Studying ways to increase the delta’s resilience
This article was featured in Eurofish Magazine 3 2025.
The Danube Delta National Institute for Research and Development (DDNI) in Tulcea is one of Romania’s foremost environmental research institutes, dedicated to the sustainable management, restoration, and conservation of the Danube Delta and other wetland ecosystems.
With a legacy dating back to 1926, DDNI has evolved into a modern research institution at the intersection of biodiversity science, ecological restoration, and advanced environmental monitoring. The knowledge that the institute’s researchers produce is vital to understand and mitigate some of the influences that threaten the health of the delta’s ecosystems.
From exploitation to conservation
The history of DDNI is deeply entwined with the broader development and shifting views on the Danube Delta. In the socialist era, the delta was regarded primarily as a source of exploitable natural resources. An economic centre for the Danube Delta was established in 1970 to coordinate large-scale industrial uses of its land and water, including agriculture, reed harvesting, forestry, and fisheries. The scientific activities of the time were subordinated to these economic priorities.
The transformation began in 1989, amid a broader democratic and environmental awakening. With the designation of the Danube Delta as a Biosphere Reserve in 1990, DDNI shifted decisively towards ecological research and environmental protection. This change in orientation was driven in part by scientists like Dr Iulian Nichersu, who advocated for the prioritisation of ecological health and biodiversity over industrial development.
Cross disciplinary research to address environmental challenges
Today, DDNI is structured around five main departments: biodiversity conservation and sustainable use of natural resources; ecological restoration and species recovery; geomatics and geoinformation systems; laboratories and research stations; and transborder and emergent diseases and zoonoses. These departments collaborate across disciplines to tackle pressing environmental challenges in the Danube Delta and other significant wetland regions, such as the Danube floodplain and tributary systems.
The institute’s mission is to conduct scientific research that supports both conservation and the sustainable use of natural resources. This includes long-term environmental monitoring, development of ecological restoration methodologies, spatial planning, environmental impact assessments, and technological innovation. A dedicated dissemination department ensures the translation of research findings into policy and practice, while informal research groups delve deeper into topics such as sturgeon conservation, invasive species, and molecular ecology. Stock status is another subject that is studied by researchers at DDNI. Dr Nichersu points out that climate change can have an impact on stocks because in times of drought when water levels fall the sun can heat up the water to the point where it gets too warm for the fish to spawn. We are seeing declines in stocks from year to year, he says, and we need to study this to try and find solutions.
Genetics and the frontier of eDNA
In recent years, DDNI has invested significantly in molecular biology and genetics. One of its newest laboratories, led by Daniela Porea and Daniela Holostencu , focuses on genetic research to assess biodiversity and preserve native species, particularly in the face of threats from habitat degradation, climate change, and invasive species. Among the most promising innovations at the institute is the use of environmental DNA (eDNA) to assess both the presence and abundance of aquatic species. The technique is especially valuable for monitoring rare or elusive organisms, such as sturgeon, without the need for invasive sampling. As Dr Porea explained, while the methodology is still evolving and dependent on the quality of reference databases like GenBank and BOLD, DDNI is contributing new local data and sequences to improve these global resources. Their ongoing eDNA project focuses on fish and macroinvertebrates. For fish, results have already demonstrated the viability of the technique, revealing rich species diversity. The macroinvertebrate data has been more difficult to interpret, due to incomplete international genetic databases. As a result, the institute is working to expand the DNA reference material for local species, enabling more accurate biodiversity assessments in future studies.
DDNI works to conserve sturgeon populations in the Danube which have suffered declines due to habitat destruction, poaching, and climate impacts.
Sturgeon: a flagship for ecosystem restoration
The plight of sturgeon species in the Danube has become emblematic of broader ecological challenges. Overharvested for decades and blocked from their natural spawning grounds by the Iron Gates dam, sturgeons—especially the Russian sturgeon (Acipenser gueldenstaedtii)—have suffered dramatic population declines. Although fishing is now prohibited, poaching continues due to the high market value of wild caviar. DDNI is at the forefront of efforts to conserve sturgeon populations. Its researchers argue that restocking must be balanced with habitat restoration and stringent law enforcement. Artificial reproduction can increase numbers but risks diminishing genetic diversity if the population base is too narrow. The institute thus supports limited, carefully managed restocking while prioritising natural recovery and spawning, as well as habit restoration and maintenance, fishing prohibitions, and law enforcement. These efforts will not only benefit sturgeons but also other species. Projects have shown that habitat improvements in the lower Danube can produce results. In 2022, DDNI scientists detected wild-born Russian sturgeon for the first time in over a decade, suggesting that carefully targeted restocking and ecosystem restoration efforts can yield tangible conservation outcomes.
