Spatial patterns and response to wave exposure of shallow water algal assemblages across the Canarian Archipelago: a multiscaled approach

We conducted a mensurative survey to investigate spatial variability and the effect of wave exposure at a range of spatial scales including islands (100s of kilometres apart), locations within islands (10s of kilometres apart), and sites within locations (100s of meters apart), on the composition, abundance and distribution of shallow water algal assemblages across subtidal hard bottoms of the Canarian Archipelago (eastern Atlantic). A multi-scaled hierarchical sampling design provided the framework for quantifying the variation among samples due to each spatial scale and level of wave exposure. Haphazardly placed 50 x 50 cm quadrats were deployed in shallow rocky-reefs to assess community structure and dominance. Non-parametric multivariate techniques, as well as univariate tests, provided evidence to collectively suggest that shallow water algal assemblages differed between protected (leeward) and exposed (windward) shores, with a consistency of its effects across islands, while different spatial scales were also involved in the variability and patchiness of these assemblages. In this sense, differences were clearly taxon and/or group-specific. In general, the presence and abundance of frondose fucoid species was greater at exposed shores compared to protected shores, whereas turf-algae dominated protected shores at each island. Dissimilarities between islands for the overall algal assemblage generally increased with the distance between islands. In particular, the presence and abundance of fucoid species was larger in the eastern islands, while in contrast turf and bush-like algae increased in the western islands. The large-scale gradient of the oceanographic conditions in an east-to-west direction across the Canarian Archipelago provided a parsimonious explanation for this observation, yet some inconsistencies were observed in the overall regional pattern

Spatial patterns and response to wave exposure of shallow water algal assemblages across the Canarian Archipelago: A multi-scaled approach

We conducted a mensurative survey to investigate spatial variability and the effect of wave exposure at a range of spatial scales including islands (100s of kilometres apart), locations within islands (10s of kilometres apart), and sites within locations (100s of meters apart), on the composition, abundance and distribution of shallow water algal assemblages across subtidal hard bottoms of the Canarian Archipelago (eastern Atlantic). A multi-scaled hierarchical sampling design provided the framework for quantifying the variation among samples due to each spatial scale and level of wave exposure. Haphazardly placed 50 x 50 cm quadrats were deployed in shallow rocky-reefs to assess community structure and dominance. Non-parametric multivariate techniques, as well as univariate tests, provided evidence to collectively suggest that shallow water algal assemblages differed between protected (leeward) and exposed (windward) shores, with a consistency of its effects across islands, while different spatial scales were also involved in the variability and patchiness of these assemblages. In this sense, differences were clearly taxon and/or group-specific. In general, the presence and abundance of frondose fucoid species was greater at exposed shores compared to protected shores, whereas turf-algae dominated protected shores at each island. Dissimilarities between islands for the overall algal assemblage generally increased with the distance between islands. In particular, the presence and abundance of fucoid species was larger in the eastern islands, while in contrast turf and bush-like algae increased in the western islands. The large-scale gradient of the oceanographic conditions in an east-to-west direction across the Canarian Archipelago provided a parsimonious explanation for this observation, yet some inconsistencies were observed in the overall regional pattern

Patrones espaciales en la estructura poblacional del caracol Stramonita haemastoma (Linnaeus, 1766) (Gastropoda: Muricidae) en el Archipiélago Canario (Atlántico oriental).

The goal of this study was to determine the consistency of the vertical distribution patterns of the predatory whelk, Stramonita haemastoma, in the rocky intertidal zone of the Canarian Archipelago (eastern Atlantic) across a hierarchy of five orders of magnitude of horizontal spatial variability (from tens of m to hundreds of km). In general, this species showed a consistent vertical zonation pattern across islands, with the majority of the specimens (74.65%) found in the mid intertidal zone. This result most likely reflects the whelk’s preference for a habitat with a large amount of potential prey but minimal stress induced by swells and desiccation. The mean abundance (0 to 1.73 ± 0.40 ind m-2, mean ± SE) and size structure (7 to 45 mm in shell length) of S. haemastoma in the Canarian Archipelago was considerably lower compared to those from continental areas in the Atlantic Ocean, which suggests that there are some differences between these populations. Natural mechanisms (e.g. isolation or poor recruitment events) and human perturbations (e.g. exploitation of intertidal resources) might influence the spatial distribution patterns.El objetivo de este estudio fue determinar la consistencia de los patrones de distribución vertical del caracol predador, Stramonita haemastoma, en el intermareal rocoso del archipiélago Canario (Atlántico oriental), a través de un modelo jerárquico que incluyó cinco órdenes de magnitud de variabilidad espacial horizontal (desde decenas de m hasta centenares de km). En general, esta especie mostró un patrón de zonación vertical consistente entre islas, con la mayoría de los ejemplares (74.65%) presentes en la zona intermareal media. Este resultado probablemente refleja una preferencia hacia un hábitat con mayor disponibilidad de presas, pero minimizando el estrés inducido por la exposición al oleaje y la desecación. El rango de abundancias (0 a 1.73 ind m-2, media ± SE) y la estructura de tallas (7-45 mm en longitud de concha) fueron notablemente bajos en relación a los observados en la costa continental del Atlántico, sugiriendo diferencias entre dichas poblaciones. Procesos naturales (e.g. aislamiento o eventos de escaso reclutamiento) y perturbaciones humanas (e.g. explotación de los recursos intermareales) pueden haber influido sobre estos patrones de distribución espacial

