Los procesos de movilización y protesta han experimentado una innegable transformación en los últimos años. A partir de la ya clásica definición de “nuevos movimientos sociales” esbozada por Alain Touraine en los años ochenta, o la de “movimientos populares” de Leopoldo Múnera en los noventa, la discusión posteriormente se transformó desde orillas diferentes bajo el paradigma interseccional y la teoría crítica. En la actualidad, una cuarta generación de formas de movilización (4.0), ha venido emergiendo en el marco de profundos procesos de individualización social, universalización de las redes sociales, precarización y aumento de las brechas de desigualdad.
 Estas formas de organización colectiva son profundamente horizontales, tienen dificultades, o no reconocen totalmente los mecanismos de representación tradicional de la izquierda. Se movilizan a modo de enjambre, como esboza Byung-Chul Han, e invitan a repensar o deconstruir la fácil conceptualización oficial del “vándalo”. Asimismo, plantean la necesidad de pensar espacios de diálogo social multinivel y multisituados.
 A esta nueva forma de interpelación y organización social la hemos sintetizado, para esta convocatoria, bajo la categoría temporal de Paros 4.0. Dicha invitación fue acogida por varios grupos e individuos, que buscan aportar a pensar estos nuevos fenómenos sociales que seguramente seguirán profundizándose como lineamientos de la acción colectiva organizada.
 Como podrá observarse en los articulos que hacen parte del presente número, los principales actores de las protestas representaban los sectores víctimas de la desigualdad y de la exclusión histórica en Colombia. Jóvenes desempleados o sin acceso a la educación, trabajadores informales, colectivos étnicos y culturales, desplazados, víctimas del conflicto, personas vinculadas con trabajos ilícitos, actores armados en proceso de reincorperación, entre otros, hicieron un llamado a ser tenidos en cuenta tanto por sus semejantes, como por las instituciones del poder.
Abstract. Diatoms are generally the dominant contributors to the Arctic Ocean spring bloom, which is a key event in regional food webs in terms of capacity for secondary production and organic matter export. Dissolved silicic acid is an obligate nutrient for diatoms and has been declining in the European Arctic since the early 1990s. The lack of regional silicon cycling information precludes understanding the consequences of such changes for diatom productivity during the Arctic spring bloom. This study communicates the results from a cruise in the European Arctic around Svalbard, which reports the first concurrent data on biogenic silica production and export, export of diatom cells, the degree of kinetic limitation by ambient silicic acid, and diatom contribution to primary production. Regional biogenic silica production rates were significantly lower than those achievable in the Southern Ocean and silicic acid concentration limited the biogenic silica production rate in 95 % of samples. Compared to diatoms in the Atlantic subtropical gyre, regional diatoms are less adapted for silicic acid uptake at low concentration, and at some stations during the present study, silicon kinetic limitation may have been intense enough to limit diatom growth. Thus, silicic acid can play a critical role in diatom spring bloom dynamics. The diatom contribution to primary production was variable, ranging from <10 % to ∼100 % depending on the bloom stage and phytoplankton composition. While there was agreement with previous studies regarding the export rate of diatom cells, we observed significantly elevated biogenic silica export. Such a discrepancy can be resolved if a higher fraction of the diatom material exported during our study was modified by zooplankton grazers. This study provides the most direct evidence to date suggesting the important coupling of the silicon and carbon cycles during the spring bloom in the European Arctic.
Меры по сохранению морской флоры и фауны приносят свои плоды: они уже позволили остановить сокращение численности некоторых видов и восстановить нарушен- ные морские экосистемы. Однако для восстановления здоровья океана в больших масштабах нужно активнее бороться с загрязнением, чрезмерным выловом рыбы и последствиями изменения климата.
