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

Heat fluxes between the Guadalquivir river and the Gulf of Cádiz Continental Shelf

An 18-year time series of daily sea surface temperature of Gulf of Cadiz and an 18-month time series of temperature collected in the vicinity of the Guadalquivir estuary mouth have been analyzed to investigate the heat exchange between the estuary and the adjacent continental shelf. The first time identifies a continental shelf area where seasonal thermal oscillation signal (amplitudes and phase) changes abruptly. In order to explain this anomaly, the second data set allows a description of thermal fluctuations in a wide range of frequencies and an estimation of the upstream heat budget of the Guadalquivir estuary. Results show that high frequency thermal signal, diurnal and semidiurnal, and water flux signal through Guadalquivir mouth, mainly semidiurnal, apparently interact randomly to give a small exchange of thermal energy at high frequency. There is no trace, at the estuary's mouth, of daily heat exchanges with intertidal mudflats probably because it tends to cancel on daily time scales. Results also show that fluctuations of estimated air-sea fluxes force fluctuations of temperature in a quite homogeneous estuarine, with a delay of 20 days. The along-channel thermal energy gradient reaches magnitudes of 300-400 J m-4 near the mouth during the summer and winter and drives the estuary-shelf exchange of thermal energy at seasonal scale. Particularly, the thermal heat imported by the estuary from the shelf area during late fall-winter-early spring of 2008/2009 is balanced by the thermal heat that the estuary exports to the shelf area during late spring-summer of 2008. In summary, Guadalquivir river removes/imports excess of thermal energy towards/from the continental shelf seasonally, as a mechanism to accommodate excess of heat from one side respect to the other side.

The importance of marine subsidies for terrestrial consumers in coastal Peru

The Peruvian coast is one the best examples of cross-ecosystem food web exchanges, in which resources from one of the richest marine ecosystems subsidize consumers in one of the driest deserts on Earth. Marine subsidies are resources that originate in the marine ecosystem, and that contribute to increase the density of consumers in the recipient ecosystem. I examined the effects of marine subsidies on animal populations in the Peruvian coastal desert. I combined several approaches to study the linkages between marine resources and terrestrial consumers, such as surveying the spatial distribution and estimating the relative abundance of terrestrial consumers, studying the diet of geckos and lizards through stomach content analyses, and examining the desert food web with carbon and nitrogen stable isotope analyses. I found that the distribution and diet of desert consumers were tightly coupled to the availability of marine subsidies. I revealed linkages along two pathways of nutrient fluxes: tidal action that washes ashore macroalgae and cadavers of marine organisms, and animal transport in places where pinnipeds and seabirds congregate for reproduction. In the first pathway, intertidal algivivores made marine resources available to terrestrial consumers by moving between the intertidal and supratidal zone. The relative contribution of terrestrial and algal carbon sources varied among terrestrial consumers, because scorpions assimilated a lower proportion of energy from macroalgae than did geckos and solifuges. In the second pathway, I found that pinniped colonies influenced the diet of desert consumers, and contributed to support large populations of lizards and geckos. By combining field observations, and stomach and stable isotope analyses, I constructed a simplified food web for a large sea lion colony, showing the number of trophic levels that originate from pinniped-derived nutrients. My study demonstrates the enormous importance of marine resources for the diet of desert consumers. The near absence of rainfall along the Peruvian coast promotes an extreme dependence of terrestrial consumers on marine resources, and causes permanent food web effects that are affected by temporal variability in marine productivity, rather then temporal patterns of desert plant growth.

