Persistent organic pollutants and trace metals in selected marine organisms from the Akanda National Park, Gabon (Central Africa).

Akanda National Park (ANP) is composed of mangrove ecosystems bordering Libreville, Gabon's capital. The contamination of aquatic resources from the ANP by persistent organic pollutants (POPs) and trace metals (TMs) was never evaluated. To provide a basis for their monitoring in the ANP, five species (two fish, two mollusks, and one crustacean) were analyzed from three sampling sites in 2017. Contamination levels for POPs and TMs were below maximum acceptable limits for seafood, including Cd and Pb. No DDT was found in any sample. Inter-specific differences were more obvious than the differences among sites, although the results may be biased by an unbalanced sampling design. The oyster Crassostrea gasar was the most contaminated species, making this species a good candidate to assess environmental contamination in the area. The studied species also contained essential elements, such as Fe, Zn and Mn at interesting levels in a nutritional point of view.

Lipid-correction models for δ13C values across small pelagic fishes (Clupeiformes) from the Atlantic Ocean.

The interpretation of δ13C values in trophic ecology requires standardization of the lipid content of organisms estimated through their C:N ratio. To avoid time-consuming lipid extractions, the use of mathematical corrections has been developed for many years, and the conclusions generally point in the direction of species-specific adjustment of the models. This study aimed at defining the maximum taxonomic level required to obtain the best corrected δ13C values in small pelagic fish of the order Clupeiformes. δ13C values of six species were analyzed bulk and lipid-free, and were used to fit and validate linear and mass-balance models at different taxonomic levels. Despite a species effect combined with the C:N ratio effect, the corrected δ13C values produced by a global model for the Clupeiformes were as good as or better when compared to lipid-free samples than those produced by species-specific models, paving the way for possible generalization to other species in this order. At the order level, the linear model outperformed the mass-balance model.

Biology and ecology of sea catfish (Ariidae) of estuarine, lagoon and coastal ecosystems in West Africa.

The family Ariidae, sea catfish of the order Siluriformes, is widely distributed throughout the world, particularly in tropical and subtropical areas. The three species of Ariidae found on the coasts and estuaries of West Africa are the smoothmouth catfish Carlarius heudelotii (Valenciennes 1840), the rough-head catfish Carlarius latiscutatus (Günther 1864) and the Guinean sea catfish Carlarius parkii (Günther 1864). They have been increasingly exploited by artisanal and industrial coastal fisheries in recent decades, but there is still little information available on their ecology and biology. The aim of this study was to deepen our knowledge of these three West African Ariidae species based on a dataset collected between 1980 and 2013 during experimental fishing programmes. They were carried out in Mauritania in the Banc d'Arguin National Park, in Senegal in the Sine Saloum estuary including the Bamboung Marine Protected Area (MPA), in The Gambia in the Gambia estuary, in Guinea-Bissau in the Urok Islands MPA in the Bijagos archipelago, in Guinea in the Fatala estuary and Dangara inlet, and in Côte d'Ivoire in the Ebrié Lagoon. C. latiscutatus accounted for 65%, C. parkii for 29% and C. heudelotii for 6% of total number of Ariidae sampled. C. latiscutatus was abundant in the Sine Saloum and Gambia estuaries as well as in Guinea and Guinea-Bissau and was the only species present in the Ebrié Lagoon. C. parkii was in the majority in Mauritania. The three species were recorded in a salinity range of 0 to 50, a temperature range of 19 to 34°C, in areas 1.7 to 15 m depth, and transparency ranging from 0.1 to 4 m (Secchi disk depth). C. heudelotii was present in less saline (25 vs. 32-34), less warm (27 vs. 29°C) and less transparent (0.8 m vs. 1.6 m) waters than the two other species. The maximum sizes (453 mm, 614 mm and 525 mm for, respectively, C. heudelotii, C. latiscutatus and C. parkii) were comparable to those recorded at sea. Length-weight relationships calculated for each species showed b coefficients greater than 3. Sex ratios were always in favour of females. The number of mature individuals and their smallest size at maturity were calculated per species, sex and study area. A size of 27-28 cm at first maturity was estimated for females of C. latiscutatus. A few dozen records made it possible to describe fecundity and cases of oral incubation by females. The diet of the three species was composed of crustaceans, fish and molluscs, confirming their classification as generalist predators. Thanks to their high environmental tolerance, these sea catfish populations are able to occupy both the continental shelf and adjacent estuaries throughout their life cycle, with the exception of spawning, which generally takes place at sea.

Resilience of Key Biological Parameters of the Senegalese Flat Sardinella to Overfishing and Climate Change.