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 207:1-11 (2000) - doi:10.3354/meps207001 Nutrient accumulation at different supply rates in experimental Mediterranean planktonic communities Montserrat Vidal*, Carlos M. Duarte Instituto Mediterráneo de Estudios Avanzados (IMEDEA), CSIC - Universitat de les Illes Balears, Miquel Marqués 21, 07190 Esporles (Mallorca, Islas Baleares), Spain *Present address: Laboratoire d¹Océanographie Biologique- UMR 7621, Laboratoire Arago, BP 44, 66651 Banyuls-sur-Mer Cedex, France. E-mail: mvidal@arago.obs-banyuls.fr ABSTRACT: A mesocosm experiment was conducted between June 18 and July 8, 1997, in the Bay of Blanes (NE Spain) to test for the effect of nutrient inputs on Mediterranean plankton communities. The experiment involved a gradient of daily nutrient additions to mesocosms (14 m high, 4.2 m2 cross-sectional area and 33 m3 effective volume), which were scaled to the nutrient loading of the Bay of Blanes in summer (0.64 µM N d-1, referred to as the Œbusiness as usual¹ control). This paper deals with the accumulation of nutrients in different size components (0.2-2, 2-20 and 20-200 µm) of the community and the efficiency with which these size components retain the added nutrients. Summer Mediterranean plankton responded significantly to nutrient additions by increasing their biomass, up to more than 100-fold that initially present in the enclosed water, and by changing the community structure, from an initial dominance of picoplankton to increased dominance of the 2-20 µm size component of the community (which contributes to more than 90% of the accumulated N and P) as the nutrient load increased. Though the initial community was able to accumulate nutrients exceeding the already high summer loading of the Bay of Blanes and thus acted as strong nitrogen (N) and phosphorus (P) sink, it was unable to trap the nutrients above a certain threshold: 4-fold (for N) and 8-fold (for P) the Œbusiness as usual¹ load. Conspicuous biomass increases were most noticeable after the nutrient inputs were increased 16-fold that value. Nevertheless, the biomass response was relatively low and involved a low efficiency (8%) in the trapping of added nutrients. As efficiencies were transiently higher (of 50% or even greater, between consecutive sampling days) we suggest factors other than a low assimilation by osmotrophs as responsible for the resilience of the plankton community for the trapping of nutrients in biomass in response to nutrient additions. The tendency of a lower biomass response to nutrient additions in the warm oligotrophic Mediterranean waters than in more eutrophic waters, if confirmed, should have profound consequences concerning the management of the coastline and the delineation of critical nutrient loadings. KEY WORDS: Nutrient accumulation · Coastal plankton · Size structure · Eutrophication · Mesocosm · NW Mediterranean Sea Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 207. Online publication date: November 22, 2000 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2000 Inter-Research.
Ultraviolet-B (UVB) radiation is a global stressor that has profound impacts on freshwater and marine ecosystems. However, an analysis of the patterns of sensitivity to UVB radiation across aquatic photosynthetic organisms has not yet been published. Here, we performed a meta-analysis on results reported in 214 studies compiled from the published literature to quantify and compare the magnitude of responses of aquatic photosynthetic organisms to changes in UVB radiation. The meta-analysis was conducted on observations of marine (n = 893) and freshwater macroalgae (n = 126) and of marine (n = 1087) and freshwater (n = 2889) microalgae (total n = 4995). Most of these studies (85%) analysed the performance of organisms exposed to natural solar radiation when UVB was partially or totally reduced compared with the organismal performance under the full solar radiation spectrum, whereas the remaining 15% of the studies examined the responses of organisms to elevated UVB radiation mostly using artificial lamps. We found that marine photosynthetic organisms tend to be more sensitive than freshwater photosynthetic organisms to UVB radiation; responses to either decreased or increased UVB radiation vary among taxa; the mortality rate is the most sensitive of the trait responses to elevated UVB radiation, followed by changes in cellular and molecular traits; the sensitivity of microalgae to UVB radiation is dependent on size, with small-celled microalgae more sensitive than large-celled microalgae to UVB radiation. Thick macroalgae morphotypes were the less sensitive to UVB, but this effect could not be separated from phylogenetic differences. The high sensitivity of marine species, particularly the smallest photosynthetic organisms, to increased UVB radiation suggests that the oligotrophic ocean, a habitat comprising 70 % of the world's oceans with high UVB penetration and dominated by picoautotrophs, is extremely vulnerable to changes in UVB radiation.
