Is light involved in the vertical growth response of seagrasses when buried by sand?

5 pages, 3 figures.Involvement of light in the vertical growth response of Cymodocea nodosa (Ucria) Ascherson seedlings to sand burial was tested by comparing the growth response of seedlings that were buried and seedlings that were buried but had the shoot meristem illuminated using an optic fiber. Mortality of shoots was higher in the buried and illuminated shoots than in those only buried. The number of new leaves and the length of the vertical rhizome internodes produced during the experiment tended to decrease when the shoots were buried and illuminated, while the length of the leaf sheaths was not affected. Results indicate that light is one of the environmental signals that control the vertical growth response of C. nodosa when buried by sand, and that the shoot meristem is the place where the changes in the light environment of the shoot are detected.This study was funded by the project AMB94-0746 of the Spanish Interministerial Commission of Science and Technology (CICYT).Peer reviewe

La Biomasa de epífitos de la angiosperma marina Posidonia oceanica (L.) Delile no es indicadora de aportes antropogénicos de nutrientes en el Parque Nacional Archipiélago de Cabrera (Islas Baleareas, Mediterráneo Occidental)

The epiphyte load on the leaves of the seagrass Posidonia oceanica (L.) Delile was estimated at the end of summer in three sites and two depths (7 m and 17 m) of the Cabrera Archipelago National Park (Balearic Islands, Western Mediterranean) from 2004 to 2006 to evaluate if epiphyte load could be used as an indicator of anthropogenic nutrient loading in the shallow marine ecosystems of the park. Asymmetrical ANOVA was used to divide data variability into two components: the contrast between the site receiving direct anthropogenic inputs of nutrients and organic matter (Es Port) and the two control sites (Cala Santa María, Es Burri); and the variability between the control sites. The nitrogen concentration in P. oceanica leaves was higher in Es Port than in Cala Santa María and Es Burri but only at 7 m depth. There was no difference between the epiphyte load on P. oceanica shoots in Es Port and the sites without inputs at both 7 m and 17 m. However, the epiphyte load in Es Burri was higher than that in Cala Santa María at both depths. The results show that the epiphyte load on P. oceanica shoots was not a sensitive indicator of anthropogenic nutrient and organic matter loading in Cabrera Archipelago National Park.La biomasa de epífitos y el contenido en cenizas de los mismos, la biomasa foliar del haz, el contenido en nitrógeno de las hojas y la densidad de haces de la angiosperma marina Posidonia oceanica (L.) Delile se midieron en tres localidades y a dos profundidades (7 m, 17 m) del Parque Nacional Archipiélago de Cabrera (Islas Baleares, Mediterráneo Occidental) en los meses de septiembre del período 2004-2006 para evaluar el valor de la biomasa de epífitos como indicador de aportes antropogénicos de nutrientes a los ecosistemas del Parque. La variabilidad total de los datos se repartió por medio de un ANOVA asimétrico en dos componentes: el contraste entre la localidad receptora de aportes antropogénicos de nutrientes y materia orgánica (Es Port) y dos localidades control (Cala Santa María, Es Burri) por un lado, y la variabilidad entre las dos localidades control por otro. La concentración de nitrógeno en las hojas de P. oceanica fue superior en Es Port que en Cala Santa María y en Es Burri, pero sólo a la profundidad de 7 m. La biomasa de epífitos sobre las hojas de P. oceanica fue similar en Es Port y en las dos localidades control tanto a 7 m como a 17 m de profundidad. Sin embargo, la biomasa de epífitos en Es Burri fue superior a la de Cala Santa María en las dos profundidades estudiadas. Los resultados obtenidos muestran que la biomasa de epífitos sobre las hojas de P. oceanica no es un buen indicador de los aportes antropogénicos de nutrientes y materia orgánica en los ecosistemas costeros del Parque Nacional Archipiélago de Cabrera

Preferencia alimentaria de los anfípodos Ampithoe ramondi and Gammarella fucicola sobre hojas y semillas de Posidonia oceanica

