Hotspots of predation persist outside marine reserves in the historically fished Mediterranean Sea

8 páginas, 4 figuras, 2 tablas.The Mediterranean Sea has sustained historically high levels of fishing since pre-Roman times. This onceabundant sea has witnessed major declines in apex predators, now largely restricted to isolated pockets within marine reserves. This depletion could critically impact macrophyte communities that are strongly structured by top-down processes.We evaluated rates of predation on the sea urchin Paracentrotus lividus, a key herbivore of macroalgal and Posidonia oceanica seagrass seascapes, across a large stretch of the Western Mediterranean coastline. Fish predation was generally higher inside reserves, but was equally high at several locations outside these boundaries. Although critically low at some locations compared to reserves, predation was functionally ubiquitous in most habitats, seasons and sites. Fish were still primarily responsible for this predation with no clear evidence of meso-predator release. Macroalgal habitats were consistently subject to higher predation than in seagrass meadows, functionally critical given the vulnerability of macroalgal systems to overgrazing. Predation hotspots were clearly associated with high fish predator numbers and low refuge availability. Taken together, these results suggest that long-term overfishing may not necessarily reflect a complete loss of trophic function. Pockets of fish predation may still persist, linked to habitat complexity, predator behavioral adaptations and landscape-level features. Given the essential role top-down control plays in macroalgal communities, regulating fishing at these predation hotspots is vital to effectively conserve habitats from future hysteretic shifts. Even historically fished seas may retain areas where trophic function persists; identifying these areas is critical to preserving the remaining ecological integrity of these coastlines.This research was funded by the Spanish Ministry of Science and Innovation (projects CTM2010-22273-C02-01-02 and CTM2013-48027-C03-R) and supported J. B. (scholarship BES-2011-043630) and CSIC- 201330E062 supported R. A.'s visitorship.Peer reviewe

Immanent conditions determine imminent collapses: nutrient regimes define the resilience of macroalgal communities

Este artículo contiene 9 páginas, 5 figuras.Predicting where state-changing thresholds lie can be inherently complex in ecosystems characterized by nonlinear dynamics. Unpacking the mechanisms underlying these transitions can help considerably reduce this unpredictability. We used empirical observations, field and laboratory experiments, and mathematical models to examine how differences in nutrient regimes mediate the capacity of macrophyte communities to sustain sea urchin grazing. In relatively nutrient-rich conditions, macrophyte systems were more resilient to grazing, shifting to barrens beyond 1 800 g m22 (urchin biomass), more than twice the threshold of nutrient-poor conditions. The mechanisms driving these differences are linked to how nutrients mediate urchin foraging and algal growth: controlled experiments showed that low-nutrient regimes trigger compensatory feeding and reduce plant growth, mechanisms supported by our consumer–resource model. These mechanisms act together to halve macrophyte community resilience. Our study demonstrates that by mediating the underlying drivers, inherent conditions can strongly influence the buffer capacity of nonlinear systems.The Spanish Ministry of Science and Innovation funded this research (projects CMT2010-22273-C02-01-02 and CMT2013- 48027-C03-R) and supported J.B. (scholarship BES-2011-043630) and D.A. (Ramon y Cajal fellowship). The Spanish National Research Council supported R.A.’s visitorship (CSIC-201330E062).Peer reviewe

Science in the wilderness: the predicament of scientific research in India’s wildlife reserves

Ecology and allied scientific disciplines aim to understand patterns and processes pertaining to wild species, their ecosystems and their relationships with humans. India’s wildlife reserves are important ‘living laboratories’ for these disciplines. Today, there is a disturbing trend across India where scientists are increasingly denied access to wildlife reserves for scientific research or are seriously impeded, without scope for redress. Although official wildlife management rhetoric emphasizes the need for scientific research, in reality, it is viewed as undesirable and permitted, if at all, as a concession, subject to the discretion of individual forest officials. With no enabling legislative or policy framework to promote and apply science in our wildlife reserves, we are concerned that the future of many scientific disciplines in India is being jeopardized. Here, we provide an analysis of this issue and outline steps needed to promote scientific research in our natural areas

