Tintinnid ciliate diversity in the Mediterranean Sea: longitudinal patterns related to water column structure in late spring-early summer

Abstract

Globally, north-south gradients in diversity are well known, and in the world ocean they have been related to north-south gradients in water column structure. Here diversity in planktonic ciliates, both taxonomic and morphological, is explored in the Mediterranean Sea, which displays west-east gradients in the water column characteristics of chlorophyll concentrations and distributions. Tintinnids, which are loricate planktonic ciliates, were enumerated and identified in samples from 23 stations between 2 and 32°E, obtained from the Catalan Sea in June 1993 and from a crossMediterranean transect in May-June 1996. From west to east, concentrations of tintinnids showed little variability, while numbers of species and genera, as well as diversity indices (H ' values), increased. These parameters were positively related to depths of the chlorophyll maximum layer and negatively correlated with chlorophyll concentrations. Corresponding to the west to east increases in diversity were increases in community averages of lorica oral diameter and overall length, again positively correlated to deepening of chlorophyll maximum depths, and negatively related to average chlorophyll concentrations. Morphological diversity was related to species diversity, not as variability in lorica oral diameters, but as variability in average lorica length. In the Mediterranean Sea, a gradient of taxonomic and morphological diversity is relatable to a specific feature of the water column, the depth of the chlorophyll maximum layer. Trophic specialization as a dominant mechanism underlying diversity was not supported by data on lorica oral diameters.

The "neutral" community structure of planktonic herbivores, tintinnid ciliates of the microzooplankton, across the SE Tropical Pacific Ocean

“…The relationships of diversity of these micrograzers and food resources were similar to those found examining trends across the Mediterranean in the late spring/early summer (Dolan, 2000). Total abundance of tintinnids increased with chlorophyll while diversity decreased.…”

“…9). These species can be described as wide-spread, having all been found in both the Mediterranean and New Caledonia (Dolan, 2000;Dolan et al, 2006). Overall we found evidence that tintinnid communities in the SE Pacific could be described by Hubbell's neutral theory.…”

“…In a subsequent study, based on samples taken at different stations in early fall from the Atlantic coast of Morocco to the Eastern Mediterranean, the only significant relationships found were between chlorophyll sizediversity and tintinnid diversity (Dolan et al, 2002). While in the SE Pacific average concentrations of chlorophyll encountered were of a range very similar to that reported in the Mediterranean transects, tintinnid abundances were lower by about half compared to the Mediterranean (Dolan, 2000;Dolan et al, 2002). The apparent variable relationships between tintinnid diversity and resources as chlorophyll led us to examine the patterns of species assembly using rank abundance distributions.…”

“…Compared to recent geographic surveys of other areas, we recorded 149 species compared to a total of 87 tintinnid species found along a transect from 42 • N to 42 • S from Italy through the Indian Ocean to New Zealand (Modigh et al, 2003), or the 70-80 species recorded from west to east Mediterranean transects (Dolan et al, 2000(Dolan et al, , 2002. We found about 30 species per location and this taxonomic diversity was paired with morphological diversity.…”

“…Relationship between taxonomic diversity of the tintinnid community and the depth of the chlorophyll maximum layer. (Dolan, 2000). In a subsequent study, based on samples taken at different stations in early fall from the Atlantic coast of Morocco to the Eastern Mediterranean, the only significant relationships found were between chlorophyll sizediversity and tintinnid diversity (Dolan et al, 2002).…”