Macroalgae contribute to the diet of Patella vulgata from contrasting conditions of latitude and wave exposure in the UK

Analysis of gut contents and stable isotope composition of intertidal limpets (Patella vulgata) showed a major contribution of macroalgae to their diet, along with microalgae and invertebrates. Specimens were collected in areas with limited access to attached macroalgae, suggesting a major dietary component of drift algae. Gut contents of 480 animals from 2 moderately wave-exposed and 2 sheltered rocky shores in each of 2 regions (western Scotland, 55-56°N; and southwest England, 50°N), were analysed in 2 years (n = 30 site-1 yr-1). The abundance of microalgae, macroalgae and invertebrates within the guts was quantified using categorical abundance scales. Gut content composition was compared among regions and wave exposure conditions, showing that the diet of P. vulgata changes with both wave exposure and latitude. Microalgae were most abundant in limpet gut contents in animals from southwestern sites, whilst leathery/corticated macroalgae were more prevalent and abundant in limpets from sheltered and northern sites. P. vulgata appears to have a more flexible diet than previously appreciated, and these keystone grazers consume not only microalgae, but also large quantities of macroalgae and small invertebrates. To date, limpet grazing studies have focussed on their role in controlling recruitment of macroalgae by feeding on microscopic propagules and germlings. Consumption of adult algae suggests that P. vulgata may also directly control the biomass of attached macroalgae on the shore, whilst consumption of drift algae indicates that the species may play important roles in coupling subtidal and intertidal production.

Macroalgae contribute to the diet of Patella vulgata from contrasting conditions of latitude and wave exposure in the UK

Analysis of gut contents and stable isotope composition of intertidal limpets (Patella vulgata) showed a major contribution of macroalgae to their diet, along with microalgae and invertebrates. Specimens were collected in areas with limited access to attached macroalgae, suggesting a major dietary component of drift algae. Gut contents of 480 animals from 2 moderately wave-exposed and 2 sheltered rocky shores in each of 2 regions (western Scotland, 55-56°N; and southwest England, 50°N), were analysed in 2 years (n = 30 site-1 yr-1). The abundance of microalgae, macroalgae and invertebrates within the guts was quantified using categorical abundance scales. Gut content composition was compared among regions and wave exposure conditions, showing that the diet of P. vulgata changes with both wave exposure and latitude. Microalgae were most abundant in limpet gut contents in animals from southwestern sites, whilst leathery/corticated macroalgae were more prevalent and abundant in limpets from sheltered and northern sites. P. vulgata appears to have a more flexible diet than previously appreciated, and these keystone grazers consume not only microalgae, but also large quantities of macroalgae and small invertebrates. To date, limpet grazing studies have focussed on their role in controlling recruitment of macroalgae by feeding on microscopic propagules and germlings. Consumption of adult algae suggests that P. vulgata may also directly control the biomass of attached macroalgae on the shore, whilst consumption of drift algae indicates that the species may play important roles in coupling subtidal and intertidal production.

Benthic assemblages associated with native and non-native oysters are similar

Invasive species can impact native species and alter assemblage structure, which affects associated ecosystem functioning. The pervasive Pacific oyster, Crassostrea gigas, has been shown to affect the diversity and composition of many host ecosystems. We tested for effects of the presence of the invasive C. gigas on native assemblages by comparing them directly to assemblages associated with the declining native European oyster, Ostrea edulis. The presence of both oyster species was manipulated in intertidal and subtidal habitats and reefs were constructed at horizontal and vertical orientation to the substratum. After 12 months, species diversity and benthic assemblage structure between assemblages with C. gigas and O. edulis were similar, but differed between habitats and orientation, suggesting that both oyster species were functionally similar in terms of biodiversity facilitation. These findings support evidence, that non-native species could play an important role in maintaining biodiversity in systems with declining populations of native species.

