Pertti Eloranta

Ecological status of some Finnish rivers evaluated using benthic diatom communities

The applicability of some diatom methods to quality assessment of differenttypes of Finnish rivers was compared using dominant taxa of diatomcommunities and nutrient level estimations using Trophic Diatom Index(TDI) and a new Phosphorus Diatom Equation (PDE) [Tot. Pcalc (μg l-1) = 39 – 0.278 ol-% – 0.117 olme-% – 0.346me-% – 0.006 meeu-% + 1.193 eu-%; n = 97; r2 = 0.742;SE = 17.4]. The overall quality estimations were done by Index ofPollution Sensitivity (IPS) and by Generic Diatom Index (GDI); limit valuesfor quality classes are proposed.

Seasonal persistence and stability of diatom communities in rivers: are there habitat specific differences?

Epilithic, epiphytic and epipelic diatoms were sampled at four sampling stations monthly from June to October in three boreal rivers in South Finland to examine the seasonal community persistence and stability of diatom communities in three habitats. The variation of successive samples in ordination space using Non-Metric Multidimensional Scaling was substantial and without an evident pattern; there were no clear differences between community stability on three different substrata. At two stations, Multi Response Permutation Procedures showed significant among-group differences indicating that diatom communities were distinctly different among the three substrata. According to Indicator Species Analysis, we found several species showing significant (p < 0.05) specificity for, and fidelity to, certain substrata at two stations. The stability between sampling months in the rank abundance of diatom taxa was lowest among epiphytic communities. At each station, Spearman rank correlation decreased substantially until August indicating a distinct change in rank abundances. Communities tended to revert to their pre-disturbance state toward autumn after a major spate in the end of August. Using linear regression, we found that changes in total P were significantly (p < 0.05) related to community stability in the epilithon. Species turnover seemed to be highest among epiphyton and lowest among epipelic communities. Although these differences could partly result from lower diversity in epiphyton, they probably reflect lower persistence among epiphytic communities in these boreal rivers.

The supremacy of invertebrate predators over fish: factors behind the unconventional seasonal dynamics of cladocerans in Lake Hiidenvesi

In the eutrophic Lake Hiidenvesi (30.3 km 2 ), the early summer biomass maximum of cladoceran zooplankton is missing and the highest biomass is found unusually in mid summer. The contribution of the phantom midge Chaoborus flavicans to the unconventional seasonal dynamics of cladocerans was studied. The seasonal development of the C. flavicans population and the zooplankton community was studied together with food consumption by chaoborids and the most common vertebrate predator, smelt. The population density of Chaoborus peaked in June and collapsed in mid summer. Thereafter, another peak occurred at the end of August. The maximum density of chaoborids in the water column varied between 5,500 and 8.700 inc./m 2 . In early summer, the most common food items of Chaoborus were bosminids while later in summer the share of daphnids increased. Food consumption by the Chaoborus population peaked at 26-46 μg Cl -1 d -1 in June and clearly exceeded the production rate of cladocerans. Cladoceran consumption by smelt population reached its maximum, 1.13 μg Cl -1 d -1 , in early July. Cladocerans showed a 20-40 μg C/l biomass peak in July-August, coincidently with the minimum density of chaoborids. When predation pressure decreased, the mean size of cladocerans increased at 10-15 m, the depth occupied by chaoborids during daytime. The results suggest that in early summer the high predation pressure prevents cladocerans from reaching a sufficient body length to defend them against Chaoborus and that the timing of the cladoceran biomass peak is determined by the relaxation of chaoborid predation.

Diversity and succession of the phytoplankton in a small lake over a two-year period

Phytoplankton in the small central Finnish lake, Vasikkalampi, was studied over a two-year period by weekly sampling simultaneously with monitoring of physical and chemical properties of water, solar radiation energy and zooplankton. In the present paper, the fluctuations in phytoplankton diversity were studied in relation to environmental factors. The special aim for the study was to detect a relation between environmental disturbances and phytoplankton diversity.

