Structure of fish assemblages on coastal rocky shores of the Azores

Bol. Mus. Mun. Funchal, Sup. N.º 6: 127-138, 2001The structure of fish assemblages was investigated from the surface down to 25 m depth on Azorean rocky shores. A total of 57 fish species was recorded by visual censuses, most species (66%) occurring in the whole depth range studied. Fish abundance was dominated by 11 species, mainly sparids, labrids, carangids and pomacentrids, which constituted over 88% of the total number of individuals recorded. The trophic structure of the fish assemblages studied in the Azores was characterized by the dominance of benthic mesocarnivores and high proportions of herbivores and pelagic macrocarnivores.A estrutura das comunidades ictiológicas dos fundos rochosos dos Açores foi estudada desde a superfície até aos 25 m de profundidade. Um total de 57 espécies de peixes foi identificado com recurso a censos visuais. A maioria das espécies (66%) ocorreu em toda a gama de profundidades estudada. A fauna ictiológica era dominada, em termos de abundância, por 11 espécies, principalmente pertencentes às famílias Sparidae, Labridae, Carangidae e Pomacentridae, os quais constituíram mais de 88% do número total de indivíduos observados. A estrutura trófica das comunidades ictiológicas estudadas nos Açores apresentouse dominada por meso-carnívoros bentónicos e proporções elevadas de herbívoros e macro-carnívoros pelágico

Evaluación de los sitios de asentamiento de Diplodus spp. (Sparidae) a lo largo de la costa rocosa de Marsella (Francia, Mediterráneo Noroccidental).

This work aimed at performing a large scale assessment of Diplodus spp. (Sparidae) nurseries along the rocky shore of Marseilles (France, NW Mediterranean) by locating and quantifying nursery microhabitats and estimating the settlement pattern along this shore in 2004. Nursery grounds of Diplodus spp. represented only 9% of the 52 km-long rocky shore of Marseilles. Their location, shallow rocky habitats sheltered within coves, made them vulnerable to human-induced habitat transformations. D. vulgaris settled along this coast at the end of February 2004 and D. puntazzo settled a couple of months earlier. Maximum densities observed reached 215 and 67 ind./100 m for D. vulgaris and D. puntazzo respectively. The settlement rates were spatially variable. At a regional scale, lower settlement rates were observed within the south and centre zones, compared to those observed in the west, east, and the Marseilles Bay zones. Suitable nurseries along this shore seem insufficient for the replenishment of adult assemblages, which suggests that they depend on the migration of adults from other areas. Along the Marseilles rocky shore, coastal development projects leading to the destruction of habitats would represent a major threat to the Diplodus life cycle, which could be even greater than usual given the vulnerability and small size of the nurseries. These results show that it is necessary to protect these scarce local nursery habitats and manage other nearby nurseries to ensure the survival of fish at a critical life stage and the replenishment of adult assemblages.Este estudio tiene por objetivo realizar una evaluación a gran escala de las áreas adecuadas para el asentamiento de Diplodus spp. a lo largo de la costa rocosa de Marsella (Francia, Mediterráneo Noroccidental) a través del estudio de la ubicación y abundancia de estos microhábitats y del patrón de asentamiento durante el año 2004. Los microhábitats de asentamiento representaron tan sólo el 9% de los 52 km de las extensas costas rocosas de Marsella. Su ubicación en el interior de las calas, en substratos rocosos protegidos y a poca profundidad, los convierte en hábitats vulnerables a las transformaciones inducidas por el hombre. El asentamiento a lo largo de esta costa tuvo lugar a finales de febrero 2004 para D. vulgaris, y dos de meses antes para D. puntazzo. Las máximas densidades observadas por cada 100 metros de costa alcanzaron 215 y 67 individuos de D. vulgaris y D. puntazzo respectivamente. Las tasas de asentamiento fueron variables en el espacio. A escala regional, las tasas de asentamiento menores fueron observadas en las zonas sur y central. Los lugares de asentamiento adecuados a lo largo de esta costa parecieron insuficientes para abastecer las poblaciones adultas, lo que sugiere que éstas dependen de la migración de adultos desde otras áreas. La urbanización de la costa produciría destrucción de estos microhábitats, lo que pondría en peligro el ciclo vital de Diplodus, dada la vulnerabilidad y rareza de dichos microhábitats. Nuestros resultados mostraron la necesidad de proteger estos escasos hábitats de asentamiento y gestionar zonas de asentamiento a su alrededor para asegurar la conectividad entre hábitats, la supervivencia de determinadas fases críticas de los peces y el suministro de individuos a las poblaciones adultas

Preliminary results on production and calcification of coral reefs communities of Tikehau atoll

The carbon and oxygen metabolism of some coral reef communities of Tikehau atoll were studied in November 1989. Calcification, photosynthèse and respiration were measured during incubation experiments in transparent plastic bags. Over 24 hours period, we observed a net calcification rate for the three studied communities. However, only #Halimeda$ community presented an excess production. (Résumé d'auteur

Influence des apports rhodaniens sur les traits d'histoires de vie de la sole commune (Solea Solea) (apports de l'analyse structurale et minéralogique des otolithes.)

