The coastal margin is ecologically distinctive because it is governed by processes that rarely operate together elsewhere in the reserve. Sand movement, salt accumulation, groundwater levels, temporary flooding, wave exposure, wind action, and local human use combine to create a discontinuous mosaic of plant communities rather than a uniform vegetation belt. Open beach vegetation, embryonic dunes, fixed dunes, saline depressions, humid interdunes, and coastal shrubs can occur in close contact, often changing over only a few tens of meters. This coupling of vegetation, sediment transport, and disturbance is a defining feature of coastal-dune systems internationally, and it is particularly important for plants with narrow ecological requirements. Some species colonise bare or weakly stabilised sand; others are restricted to saline or brackish depressions, dune edges, or relatively undisturbed backshore habitats. Several of these taxa have small populations, fragmented distributions, or conservation statuses that warrant attention under Romanian red-list sources.

The floristic total of 661 taxa confirms the coastal area’s botanical importance and spans several ecological groups: psammophilous plants of open sand, halophytes of salt-affected soils, hygrophilous species of wet depressions, grassland and shrub species, and ruderal elements occurring locally under human influence. Poaceae was the richest family in the coastal inventory, with 101 taxa representing 15.3 percent of the total flora, followed by Asteraceae with 86 taxa (13.0 percent) and Chenopodiaceae with 53 taxa (8.0 percent). Together, these three families accounted for 240 taxa, or 36.3 percent of the recorded vascular flora. Other well-represented families included Brassicaceae with 35 taxa, Caryophyllaceae with 33, Fabaceae and Cyperaceae with 32 each, and Lamiaceae with 24. The prominence of grasses, chenopods, sedges, brassicas, and pinks is consistent with the extensive representation of grasslands, dunes, saline surfaces, wet depressions, and pioneer habitats within the coastal mosaic.

The 47 vegetation associations recorded in the dataset indicate that coastal vegetation is not a simple linear sequence from the sea inland. Annual pioneer communities develop on open beaches and freshly disturbed sand; dune-building communities occur where sand begins to accumulate; perennial dune grasslands occupy more stable sites; saline depressions support halophilous assemblages; and locally developed shrubs mark sectors with greater substrate stability or lagoonal influence. Beach and strandline vegetation form the first living cover above the active shore, often sparse and seasonal yet ecologically important because they initiate colonisation of open sand and may trap organic material and sediment. Embryonic dunes and mobile dune communities form where sand accumulation stabilises, and their plant species tolerate shifting sand, wind exposure, and low nutrient availability. By capturing sand and reducing substrate mobility, they create conditions for later successional stages, and damage to these communities can disrupt dune formation and increase the shoreline’s vulnerability.

Wet interdune depressions and saline flats add further ecological complexity. Temporary flooding, groundwater mineralisation, evaporation, and microrelief shape these sites, which can support halophytes, hygrophilous species, and mixed communities that differ markedly from the adjacent dry dunes. Coastal shrubs and Tamarix-related vegetation enhance habitat structure in protected sectors or lagoon-facing positions. The most valuable sectors are those where natural beach dynamics, dune development, and saline or wet depressions coexist, creating conditions for many specialised species. Conversely, sectors subject to repeated mechanical disturbance, trampling, or overgrazing tend to lose this fine-scale structure and become floristically simplified.

The conservation analysis identified 58 taxa with Romanian Red List status among the 661 recorded taxa, meaning 603 taxa, or 91.2 percent, carried no conservation category in the sources consulted. The remaining 58 taxa included 43 classified as rare, nine as vulnerable/rare, three as endangered/rare, two as endangered, and one as vulnerable. These categories reflect historical national conservation sources and should not be interpreted as a new assessment under current IUCN criteria, but they identify a substantial group requiring periodic field verification and population monitoring. Among the flagship species are Crambe maritima, a recognisable coastal plant of natural beaches and dune margins; Eryngium maritimum, a typical dune species with ornamental value; and Stachys maritima, one of the rarest sandy-habitat specialists recorded, found only at Portița and Corbu with a very small population.

Several detailed species accounts illustrate the range of habitats and conservation challenges along the coast. Argusia sibirica, considered critically endangered in the Romanian Red Book, is a characteristic maritime species linked to the Black Sea coast, central Russia, northern Anatolia, and a broader Eurasian range extending eastward to Japan. The project dataset confirmed it at all previously known Romanian coastal areas as well as on Musura Island and between Perișor and Periteașca. Centaurea pontica, one of the most important endemic elements of the Romanian coastal flora, was confirmed in the Sulina urban area but not recently found at Ciotic, where renewed field verification is required. Asparagus brachyphyllus, treated as critically endangered in the Romanian Red Book, was not detected at its historical sites of Istria and Grindul Chituc, but a few individuals were identified in the Periteașca-Perișor sector, making this one of the most important field confirmations in the dataset.

Convolvulus persicus, a critically endangered Ponto-Caspian coastal plant, was confirmed at Sfântu Gheorghe, Sulina, north of Sfântu Gheorghe, Perișor, and Sacalin Island, but the notes indicate that one monitored site had already lost the species and that Perișor hosted only a few individuals, confirming the highly uneven and vulnerable distribution of the species along the coast. Dianthus bessarabicus, a rare and subendemic psammophilous species, was field-confirmed in the Sfântu Gheorghe, Grindul Sărăturile, Perișor, Periteașca, and Sulina sectors. Limonium bellidifolium, a rare halophilous species treated as critically endangered in the Romanian Red Book, was confirmed at Sfântu Gheorghe, Sacalin Island, Grindul Lupilor, Sulina, and Grindul Sărăturile, usually in small numbers, with recent taxonomic discussions treating Danube Delta populations under Limonium bellidifolium subsp. danubiale.