Study of environmental radioactivity in Las Canteras beach

[EN]In this final degree work an assessment of the impact of environmental radioactivity, mainly on bathers of the most important beach in Las Palmas de Gran Canaria (Las Canteras), has been done. For this purpose, the main radionuclides contained in intertidal superficial sand samples have been measured by using gamma spectrometry analysis. Also alpha activity of the beach water was determinated by means of ZnS(Ag) scintillation detector. The radioactivity detected was due to the natural occurring radionuclides 226Ra (238U- series), 232Th and 40K in sand samples with an average activity concentrations of 14.6±1.0, 17.4±1.0 and 528±24 Bq/kg, respectively. From these values, the outdoor annual effective dose was of 0.047 mSv/y, which is below to the world’s average value (0.07 mSv/y)

Ancient clam gardens, traditional management portfolios, and the resilience of coupled human-ocean systems

Indigenous communities have actively managed their environments for millennia using a diversity of resource use and conservation strategies. Clam gardens, ancient rock-walled intertidal beach terraces, represent one example of an early mariculture technology that may have been used to improve food security and confer resilience to coupled human-ocean systems. We surveyed a coastal landscape for evidence of past resource use and management to gain insight into ancient resource stewardship practices on the central coast of British Columbia, Canada. We found that clam gardens are embedded within a diverse portfolio of resource use and management strategies and were likely one component of a larger, complex resource management system. We compared clam diversity, density, recruitment, and biomass in three clam gardens and three unmodified nonwalled beaches. Evidence suggests that butter clams (Saxidomus gigantea) had 1.96 times the biomass and 2.44 times the density in clam gardens relative to unmodified beaches. This was due to a reduction in beach slope and thus an increase in the optimal tidal range where clams grow and survive best. The most pronounced differences in butter clam density between nonwalled beaches and clam gardens were found at high tidal elevations at the top of the beach. Finally, clam recruits (0.5-2 mm in length) tended to be greater in clam gardens compared to nonwalled beaches and may be attributed to the addition of shell hash by ancient people, which remains on the landscape today. As part of a broader social-ecological system, clam garden sites were among several modifications made by humans that collectively may have conferred resilience to past communities by providing reliable and diverse access to food resources.

Length-weight relationship of benthic bivalves of the Andoni Flats, Niger Delta, Nigeria

The length weight relationship of three benthic bivalves namely, Senilia (= Anadara) senilis (bloody cockle), Tagelus adansonii (knife clam), Tellina nymphalis (soft shell clam) from the Andoni Flats were determined. The bivalves which are of ecological importance were obtained from the intertidal areas of the Andoni Flats. Shell lengths of the bivalves were measured and corresponding dry weight measurements were also taken. The data obtained were then subjected to regression analysis using the FAO-ICLARM Fish Stock Assessment Tools (FiSAT). The length weight relationships obtained from the FiSAT analysis indicated isometric growth for Senilia (= Anadara) senilis, with slope (b) value of 2.942; positive allometric growth for Tagelus adansonii, with a ‘b’ value of 3.395 and negative allometric growth for Tellina nymphalis with ‘b’ value of 2.633. KEYWORDS: bivalves, length-weight, isometric growth, allometric growth, cockle, clam.

La Nouvelle-Calédonie : Atouts et enjeux maritimes d'un pays "doué"

The publication draws up a balance sheet about the natural marine assets of New Caledonia by distinguishing the coast and the intertidal zones, the coral reefs and lagoons, the open sea or "deep blue". A set of assets relative to the living and mineral natural resources, to the characteristics of the shallow and deep marine biodiversity, to the potential marine energy resources are discussed. This publication, edited in a Consumer directed free magazine, draws up a set of perspectives relative to a blue economy to be built in a country still very centred on its ground resources, essentially the nickel mining industry.

Variação sazonal na dieta da lontra-neotropical no sul do Brasil

O conhecimento de como os mamíferos carnívoros de médio e grande porte Neotropicais capturam e manipulam suas presas é incipiente, e algumas espécies podem somente ser investigadas por análises das fezes, e certos presupostos teóricos sobre forrageo podem ser aplicados e testados a partir da análise da dieta. Lontra longicaudis é um mamífero aquático cuja as fezes podem ser facilmente reconhecidas e coletadas para fornecer informação básica referentes a ecologia de forrageamento da espécie. Com base nessa situação, foram desenvolvidas duas questões relacionadas a dieta, como: (I) Se a 30 composição de presas na dieta varia entre as estações ao longo do ano? E qual o tamanho da magnitude do efeito deste fator? (II) Se a amplitude da dieta varia entre as estações? Nós respondemos estas questões por meio da análise das fezes. Foram realizadas 12 expedições mensais para as coletas, em um trecho de 13 quilômetros do baixo curso do Arroio Grande. Cada fezes foi coletada individualmente, e dados como data e posição geografica anotados. As presas foram classificadas por categorias alimentares (peixes, mamíferos, aves, anfíbios, serpentes, crustaceos e insetos) e em nível de família. A alimentação de L. longicaudis foi a baseada em peixes, com uma amplitude de dieta estreita. As famílias Cichlidae e Callichthyidae predominaram na dieta ao longo do ano. A composição de peixes na dieta variou sazonalmente, porém, a amplitude da dieta não variou. Assim Lontra longicaudis caça presas e mantém certo grau de felxibilidade alimentar ao longo do ano.