The stock of the Senegalese flat sardinella, Sardinella maderensis, is highly exploited in Senegal, West Africa. Its growth and reproduction parameters are key biological indicators for improving fisheries management. This study reviewed these parameters using landing data from small-scale fisheries in Senegal and literature information dated back more than 25 years. Age was estimated using length-frequency data to calculate growth parameters and assess the growth performance index. With global climate change there has been an increase in the average sea surface temperature along the Senegalese coast but the length-weight parameters, sex ratio, size at first sexual maturity, period of reproduction and condition factor of S. maderensis have not changed significantly. The above parameters of S. maderensis have hardly changed, despite high exploitation and fluctuations in environmental conditions that affect the early development phases of small pelagic fish in West Africa. This lack of plasticity of the species regarding of the biological parameters studied should be considered when planning relevant fishery management plans.

Ectomycorrhizal fungal communities of Coccoloba uvifera (L.) L. mature trees and seedlings in the neotropical coastal forests of Guadeloupe (Lesser Antilles).

We studied belowground and aboveground diversity and distribution of ectomycorrhizal (EM) fungal species colonizing Coccoloba uvifera (L.) L. (seagrape) mature trees and seedlings naturally regenerating in four littoral forests of the Guadeloupe island (Lesser Antilles). We collected 546 sporocarps, 49 sclerotia, and morphotyped 26,722 root tips from mature trees and seedlings. Seven EM fungal species only were recovered among sporocarps (Cantharellus cinnabarinus, Amanita arenicola, Russula cremeolilacina, Inocybe littoralis, Inocybe xerophytica, Melanogaster sp., and Scleroderma bermudense) and one EM fungal species from sclerotia (Cenococcum geophilum). After internal transcribed spacer (ITS) sequencing, the EM root tips fell into 15 EM fungal taxa including 14 basidiomycetes and 1 ascomycete identified. Sporocarp survey only weakly reflected belowground assessment of the EM fungal community, although 5 fruiting species were found on roots. Seagrape seedlings and mature trees had very similar communities of EM fungi, dominated by S. bermudense, R. cremeolilacina, and two Thelephoraceae: shared species represented 93 % of the taxonomic EM fungal diversity and 74 % of the sampled EM root tips. Furthermore, some significant differences were observed between the frequencies of EM fungal taxa on mature trees and seedlings. The EM fungal community composition also varied between the four investigated sites. We discuss the reasons for such a species-poor community and the possible role of common mycorrhizal networks linking seagrape seedlings and mature trees in regeneration of coastal forests.

Assessment of DNA extraction methods for detection of arbuscular mycorrhizal fungi in plant roots by nested-PCR / Avaliação de métodos de extração de ADN para detecção de fungos micorrízicos arbusculares em raízes de plantas por nested-PCR

DNA extraction methods were evaluated for the yield and purity of DNA recovered from mycorrhized roots and whether the recovered DNA is suitable for amplification of arbuscular mycorrhizal (AM) fungal SSU rDNA. The DNeasy Plant Mini Kit and three extraction buffers were used alone or in combination with either polyvinylpyrrolidone (PVP), polyvinylpolypyrrolidone (PVPP) and/or activated charcoal (AC). Among the extraction methods tested, those based on the CTAB buffers yielded more DNA than those based on the TE buffer and the DNeasy Plant Mini Kit. Moreover, the use of AC alone or in combination with PVPP reduced DNA yield, while it significantly improved the purity of recovered DNA, whatever the extraction buffer. On the other hand, the success of nested-PCR amplification was negatively correlated with the amount of template DNA and positively correlated with the purity of recovered DNA. Three methods based on the TE buffer, two on the CTAB-ßM buffer and one on the DNeasy Plant Mini Kit produced high-quality DNA in terms of purity and PCR performance. However, the TE buffer-based methods are less time consuming than the CTAB-ßM buffer-based methods, and cheaper than the method based on the DNeasy Plant Mini Kit.

Diferentes métodos de extração de ADN, a partir de amostras de raízes, foram testados e o ADN obtido foi avaliado para a amplificação de genes ribossomais de fungos micorrízicos arbusculares (AM). Três tampões de extração foram utilizados isoladamente ou em combinação com polivinilpirrolidona (PVP), polivinipolipirrolidona (PVPP) e/ou carvão ativado (CA), além do DNeasy Plant Mini Kit. Entre os métodos de extração testados, aqueles com base no tampão CTAB renderam mais ADN do que os baseados no tampão TE e o DNeasy Plant Mini Kit. A utilização de CA ou PVPP nos diferentes tampões reduziram o rendimento de ADN, contudo, melhoraram significativamente a pureza do ADN recuperado, independentemente do tampão de extração. Por outro lado, o sucesso da amplificação por Nested-PCR foi negativamente correlacionado com a quantidade de DNA molde, e positivamente correlacionada com a pureza do ADN. Três métodos baseados no tampão TE, dois no tampão CTAB-ßM e o DNeasy Plant Mini Kit produziram ADN de alta qualidade, em termos de pureza e rendimento da PCR. No entanto, os métodos baseados em tampão TE demandam menos tempo do que os métodos baseados em tampão CTAB-ßM e são mais baratos do que o uso do DNeasy Plant Mini Kit.