Carla Kruk

Bio: Carla Kruk is an academic researcher from University of the Republic. The author has contributed to research in topics: Phytoplankton & Species richness. The author has an hindex of 22, co-authored 56 publications receiving 4181 citations. Previous affiliations of Carla Kruk include Wageningen University and Research Centre.

Towards a functional classification of the freshwater phytoplankton

Abstract: This paper considers the structure of freshwater phytoplankton assemblages and promotes a scheme of vegetation recognition', based upon the functional associations of species represented in the plankton. These groups are often polyphyletic, recognizing commonly shared adaptive features, rather than common phylogeny, to be the key ecological driver. Thirty-one such associations are outlined and the basic pattern of their distinctive ecologies is outlined. An invitation to other plankton scientists to assist in the development of this scheme is issued.

Warmer climates boost cyanobacterial dominance in shallow lakes

Abstract: Dominance by cyanobacteria hampers human use of lakes and reservoirs worldwide. Previous studies indicate that excessive nutrient loading and warmer conditions promote dominance by cyanobacteria, but evidence from global scale field data has so far been scarce. Our analysis, based on a study of 143 lakes along a latitudinal transect ranging from subarctic Europe to southern South America, shows that although warmer climates do not result in higher overall phytoplankton biomass, the percentage of the total phytoplankton biovolume attributable to cyanobacteria increases steeply with temperature. Our results also reveal that the percent cyanobacteria is greater in lakes with high rates of light absorption. This points to a positive feedback because restriction of light availability is often a consequence of high phytoplankton biovolume, which in turn may be driven by nutrient loading. Our results indicate a synergistic effect of nutrients and climate. The implications are that in a future warmer climate, nutrient concentrations may have to be reduced substantially from present values in many lakes if cyanobacterial dominance is to be controlled.

A morphological classification capturing functional variation in phytoplankton

Abstract: 1. A logical way of distinguishing functional groups of phytoplankton is to cluster species according to their functional traits, such as growth rate and nutrient assimilation constants. However, data for such an approach are lacking for the vast majority of the species. 2. In this study, we show that a classification based on simple morphological traits may capture much of the variability in functional properties among the phytoplankton. We used information on more than 700 freshwater species, from more than 200 lakes situated in climate zones ranging from subpolar to tropical. 3. Morphological characteristics correlated well with functional properties, such as growth rate and sinking rate, and also with the population size and biomass attained in the field. This suggests that morphology is a good predictor of the functional characteristics of species. 4. Cluster analysis was used to define seven species groups based on morphology. Although some of the clusters are taxonomically homogeneous, others include species of several separate divisions. Functional traits (not used for the classification) differed significantly among the clusters, suggesting that the clusters may indeed represent meaningful functional groups. 5. Advantages of our morphological approach to classification include its objectivity, its independence from taxonomic affiliations, and the relative ease of its application to the majority of species for which physiological traits are unknown and are not readily determined.

Classification schemes for phytoplankton: a local validation of a functional approach to the analysis of species temporal replacement

Abstract: During ecosystem succession, phytoplankton species composition is hard to predict and although it is tempting to use taxonomic groups for predictive purposes, the conditions favouring their development are often cross-phyletic and, frequently, overlap. Another alternative is to consider functional groups. Reynolds (1997) proposed phytoplankton associations according to functional criteria, based upon identified coherent morphological and ecological properties. Here we apply data from the phytoplankton community of Lake Rodo in Montevideo, Uruguay (small, shallow, polymictic and hypertrophic lake under restoration) to test and quantify the effectiveness of the approach. The phytoplankton species were sorted into their main taxonomic groups and into the associations proposed by Reynolds. A canonical variate analysis was use to test the non-random occurrence of these classification schemes and to determine their discriminatory power. Both classification schemes, taxonomic and functional, showed a significant result, but classification into functional associations had a higher discriminatory power. The eigenvalue for the canonical correspondence analysis first axis for the functional associations was 0.708 and the cumulative explained variance for the species-environmental relationship was 78. 6%. The environmental factors showed similar patterns between associations and individual species. Our data indicate that the scheme using functional associations does indeed capture much of the ecology of the phytoplankton.

The Theory of Island Biogeography

Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

The Ecology of Phytoplankton

Abstract: Communities of microscopic plant life, or phytoplankton, dominate the Earth's aquatic ecosystems. This important new book by Colin Reynolds covers the adaptations, physiology and population dynamics of phytoplankton communities in lakes and rivers and oceans. It provides basic information on composition, morphology and physiology of the main phyletic groups represented in marine and freshwater systems and in addition reviews recent advances in community ecology, developing an appreciation of assembly processes, co-existence and competition, disturbance and diversity. Although focussed on one group of organisms, the book develops many concepts relevant to ecology in the broadest sense, and as such will appeal to graduate students and researchers in ecology, limnology and oceanography.

Towards a functional classification of the freshwater phytoplankton

Abstract: This paper considers the structure of freshwater phytoplankton assemblages and promotes a scheme of vegetation recognition', based upon the functional associations of species represented in the plankton. These groups are often polyphyletic, recognizing commonly shared adaptive features, rather than common phylogeny, to be the key ecological driver. Thirty-one such associations are outlined and the basic pattern of their distinctive ecologies is outlined. An invitation to other plankton scientists to assist in the development of this scheme is issued.