Pontocaspian habitat polygon shapefiles from: Decline of unique Pontocaspian biodiversity in the Black Sea Basin: a review

<p>The unique aquatic Pontocaspian (PC) biota of the Black Sea Basin (BSB) is in decline. The lack of detailed knowledge on the status and trends of species, populations and communities hampers a thorough risk assessment and precludes effective conservation. This paper  reviews PC biodiversity trends in the BSB ( Bulgaria, Romania, Moldova, Ukraine and Russia) using endemic molluscs as a model group. We aim to assess changes in PC habitats, community structure and species distribution over the past century and to identify direct anthropogenic threats. Presence/absence data of target mollusc species was assembled from literature, reports and personal observations. Pontocaspian biodiversity trends in the north-western BSB coastal regions were established by comparing 20^th and 21^st century occurrences. Direct drivers of habitat and biodiversity change were identified and documented. A pronounced decline of PC species and communities is driven by a) damming of rivers, b) habitat modifications that disturbed previous natural salinity gradients and settings in the studied area c) pollution and eutrophication, d) invasive alien species and e) climate change. Four out of the 10 studied regions, namely, the Danube Delta – Razim Lake system, Dniester Liman, Dnieper-Bug Estuary and Taganrog Bay-Don Delta contain the entire spectrum of ecological conditions to support PC communities and still host threatened endemic PC mollusc species. Distribution data is incomplete, but the scale of deterioration of PC species and communities is evident from the assembled data, as are major direct threats. Pontocaspian biodiversity in the BSB is profoundly affected by human activities. Standardised observation and collection data as well as precise definition of PC biota and habitats are necessary for targeted conservation actions. This study will help to set the research and policy agenda required to improve data collection to accommodate effective conservation of the unique PC biota.</p>