The functional importance of herbivory in seagrass beds is highly variable among systems. In Mediterranean seagrass meadows, macroherbivores, such as the fish Sarpa salpa and the sea urchin Paracentrotus lividus, have received most research attention, so published evidence highlights their importance in seagrass consumption. The role of small crustaceans in seagrass consumption remains less studied in the region. Herbivory on Posidonia oceanica seeds has not previously been reported. In turn, crustacean herbivory on P. oceanica leaves is broadly recognized, although the species feeding on the seagrass are mostly unknown (except for Idotea baltica). This work evaluates P. oceanica consumption by two species of amphipod crustaceans commonly found in seagrass meadows. Ampithoe ramondi and Gammarella fucicola actively feed on P. oceanica leaves and seeds. Both species preferred seeds to leaves only when the seed coat was damaged. This study provides the first direct evidence of consumption of P. oceanica seeds by the two named amphipod crustaceans, and confirms that they also consume leaves of this seagrass species.La herbivoría tiene una importancia funcional muy variable entre los sistemas de praderas de angiospermas marinas. En las praderas mediterráneas, el papel de los macroherbívoros, como el espárido Sarpa salpa y el erizo marino Paracentrotus lividus, ha concentrado buena parte de la atención científica y, en consecuencia, la evidencia y bibliografía científica enfatizan su importancia como consumidores de angiospermas marinas. Los trabajos de investigación sobre el papel de pequeños crustáceos como consumidores de angiospermas marinas en la región mediterránea es todavía escasa. La herbivoría sobre semillas de Posidonia oceanica no se había reportado hasta la fecha. En cambio, el consumo de hojas de P. oceanica por crustáceos sí está ampliamente aceptado, aunque las especies responsables de este consumo son en su mayoría desconocidas (con la excepción de Idotea baltica). Este trabajo evalúa el consumo de semillas y hojas de P. oceanica por dos especies de anfípodos gammáridos frecuentes en las praderas de angiospermas marinas mediterráneas y su preferencia alimentaria entre ambos tejidos. Nuestros resultados indican que Ampithoe ramondi y Gammarella fucicola consumen activamente tanto las hojas como las semillas P. oceanica. Ambas especies prefirieron consumir las semillas de P. oceanica a las hojas, pero sólo cuando la cubierta exterior de la semilla estaba dañada. Este estudio es la primera evidencia de consumo directo de semillas de P. oceanica por anfípodos y confirma que las dos especies estudiadas consumen hojas

Relationship between the presence of the invasive macroalgae Caulerpa racemosa var. cylindracea (Sonder) Verlaque, Huisman et Boudouresque and substrate typology at the bay of Palma (Mallorca)

Abstract not availabl

Is the apical growth of Cymodocea nodosa dependent on clonal integration?

8 pages, 5 figures, 3 tables.The importance of clonal integration for the production of biomass by the apical meristem of Cymodocea nodosa (Ucria) Ascherson was tested in situ by experimental manipulation. The production of new biomass by the apical meristem of a horizontal rhizome, as well as the leaf growth of the remaining shoots, was greatly reduced when the horizontal rhizome was severed, even when up to 11 shoots were left connected to the apical meristem of the rhizome. In contrast, the elimination of up to 8 shoots after the 3 apical shoots on a horizontal rhizome did not affect the production of biomass by the apical meristem. These results show that growth at the apical meristem of a C. nodosa rhizome depends on resources translocated along the rhizome from shoots situated further than 50 cm from the rhizome apex and that all the individual shoots (ramets) in a C. nodosa clone should be considered as one unit. Clonal integration does not depend on the presence of living shoots along the translocation route but is dependent on the integrity of the horizontal rhizome.This study was funded by the project AMB94-0746 of the Spanish Interministerial Commission of Science and Technology (CICYT). W.J.K. was supported by the sabbatical program of the Ministry of Education and Science of Spain.Peer reviewe

Recreational boaters support the use of mooring buoys to reduce anchor damage to Posidonia oceanica (L.) Delile meadows

