The Mureș Floodplain Natural Park has an ecosystem that is typical for wetlands, with running and still waters, large forests and periodic floods (every several years).
Flora
The vegetation in the park grows in a continental climate, with warm summers and moderate winters. The annual average temperature is 10.5 degrees Celsius and the average annual rainfall is 550 mm. Many plants within the park need the periodic flooding in order to germinate and to consume the nutrients freshly dissolved in the water.
A large number of plants in the park are on "the red list of superior plants in Romania", meaning they are vulnerable or rare species. Some of these include: yarrow (Achillea thracica), water soldier (Stratiotes aloides), common corncockle (Agrostemma githago), Cirsium brachycephalum, prostrate false pimpernel (Lindernia procumbens), brittle waternymph (Najas minor), hog's fennel (Peucedanum officinale), lesser butterfly-orchid (Platanthera bifolia), Scottish dock (Rumex aquaticus), French vetch (Vicia narbonensis L. ssp. serratifolia).
Besides this, there are also three species which are strictly protected according to the Bern Convention: European waterclover (Marsilea quadrifolia), floating watermoss (Salvinia natans), water caltrop (Trapa natans).
Stands of oak (Quercus robur) and ash (Fraxinus angustifolia) are predominant in the park, together with the coppices of black and white poplar (Populus nigra and Populus alba) and white willow (Salix alba). These species are mostly found in the small forest in the Cenad area and in the 6,000-ha forest along the Mureș River between Arad and the village of Semlac (which includes the Ceala Forest).
Fauna
The fauna in the park encompasses a multitude of species, from large mammals to species living on the river bottom.
There are large populations of mammal species living within the park. Among these are: European hamster (Cricetus cricetus), European polecat (Mustela putorius), brown long-eared bat (Plecotus auritus), otter (Lutra lutra), European wildcat (Felis silvestris), red fox (Vulpes vulpes), red deer (Cervus elaphus), wild boar (Sus scrofa), fallow deer (Dama dama) and roe deer (Capreolus capreolus).
In 1988, the area which is now the Mureș Floodplain Natural Park was designated as an Important Bird Area because of the existence of numerous bird species. Nearly all the birds living in The Mures Floodplain Natural Park are included in the annexes of the Bern Convention and the EU's Habitats Directive. Among them is the lesser spotted eagle (Aquila pomarina), whose numbers within the park are low, but which was chosen as symbol of the natural park.
Approximately 200 species of birds live or pass through the park every year. Among these are: great cormorants (Phalacrocorax carbo), black-crowned night-heron (Nycticorax nycticorax), grey heron (Ardea cinerea), mallard (Anas platyrhynchos), black-headed gull (Larus ridibundus), Eurasian coot (Fulica atra), little bittern (Ixobrychus minutus), little grebe (Tachybaptus ruficollis), water rail (Rallus aquaticus), European bee-eater (Merops apiaster).
There is also a very large number of sand martins (Riparia riparia). Nearly half of the entire population of sand martins on the Mureș River can be found within the Mureș Floodplain Natural Park.
All six of the species of reptiles and nine species of amphibians identified within the park are mentioned in the annexes of the Bern Convention and the EU's Habitats Directive. Their inclusion in these lists is due to the regress of these species, which are considered barometers for the state of an ecosystem's health. Among these are: European pond terrapin (Emys orbicularis), dice snake (Natrix tessellata), European fire-bellied toad (Bombina bombina), and the great crested newt (Triturus cristatus).
For the fish species in the park, the periodic flooding of the Mureș River is a blessing; this process provides new spawning grounds, as well as generating new food and protection. The ichthyofauna in the park has a rich diversity and contains more fish species than any other section of the Mureș River. It is only in this section of the Mureș River that some species exist: white-eye bream (Abramis sapa), zarte (Vimba vimba), crucian carp (Carassius carassius), brown bullhead (Ameiurus nebulosus), striped ruffe (Gymnocephalus schraetser), zingel (Zingel zingel).