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

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

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

Local thermal variation modulates resilience to warming in a marine foundation species: evidence from seagrass seedlings

Trabajo presentado en ASLO Aquatic Sciences Meeting 2023, celebrado en Palma de Mallorca (España), entre el 4 y el 9 de mayo de 2023.Disturbances associated with climate change may push organisms beyond their resilience limits, and strong ecological consequences are expected when foundation species are affected. When predicting species’ responses to warming, species are typically considered as physiologically homogeneous. Yet, responses to extreme events may vary according to differences in phenotypic plasticity and local adaptation across the range of a species. Using a common-garden mesocosm experiment, we compared the resilience (i.e., response to and recovery from) to two warming events of different intensity on seagrass seedlings germinated from seeds collected at eight regions across the species’ distribution range. We show a positive relationship between resilience to warming and local thermal variability, suggesting seagrass evolutionary adaptation to local thermal conditions. Our results highlight the critical importance of incorporating intra-specific variability when making predictions and when developing conservation and restoration strategies about species vulnerability to climate change. Furthermore, strong negative lag-effects on seedlings performance were observed after the warming phase had already stopped, highlighting the importance of following species’ responses after a disturbance has finished, particularly because most experimental studies have only examined immediate, short-term, responses to stressors. Given the long-term common-garden approach used, we expect that differences in seedling responses will be mainly the result of genetic changes leading to local adaptation

Seagrass ecology: environmental conditions and processes that affect the establishment and fate of seedlings

