The NNR includes meadows and wetlands on the west bank of the Nesyt fishpond in the Nesyt depression between the railway line, road and Včelínek stream to the north of the Sedlec u Mikulova railway station and on both sides of the footpath between the station and the village. The subject of protection is the remnants of halophytic flora and fauna, including several specially protected species. The protected area was declared in 1961 on a territory of 6.76 ha, at an elevation of 176 metres in the parish of Sedlec u Mikulova in the Jihomoravský kraj - South Moravian Region.
The geological basement is formed of Holocene deluvial, deluvofluvial and fluvial sandy-clayey sediments, which are enriched with mineral salts (sulphates and chlorides) which have been leached from the Neogene clays with low permeability, which underlie the Holocene sediments.
On the NNR territory, remnants of mesic and damp saltmarsh grassland of the Scorzonero-Juncion gerardii alliance have been conserved. This alliance belongs to the Scorzonero parviflorae-Juncetum gerardii and Loto-Potentilletum anserinae associations. Very small areas of alcali-grass saltmarsh - Puccinellietum limosae association can also be found here. Small areas of annual holophytic grass growths can be seen in late summer in the man-made ditch in the western part of the salt marsh. However the seeds of both of these species – the prickle-grass Crypsis aculeata and swamp prickle grass (Heleochloa achoenoides), were brought here from elsewhere. The predominant vegetation type in these ditches is bulrush growths of the Bolboschoenetum maritimi association of the Scirpion maritimi alliance. The largest part of the saltmarsh is covered by weakly salted drier oatgrass meadows of the Arrhenatherion elatioris alliance. In some areas the predominant species is the fleabane Inula britannica. The dampest part of the reserve plays host to bankside sedge growths of the Caricetum ripariae association from the Caricion gracilis alliance, which have colonised areas which were previously covered by reedbeds of the Phragmitetum communis association with predominant common reed (Phragmites australis) due to regular cutting. If some parts of the reserve would be left without regular cutting the reedbeds would probably spread rapidly.
During the years 1993 – 2004, 284 species of vascular plants were recorded on the NNR territory. The sea arrow-grass (Triglochin maritima) has its only locality in the Czech Republic here. Three plants were found here in 2004. However, it is possible that they were planted here. Of the 15 specially protected plant species which grow here we can also find the viper’s-grass Scorzonera parviflora, the sea aster - Aster tripolium subsp. pannonicus, sea plantain (Plantago maritima subsp. ciliata), the feather-grass Stipa pennata, the spurreys Spergularia maritima and Spergularia salina, the sedge Carex secalina, water germander (Teucrium scordium), the dandelion Taraxacum bessarbicum, slender hare’s-ear (Bupleurum tenuissimum), brookweed (Samolus valerandi) and saltmarsh rush (Juncus gerardii).
The occurrence of 6 critically endangered butterfly species has been documented on the saltmarsh: the Gelechiid moths Ilseopsis samadensis and Ilseopsis salinella, the Tortricids Phalonidia affinitana and Phalonidia vectisana as well as the Lyonetiid Bucculatrix maritima and the case bearerColeophora halophilella. This is one of the few localities in the Czech Republic where other halophilous animal species can be found, e.g. the pentatomid bug Henestaris halophilus, the grasshopper Aiolopus thalassinus and the ground beetles Acupalpus elegans, Dyschirius chalceus and Dyschirius salinus. Some of the rarest spiders in the Czech Republic - Zora armillata, Heriaeus graminicola and the foliage spider Clubiona juvenis are all found here. The Slanisko u Nesytu NNR is also the only locality in the Czech Republic where the wolf spider Pardosa maisa has been recorded.
In the past the territory was used for grazing. Part of the territory was ploughed up before the Second World War but the field was soon left uncultivated when it proved to be infertile.
The glasswort Salicornia prostrata was last observed on the territory in 1976 and the seablite Suaeda prostrata was last seen here 10 years later. Further fragments of halophilous vegetation can be found on the nearby football pitch on the left bank of the Včelínek stream and by the Výtopa fishpond near the eastern bank of the larger Nesyt fishpond. The condition of the halophilous vegetation and populations of individual species are regularly monitored.