Search results for "plank"

Shape and size in phytoplankton ecology: do they matter?

2007

This paper summarises the outcomes of the 14th Workshop of the International Association of Phytoplankton Taxonomy and Ecology (IAP). The authors mostly addressed their contributions on the following topics: morphological and morpho-functional descriptors of phytoplankton, size and shape structure of phytoplankton related to different kinds of environmental variables and the role of morphological and physiological plasticity of phytoplankton in maintaining the (apparently) same populations under different environmental conditions. Case studies from different kinds of aquatic environments (deep and shallow lakes, reservoirs with different age, purpose and trophic state, floodplain wetlands m…

Spatial community concordance of summer phytoplankton and profundal macroinvertebrates in boreal lakes

2014

Reliance of profundal benthic macroinvertebrate assemblages on epilimnetic algal production — a key element of pelagic–benthic coupling — is a well-recognized phenomenon in the literature but the details are still poorly understood. In particular, the importance of taxonomic composition of algal communities and associated qualitative aspects of the settling material to benthic invertebrates is poorly known. We addressed this issue by investigating concordance of summer phytoplankton and profundal macroinvertebrate community composition using data from 47 boreal lakes. We examined community variation and environmental correlates of phytoplankton and macroinvertebrates with nonmetric multidi…

Some Critical Remarks on the Suitability of the Concept of the Photosynthetic Unit in Photosynthesis Research and Phytoplankton Ecology

1993

Based on the classical definition of the photosynthetic unit after Emerson and Arnold, new definitions are presented and their consistency subjected to critical reflection. Modern molecular approaches to determine the physiological condition or even the efficiency of the photosynthetic machinery via determination of the magnitude of the photosynthetic unit are discussed against the background of new data on the dynamics of the thylakoid membrane.

Spatial, seasonal and long-term variability of phytoplankton photosynthesis in lakes

1994

Pelagic food web as the basis of fisheries in Lake Tanganyika: A bioenergetic modeling analysis

2002

Fisheries in Lake Tanganyika, East Africa, are mainly based on two predominantly planktivorous clupeids (Stolothrissa tanganicae and Limnothrissa miodon) and a centropomid predator (Lates stappersi), caught with lift nets, purse seines, and beach seines by traditional, artisanal, and industrial fishers. The biological basis and sustainability of the present fisheries were assessed in a comprehensive project “Research for the Management of the Fisheries on Lake Tanganyika” in 1992–1998. Production in the whole lake was estimated for the entire pelagic food chain leading to the commercially important fish species. Preliminary calculations based on a constant production efficiency suggested th…

Towards a functional classification of the freshwater phytoplankton

2002

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.

Rotifer vertical distribution in a strongly stratified lake: a multivariate analysis

1998

The main source of variation of rotifer species distributions in lake Arcas-2, a small karstic lake near Cuenca (Spain), was explored by means of principal components factor (PCA) and canonical correlation (CCA) analyses. PCA was performed using rotifer densities and CCA using rotifer densities plus physical and chemical parameters. Factor 1 of PCA separated summer species from winter-spring species and Factor 2 accounted for the variation in the vertical profile. Three summer species with different food habits (Polyarthra dolichoptera, Hexarthra mira and Asplanchna girodi) were grouped together at the positive end of Factor 1, while Factor 2 separated the two hypolimnetic species (Filinia …

Hatching and viability of rotifer diapausing eggs collected from pond sediments

2006

SUMMARY 1. Planktonic rotifers inhabiting variable environments produce diapausing eggs that accumulate in the sediment of lakes and ponds, forming egg banks that may withstand adverse periods. A common assumption in zooplankton diapausing egg bank studies is to count as viable all eggs in the sediment that look healthy. This assumption should be challenged by asking how effectively ‘healthy-looking’ eggs represent viable eggs. 2. In this study, viability of more than 1100 ‘healthy-looking’ diapausing eggs belonging to the Brachionus plicatilis species complex was assessed in a laboratory hatching experiment. Eggs were collected at different depths from sediment cores obtained from 15 ponds…

An interesting association betweenNeosphaera coccolithomorphaandCeratolithus cristatus(Haptophyta)

1997

Phytoplankton studies in the North Atlantic have revealed coccoliths of Neosphaera coccolithomorpha and Ceratolithus cristatus occurring on the same cell. This may indicate that each of these species represents a stage of one coccolithophorid life cycle, in which each phase possesses a different heterococcolith type. However, definitive evidence for this is lacking.

Diel vertical movements of zooplankton in lake La Cruz (Cuenca, Spain)

2000

The study of diel vertical movements of zooplankton in a small meromictic karstic lake (lake La Cruz), presenting highly stratified waters, was performed using two different methodologies: (i) samples were taken along the vertical profile and were compared at different hours in a diel cycle; (ii) some plankton traps were located at different depths, covering different periods of time, to catch organisms going upwards and downwards. The main subject of this study has been the vertical movements affecting rotifers since they were dominant in the zooplankton of this lake, but we have also included the results obtained for other zooplankton groups. The results indicate an almost general movemen…