversos aspectos relacionados con sus fuentes de alimentación, la eficacia fotosintética de los cleptoplastos, la genética de poblaciones, la ecología química y la biología reproductiva, tanto en Mar Mediterráno como en la laguna costera del Mar Menor. E. timida presenta una fuerte interacción específica con Acetabularia acetabulum, reteniendo los cloroplastos funcionales durante al menos 45 días y obteniendo energía extra durante los periodos en que los recursos alimentarios escasean. Mediante el control de los parapodios evita la fotodestrucción de los pigmentos en condiciones de sobresaturación lumínica. También se han evaluado las relaciones ecológicas y químicas entre E. timida y su depredador potencial, el pez Thalassoma pavo, detectándose que los extractos del molusco contienen componentes polipropionados que son repelentes y de gusto desagradable. La genética de poblaciones ha demostrado la existencia de divergencia genética entre las poblaciones, presentando valores altos y significativos de FST y de distancias genéticas, detectándose al menos seis alelos privativos en las poblaciones lagunares los cuales no son compartidos por las poblaciones del Mediterráneo. Este sacogloso es una especie poecilogónica, y sus poblaciones de la laguna muestran un mayor esfuerzo reproductivo que las poblaciones mediterráneas; producen un número mayor de masas de huevos y de embriones por individuo, y las cápsulas tienen un mayor diámetro

Salinity fluctuation of the brine discharge affects growth and survival of the seagrass Cymodocea nodosa

The increase of seawater desalination plants may affect seagrasses as a result of its hypersaline effluents. There are some studies on the salinity tolerance of seagrasses under controlled laboratory conditions, but few have been done in situ. To this end, Cymodocea nodosa shoots were placed during one month at four localities: two close to a brine discharge; and the other two not affected by the discharge, and this experiment was repeated four times. The results obtained showed a decrease in growth and an increased mortality at the localities affected by the brine discharge. An increase was detected in the percentage of horizontal shoots in respect to vertical shoots at the impacted localities. It is probably that not only the average salinity, but also the constant salinity fluctuations and slightly higher temperatures associated with the brine that may have caused physiological stress thus reducing C. nodosa growth and survival.This research was financed by a grant of University of Alicante and by an ACUAMED contract

Posidonia oceanica L. (Delile) meadows regression: Long-term affection may be induced by multiple impacts

Coastal development has an undeniable impact on marine ecosystems resulting in the detriment of the more sensible communities. Posidonia oceanica meadows are climax communities which offer a wide variety of ecosystem services both ecological and socio-economic. Human-derived impact on these habitats has been widely assessed although conclusions may vary depending on the area. P. oceanica meadow regression next to the city of Alicante (SE Spain) was analyzed on the long term (1984–2014) using bionomic cartographies and side-scan sonar images and, during the last two decades (2003–2021), using cover percentage and shoot density descriptors in the remaining meadow. Results showed a 25% colonized area reduction since 1984, this process being more rapid during the 1984–1994 period and decreasing with time. Cover and density have suffered a significant decrease in the last 20 years, mainly in the upper limit of the meadow. Dead matte cover was also assessed and have shown a significant increase in the same period following an inverse trend with the other metrics. There are several coastal impacts which have co-occurred in the area in the last few decades (port enlargement, brine and sewage discharges, industrial activity) thus resulting in the regression of the meadow. The existing negative trend of the measured descriptors indicate the necessity of implementing management actions which focus on the present sources of impact and actively reduce their effect on P. oceanica beds.F. Blanco-Murillo was supported by an FPU PhD grant from Universidad de Alicante (Grant ID: FPUUA98). C.A. Sáez and F. Blanco-Murillo were financed by projects ANID InES I+D 2021 (INID210013), CORFO CAPTA (9CTIGH-121349) and Marie Skłodowska-Curie Action (888415)

Automedidas domiciliarias de presión arterial: "Situación actual y nuevas perspectivas"

El método utilizado habitualmente para el diagnóstico y seguimiento de los pacientes hipertensos ha sido la medida de la presión arterial en consulta, pero es un hecho conocido que este método plantea problemas, sesgos del observador, no detecta reacción de alerta en la clínica…, dificultades que afectan a su precisión como método diagnóstico. En los últimos años, las diferentes sociedades científicas internacionales recomiendan, de forma insistente, el uso de medidas de presión arterial fuera de la consulta (domiciliarias o ambulatorias), y con aparatos automáticos validados. Datos de algunos estudios sugieren que si solo utilizamos las medidas de la consulta nos podemos equivocar en torno al 15 o 20% de las veces que tomemos decisiones, tanto en el diagnóstico como en el seguimiento de los pacientes. Las medidas domiciliarias de presión arterial son un método sencillo y muy accesible que tienen una reproducibilidad y un valor pronóstico similar al de las medidas que se realizan con monitorización ambulatoria, cuya disponibilidad actualmente es muy limitada. Las auto medidas ambulatorias aportan además la importante utilidad de poder mejorar el control de los hipertensos. Los profesionales sanitarios y los pacientes deben conocer la metodología de uso de la medida de presión arterial domiciliaria, sus utilidades y sus limitaciones

Plant water relations and ion homoeostasis of Mediterranean seagrasses (Posidonia oceanica and Cymodocea nodosa) in response to hypersaline stress

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