Feeding ecology and life-history strategy of nesting males in a fish with long parental care, Lusitanian toadfish (Halobatrachus didactylus, Batrachoididae)

The Lusitanian toadfish, Halobatrachus didactylus, like other batrachoidids, is a benthic fish species with nesting behaviour during the breeding season. During this prolonged period it engages in mating activities and remains in the nest providing parental care. It is not known whether males feed while providing parental care but it is likely that their limited mobility may restrict their diet and influence their fitness. As a consequence, egg cannibalism could occur as a life-history strategy. The aim of the present study is to ascertain the feeding behaviour of nesting males, in comparison to mature non-nesting males, and to identify potential life-history traits related to egg cannibalism. Nest-holders were sampled from artificial nests placed in an intertidal area of the Tagus estuary, only exposed during spring low tides. The diet of nest-holders was compared with that of non-nesting mature males from the same area, captured by otter trawl. The present study demonstrates that despite their constrained mobility nest-holders feed during the breeding season, although in a more opportunistic fashion than non-nesting males. Nest-holders showed a generalist feeding behaviour, with a more heterogeneous diet. Egg cannibalism was not related to male condition, paternity or brood size but showed a higher incidence early in the season when water temperatures were lower. The results suggest a possible seasonal trade-off strategy between care and energy recovery, triggered by environmental factors, where under unfavourable conditions to sustain viable eggs the male may recover energy by eating eggs, thus benefiting future reproductive success, later in the season.

High interannual variability in connectivity and genetic pool of a temperate clingfish matches oceanographic transport predictions

Adults of most marine benthic and demersal fish are site-attached, with the dispersal of their larval stages ensuring connectivity among populations. In this study we aimed to infer spatial and temporal variation in population connectivity and dispersal of a marine fish species, using genetic tools and comparing these with oceanographic transport. We focused on an intertidal rocky reef fish species, the shore clingfish Lepadogaster lepadogaster, along the southwest Iberian Peninsula, in 2011 and 2012. We predicted high levels of self-recruitment and distinct populations, due to short pelagic larval duration and because all its developmental stages have previously been found near adult habitats. Genetic analyses based on microsatellites countered our prediction and a biophysical dispersal model showed that oceanographic transport was a good explanation for the patterns observed. Adult sub-populations separated by up to 300 km of coastline displayed no genetic differentiation, revealing a single connected population with larvae potentially dispersing long distances over hundreds of km. Despite this, parentage analysis performed on recruits from one focal site within the Marine Park of Arrábida (Portugal), revealed self-recruitment levels of 2.5% and 7.7% in 2011 and 2012, respectively, suggesting that both long- and short-distance dispersal play an important role in the replenishment of these populations. Population differentiation and patterns of dispersal, which were highly variable between years, could be linked to the variability inherent in local oceanographic processes. Overall, our measures of connectivity based on genetic and oceanographic data highlight the relevance of long-distance dispersal in determining the degree of connectivity, even in species with short pelagic larval durations.

Composition and temporal dynamics of a temperate rocky cryptobenthic fish assemblage

Temporal variation in a temperate cryptobenthic fish assemblage at the Arrabida Marine Park (Portugal) was assessed by visual Surveys during 2002 and 2003. A total of 9596 fish from 11 families and 30 species was recorded. There were no changes in structure or density at the assemblage level between years, whereas diversity changed significantly due to a higher number of abundant species in the second year. A similar seasonal trend was found between years, with a significant overall density increase in autumn. This is partially explained by the arrival of new recruits of some of the most abundant species in the assemblage. Assemblage diversity and structure also changed across seasons. A group of species encompassing Gobius xanthocephalus, Tripterygion delaisi, Parablennius pilicornis, Gobius paganellus, Lepadogaster candollii and Lepadogaster spp. were analysed in detail. The temporal patterns of two of the most abundant species, G. xanthocephalus and T delaisi, mimicked the overall temporal patterns of the assemblage. We suggest that the inter-annual stability in density of this subtidal fish assemblage may be similar to what has been reported for the intertidal and that strong post-settlement processes are probably shaping this assemblage.

