Grazing on the epiphytic community of Posidonia oceanica (L.)Delile: An assessment of its relevance as a buffering process of eutrophication effects

El incremento de disponibilidad de nutrientes produce cambios en la estructura y funcionamiento de los ecosistemas litorales. La eutrofización en los ecosistemas litorales mediterráneos favorece el predominio de algas epifitas de crecimiento rápido que compiten por la luz y los nutrientes con Posidonia oceanica. La herbivoría sobre los epifitos suministra la mayor parte del carbono que asimilan los consumidores primarios y secundarios asociados a la pradera. Esta tesis evalúa la importancia del consumo ejercido por la epifauna asociada a las praderas de P. oceanica en revertir los efectos de la eutrofización sobre la biomasa de algas epifitas. Los resultados muestran un incremento de las tasas de consumo en respuesta a una mayor disponibilidad de biomasa epifita si bien el consumo no es capaz de revertir los efectos del aumento de nutrientes sobre la biomasa epifita. La comunidad íctica tiene un papel marginal en la regulación de la biomasa epifita en la Bahía de Palma

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

Feeding ecology of pipefish species inhabiting Mediterranean seagrasses

Pipefish are a vulnerable and diverse group of ichthyofauna tightly associated with seagrass meadows, key habitats in shallow marine areas. Despite their charismatic role, the main ecological features, habitat, and diet of this group remain largely unknown. This study focuses on assessing pipefish habitat and feeding preferences, including different hosting seagrasses such as Posidonia oceanica and Cymodocea nodosa from the Balearic Islands, western Mediterranean. Four species (Syngnathus typhle, S. abaster, Nerophis ophidion, and N. maculatus) were found associated to different seagrasses. S. typhle and N. maculatus were more frequent in P. oceanica meadows, while S. abaster and N. ophidion in C. nodosa. Individuals of all species captured in P. oceanica were larger than those living in C. nodosa, suggesting a size-dependent habitat preference. Feeding preferences, however, were driven by prey availability and fish features, e.g., head/snout morphology. For the first time in the western Mediterranean, a thorough description of the diet and potential prey of this group was carried out. Epifaunal assemblages (potential prey) weredominated in both habitats by harpacticoid copepods and gammarid amphipods, and they were also the primary prey accordingto stomach contents of all species. These results can contribute to future pipefish conservation and management actions, such as targeting crucial habitat identification and designing culture and reintroduction protocols

A Tropical Macroalga (Halimeda incrassata) Enhances Diversity and Abundance of Epifaunal Assemblages in Mediterranean Seagrass Meadows

The introduction and successful expansion of tropical species into temperate systems is being exacerbated by climate change, and it is particularly important to identify the impacts that those species may have, especially when habitat-forming species are involved. Seagrass meadows are key shallow coastal habitats that provide critical ecosystem services worldwide, and they are threatened by the arrival of non-native macroalgae. Here, we examined the effects of Halimeda incrassata, a tropical alga that has recently colonized the Mediterranean Sea, on epifaunal assemblages associated with Cymodocea nodosa seagrass meadows of Mallorca Island (Western Mediterranean Sea). This invasive macroalga is an ecological engineer and thus has a high potential of modifying native habitats. A seagrass meadow colonized by H. incrassata exhibited important changes on associated epifaunal assemblages, with an increase in abundance and diversity, particularly driven by higher abundances of Gammaridae, Polychaeta, Copepoda and Caprellidae. Given the key ecological contribution of epifauna to food webs, these alterations will likely have important implications for overall food web structure and ecosystem functioning of native ecosystems.En prens

Posidonia oceanica restoration, a relevant strategy after boat anchoring degradation?