Molecular and morphological evidence for Sheathia gen. nov. (Batrachospermales, Rhodophyta) and three new species

The freshwater red algal genus Batrachospermum has been shown to be paraphyletic since the first molecular studies of the Batrachospermales. Previous research, along with this study, provides strong support for the clade Batrachospermum section Helminthoidea. This study has found that heterocortication, the presence of both cylindrical and bulbous cells on the main axis, is an underlying synapomorphy of this clade. Based on support from DNA sequences of the rbcL gene, the COI barcode region and the rDNA ITS 1 and 2, along with morphological studies, the new genus Sheathia is proposed. Seven heterocorticate species were recognized from the molecular clades. Sheathia boryana and S. exigua sp. nov. appear to be restricted to Europe, whereas S. confusa occurs in Europe and New Zealand. Sheathia involuta is widespread in the USA and reported for the first time from Europe. Sheathia americana sp. nov., has been collected in the USA and Canada, and S. heterocortica and S. grandis sp. nov. have been collected only in the USA. Sheathia confusa and S. grandis can be distinguished based on morphological characters, whereas DNA sequence data are required to conclusively distinguish the other species. Sheathia fluitans and S. carpoinvolucra also are placed within this genus based on the presence of heterocortication. These data also hint at greater diversity among non‐heterocorticate Sheathia than is recognized by the single species name S. arcuata.

Diversity of freshwater red algae in Europe

Diversity of freshwater red algae in Europe Of the total number of freshwater red algae (ca. 180 taxa), one third are found in Europe (ca. 60 taxa). Over one third (24 taxa) of European taxa have been found at only one single location or at very few locations. The majority of taxa live in running waters, but some occur in lakes, on wet ground, in hot springs or in garden ponds. Diversity in the Nordic countries of Sweden and Finland seems to be somewhat higher (27 and 28 taxa, respectively) than in the central and southern parts of Europe (e.g. Austria 23, Belgium 22, Hungary 9, Poland 22, Slovakia 15, Switzerland 12 and Spain 20 taxa).

Circumscription of species in the genus Sirodotia (Batrachospermales, Rhodophyta) based on molecular and morphological data

Species level taxonomy and phylogeographical distribution patterns in the freshwater rhodophyte Sirodotia are resolved through phylogenetic inferences based on rbcL and cox2–3 sequence data. Previous studies focused on the taxonomy of specific Sirodotia species or the distributions across a limited geographical region. Our molecular phylogenies included samples attributable to five recognized Sirodotia species and include collections from Australia, Brazil, Costa Rica, Canada, Finland, Mexico, New Zealand, South Africa and the United States. Both rbcL and cox2–3 phylogenies inferred S. suecica, S. tenuissima and S. goebelii as a monophyletic group with little sequence divergence. This result supports the synonymy of S. tenuissima and S. goebelii with S. suecica (the species name with priority). Within this clade, samples collected from Australia and New Zealand formed a monophyletic group with no other discernible phylogeographical patterns within S. suecica. This result seems to be somewhat unusual in the Batrachospermales, as other species have shown greater genetic variation among geographically distant locations. As in previous studies, S. huillensis and S. delicatula were inferred as a separate species based on the rbcL phylogeny, supporting the current taxonomy. A specimen of S. aff. huillensis from South Africa, may represent a new species but further research is necessary before it can be designated as such.

Periphytic Diatoms in the Acidification Project Lakes

Periphytic diatoms growing attached on the solid substrata in the littoral are sensitive indicators of the recent water quality, especially of the water pH. In the most acid lakes planktonic diatoms are missing but periphytic diatoms can be still abundant in the littoral of these lakes. Periphytic diatom communities reflect besides the water pH and alkalinity also the content of organic matter in the water. Acidophilic and acidobiontic taxa dominated both in the clear- and brown-water lakes with zero or negative alkalinity (and low pH), whereas in lakes with positive alkalinity the periphytic diatom communities have higher species richness and the relative proportions of neutrophilic and alkaliphilic taxa are higher. Using K- means clustering eight community types were formed. The number of diatom taxa per sample decreased with decreasing water pH. For the interpretation of water pH by periphytic communities an equation was calculated:

Water quality of the River Vantaanjoki (South Finland) described using diatom indices

River water quality is monitored in Finland almost always by monitoring physical an d chemical parameters such as water transparency, colour and turbidity, concentrations of oxygen, nutrients and toxic compounds, and water pH. The hygienic state of the water is also measured as well as the chlorophyll a content of the seston. The system is developed primarily to describe lake water quality but is used with some modifications also for rivers (HEINONEN &. HERVE 1987). River monitoring and evaluation is, however, rather difficult when monitoring physical and chemical variables due to the rapid changes that can occur e.g. after short rainfall, when the concentrations may change in a small river system by one or two orders of magnitude in few hours. This wellknown fact is the main reason for using biological methods for river monitoring such as indices based on benthic fauna (e.g. WooDIWISS 1964, CHANDLER 1970) or on benthic algae (see e.g. WHIITON et al. 1991, WHIITON & Rorr 1996) which reflect water quality over longer periods.