La sole commune présente au cours de son cycle de vie un changement ontogénétique d habitat. Les larves sont marines et pélagiques, les juvéniles sont benthiques et vivent dans les nourriceries côtières (lagunes et estuaires) alors que les adultes sont benthiques et marins en zones plus profondes. Les otolithes sont des concrétions minéralisées de carbonate de calcium de l oreille interne des téléostéens qui ne subissent ni dissolution ni résorption. Ils enregistrent les caractéristiques chimiques et isotopiques des milieux traversés.L étude de la croissance, de la composition chimique et isotopique des otolithes des soles des nourriceries a confirmé l existence de deux stocks de soles dans le golfe du Lion, un à l Est et l autre à l Ouest. Les faibles valeurs de 13C et les fortes valeurs de Ba/Ca des otolithes des soles de l Est du golfe ont été associées à une forte influence des apports rhodaniens sur la phase de vie larvaire lors des années où le débit du Rhône est normal. En période de crue, une forte influence du fleuve est visible sur les otolithes des soles des nourriceries de l ensemble du golfe. La croissance des otolithes des juvéniles a été plus élevée lorsque la salinité a été proche de 20 et la température comprise entre 20 et 25C (période estivale). Les signatures des otolithes de Mauguio et Berre ont présenté des 13C et Sr/Ca plus faibles que ceux de Thau (influences plus marines sur les proies et les masses d eau). La spécificité des signatures chimiques et isotopiques des otolithes a permis d élaborer des profils qui ont été retrouvés chez les populations de soles adultes du golfe, mais aussi vers Marseille et Bandol. Ces soles ont montré une influence du Rhône durant la phase de vie larvaire à 53%. Elles ont également montré une forte similarité avec les profils chimiques de type lagune de Thau (10-56%) et Rhône (19-30%) durant leur vie juvénile. Toutefois, une proportion non négligeable de soles originaires de nourriceries non caractérisées (26-50%) a été observée.The life cycle of the common sole shows an ontogenetic shift of habitats. The larvae are marine and pelagic, the juveniles are benthic in coastal nurseries (lagoons and estuaries) whereas adults are benthic and live in marine deeper areas. Otoliths are paired calcified structures from the inner ear of teletost fish. They are metabolically inert (neither resorption nor dissolution) and they record, both the age (daily and annual increments) and the chemical and isotopic characteristics of the environment inhabited. Otoliths study provides information on the life history traits of individuals.The study of growth, chemical and isotopic otolith composition of soles from nurseries confirmed the existence of two sole stocks in the Gulf of Lions, one in the Eastern part and the other in the Western part. Low values in 13C and higher values in Ba/Ca ratio measured in Eastern sole otoliths during the larval life were associated to a high influence of the Rhône River discharge during a normal flow rate periods. Conversely, the one hundred return flood of the 2nd of December 2003 was very high and visible on otoliths from all nurseries in the Gulf of Lions. Juvenile otolith growth was higher in nurseries with low salinity (~20) and temperatures between 20 and 25C than in more marine nurseries. 13C and Sr/Ca ratios of otoliths from Berre and Mauguio coastal lagoons were lower than those observed in Thau coastal lagoon (more marine influences on preys and water masses). These specificities of otolith compositions were used for the elaboration of reference profiles, which have been identified in adult populations of the Gulf of Lions, Marseilles and Bandol. Adult have shown an influence of the Rhône River during their larval life at 53%. They have shown a similarity with Thau chemical profile (10-56%) and Rhône profile (19-30%) during their juvenile life. However, 26-50% of fish from uncharacterised nurseries have been observed.AIX-MARSEILLE2-Bib.electronique (130559901) / SudocSudocFranceF

The nutritional quality of non-calcified macroalgae in Guadeloupe (Lesser Antilles) evaluated by their biochemical composition

