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Abstract Under future increased CO 2 concentrations, seagrasses are predicted to perform better as a result of increased photosynthesis, but the effects in carbon balance and growth are unclear and remain unexplored for early life stages such as seedlings, which allow plant dispersal and provide the potential for adaptation under changing environmental conditions. Furthermore, the outcome of the concomitant biochemical changes in plant-herbivore interactions has been poorly studied, yet may have important implications in plant communities. In this study we determined the effects of experimental exposure to current and future predicted CO 2 concentrations on the physiology, size and defense strategies against herbivory in the earliest life stage of the Mediterranean seagrass Posidonia oceanica . The photosynthetic performance of seedlings, assessed by fluorescence, improved under increased p CO 2 conditions after 60 days, although these differences disappeared after 90 days. Furthermore, these plants exhibited bigger seeds and higher carbon storage in belowground tissues, having thus more resources to tolerate and recover from stressors. Of the several herbivory resistance traits measured, plants under high p CO 2 conditions had a lower leaf N content but higher sucrose. These seedlings were preferred by herbivorous sea urchins in feeding trials, which could potentially counteract some of the positive effects observed.
MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 614:79-90 (2019) - DOI: https://doi.org/10.3354/meps12912 Thermal dependence of seagrass ecosystem metabolism in the Red Sea Celina Burkholz, Carlos M. Duarte, Neus Garcias-Bonet* Red Sea Research Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia *Corresponding author: neus.garciasbonet@kaust.edu.sa ABSTRACT: The Red Sea is one of the warmest seas with shallow seagrass ecosystems exposed to extreme temperatures, in excess of 35°C, during the summer months. Seagrass meadows are net autotrophic ecosystems, but respiration increases faster than primary production with temperature. This may lead to a shift from an autotrophic to a heterotrophic system at the highest temperatures. Although tropical seagrasses are adapted to high temperatures, the metabolic rates of Red Sea seagrasses have not yet been reported. Here we assessed the community metabolism of 2 seagrass ecosystems, an Enhalus acoroides monospecific meadow and a Cymodocea serrulata and Halodule uninervis mixed meadow, located in the central Red Sea. We measured in situ net community production (NCP), community respiration (R), gross primary production (GPP), activation energy and community production-irradiance curves along their natural temperature gradient over 1 yr by measuring diel fluctuations in dissolved oxygen. The results were species-specific; while the monospecific meadow was autotrophic throughout the year (annual weighted average NCP: 64.63 ± 11.89 mmol O2 m-2 d-1, GPP:R ratio: 1.42 ± 0.06), the mixed meadow was heterotrophic during the summer months (annual weighted average NCP: -4.15 ± 9.39 mmol O2 m-2 d-1, GPP:R: 1.04 ± 0.05). In both seagrass meadows, R and GPP increased with increasing temperature, but differences in activation energies indicated that the mixed meadow is more sensitive to increasing seawater temperatures. These findings suggest contrasting responses in tropical seagrass species to rising temperature, pointing out the potential vulnerability of seagrasses to ocean warming in the Red Sea. KEY WORDS: Seagrass ecosystems · Community metabolism · Thermal dependence · Activation energy · PI curves · Red Sea Full text in pdf format Supplementary material PreviousNextCite this article as: Burkholz C, Duarte CM, Garcias-Bonet N (2019) Thermal dependence of seagrass ecosystem metabolism in the Red Sea. Mar Ecol Prog Ser 614:79-90. https://doi.org/10.3354/meps12912 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 614. Online publication date: April 04, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.