Trabajo presentado al 7th Mediterranean Symposium on Marine Vegetation, celebrado en Génova (Italia), los días 19 y 20 de septiembre de 2022.The anchoring of large pleasure boats constitutes one of the main threats in shallow marine habitats and particularly for seagrass beds. In the Mediterranean, this activity has seen constant development during the last decades, causing major physical disturbances in Posidonia oceanica meadows and associated ecosystem services, notably in terms of climate change mitigation (i.e. carbon fixation and sequestration capacities). In this context, the aims of the present study are to estimate the impact of these anchoring activities on P. oceanica meadows in a particularly highlyfrequented area (Sant’Amanza gulf, SE Corsica Island) and to set up a strategy to restore this major carbon sink. Since the last decade, time-series of marine habitat maps revealed an important regression of P. oceanica meadows, with a loss of 72.9 ha, corresponding to 11% of the meadow surface and 9% decline in the total carbon fixation and sequestration performed each year. Moreover, in the most impacted part of the bay (Balistra bay), a loss of 16.6 ha (28%) has been recorded between 2011 and 2022. Following recent enforcement of anchoring regulation, prohibiting the anchoring of large units (greater than 24 m), and the lockdown linked to the COVID-19 pandemic, anchorages in the seagrass reduced by 92%, between 2018 and 2022. Natural recovery was observed at the edge of the meadow (plagiotropic rhizomes) but this growth is slow and the areas to recover are large. As a result, a transplant experiment, from cuttings harvested from the adjacent meadows, was initiated in the spring 2021. Four restoration techniques are being tested in the some pilot sites and the development of these transplants will be monitored and compared to the natural recovery.This research has been co-financed by INTERREG program (GIREPAM), Collectivity of Corsica Corse (PADDUC-CHANGE), SETEC Foundation, Environment Office of Corsica and the French Office of Biodiversity (RenforC program)

Variation in Fish Abundance, Diversity and Assemblage Structure in Seagrass Meadows across the Atlanto-Mediterranean Province

Seagrasses worldwide provide key habitats for fish assemblages. Biogeographical disparities in ocean climate conditions and seasonal regimes are well-known drivers of the spatial and temporal variation in seagrass structure, with potential effects on associated fish assemblages. Whether taxonomically disparate fish assemblages support a similar range of ecological functions remains poorly tested in seagrass ecosystems. In this study, we examined variation in the abundance, diversity (from a taxonomic and functional perspective), and assemblage structure of fish community inhabiting nine meadows of the seagrass Cymodocea nodosa across three regions in the Mediterranean (Mallorca and Alicante) and the adjacent Atlantic (Gran Canaria), and identified which attributes typifying the structure of meadows, and large-scale variability in ocean climate, contributed most to explaining such ecological variation. Despite a similar total number of species between Mallorca and Gran Canaria, the latter region had more taxonomically and functionally diverse fish assemblages relative to the western Mediterranean regions, which translated into differences in multivariate assemblage structure. While variation in the abundance of the most conspicuous fish species was largely explained by variation in seagrass structural descriptors, most variation in diversity was accounted for by a descriptor of ocean climate (mean seasonal SST), operating at regional scales. Variation in fish assemblage structure was, to a lesser extent, also explained by local variability in seagrass structure. Beyond climatic drivers, our results suggest that lower temporal variability in the canopy structure of C. nodosa meadows in Gran Canaria provides a more consistent source of food and protection for associated fish assemblages, which likely enhances the more abundant and diverse fish assemblages thereEn prens

