Publications

The increasing use of molecular tools to study populations of clonal organisms leads us to question whether the low polymorphism found in many studies reflects limited genetic diversity in populations or the limitations of the markers used. Here we used microsatellite datasets for two sea grass species to provide a combinatory statistic, combined with a likelihood approach to estimate the probability of identical multilocus genotypes (MLGs) to be shared by distinct individuals, in order to ascertain the efficiency of the markers used and to optimize cost-efficiently the choice of markers to use for deriving unbiased estimates of genetic diversity. These results strongly indicate that conclusions from studies on clonal organisms derived using markers showing low polymorphism, including microsatellites, should be reassessed using appropriate polymorphic markers.

Our planet is facing a critical challenge: climate change. This is caused by human activities that release carbon dioxide and other greenhouse gases into Earth’s atmosphere. As temperatures rise and weather becomes more extreme, scientists are searching for solutions. Blue carbon ecosystems could be part of the answer! These ecosystems include mangrove forests, tidal marshes, and seagrass meadows—ocean and coastal ecosystems that capture and store carbon, keeping it out of the atmosphere. In our research, we found that these ecosystems cover a huge area of Earth’s surface, up to the size of Mexico. They store a whopping 30 billion tons of carbon, which is huge! If we stop destroying blue carbon ecosystems and restore the ones we have lost, it could balance out 3% of the greenhouse gases we put into the atmosphere. Pretty important, right! Overall, blue carbon ecosystems are nature’s heroes in the fight against climate change.

Significance We report the results of a 10,106-person pan-European survey of public awareness, concerns, and priorities about marine anthropogenic impacts as a way to inform both science and policy initiatives in achieving marine sustainability. Results enable scientists and policymakers to understand how the public relates to the marine environment and how they frame impacts and can help make managerial, scientific, and policy priorities more responsive to public values.

Introduction The Red Sea is a narrow rift basin characterized by latitudinal environmental gradients which shape the diversity and distribution of reef-dwelling organisms. Studies on Symbiodiniaceae associated with select hard coral taxa present species- specific assemblages and concordant variation patterns from the North to southeast Red Sea coast at depths shallower than 30 m. At mesophotic depths, however, algal diversity studies are rare. Here, we characterize for the first-time host-associated algal communities of a mesophotic specialist coral species, Leptoseris cf. striatus , along the Saudi Arabian Red Sea coast. Methods We sampled 56 coral colonies spanning the eastern Red Sea coastline from the Northern Red Sea to the Farasan Banks in the South, and across two sampling periods, Fall 2020 and Spring 2022. We used Next Generation Sequencing of the ITS2 marker region in conjunction with SymPortal to denote algal assemblages. Results and discussion Our results show a relatively stable coral species-specific interaction with algae from the genus Cladocopium along the examined latitudinal gradient, with the appearance, in a smaller proportion, of presumed thermally tolerant algal taxa in the genera Symbiodinium and Durusdinium during the warmer season (Fall 2020). Contrary to shallow water corals, our results do not show a change in Symbiodiniaceae community composition from North to South in this mesophotic specialist species. However, our study highlights for the first time that symbiont communities are subject to change over time at mesophotic depth, which could represent an important phenomenon to address in future studies.