Las empresas son quizás una de las más extendidas formas de organización social de la actualidad. Como bien sabemos, estas responden a una particular manera de formalizar la contradicción clásica entre capital y trabajo, respondiendo a diversas necesidades del mercado o de una comunidad. Estas, además de responder a una función económica, están formadas por personas y para personas, lo que significa que se encuentran circunscritas a los contextos sociales que las originan. A pesar de su importancia, nuestra capacidad para pensar las empresas parece más bien limitada. Por una parte, los debates parecen remitirse a reflexiones apologéticas y narrativas institucionales, que en el mejor de los casos desembocan en los modernos discursos de sostenibilidad empresarial. Por otra parte, los ejercicios analíticos realizados desde las ciencias sociales caen fácilmente en posiciones binarias que tienden a estigmatizar de facto el rol empresarial en cualquier contexto en el que se mencione. Por lo anterior, la presente convocatoria de la edición 212 de la Revista Controversia invitó a reflexionar en torno a los diferentes modelos empresariales que conviven, compiten, dinamizan y entran en conflicto con diversos sectores de la sociedad colombiana, especialmente los de su entorno. En términos generales, se buscó comprender los vínculos y las tensiones entre el sector privado empresarial y las diversas comunidades, especialmente rurales.
Plant mortality and birth rates are critical components of plant life history affecting the stability of plant populations and the ecosystems they form. Although allometric theory predicts that both plant birth and mortality rates should be size-dependent, this prediction has not yet been tested across plants ranging the full size spectrum. Here we show that both population mortality and population birth rates scale as the -(1/4) power and plant lifespan as the (1/4) power of plant mass across plant species spanning from the tiniest phototrophs to the largest trees. Whereas the controls on plant lifespans are as yet poorly understood, our findings suggest that plant mortality rates have evolved to match population birth rates, thereby helping to maintain plant communities in equilibrium and optimizing plant life histories.
Seagrasses comprise <0.02% of the angiosperm flora, representing a surprisingly small number of species (about 50, Table 1.1) compared with any other group of marine organisms. The limited species membership of the seagrass flora has directed some (still limited) efforts to the study of their origin and their evolution in an attempt to account for this phenomenon. A second path of research has tried to find clues for the paucity of species by studying the stress factors constraining angiosperm life in the sea. This second approach has driven much effort towards the analysis of seagrass distribution and the definition of the habitat requirements of seagrasses. The attention these issues have received extends beyond scholarly concerns, for seagrasses are, despite their limited diversity, important contributors to coastal marine ecosystems, both locally and at the global scale. In this chapter we shall provide an overview of the origin, evolution and present diversity of extant seagrasses, and describe their present distribution and the basic requirements that delimit their possible habitats. The definition of how seagrass distribution is regulated leads, in turn, to the assessment of their global extent and, from this, to the evaluation of the role seagrasses play on the global ocean ecosystem.
A survey of the phytoplankton communities in 165 Florida lakes during 1980 indicated 27% of 308 samples collected had phytoplankton populations that were at or very close to their maximal achievable densities. This finding suggests that nonnutrient constraints including self-regulation by the algal community may be playing an important role in regulating phytoplankton biomass in many Florida lakes. Algal populations that were close to their maximal achievable densities had algal biomass values >10 mg liter−1 and Chl a concentrations >10 mg m−3. As nonnutrient constraints became more important, algal communities shifted from small-celled, diatom-green algal communities to communities dominated primarily by large, blue-green bacteria.
To assess the efforts deployed by different nations and territories in sequencing SARS-CoV-2 isolates, thus enabling detection of variants, known and novel, of concern.The sources of over one million full genome sequences of SARS-CoV-2 virus available in the COVID-19 virus Mutation Tracker (CovMT) were analyzed to determine the number of variants in the RBD region of the genome determining infectivity detected in the various nations and territories.The number of detected variants increased as the square root of sequencing effort by nations. Eight nations have contributed 79% of all SARS-CoV-2 isolates that have been sequenced, with two-thirds of all unique variants, adding to 1118 RBD variants, reported by five nations. The median number of sequenced isolates required to detect, on average, one novel RBD variant is 24.05, which is a threshold achieved by 70 nations.Many developing nations have not contributed any sequences due to lack of capacity. This poses a risk of dangerous virus variants in these under-sampled regions spreading globally before being detected. A collaborative program to sequence SARS-CoV-2 isolates, and other pathogens of concern, is needed to monitor, track, and control the pandemic.
