Defining centric diatoms of most relevant phytoplankton functional groups in deep karst lakes

Anamarija Ćukurin,Igor Stanković,Sunčica Bosak,Igor Špoljarić,Gordan Mršić,Marija Gligora Udovič,Aleksandra Cvetkoska,Petar Žutinić,Koraljka Kralj Borojević,Anđelka Plenković-Moraj

doi:10.1007/s10750-016-2996-z

Anamarija Ćukurin, Igor Stanković + Show 8 more

Open Access

https://doi.org/10.1007/s10750-016-2996-z

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Abstract

Phytoplankton in karst lakes is characterized by co-occurrence of chrysophytes (Chrysophyceae), dinoflagellates (Dinophyceae), and diatoms (Bacillariophyta) as the most diverse and abundant group. Using Reynolds functional approach in ecological phytoplankton investigations makes karstic lakes comparable and facilitates interpretation of their responses to changing environmental conditions. Accurate taxonomic identification to species level, based on precise resolution of specific characteristics by electron microscopy, is essential in order to correctly associate species into coda. This paper defines the most abundant centric diatoms and coexisting species in the phytoplankton of karst lakes in Croatia as a contribution to better description of phytoplankton functional groups dominated by centric diatoms. Several representatives for diatom-based Reynolds functional groups of four lakes in Croatia were described in this paper: Pantocsekiella costei and Stephanocostis chantaica for group A, Pantocsekiella ocellata and Cyclotella distinguenda for group B, and Stephanodiscus neoastraea for group C, together with their ecological preferences which clearly correspond to pertaining functional classification. Selected and coexisting functional groups define natural, oligo- to mesotrophic karst deep lake systems.

Highlights

Phytoplankton comprises extremely diverse, polyphyletic group of organisms, demonstrating a wide array of morphological, physiological, and behavioral traits (Litchman & Klausmeier, 2008)
During ecological investigations of karst lakes (Gligora et al, 2007; Gligora Udovicet al., 2011, 2015; Zutinicet al., 2014), we found that the morphology of centric diatoms is extremely variable and that the inadequate taxonomic resolution may often result in incorrect placement of species into coda, or even prevents sorting into coda
The mean dissolved oxygen (DO) profile of all lakes showed high saturation level of the euphotic layer throughout the investigated period, while the chemical oxygen demand remained very low with the highest and lowest concentrations of DO noted in Lake Kozjak (Table 2)

Summary

Introduction

Phytoplankton comprises extremely diverse, polyphyletic group of organisms, demonstrating a wide array of morphological, physiological, and behavioral traits (Litchman & Klausmeier, 2008). Due to the high phenotypic variability, phytoplankton species represent distinct ecological entities that respond to resource availability, environmental stimuli, predators, and intra- and inter-species interactions. Such high phytoplankton diversity accounts for different functions within the freshwater ecosystems, and its understanding in space and time is highly relevant and timely issue. Limnological studies have demonstrated that similar taxonomic groups can co-occur in different phytoplankton assemblages with same ecological preferences. These difficulties in species identification and their ecology have led to a development of new approaches, like the creation of phytoplankton functional groups. Data have been complemented to more than 40 coda (Padisak et al, 2009) and successfully applied to a wide range of different ecosystems: tropical coastal lagoons (Alves-de-Souza et al, 2006), tropical

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