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 466:69-79 (2012) - DOI: https://doi.org/10.3354/meps09928 Thresholds of irradiance for seagrass Posidonia oceanica meadow metabolism E. Gacia1,*, N. Marbà2, J. Cebrián3,4, R. Vaquer-Sunyer2, N. Garcias-Bonet2, C. M. Duarte2,5 1Biogeodynamics and Biodiversity Group, Centre d'Estudis Avançats de Blanes, Consejo Superior de Investigaciones Cientificas (CEAB-CSIC), Blanes 17300, Spain 2Department of Global Change Research, Mediterranean Institute for Advanced Studies (IMEDEA; UIB-CSIC), Miquel Marqués 21, Esporles 07190, Spain 3Dauphin Island Sea Lab, 101 Bienville Blvd, Dauphin Island, Alabama 36528, USA 4Department of Marine Sciences, University of South Alabama, Mobile, Alabama 36688, USA 5The UWA Oceans Institute, The University of Western Australia, 35 Stirling Highway, Crawley 6009, Western Australia, Australia *Email: gacia@ceab.csic.es ABSTRACT: Meadows of the endemic seagrass Posidonia oceanica are threatened in the Mediterranean due to a general deterioration of the light environment that becomes critical when light irradiance is insufficient to meet the carbon requirements of the system. Here, we conduct a 3 wk, in situ shading experiment (8 levels plus controls) to determine the threshold of irradiance for balanced metabolism in a shallow P. oceanica meadow and further assess the recovery of the system 1 wk later. Reduced light irradiance decreased the net community production of the meadow, which may turn negative (i.e. respiration exceeded gross community primary production) under 338 µE m−2 s−1. Shading throughout the experiment did not appear to cause sustained physiological damage to the system since values of net community production after the cessation of shading were similar to pre-experimental, ambient levels. Sediment acid volatile sulfide pools ranged between 0.002 and 0.058 mol m−2 across shading treatments, and the highest pools were observed in the most shaded sediments. At high light impairment, meristematic cell divisions were low, and carbohydrate content in young rhizomes decreased throughout the experiment. Eight days after the cessation of shading, reduced rhizome carbohydrate stores and elevated sediment sulfide levels still persisted in the previously intensively shaded areas. The present study provides evidence of resistance and resilience of the seagrass Posidonia oceanica to light impairment for short (3 wk) periods of time. Although the compensation irradiance of the system varied by ~2-fold, it provides a quantitative estimate of the irradiance threshold at which seagrass meadows may shift from being coastal carbon sinks to CO2 sources. KEY WORDS: Seagrass · Ecosystem · Production · Respiration · Compensation Irradiance · Mediterranean Full text in pdf format Supplementary material PreviousNextCite this article as: Gacia E, Marbà N, Cebrián J, Vaquer-Sunyer R, Garcias-Bonet N, Duarte CM (2012) Thresholds of irradiance for seagrass Posidonia oceanica meadow metabolism. Mar Ecol Prog Ser 466:69-79. https://doi.org/10.3354/meps09928 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 466. Online publication date: October 15, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Summary Seagrass meadows are sites of high rates of carbon sequestration and they potentially support ‘blue carbon’ strategies to mitigate anthropogenic CO 2 emissions. Current uncertainties on the fate of carbon stocks following the loss or revegetation of seagrass meadows prevent the deployment of ‘blue carbon’ strategies. Here, we reconstruct the trajectories of carbon stocks associated with one of the longest monitored seagrass restoration projects globally. We demonstrate that sediment carbon stocks erode following seagrass loss and that revegetation projects effectively restore seagrass carbon sequestration capacity. We combine carbon chronosequences with 210 Pb dating of seagrass sediments in a meadow that experienced losses until the end of 1980s and subsequent serial revegetation efforts. Inventories of excess 210 Pb in seagrass sediments revealed that its accumulation, and thus sediments, coincided with the presence of seagrass vegetation. They also showed that the upper sediments eroded in areas that remained devoid of vegetation after seagrass loss. Seagrass revegetation enhanced autochthonous and allochthonous carbon deposition and burial. Carbon burial rates increased with the age of the restored sites, and 18 years after planting, they were similar to that in continuously vegetated meadows (26.4 ± 0.8 gC org m −2 year −1 ). Synthesis . The results presented here demonstrate that loss of seagrass triggers the erosion of historic carbon deposits and that revegetation effectively restores seagrass carbon sequestration capacity. Thus, conservation and restoration of seagrass meadows are effective strategies for climate change mitigation.

Seaweed aquaculture is a rapidly growing component of marine food production, but the capacity to control seaweed growth lacks behind that of land agriculture. Seaweed growth requires nutrients, acquired from dissolved pools through their fronds, and light, and, as may also be density-dependent, but general relationships between seaweed growth, nutrient concentration and incident irradiance are not yet available. We used a dataset of 1729 experimental assessments of seaweed specific growth rates and density under various nutrient and irradiance levels retrieved from the published literature to examine the relationship between seaweed growth, density, irradiance and nutrient concentration. This analysis confirmed strong density-dependence of seaweed specific growth rates, and further confirmed that nutrient and irradiance limitation strongly impose density-dependent seaweed growth. These findings demonstrate that nutrient and irradiance limitation modulate density-dependent seaweed growth, and can help maximize growth rates in seaweed aquaculture, a rapidly growing component of global aquaculture production, by manipulating stocking density where nutrients are scarce and/or underwater light penetration poor.