Spartina alterniflora has extensively invaded the coastline of China, including in Maoyan Island of Zhejiang Province. Ecological restoration has been conducted using non-native mangrove Kandelia obovata to replace S. alterniflora in an attempt to restore the impacted intertidal zones. To illustrate the ecological effectiveness of the restoration projects, macrobenthos communities were studied among different habitats within the restored areas, including one non-restored S. alterniflora marsh (SA) and three differently-aged restored K. obovata stands planted in 2003, 2009, and 2011 respectively (KF14, KF8, and KF6). Besides, one unvegetated mudflat (MF) adjacent to the non-restored S. alterniflora marsh and one K. obovata forest transplanted in 2006 (RKF) at a previously barren mudflat without invasion history of S. alterniflora were set as reference sites. A total of 69 species of macrobenthos were collected from Maoyan Island, and the species richness was dominated by gastropoda (23 species), polychaeta (18 species), and malacostraca (16 species). There was no significant difference between the six sites in terms of the abundance of macrobenthos, with the average values of abundance peaking in KF6 (734.7 ind m−2) and being lowest in RKF (341.3 ind m−2). The six sites had significant differences in terms of the biomass of macrobenthos. The KF8 site contained the highest average biomass (168.3 g m−2), whereas the MF site had the lowest (54.3 g m−2). The Shannon-Wiener diversity index and Pielou’s evenness index of the macrobenthos did not exhibit significant differences among the six sites. However, the results of permutational multivariate analysis of variance (PERMANOVA) revealed significant spatial differences in the macrobenthos community structure between the sites. Since KF14 shared a similar macrobenthos community structure with RKF, while representing a strikingly different structure from SA, we infer that ecological restoration using K. obovata can restore the macrobenthos community to resemble to a normally planted K. obovata forest about 15 years after restoration.
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 219:149-158 (2001) - doi:10.3354/meps219149 Effects of seagrass Thalassia testudinum on sediment redox S. Enríquez1, N. Marbà2,*, C. M. Duarte2, B. I. van Tussenbroek1, G. Reyes-Zavala1 1Unidad Académica de Puerto Morelos, Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Apto. Postal 1152, 77500 Cancún, Quintana Roo, Mexico 2Grup d¹Oceanografia Interdisciplinar, Institut Mediterrani d¹Estudis Avançats (CSIC-UIB), C/Miquel Marquès 21, 07190 Esporles, Illes Balears, Spain *Corresponding author. E-mail: ieanmb@clust.uib.es ABSTRACT: The redox conditions were compared in vegetated versus unvegetated sediments across a range of contrasting Thalassia testudinum (sometimes mixed with Syringodium filiforme) meadows at Puerto Morelos Mexico reef lagoon. Moreover, the role of seagrass photosynthetic activity in affecting the redox conditions was tested in one of the meadows by experimentally reducing seagrass photosynthesis through shading. The seagrass rhizosphere extended 26 to 40 cm into the sediment, and accounted for 23 to 504 g DW m-2 of root material, mostly contributed by T. testudinum. T. testudinum placed 50% (i.e. centroidal depth) and 95% of its root biomass within 12.6 ± 0.58 and 54.4 ± 2.53 cm of the sediment surface, respectively; while S. filiforme placed 50 and 95% of its root biomass within 8.0 ± 0.87 and 34.7 ± 3.8 cm of the sediment surface, respectively. Vegetated sediments presented 50% of positive redox potential anomaly (i.e. redox potential in vegetated sediments - redox potential in adjacent bare sediments), remarkably similar (t-test, p > 0.5) to depths to the centroidal depth of the seagrass roots in the sediments. The shading experiment conducted in situ for 5 d demonstrated that the positive redox anomaly found at depth in vegetated sediments was derived from seagrass photosynthetic activity. The sediments around seagrass rhizosphere in the shaded plots were progressively reduced to reach an average decline of the redox conditions by about 45 mV by Day 5. The results presented show that seagrasses contribute to modify sediment redox conditions around their rhizosphere. KEY WORDS: Thalassia testudinum · Syringodium filiforme · Rhizosphere · Redox conditions · Mexican Caribbean Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 219. Online publication date: September 10, 2001 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2001 Inter-Research.
