Octocorals, a globally distributed class of Cnidaria, inhabit a wide range of environments, from cold to tropical waters and from shallow to deep-sea ecosystems. In the Red Sea, studies on octocoral diversity have mostly been focused on the Gulf of Aqaba and selected families or genera. While these studies have revealed a remarkable richness and diversity of shallow-water species, mesophotic and deep-sea octocoral research remains limited in the region, in particular along the Saudi Arabian coast. Here, we provide a first comprehensive assessment of this group's genetic diversity across the basin's bathymetric and latitudinal gradients. Following six Red Sea oceanographic expeditions and various biodiversity surveys conducted between 2020 to 2023, we analysed a collection of 728 octocoral specimens sampled along 13 degrees of latitude in the Saudi Arabian Red Sea, from shallow-water reefs to deep-sea habitats. We combined morphological identification and sequencing of mitochondrial barcode markers (mtMutS and COI) to delimit lineages. Our integrated results revealed the occurrence of 26 families and 56 genera in the basin from 3 to 859 m of depth. While the description of new species was beyond the scope of this work, here we provide a reference dataset for octocoral diversity from a biodiversity hotspot, as well as essential insights to inform biodiversity management and planning of conservation measures, particularly relevant for the rapidly developing Saudi Arabian Red Sea coast.
Empirical relationships between phytoplankton biomass and nutrient concentrations established across a wide range of different ecosystems constitute fundamental quantitative tools for predicting effects of nutrient management plans. Nutrient management plans based on such relationships, mostly established over trends of increasing rather than decreasing nutrient concentrations, assume full reversibility of coastal eutrophication. Monitoring data from 28 ecosystems located in four well-studied regions were analyzed to study the generality of chlorophyll a versus nutrient relationships and their applicability for ecosystem management. We demonstrate significant differences across regions as well as between specific coastal ecosystems within regions in the response of chlorophyll a to changing nitrogen concentrations. We also show that the chlorophyll a versus nitrogen relationships over time constitute convoluted trajectories rather than simple unique relationships. The ratio of chlorophyll a to total nitrogen almost doubled over the last 30-40 years across all regions. The uniformity of these trends, or shifting baselines, suggest they may result from large-scale changes, possibly associated with global climate change and increasing human stress on coastal ecosystems. Ecosystem management must, therefore, develop adaptation strategies to face shifting baselines and maintain ecosystem services at a sustainable level rather than striving to restore an ecosystem state of the past.
El siguiente articulo trata sobre un trabajo etnografico realizado en la Escuela de Combatientes del Ejercito de Liberacion Nacional en Colombia. La idea fue realizar un acercamiento a la preparacion de los aspirantes a guerrilleros y ver como este proceso construido social y simbolicamente se conforma como un rito de iniciacion. La metodologia utilizada en esta etnografia radica en la utilizacion del video como una herramienta de investigacion. De esta manera estamos frente a una etnografia de la comunicacion que combina la antropologia simbolica con la visual.
The response of Cymodocea nodosa (Ucria) Aschers.seedlings to experimental burial and erosion was examined to test the extent of couphng between fluctuations in sed~rnent depth and seagrass growth.Shoot survivorship declined with erosion and with increasing burial depth, relative to the controls Seagrass growth response, described by changes in internodal and leaf sheath length, the rate of appearance of new leaves, and shoot vertical growth showed a bell-shaped response to fluctuations in sediment depth.Shoot internodal and leaf sheath length, the rate of appearance of new leaves, and vertical growth all increased with sediment depth from minimal values under erosion to maximal values at burial of c 7 cm.These results demonstrate that C, nodosa seedlings tolerate burial < 7 cm, and that burial stimulates the growth of surviving seedlings Examination of this growth response for C. nodosa and other seagrass species, which allows quantification of tolerable changes in sediment depth, may provide useful information for conservation of seagrass populations.
Our results establish formally that phytoplankton counting error decreases with increasing biomass. When combining the individual density estimates to yield a single figure, error propagation introduces great uncertainty around succession and diversity indices. Furthermore, counting error increases the value of succession indices for communities where all species change at the same rate above the expected value of 0. Consequently, conclusions based on the comparison of succession and diversity indices should only be drawn when the uncertainty derived from counting error is considered.
Concerns over overexploitation have fueled an ongoing debate on the current state and future prospects of global capture fisheries, associated threats to marine biodiversity, and declining yields available for human consumption. Management reforms have aimed to reduce fishing pressure and recover depleted stocks to biomass and exploitation rates that allow for maximum sustainable yield. Recent analyses suggest that scientifically assessed stocks, contributing over half of global marine fish catch, have, on average, reached or even exceeded these targets, suggesting a fundamental shift in the effectiveness of fisheries governance. However, such conclusions are based on calculations requiring specific choices to average over high interstock variability to derive a global trend. Here we evaluate the robustness of these conclusions by examining the distribution of recovery rates across individual stocks and by applying a diversity of plausible averaging techniques. We show that different methods produce markedly divergent trajectories of global fisheries status, with 4 of 10 methods suggesting that recovery has not yet been achieved, with up to 48% of individual stocks remaining below biomass targets and 40% exploited above sustainable rates. Furthermore, recent rates of recovery are only marginally different from zero, with up to 46% of individual stocks trending downward in biomass and 29% of stocks trending upward in exploitation rate. These results caution against overoptimistic assessments of fisheries writ large and support a precautionary management approach to ensure full rebuilding of depleted fisheries worldwide.
Abstract Past environmental conditions in the Mediterranean Sea have been proposed as main drivers of the current patterns of distribution of genetic structure of the seagrass Posidonia oceanica , the foundation species of one of the most important ecosystems in the Mediterranean Sea. Yet, the location of cold climate refugia (persistence regions) for this species during the Last Glacial Maximum (LGM) is not clear, precluding the understanding of its biogeographical history. We used Ecological Niche Modelling together with existing phylogeographic data to locate Pleistocene refugia in the Mediterranean Sea and to develop a hypothetical past biogeographical distribution able to explain the genetic diversity presently found in P. oceanica meadows. To do that, we used an ensemble approach of six predictive algorithms and two Ocean General Circulation Models. The minimum SST in winter and the maximum SST in summer allowed us to hindcast the species range during the LGM. We found separate glacial refugia in each Mediterranean basin and in the Central region. Altogether, the results suggest that the Central region of the Mediterranean Sea was the most relevant cold climate refugium, supporting the hypothesis that long-term persistence there allowed the region to develop and retain its presently high proportion of the global genetic diversity of P. oceanica .