Processing and interpretation of the Bushveld seismic survey P1-86

An investigation into the processing and interpretation of the P1-86 reflection seismic data, acquired by the Geological Survey of South Africa in 1986, is shown in this thesis. The seismic line is geographically located west of Pretoria, from Sandpits to Swartdamstat. A non-migrated stacked section was presented in Du Plessis and Levitt (1987). The presence of structural complexities and high amplitude diffractions/out-of-plane reflections on the original seismic section prompted a decision to process the line using the methodology of interpretive data processing (Hinds et al., 1989). It was postulated that interpretive processing and migration of the data may improve the imaging of some of the structural complexities, noted in the original investigation by Du Plessis and Levitt (1987), and enhance seismic events in regions of low signal-to-noise ratio. At each step in the processing sequence, the effects of the processing on the data was evaluated. The reprocessed brute stack section revealed additional structural detail. Phase-shift migration of the stacked section restored complex reflection events to true spatial positions. Non-collapsed diffraction energy is attributed to out-of-the-plane reflections and noise. It is suggested that these diffractions may result from complex 3-D geological structure. A geological model was postulated using the interpretation derived from the final migrated and non-migrated stacked time sections. It is proposed that the Transvaal Sequence and the upper zone of the Rustenburg Layered Suite are regionally continuous across the survey. The RLS and Transvaal Sequence are identified as northerly dipping events which appear to undergo structural updoming towards the northern part of the survey. The marginal norites are proposed to pinch out, and the main zone is proposed to thin, over the anticlinal structure. The postulated updoming is possibly related to similar structures in the Brits area (Roberts, 1981), a few kilometers to the west of the survey. The anticlinal structure resulting from the postulated updoming may have caused a tensional regime in the rocks of the Transvaal Sequence and RLS. This may have resulted in complex faulting. Signal interference in this region of faulting, caused by conflicting reflectors (Ohlovich, 1964), is proposed to be one of the causes of the low signal-to-noise ratio in the northern region of the survey. A model of the subsurface imaged by the seismic survey was fitted to the regional gravity data using two-dimensional forward modeling (Talwani et al., 1959). The good fit of the calculated gravity anomaly values to the observed gravity anomaly values supports the feasibility of the seismically-derived geological model.Dissertation (MSc (Exploration Geophysics))--University of Pretoria, 1992.GeologyMSc (Exploration Geophysics)Unrestricte

Plasma Krebs Cycle Intermediates in Nonalcoholic Fatty Liver Disease

Nonalcoholic liver disease (NAFLD) is manifested with a wide spectrum of clinical symptoms and is closely associated with the metabolic syndrome, inflammation, and mitochondrial dysfunction. Although the mechanism of mitochondrial dysfunction in NAFLD is still not fully elucidated, multiple studies have demonstrated evidence of molecular, biochemical, and biophysical mitochondrial abnormalities in NAFLD. Given the association between NAFLD and mitochondrial dysfunction, the aim of this study is to analyze circulating levels of Krebs cycle intermediates in a cohort of NAFLD-affected individuals and matching healthy controls and to correlate our findings with the liver function metrics. Standard serum biochemistry and Krebs cycle intermediates were analyzed in NAFLD (n = 22) and matched control (n = 67) cohorts. Circulating levels of isocitrate and citrate were significantly (p \u3c 0.05) elevated in the NAFLD cohort of patients. The area under the curve (AUROC) for these two metabolites exhibited a moderate clinical utility. Correlations between plasma Krebs cycle intermediates and standard clinical plasma metrics were explored by Pearson’s correlation coefficient. The data obtained for plasma Krebs cycle intermediates suggest pathophysiological insights that link mitochondrial dysfunction with NAFLD. Our findings reveal that plasma isocitrate and citrate can discriminate between normal and NAFLD cohorts and can be utilized as noninvasive markers of mitochondrial dysfunction in NAFLD. Future studies with large populations at different NAFLD stages are warranted

