Science is addressing global societal challenges, and due to limitations in research financing, scientists are turning to the public at large to jointly tackle specific environmental issues. Citizens are therefore increasingly involved in monitoring programs, appointed as citizen scientists with potential to delivering key data at near to no cost to address environmental challenges, therein fostering scientific knowledge and advising policy- and decision-makers. One of the first and most successful examples of marine citizen science in the Mediterranean is represented by the integrative and collaborative implementation of several jellyfish-spotting campaigns in Italy, Spain, Malta, and Tunisia starting in 2009. Altogether, in terms of time coverage, geographic extent, and number of citizen records, these represent the most effective marine citizen science campaigns thus far implemented in the Mediterranean Sea. Here, we analyzed a collective database merging records over the above four countries, featuring more than 100,000 records containing almost 25,000 observations of jellyfish specimens collected over a period of 3 to 7 years (from 2009 to 2015) by citizen scientists participating in any of the national citizen science programs included in this analysis. Such a wide citizen science exercise demonstrates a valuable and cost-effective tool to understanding ecological drivers of jellyfish proliferation over the Western and Central Mediterranean basins, as well as a powerful contribution to developing tailored adaptation and management strategies; mitigating jellyfish impacts on human activities in coastal zones; and supporting implementation of marine spatial planning, Blue Growth, and conservation strategies.

Jellyfish (Cnidaria and Ctenophora) are an essential component of marine ecosystems and represent a potential effect, positive or negative, for several economic activities. Jellyfish blooms and non-indigenous species (NIS) introduction can shift ecological community structure and energy transfer. Despite their importance in ecosystem function and services, knowledge of jellyfish fauna diversity and phenology are largely lacking for the southern Mediterranean Sea. Here, we present an overview of the current state of jellyfish biodiversity in Tunisia. Based on a comprehensive literature survey, historical records and unpublished data, 66 jellyfish species, including 11 non-indigenous species, have been recorded in Tunisia between 1994 and 2020. Additionally, based on field surveys and a citizen science sighting program between 2004 and 2020, we present data on the spatial distribution of 13 conspicuous jellyfish taxa and the phenology of the eight most frequently detected species (Aurelia solida, Cotylorhiza tuberculata, Pelagia noctiluca, Phyllorhiza punctata, Rhizostoma pulmo, Rhopilema nomadica, Olindias muelleri and Velella velella) in Tunisian two ecoregions, the Western Mediterranean and the Tunisian Plateau. The 17 year survey showed a shift in R. pulmo, A. solida and P. noctiluca phenology. Additionally, citizen science revealed an increase in the spatial range of P. punctata (NIS) and the distinct phenologies of populations in the two ecoregions.

Photodegradation is an important mechanism that affects carbon and nutrient cycling; a significant amount of data has been reported previously. The present review includes the effect of a wider spectrum of solar radiation (sun light, UV, and visible light) on plant litter decay in terrestrial ecosystems. Although the positive effect of photodegradation on decomposition is most common, a substantial number of studies reports contrasting results. Litter from 148 plant species, from 41 families, have been used in photodegradation studies, representing functional groups of trees (33%), graminoids (30%), shrubs (23%), forbs (11%), and peat (1%). Although the majority of studies focused on mass loss, a growing number focuses on nutrient release. Positive effects on mass loss are most common across different climate regions and laboratory studies, whereas “positive” influence and “no effect” on nitrogen and lignin release are equally common in temperate and sub-tropical environments. This may potentially be due to other decomposition processes which increase in relevance with increasing moisture and can facilitate microbial activity, leaching, and fractioning by soil fauna. In addition to climate region, initial litter quality influences photodegradation. Field-based and laboratory experiments frequently obtain contrasting results, suggesting that the mechanisms controlling the responses are unclear and might be dependent on several interactions, and/or the differences in experimental approaches (such as UV filters), or coverage by particles. Future research should focus on interactions between different factors, and on conducting experiments that test specific relationships such as the potential interaction between photodegradation, soil moisture, microbial communities, soil fauna, and their effects on litter decomposition (both mass loss and nutrient release). Furthermore, the topic would benefit from international studies applying the same experimental approach, as has successfully been conducted in other fields.

Environmental DNA (eDNA) metabarcoding has transformed marine biodiversity monitoring by allowing non-invasive, cost-effective detection of species with high resolution across diverse marine habitats. A systematic literature search was conducted using Google Scholar, Scopus, and the Qatar University Library databases. Relevant peer-reviewed publications were screened and selected based on predefined inclusion criteria to ensure comprehensive coverage of studies. This review synthesizes advances in global and regional eDNA applications, emphasizing the Middle East and North Africa (MENA) region, which faces unique environmental extremes, high endemism, and significant data gaps. eDNA metabarcoding often outperforms traditional methods under comparable sampling effort to traditional surveys in detecting rare, cryptic, and invasive taxa, but technical challenges like incomplete reference databases, primer biases, PCR inhibitors, and inconsistent methodologies limit their effectiveness, particularly in understudied areas such as MENA. Recent developments, including multi-marker approaches, autonomous samplers, and next-generation sequencing, are enhancing detection precision and enabling broader, real-time monitoring. In the MENA region, early studies have revealed eDNA’s potential for habitat distinction, biogeographic research, pollution assessment, and the early discovery of non-indigenous species, although progress is hindered by gaps in reference libraries, infrastructure, and regulation. This review underscores the urgent need for regional collaboration, standardized protocols, and capacity-building. By integrating eDNA with traditional methods and leveraging emerging technologies, the MENA region can establish itself as a leader in marine biomonitoring under extreme environmental conditions, providing actionable insights for conservation and sustainable management of its unique marine ecosystems.

This study investigates the impact of elevated salinity levels on the growth and photosynthetic efficiency of the coral endosymbiont Symbiodinium sp. isolated from Platygyra daedalea in the coral reefs of Qatar. Cultures were exposed to a range of salinities (30-70 psu) over a 11-day incubation period under controlled laboratory conditions. Results revealed a significant decline in cell density and growth rate at salinities above 55 psu. Photosynthetic performance, assessed using the OJIP chlorophyll fluorescence protocol, showed a marked reduction in key parameters-including ABS/RC, DIo/RC, TRo/RC, ETo/RC, Vi, Vj, Mo, and Fv/Fm-at salinities exceeding 55 psu, indicating substantial stress and inactivation of PSII reaction centers. Interestingly, a partial recovery in photosynthetic efficiency was observed at 55 and 60 psu following initial decline. This is the first study to examine the physiological response of Symbiodinium sp. to salinity stress in the Arabian Gulf, providing valuable insights for coral reef restoration initiatives in this high-salinity environment amid ongoing climate change and coastal development.