Review of the marine phycological studies in the Macaronesian Archipelagos

International Symposium FloraMac 2012. Colégio dos Jesuítas, Funchal, Madeira, 5-8 de Setembro

New foliose and gelatinous red macroalgae (Rhodophycota) from the Azores: morphological and geographical observations.

Copyright © 2002 Published by Elsevier Science B.V.The following four species of foliose and gelatinous red algae (Rhodophycota) are newly recorded for the Azores archipelago (North Atlantic Ocean): Gracilaria multipartita (Clemente) Harvey, Meristotheca decumbens Grunow (Solieriaceae), Asteromenia peltata (W.R. Taylor) Huisman and A.J.K. Millar (Rhodymeniaceae), and Agardhinula browneae (J. Agardh) De Toni (Faucheaceae). The species are described, and information on reproductive status, ecology and biogeographical relationships is provided

Rendimiento foto-fisiológico y aclimatación a corto plazo de dos macrófitos coexistentes (Cymodocea nodosa y Caulerpa prolifera) con la profundidad

Marine macrophytes are vertically distributed according to their ability to optimize their photosynthetic performance. We assessed the photo-physiological performance of the seagrass Cymodocea nodosa and the green seaweed Caulerpa prolifera at varying depth at Gran Canaria Island (Canary Islands, eastern Atlantic). The biomass of C. nodosa decreases with depth, while the opposite occurs for C. prolifera. Photochemical responses of both macrophytes were measured in shallow (5 m) and deep (20 m) waters at two times via chlorophyll a fluorescence and internal content of photoprotective pigments and antioxidant activity. We additionally carried out a reciprocal transplant experiment by relocating shallow and deep vegetative fragments of both macrophytes to assess their short-term photo-physiological acclimation. Overall, C. nodosa behaves as a ‘light-plant’, including a larger optimum quantum yield and ETRmax under scenarios of high photosynthetically active radiation and a larger antioxidant activity. In contrast, C. prolifera is a ‘shade-adapted’ plant, showing a larger carotene content, particularly in shallow water. Deep-water C. nodosa and C. prolifera are more photochemically efficient than in shallow water. The alga C. prolifera shows a rapid, short-term acclimation to altered light regimes in terms of photosynthetic efficiency. In conclusion, decreased light regimes favour the photosynthetic performance of the green alga when both species coexist.Los macrófitos marinos se distribuyen verticalmente de acuerdo a sus capacidades para optimizar su rendimiento fotosintético. Evaluamos el rendimiento foto-fisiológico de la fanerógama marina Cymodocea nodosa y el alga verde Caulerpa prolifera a diferentes profundidades en la isla de Gran Canaria (Islas Canarias, Atlántico oriental). La biomasa de C. nodosa decrece con la profundidad, mientras que para C. prolifera ocurre lo contrario. Las respuestas foto-químicas de ambos macrófitos se midieron en aguas someras (5 m) y profundas (20 m), en dos tiempos, a través de la fluorescencia de la clorofila a y los contenidos internos en pigmentos fotoprotectores y la actividad antioxidante. Además, ejecutamos un experimento de trasplante recíproco, recolocando fragmentos vegetativos de ambos macrófitos entre aguas someras y profundas para determinar su aclimatación a corto plazo. En general, C. nodosa se comporta como “planta de sol”, con mayor rendimiento cuántico óptimo y ETRmax bajo escenarios de alta radiación PAR y mayor actividad antioxidante. Contrariamente, C. prolifera es una “planta de sombra”, mostrando mayor cantidad de carotenos, en particular a poca profundidad. Ejemplares profundos de ambos macrófitos son más eficientes foto-químicamente que los de aguas someras. El alga C. prolifera muestra una aclimatación rápida, a corto plazo, de su eficiencia fotosintética ante cambios en el régimen luminoso. En conclusión, regímenes depauperados lumínicamente favorecen el rendimiento fotosintético del alga verde

Changes in Demersal Wild Fish Aggregations Beneath a Sea-cage Fish Farm after the Cessation of Farming