[eng] Recruitment of new individuals into a reproductive plant population is a multistage process, from seed production, propagule dispersal and seed germination, to seedling establishment and further survival. This multistage process is decisive in plant life story, since it will determine the trajectory of plant community assembly. Importantly, the transition between seed germination and seedling establishment and further seedling survivorship represents a “bottleneck” for plant populations, limiting their recruitment success. To successfully overcome this transition, seedlings must surmount a series of biotic and abiotic environmental filters, and simultaneously be capable of resisting the progressively more abundant and frequent anthropogenic threats. Seagrasses form extensive meadows in coastal waters, carrying out important ecosystem functions that provide essential services to society. Nonetheless, seagrasses are suffering a strong decline worldwide due to multiple anthropogenic stressors. In this context, early life stages are an essential step to guarantee population survivorship since propagules provide an essential genetic diversity source, necessary to adapt to environmental changes, and their dispersal allow seagrasses to colonize new areas. The present thesis examines how some abiotic and biotic factors, including anthropogenic disturbances, influences propagule dispersal and successful seedling establishment. Throughout this thesis I have determined that seagrass recruitment is considerably affected by the hydrodynamic conditions imposed by waves and currents, which have a key role in determining propagule dispersal, as well as establishment and survivorship of the three species analysed (Cymodocea nodosa, Posidonia oceanica and Zostera marina,). Additionally, substratum type and complexity affect seedling establishment success, since more complex substrata reduce flow velocity and increase the bottom boundary layer thickness, enhancing seed and seedling retention. Once established, seedlings increase their survival in locations sheltered from waves, where the energy flux is lower. The hydrodynamic energy also varies with depth, and in shallow waters (i.e. 0.5- 6 m), higher depths are associated to higher survival. Furthermore, certain biotic factors, such as the macroalgal community present at the settlement location, also affect seedling anchorage to the substrate and subsequent seedling survivorship. In addition to the above-mentioned factors, threats derived from global change narrow even more this population bottleneck, since they directly influence seedling development and survival. Seawater warming (29ºC) negatively affects the development of P. oceanica seedlings and damages their photosynthetic apparatus. When the increase in temperature occurs in terms of marine heatwaves, different populations of the same species (C. nodosa) exhibit different responses. Although seedlings from all regions suffer a reduction in development and survival, being the effects much more severe under a marine heatwave of 32ºC than under the one of 29ºC, there are important regional differences in seedling responses. Seedlings from regions with higher thermal variability are more resistant than those seedlings from more stable regions, which highlights the importance of the intraspecific variability, basic for species evolution and distribution. On the other hand, the studied invasive algae (Caulerpa cylindracea and Lophocladia lallemandii) do not have negative effects on P. oceanica seedlings, and thus, additive effects to those caused by a simultaneously increase in temperature were not detected when seedlings where growing under both disturbances. The present research takes a step forward towards the understanding of those environmental factors and processes that affect the establishment and fate of seedlings, thus contributing to seagrass meadow conservation, ecosystems of a paramount ecological and socio-economic importance.[spa] El reclutamiento de nuevos individuos a una población de plantas adultas es un proceso crítico que determina la trayectoria de la comunidad. Este proceso consta de varias etapas, desde la dispersión de los propágulos y la germinación de las semillas, hasta el establecimiento de las plántulas y su posterior supervivencia. La transición entre la germinación de las semillas y el establecimiento y posterior supervivencia de las plántulas supone un “cuello de botella” para la población. Para superar con éxito esta transición en su ciclo vital, las plántulas deben atravesar una serie de filtros bióticos y abióticos, y ser capaces de resistir las amenazas de origen antrópico. Las fanerógamas marinas forman extensas praderas en aguas costeras, desarrollando funciones ecológicas que suministran importantes servicios a la sociedad. Sin embargo, están sufriendo una fuerte regresión a nivel mundial como resultado de muchas perturbaciones antrópicas. En este contexto, los estadios juveniles suponen un eslabón esencial para asegurar la supervivencia de las poblaciones, pues contribuyen a mantener la diversidad genética de la población, fundamental para su adaptación a los cambios, y su dispersión permite la colonización de nuevas áreas. La presente tesis analiza cómo actúan algunos factores abióticos y bióticos, incluyendo perturbaciones humanas, sobre la dispersión de propágulos y el establecimiento exitoso de las plántulas. En esta tesis he comprobado que el reclutamiento de fanerógamas marinas está considerablemente afectado por las condiciones hidrodinámicas establecidas por olas y corrientes, las cuales tienen un papel clave en determinar la dispersión, establecimiento y supervivencia de los propágulos de Cymodocea nodosa, Posidonia oceanica y Zostera marina. Asimismo, el tipo de sustrato y su complejidad afectan al éxito del establecimiento, pues sustratos más complejos disminuyen la velocidad de la corriente y aumentan el espesor de la capa límite del fondo, facilitando la retención de semillas y plántulas. Una vez establecidas, las plántulas aumentan su supervivencia en zonas más protegidas de la influencia de las olas, donde el flujo de energía asociado a éstas es menor. La energía hidrodinámica también cambia con la profundidad, y en aguas someras (i.e. 0.5-6 m), mayores profundidades están asociadas a mayor supervivencia. Además, ciertos factores bióticos, como la comunidad de macroalgas presente en el lugar de asentamiento, también influyen en el anclaje al sustrato y la supervivencia de las plántulas. Asimismo, las amenazas derivadas del “cambio global” estrechan todavía más este cuello de botella poblacional, al influir directamente en el desarrollo y supervivencia de las plántulas. El calentamiento del agua (29ºC) afecta negativamente el desarrollo de plántulas de P. oceanica y daña su aparato fotosintético. Cuando este calentamiento se produce en forma de olas de calor, las poblaciones de una misma especie (C. nodosa) responden de manera diferente. Si bien todas las regiones ven afectado su desarrollo y supervivencia, siendo los efectos más dañinos en la ola de calor de 32ºC que en la de 29ºC, la respuesta a nivel regional difiere. Aquellas plántulas que proceden de regiones con mayor amplitud térmica son más resistentes a este aumento de temperatura que regiones con un régimen térmico más estable, lo cual resalta la importancia de las variaciones intraespecíficas, básicas en la evolución y distribución de las especies. Por otro lado, las algas invasoras Caulerpa cylindracea y Lophocladia lallemandii no tienen efectos negativos en P. oceanica cuando esta se ve sometida a calentamiento. La presente investigación da un paso hacia delante en la comprensión de los factores ambientales y los procesos que afectan el asentamiento y destino de las plántulas, contribuyendo así a la conservación de las praderas de fanerógamas marinas, ecosistemas de gran importancia ecológica y socio-económica.[cat] El reclutament de nous individus a una població de plantes adultes és un procés crític que determina la trajectòria de la comunitat. Aquest procés es composa de diferents etapes, des de la dispersió de propàguls i la germinació de llavors, fins a l’establiment de les plàntules i la seva posterior supervivència. La transició entre la germinació de les llavors i l’establiment i posterior supervivència de les plàntules suposa un coll d’ampolla per a la població. Per a poder superar amb èxit aquesta transició en el seu cicle vital, les plàntules han de travessar un seguit de filtres biòtics i abiòtics i, alhora, tenir la capacitat de resistir les amenaces d’origen antròpic. Les fanerògames marines formen praderies en aigües costeres, desenvolupant funcions ecològiques que subministren serveis importants per a la societat. Tot i això, aquestes estan patint una forta regressió a nivell mundial com a resultat de moltes pertorbacions antròpiques. En aquest context, els estadis juvenils suposen una etapa essencial per a assegurar-ne la supervivència, contribuint en el manteniment de la diversitat genètica de les poblacions, la qual és fonamental per a la seva adaptació als canvis, essent la seva dispersió la que permet la colonització de noves àrees. Aquesta tesi analitza com actuen alguns factors abiòtics i biòtics, incloent-hi pertorbacions humanes, sobre la dispersió de propàguls i l’establiment exitós de les plàntules. En aquesta tesi he comprovat que el reclutament de plàntules de fanerògames marines està fortament afectat per les condicions hidrodinàmiques establertes per l’onatge i les corrents, les quals tenen un paper clau en la determinació de la dispersió, l’establiment i la supervivència dels propàguls de Cymodocea nodosa, Posidonia oceanica i Zostera marina. No obstant, el tipus de substrat i la seva complexitat afecten l’èxit de l’establiment; els substrats més complexes disminueixen la velocitat de la corrent i augmenten el gruix de la capa límit de fons, facilitant la retenció de llavors i plàntules. Un cop establertes, les plàntules augmenten la seva supervivència en zones més protegides de la influència de l’onatge, on el flux d’energia associat a aquestes és menor. L’energia hidrodinàmica canvia amb la profunditat i, en aigües poc fondes (i.e. 0.5-6 m) les majors profunditats estan associades a una major supervivència. A més a més, alguns factors biòtics, com per exemple la comunitat de macroalgues existent en el lloc de l’assentament, també influeixen en l’ancoratge al substrat i la supervivència de les plàntules. A més a més, les amenaces derivades del «canvi global» estrenyen encara més el coll d’ampolla poblacional, exercint una influència directa en el desenvolupament i la supervivència de les plàntules. L’escalfament de l’aigua (29ºC) afecta negativament el desenvolupament de plàntules de P. oceanica i malmet el seu aparell fotosintètic. Quan aquest escalfament es produeix en forma d’onades de calor, les poblacions d’una mateixa espècie (C. nodosa) responen de manera diferent. Si bé les plàntules de totes les regions es veuen afectades negativament tant en desenvolupament com supervivència, essent els efectes de la onada de calor més nocius a 32ºC que a 29ºC, la resposta regional canvia. Aquelles plàntules que provenen de regions amb una major amplitud tèrmica són més resistents a aquest augment de temperatura en comparació amb les que provenen de regions amb règims tèrmics més estables, resultat que ressalta la importància de les variacions interespecífiques, bàsiques en l’evolució i la distribució d’espècies. D’altra banda, les algues invasores Caulerpa cylindracea i Lophocladia lallemandii no tenen efectes negatius en P. oceanica quan aquesta està sotmesa a l’escalfament. Aquesta investigació dóna un pas endavant en la comprensió dels factors ambientals i els processos que afecten l’assentament i el destí de les plàntules, contribuint així a la conservació de les praderies de fanerògames marines, ecosistemes de gran importància ecològica i sòcio-econòmica

