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

Citation

Gogaladze, Aleksandre et al. (2021), Pontocaspian habitat polygon shapefiles from: Decline of unique Pontocaspian biodiversity in the Black Sea Basin: a review, Dryad, Dataset, https://doi.org/10.5061/dryad.34tmpg4kt

Abstract

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 20th and 21st 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.

Methods

Freshwater habitat polygons were retreived from the HydroLAKES dataset (https://www.hydrosheds.org/pages/hydrolakes) to map the Pontovaspian (PC) habitats in the Black Sea Basin (BSB) using QGIS 3.10 “A Coruña”. Those polygons that did not cover the PC habitats, such as swamps and marshes, were manually edited based on published literature and expert knowledge. Lagoons and bays of Pontocaspian habitats, which are not part of the HydroLAKES dataset were also manually drawn based on published accounts and expert knowledge. Given the densely aggregated small lakes in the Danube Delta with surface areas lesser than 0.2 km2 we merged the Chilia branch of the Danube River and outer delta lakes both upstream and downstream of Vilkovo.

Usage Notes

The dataset can be opened and used via Geographic Information Systems, such as ArcGIS or Qgis.