DataS1. Caspian Sea environmental variables: an extension of the Bio-ORACLE ocean data set

The Caspian Sea hosts unique
native and endemic faunas. However, it is also source and sink of invasive alien
species (IAS) with some listed among the worst 100 invasive species by the
IUCN. A common approach to study biodiversity and biogeographic patterns or to
predict the invasive potential of species is the application of ecological
niche models and species distribution models. These are statistical methods using
spatially gridded environmental data and species occurrence information. As the
Caspian Sea is not connected to the world oceans, spatially gridded
environmental data for the Caspian Sea are not available in the widely used
Bio-ORACLE marine data set. To address this issue, we compiled 28 ecologically
relevant spatially gridded environmental variables using Kriging interpolation
of point data to model minimum, maximum, mean and range of temperature,
salinity and dissolved oxygen for the surface and benthic zones of the Caspian
Sea. Data were retrieved from the World Ocean Dataset. Additionally, we
utilized raster statistics to create surface layers of maximum, mean, minimum
and range of chlorophyll a from
remotely sensed data. We developed these environmental variables as they were
previously confirmed to be relevant for the biogeographical classification of
the Caspian Sea. To allow projections of models across the world oceans into
the Caspian Sea (and vice versa), we matched our raster dimensions with those
of the Bio-ORACLE data set. Our extension of the Bio-ORACLE data set with data
from the Caspian Sea provides an important basis for the monitoring and
evaluation of suitable habitats for native species as well as predicting the
invasive potential of Caspian Sea species into the World oceans.

Keywords:
Sea surface temperature, salinity, oxygen, Chlorophyll a, ecological modelling, invasive alien species