Demersal, non-cryptic, wild fish were counted in replicate 100 m2 transects beneath a floating sea-cage fish farm and two nearby sandy locations at Gran Canaria (Canary Islands, eastern Atlantic) four times before and after the cessation of farming. Cessation of farming involved the removal of farmed fish and ceasing of the daily feeding, although farm structures (cages and moorings) remained. A “beyond-BACI” sampling design provided the framework to detect the effect of the cessation of farming, which produced qualitative and quantitative changes in the composition and structure of the fish assemblages beneath the sea-cage fish farm compared with two nearby controls. The aggregative effect on wild fish due to the existence of the farm decreased from approximately 50 times compared to nearby controls when the farm was in full operation to \u3c2 times when only the farm structures remained. Abundances of POM feeders\u3e(large-sized mugilids), large benthic chondrichthyid rays and Pagellus spp. declined markedly at the fish farm after the cessation of farming, suggesting that the removal of daily feeding was responsible for their disappearance. In contrast, abundances of herbivores, benthic macro- and meso-carnivores were similar beneath the fish farm both before and after the cessation of farming. Benthic macro-carnivores, however, were more abundant beneath the sea-cages compared to control locations, supporting the hypothesis that the increase in the physical structure beneath farms plays a role in aggregating these species. Sparids occurred beneath the sea-cages only after the cessation of farming, while the two natural control locations did not show differences from before to after the cessation of farming. Overall, the results show that the wild fish assemblage beneath the farm partially changed after the cessation of farming to a more natural state, approaching the assemblages observed at the control sites

Regresión aguda de los bosques de Cystoseira abies-marina en la isla de Gran Canaria (Islas Canarias, Atlántico este)

Brown macroalgae within the genus Cystoseira are some of the most relevant “ecosystem-engineers” found throughout the Mediterranean and the adjacent Atlantic coasts. Cystoseira-dominated assemblages are sensitive to anthropogenic pressures, and historical declines have been reported from some regions. In particular, Cystoseira abies-marina, thriving on shallow rocky shores, is a key species for the ecosystems of the Canary Islands. In this work, we analyse changes in the distribution and extension of C. abies-marina in the last decades on the island of Gran Canaria. This alga dominated the shallow rocky shores of the entire island in the 1980s; a continuous belt extended along 120.5 km of the coastline and occupied 928 ha. In the first decade of the 21st century, fragmented populations were found along 52.2 km of the coastline and occupied 12.6 ha. Today, this species is found along 37.8 km of the coastline and occupies only 7.4 ha, mainly as scattered patches. This regression has been drastic around the whole island, even in areas with low anthropogenic pressure; the magnitude of the decline over time and the intensity of local human impacts have not shown a significant correlation. This study highlights a real need to implement conservation and restoration policies for C. abies-marina in this region.Las algas pardas pertenecientes al género Cystoseira se distribuyen a lo largo del Mediterráneo y las costas atlánticas adyacentes, siendo uno de los “ingenieros ecosistémicos” más relevantes. Los bosques constituidos por especies de Cystoseira son sensibles a perturbaciones de origen antropogénico y, por esta razón, se han registrado declives históricos en distintas regiones. Concretamente, Cystoseira abies-marina, una especie que habita en costas rocosas someras, es clave para la buena salud de los ecosistemas costeros de las Islas Canarias. En este trabajo, analizamos los cambios en la distribución y extensión de C. abies-marina en las últimas 4 décadas en la isla de Gran Canaria. Esta especie dominaba las costas rocosas poco profundas de toda la isla en la década de los 80; una banda continua se extendía a lo largo de 120.5 km de costa, ocupando 928 ha. A comienzos del siglo XXI, poblaciones fragmentadas cubrían 12.6 ha, a lo largo de 52.2 km de la línea de costa. Hoy en día, se distribuye a lo largo de 37.8 km del perímetro costero, en su mayoría como parches dispersos, ocupando una extensión de tan sólo 7.4 ha. Esta regresión ha sido drástica en toda la isla, incluso en zonas con baja presión antropogénica; no encontramos una correlación significativa entre el número de impactos locales y la magnitud del declive en el tiempo. Este estudio señala la necesidad real de implementar políticas de conservación y restauración para C. abies-marina en esta región

Estructura poblacional del ‘pejepeine’, Xyrichtys novacula (Actinopterygii: Labridae), en mosaicos arena-pradera de fanerógama marina: variación espacial de acuerdo con las características del hábitat y técnicas de muestreo