Efecto de los nutrientes en la interacción entre el alga invasora Caulerpa cylindracea y los estadios juveniles de la fanerógama marina Posidonia oceanica

Peer Reviewe

Negative effects of warming on seagrass seedlings are not exacerbated by invasive algae

The observed and projected rise in sea surface temperature challenges marine biodiversity worldwide, and particularly in temperate ecosystems dealing with the arrival of novel species of tropical provenance. When the impacted biota are early life stages of ecosystem engineers, the effects of those impacts are of major concern for ecologists and coastal managers. We experimentally examined the individual and potential additive effects of seawater warming and the presence of the invasive algae on the development of seedlings of the seagrass Posidonia oceanica in a three-month mesocosm experiment. Whereas the presence of the invasive algae (Caulerpa cylindracea and Lophocladia lallemandii) did not result in detrimental effects on seedlings, warming negatively affected seedling development. Interestingly, the presence of both invasive algae may ameliorate the negative effects of warming.Support to L. Pereda-Briones was provided by a PhD Fellowship from the Balearic Islands Government and the European Social Fund. Funds for this work were provided by the Ministry of Science and Innovation (RESIGRASS project, n° ref.: CGL2014-58829-C2-2-R) to FT and JT, the Ramón y Cajal Program (RYC-2011-08572) to FT and a research contract with Red Eléctrica de España of JT.Peer reviewe

Seed and seedling transport: Hydrodynamics and substratum effects on three European seagrasses

Trabajo presentado en el 12th International Seagrass Biology Workshop, celebrado en Nant Gwyrtheryn (Wales), del 16 a 21 de octubre de 2016Peer Reviewe

Dispersal of seagrass propagules: substratum and hydrodynamic effects

Trabajo presentado en el 12th International Seagrass Biology Workshop, celebrado en Nant Gwyrtheryn (Reino Unido), del 16 al 21 de octubre de 2016Peer Reviewe

Image_1_A Tropical Macroalga (Halimeda incrassata) Enhances Diversity and Abundance of Epifaunal Assemblages in Mediterranean Seagrass Meadows.tif

1 figure.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.Peer reviewe