Macro-geographical differences influenced by family-based expression on cultured pearl grade, shape and colour in the black-lip "pearl oyster" Pinctada margaritifera: a preliminary bi-local case study in French Polynesia

In French Polynesia, the aquaculture of P. margaritifera is carried out in numerous grow-out sites, located over three archipelagos (Gambier, Society and Tuamotu). To evaluate the impact of macro-geographical effects of these growing sites on pearl quality traits, five hatcheries produced families were used as homogeneous donor oysters in an experimental graft. The molluscs were then reared in two commercial locations: Tahaa island (Society) and Rangiroa atoll (Tuamotu). At harvest, eight pearl quality traits were recorded and compared: surface defects, lustre, grade, circles, shape categories, darkness level, body and secondary colour and visual colour categories. Overall inter-site comparison revealed that: 1) all traits were affected by grow-out location except for lustre and round shape, and 2) a higher mean rate of valuable pearls was produced in Rangiroa. Indeed, for pearl grade, Rangiroa showed twice as many A-B and less reject samples than Tahaa. This was related to the number of surface defects (grade component): in Rangiroa, twice as many pearls had no defects and less pearls had up to 10 defects. Concerning pearl shape, more circled and baroque pearls were found in Tahaa (+10%). For colour variation, 10% more pearls have an attractive green overtone in Rangiroa than in Tahaa, where more grey bodycolor were harvested. Lustre does not seem to be affected by these two culture site (except at a family scale). This is the first time P. margaritifera donor family have been shown to vary in the quality of pearls they produce depending on their grow-out location.

Variação no conteúdo protéico e pigmentar em variantes cromáticas de Gracilaria domingensis nas populações naturais de Rio do Fogo-RN, BRASIL

The seaweed Gracilaria domingensis is a common species in the coast of Rio Grande do Norte. This species lives in the intertidal zone, where colour strains (red, green and brown) co-occur during the whole year. Seaweeds that live in this region are exposed to daily changes and to the rhythm of the tide. During the low tide they are exposed to dissection, hiper-or hipo-osmotic shock, high temperatures and high irradiance. The aim of this study was to analyze whether the pigment and protein content of the colour strains of G. domingensis is affected by some environmental parameters in a temporal scale. The seaweeds were collected during 10 months in the seashore of Rio do Fogo (RN). The total soluble proteins and the phycobiliprotein were extracted in phosphate buffer and the carotenoids were analyzed by a standardized method through HPLC-UV. The pigments analysis showed that phycoerithrin is the most abundant pigment in the three strains. This pigment was strongly correlated with nitrogen and the photosynthetically active radiation. Chlorophyll presented higher concentrations than carotenoids during the whole, but the ratio carotenoid/chlorophyll-a was modified by incident radiation. The most abundant carotenoid was ß-carotene and zeaxanthin, which had higher concentrations in the higher radiation months. The concentration increase of zeaxanthin in this period indicated a photoprotective response of the seaweed. The three strains presented a pigment profile that indicates different radiation tolerance profile. Our results pointed that the green strain is better adapted to high irradiance levels than the red and brown strains

Éponges intercoditales de Nha Trang (Viet Nam)

Thanks to the effort of many spongologists from worldwide, we know the most common sponges in the Indo-Pacific area. The author gives a description of 28 intertidal sponges collected in Nha Trang, Vietnam.

Contribution à l'étude du peuplement du littoral rocheux du Vietnam (sud)

In this part 1, after a brief description of the habitat, the author describes in details (in descending order) the supralittoral, littoral and infralittoral zones. The author describes many permanent groups of Cyanophyceae in the higher horizon of intertidal zone, the cosmopolitan group of Navicula Grevillei, Hildenbrandtia prototypus, the pantropical group of Calothrix pilosa, Chaetomorpha antennina, indopacific group of Dermonema Frappieri, Sargassum, Padina, Thatassia Hemprichii, Halophila. The group of cold or temperate habitat with Bangiophycideae are present in winter. Some are described, formed by the oysters, Vermetus or Cirripeds, or by the algae (Calothrix, Brachytrichia, Gelidium, Dermonema, Chaetomorpha).