Sygnathids of Atlantic islands of Galicia and Cabrera archipelago national parks

39 pages[EN] Syngnathid fishes (Actinopterygii, Syngnathidae), including seahorses and pipefishes, are flagship vulnerable species highly associated with seaweed and seagrass habitats. Our multidisciplinary study provides the first insights for syngnathid populations in Atlantic Islands of Galicia (Cíes Archipelago, Atlantic Ocean) and Cabrera Archipelago (Mediterranean Sea) Spanish National Parks. Syngnathid fishes were collected on several sites in the first year of the study, and habitat characteristics were also determined. From the results achieved, a further two-years monitoring was performed seasonally in selected sites. The fishes were analyzed for size, weight, sex and sexual maturity, stable isotope signatures and genetics. Epifauna and gut contents were also analyzed for further dietary assessment of syngnathids. Diversity and abundances were generally low, with four species (including seahorses) identified in the Atlantic Islands of Galicia National Park and five (only pipefishes) at Cabrera National Park. Syngnathids from both national parks differed in size, isotopic values and prey regime. Syngnathids preferred less exposed sites in macroalgal assemblages (Atlantic) or Cymodocea meadows (Mediterranean). Population characteristics in the Atlantic Islands of Galicia National Park suggests that syngnathids mainly comprise breeders that migrate seasonally, with preference for less exposed sites on shallow complex rocky-sandy substrates covered by macroalgae. Prey preferences would rely mainly on the consumption of copepods and gammarids. In the Mediterranean, syngnathids were likely limited by the depth of the studied sites, showing preference for Cymodocea meadows over Posidonia, and for the capture of a wider range of prey compared to the Atlantic populations. Borrón (Atlantic) and Es Burri (Mediterranean) would be preferential sites to undertake conservations plans for syngnathids. Several research topics are suggested for further management of syngnathids populations in both national parks[ES] Los signátidos (Actinopterygii, Syngnathidae) son una familia de peces que incluye caballitos de mar y peces pipa. Se trata de especies vulnerables estrechamente asociadas a las comunidades vegetales. Este estudio multidisciplinar en signátidos es el primero realizado en los Parques Nacionales Marítimo-Terrestres de las Islas Atlánticas de Galicia (Archipiélago de Cíes, Atlántico) y del Archipiélago de Cabrera (Mediterráneo). En el primer año de estudio, se estudiaron los signátidos en diversas zonas de ambos parques nacionales, así como las características de sus hábitats. Los resultados alcanzados permitieron establecer zonas preferentes para la realización de un estudio bianual posterior. En los peces capturados se determinaron las siguientes características: talla, peso, sexo y madurez sexual, isótopos estables y características genéticas. También se analizó la epifauna y los contenidos digestivos para determinar preferencias alimentarias. La diversidad y las abundancias fueron reducidas, con cuatro y cinco especies identificadas en el Atlántico y Mediterráneo, respectivamente, con presencia de caballitos de mar solo en la vertiente atlántica. Se observaron diferencias importantes en los signátidos de ambas zonas en lo relacionado con talla, valores isotópicos y preferencias alimentarias, Los signátidos atlánticos mostraron preferencia por zonas someras menos expuestas en hábitats macroalgales complejos arenoso-rocosos, con preferencia por el consumo de gammáridos y copépodos. Las especies del mediterráneo estuvieron mejor representadas en praderas de Cymodocea comparado con las de Posidonia, con una mayor variedad de fuentes alimenticias que en el atlántico, dependiendo de la especie. Las zonas de mayor interés, de cara a futuros planes de conservación, fueron Borrón (Atlántico) y Es Burri (Mediterráneo). Se proponen diversas actuaciones para el estudio futuro de las poblaciones estudiadasEste proyecto fue financiado por el Organismo Autónomo Parques Nacionales del Ministerio para la Transición Ecológica y el Reto Demográfico (HIPPOPARQUES, Ref. 1541S/2015), estando coordinado con el proyecto 1580S/2015. J. Hernández-Urcera disfrutó de un contrato postdoctoral Juan de la Cierva (FJCI-2016-30990; Ministerio de Ciencia, Innovación y Universidades)N

Grazing on the epiphytic community of Posidonia oceanica L. Delile: An assessment of its relevance as a buffering process of eutrophication effects

Peer Reviewe

Ecosystem functioning recovery after restoration of seagrass Posidonia oceanica

Resumen del trabajo presentado a la 9th World Conference on Ecological Restoration: A New Global Trajectory, celebrado virtualmente del 21 al 24 de junio de 2021.Peer reviewe

Poor success of seagrass Posidonia oceanica transplanting in a meadow disturbed by power line burial

Local disturbances drive the decrease of the area covered by Posidonia oceanica in the Mediterranean. Mechanical impacts during the development of coastal infrastructures alter sea floor and the recolonization of benthic community will depend on the recovery of pre-disturbance environmental conditions and on the intrinsic characteristics of the local community that was disturbed. We transplanted 468 rhizome fragments and 450 seedlings of P. oceanica in a meadow disturbed by the trenching and deployment of a power line to evaluate the suitability of the disturbed sea floor for rehabilitating P. oceanica meadows. We quantify and compare the survivorship and vegetative development of the transplanted/planted (i.e. fragments/seedlings) material in the two types of the unconsolidated substrata left after infrastructure deployment works finished: sand and burlap bags filled with coarse gravel. The latter was used as a corrective measure for topographic restoration. Three experimental plots with sixteen transplanted fragments or twenty-five seedlings were placed at each substratum type at three different depths (i.e. 15, 20 and 25 m). Our results show that the transplanting of P. oceanica rhizome fragments in the disturbed substrata had low survival rates (0–31%) after 40–48 months. The survivorship of seedlings was lower than that of fragments. Our results highlight the importance of substratum for P. oceanica recovery after mechanical impact; disturbed, non-consolidated substrata will preclude P. oceanica rehabilitation through planting. Preservation of meadow substratum (i.e. dead matte) is a critical element that coastal infrastructure projects should consider to enable future recovery of P. oceanica meadows.The work was funded by the Red Eléctrica de España through the contract “Use of seeds and fragments of Posidonia oceanica for the recovery of areas affected by Red Eléctrica de España's activity” awarded to CSIC