What global biogeochemical consequences will marine animal-sediment interactions have during climate change?

Benthic animals profoundly influence the cycling and storage of carbon and other elements in marine systems, particularly in coastal sediments. Recent climate change has altered the distribution and abundance of many seafloor taxa and modified the vertical exchange of materials between ocean and sediment layers. Here, we examine how climate change could alter animal-mediated biogeochemical cycling in ocean sediments.The fossil record shows repeated major responses from the benthos during mass extinctions and global carbon perturbations, including reduced diversity, dominance of simple trace fossils, decreased burrow size and bioturbation intensity, and nonrandom extinction of trophic groups. The broad dispersal capacity of many extant benthic species facilitates poleward shifts corresponding to their environmental niche as overlying water warms. Evidence suggests that locally persistent populations will likely respond to environmental shifts through either failure to respond or genetic adaptation rather than via phenotypic plasticity. Regional and global ocean models insufficiently integrate changes in benthic biological activity and their feedbacks on sedimentary biogeochemical processes. The emergence of bioturbation, ventilation, and seafloor-habitat maps and progress in our mechanistic understanding of organism-sediment interactions enable incorporation of potential effects of climate change on benthic macrofaunal mediation of elemental cycles into regional and global ocean biogeochemical models.SCOPUS: re.jinfo:eu-repo/semantics/publishe

Dynamics of competition between wild oats (Avena fatua L.) and winter cereals

This study examined the effects of competition on the growth of Avena fatua, winter wheat and winter barley. Plants were sampled at frequent intervals from replacement series experiments at two contrasting sites in the U.K. A. fatua was much slower to establish than the two cereals, but thereafter exhibited a faster rate of growth. In monoculture, it took a considerable time for A. fatua to reach a size equal to that of the cereals, but by the end of the experiments it was the largest of the three species. The change-over from cereal dominance in mixtures to A. fatua dominance was rapid, and in three cases coincided with cereal flag leaf emergence. In the fourth case, it appeared to coincide with the start of canopy height extension. At one site the order of competitiveness at anthesis was A. fatua = barley > wheat, and at the other site the order was A. fatua > wheat > barley. In order to explain and predict differences between years and sites, more studies are required on morphological development in relation to abiotic variables

Physiological responses of two tropical weeds to shade: II. Leaf gas exchange and nitrogen content Respostas fisiológicas de duas plantas invasoras tropicais ao sombreamento: II. Troca gasosa e conteúdo de nitrogênio foliar

Ipomoea asarifolia (Desr.) Roem. & Schultz (Convolvulaceae) and Stachytarpheta cayennensis (Rich) Vahl. (Verbenaceae), two weeds found in pastures and crop areas in the Brazilian Amazonia, Brazil, were grown in controlled environment cabinets under high (800-1000 µmol m-² s-¹) and low (200-350 µmol m-² s-¹) light regimes during a 40-day period. The objective was to determine the effect of shade on photosynthetic features and leaf nitrogen content of I. asarifolia and S. cayennensis. High-irradiance grown I. asarifolia leaves had significantly higher dark respiration and light saturated rates of photosynthesis than low-irradiance leaves. No significant differences for these traits, between treatments, were observed in S. cayennensis. Low-irradiance leaves of both species displayed higher CO2 assimilation rates under low irradiance. High-irradiance grown leaves of both species had less nitrogen per unit of weight. Low-irradiance S. cayennensis had more nitrogen per unit of leaf area than high-irradiance plants; however, I. asarifolia showed no consistent pattern for this variable through time. For S. cayennensis, leaf nitrogen content and CO2 assimilation were inversely correlated to the amount of biomass allocated to developing reproductive structures. These results are discussed in relation to their ecological and weed management implications.<br>Ipomoea asarifolia (Desr.) Roem. & Schultz (Convolvulaceae) e Stachytarpheta cayennensis (Rich) Vahl. (Verbenaceae), duas plantas invasoras encontradas em pastagens e áreas agrícolas da Amazônia brasileira, foram cultivadas durante 40 dias, em câmaras de crescimento sob alto (800-1000 µmol m-² s-¹) e baixo (200-350 µmol m-² s-¹) regime de luz. O objetivo foi estudar o efeito do sombreamento nas características fotossintéticas e no teor de nitrogênio de I. asarifolia e S. cayennensis. As folhas de I. asarifolia cultivadas sob regime de luz alta apresentaram valores de respiração no escuro e taxa máxima de fotossíntese significativamente maiores que das folhas cultivadas sob baixa luz. Em S. cayennensis, não houve diferença significativa, entre tratamentos, quanto a esses parâmetros. Em ambas espécies, folhas desenvolvidas sob baixa irradiância apresentaram maiores taxas de assimilação de CO2 sob baixos níveis de irradiância. Em ambas as espécies, plantas cultivadas em luz alta apresentaram menores teores de nitrogênio por unidade de peso foliar. Em S. cayennensis, folhas de baixa irradiância tiveram maior teor de N por unidade de área que em folhas de plantas de luz alta; no entanto, em I. asarifolia não foi observado um padrão definido quanto a essa variável durante o período experimental. O conteúdo de N foliar e a assimilação de CO2 em S. cayennensis foram inversamente correlacionados com o percentual de biomassa alocado para estruturas reprodutivas. Esses resultados são discutidos com relação a suas importâncias ecológica e de manejo

A lei e o corpo Law and the body

Partindo do conceito do arbitrário cultural, no qual se relativiza a categoria de enfermidade e se evidencia a inserção desta no campo da significação, o ensaio discute a problemática da autonomia do organismo e da saúde como constituinte da lei, para estabelecer então as relações entre as categorias de causalidade, desvio e ordem jurídica, que se desdobram na discussão entre corpo e história.<br>Starting from the concept of cultural arbitrariness, where the category of "sickness" is relativized and where its insertion in the realm of meaning is evidenced, this essay discusses the issue of the autonomy of the organism and of health as components of law. It goes on to establish relations between the notions of causality, deviance, and judicial order, leading into a discussion of the body and history