Habitat structure affects the distribution of fishes, particularly across reef-dominated habitats, but few studies have connected patterns in the abundance of soft-bottom fishes with the structure of the habitat. The spatial and temporal patterns of variation in the abundance, biomass and population structure of the pearly razorfish, Xyrichtys novacula, inhabiting sand-Cymodocea nodosa seagrass mosaics were described through two complementary techniques: underwater visual counts and seine nets. We sought to analyse whether biotic (seagrass shoot density, leaf length and meadow cover) and abiotic (sediment composition and particle size) structural elements explained variation in patterns of abundance and biomass. Underwater visual counts registered a larger abundance of individuals and proved significant variation in fish abundance and biomass at the scale of locations, which was otherwise not detected through seine nets. Seasonal variation in fish abundance and biomass was, in all cases, minor. Habitat structural elements helped to explain patterns in fish abundance and biomass. This fish species was particularly abundant in sediments dominated by coarse sands in continuous meadows of C. nodosa ( > 90% seagrass cover) with intermediate densities of 500 to 1000 shoots m–2, followed by large-sized seagrass patches with >1000 shoots m–2. A trade-off between protection provided by seagrass canopies and protection derived from its burial behaviour, limited under high seagrass shoot densities, may explain spatial variation patterns.La estructura del hábitat afecta a la distribución de los peces, particularmente en los hábitats dominados por arrecifes. Sin embargo, los estudios que conectan patrones de abundancia de peces en fondos blandos con la estructura del hábitat son, comparativamente, más escasos. En este estudio, se describen los patrones espacio-temporales de variación en abundancia, biomasa y estructura poblacional del ‘pejepeine’, Xyrichtys novacula, en hábitats de arena y praderas de fanerógamas marinas constituidas por Cymodocea nodosa, empleando dos técnicas complementarias: censos visuales subacuáticos (UVCs) y arrastres (SNs). Se analizó si los elementos estructurales bióticos (densidad de pies, longitud de hoja y cobertura de la pradera) y abióticos (composición del sedimento y tamaño de las partículas) contribuyen a explicar la variación en los patrones de abundancia y biomasa. Los UVCs registraron una mayor abundancia de individuos y demostraron una variación significativa en abundancia y biomasa a escala de localidades, estas variaciones no fueron detectadas por los arrastres. La variación estacional en la abundancia y biomasa de individuos fue mínima en todos los casos. Los elementos estructurales del hábitat contribuyen a explicar los patrones de abundancia y biomasa de peces. Esta especie fue particularmente abundante en fondos dominados por arenas gruesas con praderas continuas de C. nodosa (cobertura > 90%) con densidades de pies intermedias de 500 1000 pies m–2. Un equilibrio entre la protección provista por la bóveda foliar y la protección derivada de su comportamiento de enterramiento, el cual está limitado por densidades de pies altas, puede explicar los patrones de variabilidad espacial de esta especie

Explosión demográfica de un hidrozoo exótico en una isla oceánica

The arrival of non-indigenous species into new areas is one of the main processes altering the oceans globally. Macrorhynchia philippina is a large-sized colonial hydrozoan of an invasive nature. To obtain a deeper understanding of the process of colonization of new areas, it is essential to describe the ecological pattern through scales of temporal and spatial variation. In this study, we describe the colonization by M. Philippina of an oceanic island (Gran Canaria Island, Canary Islands, eastern Atlantic). We describe the abundance and size structure patterns of M. Philippina in three nearshore habitats, rocky reefs, seagrass meadows and rhodolith seabeds, at times before (2014), during (2016) and after (2017) the demographic explosion of this species. On rocky reefs and rhodolith seabeds, the abundance of colonies increased dramatically in 2017 rel­ative to 2014, e.g. from 0 to 138 colonies/100 m2. On seagrass meadows, however, the colonies were smaller. In summary, M. Philippina shows an ecological plasticity to rapidly colonize different types of nearshore habitats, but with varying success.La aparición de especies exóticas es uno de los principales factores que alteran los océanos de forma global. Mac­rorhynchia philippina es un hidrozoo colonial de tamaño grande y naturaleza invasora. Para tener un mejor conocimiento del proceso de colonización es fundamental describir los patrones ecológicos a escalas de variación temporal y espacial. En este estudio, describimos el proceso de colonización por M. Philippina en una isla oceánica (Gran Canaria, Islas Canarias, Atlántico oriental). Se describen los patrones de abundancia y estructura de tallas de M. Philippina en tres hábitats costeros: arrecifes rocosos, praderas de fanerógamas marinas y fondos de rodolitos, antes (2014), durante (2016) y después (2017) de la explosión demográfica de la especie. Sobre arrecifes rocosos y en fondos de rodolitos, la abundancia de las colonias se incrementó drásticamente en 2017 con relación a 2014, e.g. desde 0 hasta 138 colonias/100 m2; este incremento fue menor en las praderas de fanerógamas marinas. En las praderas marinas, la longitud de las colonias fue más pequeña que sobre ar­recifes rocosos y fondos de rodolitos. Consecuentemente, la colonización rápida por M. Philippina demuestra su plasticidad ecológica para colonizar diferentes tipos de hábitats costeros, aunque con diferente éxito