Abstract Seagrass meadows store globally significant organic carbon (C org ) stocks which, if disturbed, can lead to CO 2 emissions, contributing to climate change. Eutrophication and thermal stress continue to be a major cause of seagrass decline worldwide, but the associated CO 2 emissions remain poorly understood. This study presents comprehensive estimates of seagrass soil C org erosion following eutrophication‐driven seagrass loss in Cockburn Sound (23 km 2 between 1960s and 1990s) and identifies the main drivers. We estimate that shallow seagrass meadows (<5 m depth) had significantly higher C org stocks in 50 cm thick soils (4.5 ± 0.7 kg C org /m 2 ) than previously vegetated counterparts (0.5 ± 0.1 kg C org /m 2 ). In deeper areas (>5 m), however, soil C org stocks in seagrass and bare but previously vegetated areas were not significantly different (2.6 ± 0.3 and 3.0 ± 0.6 kg C org /m 2 , respectively). The soil C org sequestration capacity prevailed in shallow and deep vegetated areas (55 ± 11 and 21 ± 7 g C org m −2 year −1 , respectively), but was lost in bare areas. We identified that seagrass canopy loss alone does not necessarily drive changes in soil C org but, when combined with high hydrodynamic energy, significant erosion occurred. Our estimates point at ~0.20 m/s as the critical shear velocity threshold causing soil C org erosion. We estimate, from field studies and satellite imagery, that soil C org erosion (within the top 50 cm) following seagrass loss likely resulted in cumulative emissions of 0.06–0.14 Tg CO 2‐eq over the last 40 years in Cockburn Sound. We estimated that indirect impacts (i.e. eutrophication, thermal stress and light stress) causing the loss of ~161,150 ha of seagrasses in Australia, likely resulted in the release of 11–21 Tg CO 2 ‐eq since the 1950s, increasing cumulative CO 2 emissions from land‐use change in Australia by 1.1%–2.3% per annum. The patterns described serve as a baseline to estimate potential CO 2 emissions following disturbance of seagrass meadows.
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 206:73-85 (2000) - doi:10.3354/meps206073 Experimental induction of a large phytoplankton bloom in Antarctic coastal waters Susana Agustí*, Carlos M. Duarte Instituto Mediterráneo de Estudios Avanzados (IMEDEA), CSIC-Universitat de les Illes Balears, C/Miguel Marqués 21, 07190 Esporles, Mallorca, Islas Baleares, Spain *E-mail: sagusti@uib.es ABSTRACT: The experimental enclosure of an Antarctic planktonic community in a large (35 m3) mesocosm moored in Johnson¹s Dock (62°39.576¹ S, 60°22.408¹ W, Livingston Island, Bransfield Sector, Antarctica) was followed by a large phytoplankton bloom. This bloom, dominated by the large diatom Thalassiosira antarctica, reached a biomass 1000-fold greater than in the ambient waters. The net growth rate of T. antarctica averaged 0.53 ± 0.17 d-1, with maximum net growth rates close to 1.0 d-1, exceeding the predicted maximal population growth rates by 60 to 200%. The gross primary production in the mesocosm (49 mmol C m-3 d-1) was about 30 times greater than the concurrent gross production in the ambient waters, while sedimentation losses removed only between 2.1 to 13% of the biomass d-1 and cell mortality was negligible. The bloom development led to a decline of dissolved inorganic nutrient concentrations to values several times lower than those in the ambient waters, indicating that the ambient nutrients were both available and sufficient to allow the development of the massive algal bloom observed. Light-limitation of the phytoplankton community was likely the factor responsible for the low biomass and production in ambient waters relative to the mesocosm, as indicated by: (1) limited water transparency of about 1 m, which increased up to 6 m as a result of the sedimentation of the glacial flour in the mesocosm; (2) dense pigment packaging (14.7 ± 3 pg chl a µm-3) inside the phytoplankton cells of the community in the ambient waters compared to much lower values (4.2 ± 0.8 pg chl a µm-3) in the mesocosm community; (3) a specific light absorption of the phytoplankton community in the ambient waters 10 times higher (average specific PAR absorption ± SE = 0.018 ± 0.0038 m-1 mg chl a-1) than in the mesocosm community (0.0087 ± 0.002 m-2 mg-1 chl a); and (4) a high apparent quantum yield of the phytoplankton in the ambient waters (0.091 mol O2 [mol photon absorbed]-1), 4-fold higher than that for the community developed in the mesocosm. KEY WORDS: Southern Ocean · Phytoplankton bloom · Mesocosms · Light limitation · Growth rates · Light absorption · Diatoms Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 206. Online publication date: November 03, 2000 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2000 Inter-Research.