Exploring coexistence mechanisms in a three-species assemblage

Interactions among species are essential in shaping ecological communities, although it is not always clear under what conditions they can persist when the number of species involved is higher than two. Here we describe a three-species assemblage involving the seagrass Cymodocea nodosa, the pen shell Pinna nobilis and the herbivore sea urchin Paracentrotus lividus, and we explore the mechanisms allowing its persistence through field observations and manipulative experiments. The abundance of pen shells was higher in seagrass beds than in bare sand, suggesting a recruitment facilitation. The presence of sea urchins, almost exclusively attached or around pen shells, indicated habitat facilitation for sea urchins, which overgrazed the meadow around the pen shells forming seagrass-free halos. Our results suggest that this system persists thanks to: (i) the behavioral reluctance of sea urchins to move far from pen shells, making their impact on seagrass strictly local, (ii) the sparse distribution of pen shells and (iii) the plant's resistance mechanisms to herbivory. Unpacking these mechanisms allows a better understanding of how ecological communities are assembled

Long-term persistence of large dugong groups in a conservation hotspot around Hawar Island, Kingdom of Bahrain

1.Predictable aggregations of large marine mammals are valuable conservation targets, but aggregated populations can also be exposed to site-level threats. 2.The globally vulnerable Dugong dugon has a wide distribution but is found in large numbers mainly in Australia and the Arabian Gulf. Though Australian dugong populations are well studied, much less is known of the dugongs in the Arabian Gulf. 3.The spatial and temporal persistence of dugongs around Bahrain, with a focus on large dugong groups (>50 dugongs), was determined using an occupancy modelling framework supported by historical records, structured interviews, citizen science network reports, and small-scale boat and unmanned aerial vehicle surveys. 4.Historical records and current distributional studies confirmed that large dugong groups have been reliably sighted around Hawar Island (Bahrain) since at least 1986, forming large, clumped groups that persist almost year round. The largest recorded so far in the world, these fluid groups (maximum of ~700 dugongs) account for ~60% of the dugongs found in Bahrain and ~12% of all dugongs in the Arabian Gulf. 5.The delineated occupancy core area of large dugong groups (~145 km2) straddles the Bahrain–Qatar border, reflecting the transboundary nature of these groups. 6.Careful management of human-induced stressors (in particular, fishing, boating, and coastal development) combined with regular monitoring of Hawar Island's large dugong groups and their seagrass habitat is critical to safeguard this globally important population. 7.The effectiveness of any conservation management is predicated on strengthening cooperation among all range states in the Arabian Gulf. A key recommendation of this study is to establish a regional network of marine protected areas encompassing core aggregation sites for dugongs, particularly the Hawar Islands in Bahrain, the north-western waters of Qatar, Marawah Island in the United Arab Emirates in addition to the shallow waters between Saudi Arabia, Qatar, and United Arab Emirates

The dominant seagrass herbivore Sarpa salpa shifts its shoaling and feeding strategies as they grow

The relative benefits of group foraging change as animals grow. Metabolic requirements, competitive abilities and predation risk are often allometric and influenced by group size. How individuals optimise costs and benefits as they grow can strongly influence consumption patterns. The shoaling fish Sarpa salpa is the principal herbivore of temperate Posidonia oceanica seagrass meadows. We used in-situ observations to describe how ontogeny influenced S. salpa individual feeding behaviour, shoaling behaviour and group foraging strategies, and its potential consequences to seagrass meadows. Shoaling was strongly influenced by body length: shoals were highly length-assorted and there was a clear positive relationship between body length and shoal size. Foraging strategies changed dramatically with shoal size. Small shoals foraged simultaneously and scattered over large areas. In contrast, larger shoals (made of larger individuals) employed a potentially cooperative strategy where individuals fed rotationally and focused in smaller areas for longer times (spot feeding). Thus, as individuals grew, they increased their potential impact as well, not merely because they consumed more, but because they formed larger shoals capable of considerably concentrating their grazing within the landscape. Our results indicate that ontogenetic shifts in group foraging strategies can have large ecosystem-wide consequences when the species is an important ecosystem modifier