The supplementary spatial analysis summarised 1,243 occurrence records representing 111 species profiles across 134 source grid squares, of which 841 records, or 67.7 percent, intersected at least one mapped Natura 2000 habitat at the grid-square level. Species richness by habitat was highest for habitat 1410, with 96 profiles representing 86.5 percent of all profiles, and habitat 1310, with 90 profiles representing 81.1 percent, followed by 2110, 2160, 1210, and 2130. The strongest compositional overlap occurred between habitats 1310 and 1410, with 83 shared profiles and a Jaccard coefficient of 0.806 and a Sørensen coefficient of 0.892, followed by 2110 and 2160 with 60 shared profiles and a Jaccard coefficient of 0.750. This overlap indicates conservation interfaces within a fine-scale mosaic of beaches, dunes, saline surfaces, wet depressions, grasslands, and shrub communities, rather than interchangeable habitat units. Qualitative population dynamics were reported as stable for 52 profiles, decreasing for 50, increasing for six, and unclear for three, showing that high regional richness does not necessarily mean that local populations are secure.

Keyword screening of the species accounts identified grazing or overgrazing in 98 profiles, or 88.3 percent, tourism or development in 50 profiles, or 45.0 percent, beach cleaning or mechanical disturbance in 46 profiles, or 41.4 percent, restricted or reduced habitat area in 44 profiles, or 39.6 percent, and low reproductive or dispersal capacity in 36 profiles, or 32.4 percent. These pressure frequencies are non-exclusive summaries of the species accounts, not estimates derived from a controlled impact-sampling design. Mechanical beach cleaning is especially relevant because it can remove seedlings, seeds, and organic material needed for pioneer vegetation to develop, and while cleaning may be necessary in recreational sectors, it should be selective and should avoid natural beaches with rare species or embryonic dune vegetation. Grazing also requires careful interpretation: moderate grazing may keep some grassland habitats open, but excessive grazing leads to compaction, nutrient enrichment, ruderalization, and the loss of sensitive plants. The most vulnerable situations occur where small, rare-plant populations coincide with accessible beaches, narrow dunes, or fragmented habitats, where even an apparently minor local disturbance can produce disproportionate conservation effects.

The study’s authors stress that the results represent a regional historical baseline rather than standardised estimates of occupancy or trend, because survey effort was heterogeneous across years and sectors and habitat links were assigned at grid-square level. The descriptive design supports identifying spatial patterns and management hypotheses but does not demonstrate causal relationships between pressures and vegetation change, and contemporary resurveys using a documented, repeatable design are needed to test persistence, trend, and management effectiveness. Nevertheless, the synthesis establishes an essential benchmark for future conservation action. The first management priority is to update the floristic and habitat inventory periodically, with repeated mapping focused on rare-species locations, embryonic dune sectors, saline depressions, wet interdunes, and heavily visited beaches. The second priority is microhabitat protection, since rare plants often depend on small-scale local conditions rather than large continuous habitat blocks, and a small dune ridge, a moist hollow, a salt-affected patch, or an undisturbed upper beach may be critical for a local population.

The third priority is better visitor management, because natural beaches with vegetation may look less clean than mechanically maintained recreational beaches but are far more valuable ecologically, and information panels, guided routes, and communication with local tourism operators can reduce accidental damage. The fourth priority is combining in situ and ex situ conservation, including protecting known populations, avoiding destructive interventions, maintaining habitat processes, seed collection, storage in germplasm banks, and cultivation in botanical gardens, especially for taxa with very small or declining populations. The central result is that conservation value is concentrated not only in individual rare-species locations but also at interfaces among habitat types, and management that treats each mapped habitat polygon in isolation may overlook the short environmental gradients, transitional zones, and disturbance regimes that permit specialised taxa to persist. Future action should combine repeatable resurveys, protection of rare-species microhabitats, maintenance of natural sedimentary and hydrological processes, and differentiated control of beach cleaning, vehicles, tourism, and grazing, with the dataset serving as a benchmark against which future persistence, redistribution, and management effectiveness can be tested.

Subject of Research: Coastal vascular plant diversity, vegetation mosaics, and conservation priorities of the Danube Delta Biosphere Reserve's Black Sea margin

Article Title: Coastal vascular plant diversity of the Danube Delta Biosphere Reserve: Rare plants, vegetation mosaics, and conservation priorities

Article References: Doroftei, M., Covaliov, S., Chirilă, S. D., & Tudose, F. (2026). Coastal vascular plant diversity of the Danube Delta Biosphere Reserve: Rare plants, vegetation mosaics, and conservation priorities. Scientific Annals of the Danube Delta Institute, 31, 25-46. https://doi.org/10.3897/saddi.31.206519

Image Credits: AI Generated

DOI: 10.3897/saddi.31.206519

Keywords: Danube Delta, biodiversity, coastal ecology, plant conservation, Natura 2000, rare species, Black Sea, habitat mosaic, Coastal, vascular, plant, diversity