Biochemical compositions of 15 species and 1 genus of macroalgae were studied. Concentrations of macronutrients were measured to evaluate their nutritional quality. High concentrations of proteins, lipids and soluble carbohydrates generally indicate a high nutritional quality because these compounds are readily metabolically available for consumers and provide a large proportion of energy. Insoluble carbohydrates are more difficult to digest and high concentrations indicate a low nutritional quality. Three groups of macroalgae were identified according to their biochemical characteristics. The first group clusters Ceramium cf nitens, Ulva cf lactuca and Lobophora cf variegata due to their high concentrations of proteins and soluble carbohydrates, and low proportion of ashes. These species presented high nutritional qualities and, according to previous studies, are preferredby herbivorous fishes. A second group constituted by Dictyota cf pulchella, Caulerpa cupressoides, C. sertularioides and Sargassum cf polyceratium presented intermediate nutritional qualities due to higher concentrations of lipids and insoluble carbohydrates. Finally, the others species and genus are characterized by a high proportion of ashes and a low nutritional quality. However, some of these species (Acanthophora spicifera, Padina cf sanctae-crucis or Laurencia cf chondrioides) are cited as preferred macroalgae for some herbivorous fishes. The present study indicates that the biochemical composition in macronutrients only partially explains the food choice made by fishes. The consumption of macroalgae by herbivores depends also on the presence of deterrent molecules, the composition in micronutrients, and their palatability that often decreased with increasing size. Most of macroalgae are preferentially consumed when young and small

Linking benthic biodiversity to the functioning of coastal ecosystems subjected to river runoff (NW Mediterranean)

Continental particulate organic matter (POM) plays a major role in the functioning of coastal marine ecosystems as a disturbance as well as an input of nutrients. Relationships linking continental inputs from the Rhone River to biodiversity of the coastal benthic ecosystem and fishery production were investigated in the Golfe du Lion (NW Mediterranean Sea). Macrobenthic community diversity decreased when continen¬tal inputs of organic matter increased, whereas ecosystem production, measured by common sole (Solea solea) fishery yields in the area, increased. Decreases in macrobenthic diversity were mainly related to an increasing abundance of species with specific functional traits, particularly deposit-feeding polychaetes. The decrease in macrobenthic diversity did not result in a decrease, but an increase in ecosystem production, as it enhanced the transfer of continental POM into marine food webs. The present study showed that it is necessary to consider functional traits of species, direct and indirect links between species, and feedback loops to understand the effects of biodiversity on ecosystem functioning and productivity

Use of stable isotope signatures (δ13C & δ15N) in the Black Sea Danubian area – new approach for understanding the influence of terrestrial discharge upon the marine ecosystem

Abstract. Coastal marine zones located in front of large rivers are of major biological interest. In these areas, the origin of the organic matter is complex and highly variable. The continental inputs, added to the nutrients already present in the marine environment, influence considerably the productivity and functioning of the ecosystems. Used for the first time in aquatic ecology on the Romanian coast, the proportion of stable isotopes of carbon (13C/12C) and nitrogen (15N/14N) allowed the identification of the organic material sources (terrestrial and marine) as well as the analysis of the food webs due to the predictable isotopic relation between consumers and their food. Preliminary analyses of stable isotopes of the particulate organic matter POM of the Danube water as well as marine POM, sediments and marine organisms were made on 186 samples collected at 10 stations in October 2004. The identification of the isotopic signatures of the main sources of organic material (terrestrial and marine) was achieved along with those of some groups of marine organisms present in this area (macrophytes, bivalves, polychaetes, amphipods, macrurans, brachyurans and fish). The results obtained in the Black Sea were compared with those of the Mediterranean Sea seawards the Rhone river and showed that the isotopic signatures of the two river POM were close to each other, whereas they largely differed in marine phytoplankton and macrophytes

How Episodic Coral Breakage Can Determine Community Structure: A South African Coral Reef Example

Africa\u27s southernmost coral reefs are situated in Natal Province, South Africa. The Natal coast is exposed to open Ocean swells and episodic storm swell conditions. Benthic communities on these reefs differentiated into three community types: shallow reefs (8–18 m) were dominated by alcyonacean corals and low-growing, massive Scleractinia; intermediate reefs (18–25 m) were dominated chiefly by branching and tabular Scleractinia of the genus Acropora (A. austera, A. clathrata); deep reefs were not dominated by corals but by sponges. Breakage and recovery experiments indicated that the difference in Acropora dominance between shallow and intermediate sites was caused by breakage in high swell conditions. Survival of experimentally produced A. austera fragments was significantly higher in intermediate than in shallow sites, where higher surge made re-attachment and regeneration unlikely. Also, colony morphology was adapted to differential surge conditions: colonies on the shallow reefs were smaller with shorter branches, while on intermediate reefs they were much bigger with long, widely spreading branches. Episodic breakage and low fragment survival due to high water-motion thus excluded branching corals from shallow reef sites