Climate change and ecological restoration
Climate change has added a new layer of urgency to DDNI’s work. Decreased water levels in the Danube, rising air and water temperatures, and altered seasonal precipitation patterns are affecting fish reproduction and wetland ecology across the delta. As Dr Nichersu explains, the impacts of even small temperature increases can cascade through entire ecosystems. More heat means more evapotranspiration, which stresses water availability, reduces plant productivity, and weakens the food web. Saltwater intrusion, exacerbated by sea level rise and declining groundwater levels, is threatening coastal wetlands and saltmarsh ecosystems. According to DDNI, these areas are among the most vulnerable to desertification. To address such risks, the institute promotes adaptive and forward-looking restoration strategies. Since 1993, DDNI has led multiple ecological restoration projects, including the rewilding of former agricultural polders like Babina Island. However, the institute recognises that restoration is not static. Landscapes continue to evolve, and long-term monitoring is essential. Restoration designs must therefore include mechanisms for periodic reassessment and re-intervention.
A laboratory with tanks for monitoring sturgeon. DDNI favours limited and carefully managed sturgeon restocking to prevent the risk of diminishing genetic diversity if the population base is too narrow.
The Danubius Research Infrastructure
DDNI is also a core partner in the Danubius-RI (Research Infrastructure), an EU-funded project establishing a pan-European platform for integrated river-sea system studies. Based in Murighiol, the new centre will house laboratories for aquatic ecosystem research, aquaculture systems, and water quality monitoring. When complete, it will provide continuous environmental data from 52 points across the Danube Delta. This infrastructure will support advanced modelling and analysis using artificial intelligence and satellite data, enabling researchers across Europe to access and interpret environmental changes in real time. For DDNI, this represents a strategic opportunity to centralise its data, expand its research collaborations, and contribute to broader European objectives under the EU’s Mission Ocean and Blue Economy frameworks.
Each year, DDNI hosts an international symposium focused on its three core areas—biodiversity conservation, ecological restoration, and geomatics—as well as related topics such as the circular economy, the European Green Deal, and marine spatial planning. The institute also organises workshops for international project partners, civil society, and local stakeholders. These events provide a platform to share findings, refine methodologies, and align research with evolving policy demands. Although DDNI is not a teaching institution, it maintains partnerships with Romanian universities and offers practical placements for undergraduate and postgraduate students. The institute recently hosted Erasmus students and hopes that closer collaboration with academic institutions will help train the next generation of wetland ecologists and geneticists. Dr Nichersu has repeatedly advocated for the establishment of a university branch in Tulcea or Murighiol, arguing that sustained research investment must be accompanied by parallel investments in education. Without a pipeline of trained specialists, DDNI and similar institutions will struggle to maintain their capacity.
Fisheries and aquaculture in transition
Fisheries remain a traditional livelihood in the Danube Delta, though the sector is under increasing pressure from declining fish stocks. Commercial fishing is regulated through licensing and quotas set by the Biosphere Reserve Authority, based on assessments of stock biomass. Despite quotas being lowered over the years, the number of licences has remained largely unchanged, leading to challenges in aligning fishing capacity with ecological sustainability. Aquaculture, once a prominent activity in the delta, has largely collapsed. After 1990, the closure of energy-intensive fish farms and the end of state subsidies led many former aquaculture workers to enter commercial fishing. However, DDNI is now testing new models of sustainable aquaculture, using recirculating aquaculture systems (RAS) in experimental facilities like the one in Caraorman. These efforts aim to demonstrate that modern aquaculture can support livelihoods while reducing pressure on wild stocks.
Using environmental DNA (eDNA) DDNI assesses the presence and abundance of aquatic species. Pictured, the process for filtering and preserving water samples.
Invasive species are an emerging concern for DDNI. Non-native crayfish introduced from Ukrainian aquaculture ponds have established themselves in parts of the delta, while species like Perccottus glenii—a small predatory fish that feeds on fish eggs—are threatening native species such as perch. The institute uses eDNA to detect and monitor the spread of these species and is working to expand marker databases so that new invaders can be more easily identified in environmental samples. Although some invasive species have commercial value—such as certain crayfish now found in local gastronomy—DDNI warns that the ecological risks often outweigh the potential benefits. Effective detection, monitoring, and public awareness are crucial to prevent further spread and ecological disruption.
Research is critical to ensure the long-term health of the Danube Delta
Throughout its work, DDNI maintains a long-term perspective, inspired by the vision of Grigore Antipa. This means not only restoring ecosystems but also building a comprehensive data thesaurus for future generations, embracing new technologies, and confronting environmental threats with both urgency and scientific rigour. As the institute approaches its centenary in 2026, it continues to play a vital role in shaping sustainable policy and research in the Danube Delta. Its integrated approach—linking genetics to geomatics, conservation to aquaculture, and research to practice—makes it a model for researchers studying wetland and river delta systems around the world.
