DOI: 10.5061/dryad.q6m40r0
title: Data from: Phytoplankton species richness along coastal and estuarine salinity continua

description: High number of freshwater species at low salinity, and a corresponding
 high number of marine species at high salinity, enveloping a conspicuous
 richness minimum at intermediate salinities, has shaped our basic
 understanding of biodiversity along a coastal salinity gradient for almost
 80 years. Visualized as the ‘Remane curve’, this iconic concept was
 originally based on sedentary macroinvertebrates in the Baltic Sea. To
 what extent the concept can be generalized, particularly to free-drifting
 organisms, is currently debated. Here we use ca 16 000 phytoplankton
 samples from 2 large coastal ecosystems, the Baltic Sea and the Chesapeake
 Bay, to analyze the relationship between salinity and phytoplankton
 species richness. Alpha diversity showed a consistent variation along the
 salinity gradient, with a minimum at mesohaline salinities at around 7 –
 9. Rarefied species pools at narrow salinity intervals also showed reduced
 diversity at intermediate salinities, surrounded by high richness towards
 both ends of the gradient. The cumulative likelihood of species presence
 validated the minimum at intermediate salinities. Community composition
 changed abruptly at the α diversity minimum in the Baltic Sea, while it
 changed gradually along the salinity gradient in the Chesapeake Bay. We
 conclude that the Remane concept is in every respect valid for
 phytoplankton.
description: Count
 tableA 4 columns
 (descriptors) x 478018 rows (records) data table of phytoplankton species
 specific counts. Column 1: sampleID [character] - unique ID code for each
 phytoplankton saample; Column 2: name [character] - valid taxonomic latin
 name of the taxon; Column 3: AphiaID [integer] - WORMS unique ID code for
 the taxon; Column 4: biomass [numeric] - biomass of the taxon in the
 particular sample (µg / L). The records are linked with the sample table
 by the sampleID code, and with the taxon table by the AphiaID
 code.count.txtSample tableA 7 columns (descriptors) x 15640 rows (samples) data table, containing the meta data about each phytoplankton sample used in the analysis. Column 1: sampleID [character] - unique ID code for each sample; Column 1: date [character] - year and date when the sample was taken; Column 3: basin [character] - sample location, either bs (the Baltic Sea) or chesa (the Chesapeake Bay); Column 4: lon [numeric] - longitude coordinate (degrees); Column 5: lat [numeric] - latitude coordinate (degrees); Column 6: Temp [numeric] - water temperature (°C) of the sample; Column 7: Salin [numeric] - salinity of the sample. The records are linked wiht the count table by the sample ID code. UTF-8 text file with LF line endings.sample.txtTaxon tableA 24 columns (descriptors) x 1384 rows (taxa), containing the higher ranks of the phytoplankton taxa according to WORMS (http://www.marinespecies.org ). Column 1: AphiaID [integer] unique ID code for each taxon. Column 2: name [character] - name of the taxon, corresponding to the AphiaID in the WORMS database; Columns 3 - 23 [character] names of the respective taxonomic ranks of the taxa; Column 24: rank [character] - the lowest rank of identification of the taxon. The records are linked with the count table by AphiaID and name. UTF-8 text file with LF line endings.taxa.txt