Recreational boating is an important economic activity in the Mediterranean Sea that often leads to disturbance by anchoring of Posidonia oceanica meadows, an endemic seagrass that is a critical component of shallow coastal ecosystems. A selfadministered survey of recreational boaters that anchor in a popular mooring site (Cala Blava) in the coast of Mallorca (Balearic Islands, Western Mediterranean) was carried out during the summer season of 2011 to assess their preferences regarding the number of boats anchoring at the cove and the distance between them, their willingness to pay for the use of mooring buoys and their perception of the negative effects that recreational boating may have on the marine environment. Four hundred and twenty five surveys were obtained over a period of 23 days (11 weekend days, 14 week days) with a response rate of 95 %. The number of boats anchored was higher during weekends (30 ± 13 boats) than during the rest of the week (15 ± 5 boats). Most of the respondents considered that both the number of anchored boats and distance between them were adequate, and they were satisfied with their visit to Cala Blava. Anchor damage was identified as the main impact caused in the marine environment by recreational boating. Support for the use of mooring buoys was high (72 %) and 58 % of boaters were willing to pay a fee for buoy use. The most widely accepted fee was 5 Euros per day of use. These results suggest that the public is well aware of the damage caused by anchoring on P. oceanica meadows and that environmental regulation that would reduce this harm through the use of mooring buoys would have wide support from the main users, who would be even willing to pay for the service. This is a bright prospect for the conservation of this valuable and fragile coastal ecosystem

Fast-spreading green beds of recently introduced Halimeda incrassata invade Mallorca island (NW Mediterranean Sea)

6 páginas, 2 figuras, 1 tabla.Mediterranean marine biodiversity is undergoing a tropicalization process.We present the first record and spread dynamics of the tropical green seaweed Halimeda incrassata (Bryopsidales, Chlorophyta) fromthe Mediterranean Sea. Plants were observed at 2 sites offMallorca island (NW Mediterranean), and species identification was confirmed molecularly. Since the first observation of this alien seaweedin 2011, it has spreadrapidly inthe shallow subtidal habitat ofamarine protected area located in Palma Bay, which has a depth of up to ca. 20 m. By 2015, this species spread by a factor of 6.75 and extended to an area of 2.7 km2, covering a total of 41% of the monitored area. The dynamics of the invasion suggest rapid colonization and establishment and spreading of the species through shallow sedimentary and rocky habitats. H. incrassata has the potential to strongly alter the ecosystem services and functioning of shallow Mediterranean habitats. We encourage authorities to pay attention to the spread of this alien seaweed at larger scales and determine the positive and negative effects of the invasion in order to facilitate research- driven decision making.The data used for this study was ob - tained through the project REC2 (CTM2011-23835) and a Marie Curie grant (grant no. 327160). We thank Antoni Grau (Govern de les illes Balears) for supporting and authorizing the study in the MPAPB and Rosario Rosselló and Chiela Cremen for their help. J.A. was supported by a JdC postdoc (FJCI-2014-21239) and F.T. by a RyC grant (MINECO). The Verbruggen lab received funding from the ARC (FT110100585) and the ABRS (RFL213-08).Peer reviewe

Assesment of the perception of majorcan society of the ecological and economical values ofPosidonia oceanica (L. Delile) seagrass beds

Abstract not availabl

Influence of biotic and abiotic factors of seagrass Posidonia oceanica recruitment: Identifying suitable microsites

The period between seed germination and successful seedling establishment is considered the most vulnerable phase for plant development. To better predict recruitment patterns within plant communities, it is essential to identify the abiotic constrains and biotic interactions that allow for the colonization of substrates by plant species. We evaluated which combination of factors are associated with successful survival and development of seedlings of the seagrass Posidonia oceanica in order to identify the most important microsite features acting together on recruitment success. Our results show that P. oceanica seedlings are rather specific in their environmental requirements during their first 18 months of life, when their development and survival are favored in microsites of consolidated substratum (solid rock, and to a lesser extent P. oceanica matte) covered by macroalgae (mainly crustose algae) and located in sheltered locations (with energy flux values not exceeding 7 × 10⁵ kg s⁻² m s⁻¹). After this phase, their probability of surviving becomes more independent from external conditions.En prens