Loss of thermal refugia near equatorial range limits

This study examines the importance of thermal refugia along the majority of the geographical range of a key inter- tidal species (Patella vulgata Linnaeus, 1758) on the Atlantic coast of Europe. We asked whether differences between sun-exposed and shaded microhabitats were responsible for differences in physiological stress and ecological perfor- mance and examined the availability of refugia near equatorial range limits. Thermal differences between sun- exposed and shaded microhabitats are consistently associated with differences in physiological performance, and the frequency of occurrence of high temperatures is most probably limiting the maximum population densities sup- ported at any given place. Topographical complexity provides thermal refugia throughout most of the distribution range, although towards the equatorial edges the magnitude of the amelioration provided by shaded microhabitats is largely reduced. Importantly, the limiting effects of temperature, rather than being related to latitude, seem to be tightly associated with microsite variability, which therefore is likely to have profound effects on the way local popu- lations (and consequently species) respond to climatic changes.

O IMOBILIÁRIO-TURÍSTICO E O NORDESTE BRASILEIRO: DINÂMICAS ECONÔMICAS E URBANAS SOBRE O LITORAL

Na região nordeste, a emergência de uma sinergia que aqui se denomina “imobiliário-turístico” constitui-se na manifestação de mudanças e inovações no mercado imobiliário, no turismo e nas políticas públicas com significativos efeitos sobre o território litorâneo. O turismo foi tomado como um setor econômico relevante não apenas para atrair visitantes, mas também projetos e empreendimentos como resorts, flats, apartamentos, condomínios fechados, entre outros, voltados para uma demanda nacional e estrangeira interessada em adquirir uma residência secundária. Este trabalho objetiva dar elementos para compreender a forma de participação desse fenômeno no processo de metropolização do litoral nordestino. A análise se dá a partir da caracterização de sua intensidade, estratégias e impactos socioambientais, além da demarcação das consequências socioeconômicas e espaciais, referente a quatro metrópoles estudadas. Para tanto, a pesquisa se baseia em levantamentos de dados, construção de indicadores e análises realizados no Projeto “Metropolização Turística: Dinâmica e reestruturação dos territórios em Salvador, Recife, Fortaleza e Natal. – estudos comparativos para o Nordeste” desenvolvido pelo Instituto Nacional de Tecnologia (INCT/CNPq) – Observatório das Metrópoles. Como contribuição ao aprofundamento do debate se indica elementos para uma gestão do território orientada por eixos socioambientais em um cenário com forte dinâmica imobiliária e expansão metropolitana e turística.   Palavras-chave:

Homological and Hodge-theoretic aspects of matroids and polymatroids

In the first part of this thesis, we study the action of the automorphism group of a matroid on the homology space of the co-independent complex. This representation turns out to be isomorphic, up to tensoring with the sign representation, with that on the homology space associated with the lattice of flats. In the case of the cographic matroid of the complete graph, this result has application in algebraic geometry: indeed De Cataldo, Heinloth and Migliorini use this outcome to study the Hitchin fibration. In the second part, on the other hand, we use ideas from algebraic geometry to prove a purely combinatorial result. We construct a Leray model for a discrete polymatroid with arbitrary building set and we prove a generalized Goresky-MacPherson formula. The first row of the model is the Chow ring of the polymatroid; we prove Poincaré duality, Hard-Lefschetz theorem and Hodge-Riemann relations for the Chow ring.

The combinatorics of Hilbert-Poincaré series of matroids

In this thesis we explore the combinatorial properties of several polynomials arising in matroid theory. Our main motivation comes from the problem of computing them in an efficient way and from a collection of conjectures, mainly the real-rootedness and the monotonicity of their coefficients with respect to weak maps. Most of these polynomials can be interpreted as Hilbert--Poincaré series of graded vector spaces associated to a matroid and thus some combinatorial properties can be inferred via combinatorial algebraic geometry (non-negativity, palindromicity, unimodality); one of our goals is also to provide purely combinatorial interpretations of these properties, for example by redefining these polynomials as poset invariants (via the incidence algebra of the lattice of flats); moreover, by exploiting the bases polytopes and the valuativity of these invariants with respect to matroid decompositions, we are able to produce efficient closed formulas for every paving matroid, a class that is conjectured to be predominant among all matroids. One last goal is to extend part of our results to a higher categorical level, by proving analogous results on the original graded vector spaces via abelian categorification or on equivariant versions of these polynomials.