Edna Granéli

Ecology of harmful algae

Part A Harmful Algae and Their Global Distribution 1 An Introduction to Harmful Algae E. GRANELI and J.T. TURNER References 2 Molecular Taxonomy of Harmful Algae S. JANSON and P.K. HAYES 2.1 Introduction 2.2 Dinophyta (Dinoflagellates) 2.2.1 General Morphology 2.2.2 Dinophysis 2.2.3 Alexandrium 2.2.4 Protoperidinium, Prorocentrum 2.2.5 Karenia, Karlodinium, Takayama 2.2.6 Amphidinium, Cochlodinium, Gyrodinium 2.3 Cyanobacteria (Blue-Green Algae) 2.3.1 Anabaena, Aphanizomenon, Nodularia 2.3.2 Microcystis 2.3.3 Trichodesmium 2.4 Bacillariophyta (Diatoms) 2.4.1 Amphora, Pseudo-nitzschia, Nitzschia 2.5 Concluding Remarks References 3 The Biogeography of Harmful Algae N. LUNDHOLM and O. MOESTRUP 3.1 Biogeography and Species Concepts 3.1.1 Genetic Variation 3.2 Biogeographical Distribution 3.3 Distribution of Harmful Species 3.3.1 Dinoflagellates 3.3.2 Diatoms 3.3.3 Haptophytes 3.3.4 Raphidophyceans 3.3.5 Cyanobacteria References 4 Importance of Life Cycles in the Ecology of Harmful Microalgae K.A. STEIDINGER and E. GARCES 4.1 Introduction 4.2 Phases of Phytoplankton Bloom Development and Life Cycles 4.2.1 Initiation 4.2.2 Growth and Maintenance 4.2.3 Dispersal/Dissipation/Termination 4.3 Environmental Factors versus Biological Factors Affecting Transition 4.4 Status of Knowledge and Direction Needed References Part B The Ecology of Major Harmful Algae Groups 5 The Ecology of Harmful Dinoflagellates J.M. BURKHOLDER, R.V. AZANZA, and Y. SAKO 5.1 Introduction 5.2 GeneralEcology 5.2.1 Motility 5.2.2 Temperature, Light, Salinity and Turbulence 5.2.3 Nutrition: the Continuum from Auxotrophy to Parasitism 5.3 Blooms, Including Toxic Outbreaks 5.4 Human Influences 5.5 Conceptual Frameworks to Advance Understanding References 6 The Ecology of Harmful Flagellates Within Prymnesiophyceae and Raphidophyceae B. EDVARDSEN and I. IMAI 6.1 Introduction 6.2 Class Prymnesiophyceae (Division Haptophyta) 6.2.1 Taxonomy, Morphology and Life History 6.2.2 Distribution and Abundance 6.2.3 Autecology and Ecophysiology 6.2.4 Toxicity and Toxins 6.2.5 Ecological Strategies 6.3 Class Raphidophyceae (Division Heterokontophyta) 6.3.1 Taxonomy, Morphology and Life History 6.3.2 Distribution and Abundance 6.3.3 Autecology and Ecophysiology 6.3.4 Toxicity 6.3.5 Ecological Strategies References 7 The Ecology of Harmful Diatoms S.S. BATES and V.L. TRAINER 7.1 Introduction 7.2 Toxin-Producing Diatoms, Genus Pseudo-nitzschia 7.3 Domoic Acid in the Marine Food Web 7.4 Physiological Ecology of Pseudo-nitzschia spp 7.5 Molecular Tools for Studying Pseudo-nitzschia 7.6 Conclusions and Directions for Future Research References 8 Ecology of Harmful Cyanobacteria H.W. PAERL and R.S. FULTON III 8.1 Introduction 8.2 Environmental Factors Controlling CyanoHABs 8.2.1 Nutrients 8.2.2 Physical-Chemical Factors: Salinity and Turbulence 8.2.3 Salinity and Turbulence 8.3 CyanoHAB Interactions with Micro/Macroorganisms 8.4 CyanoHAB Management References 9 Brown Tides C. J. Gobler and W. G. Sunda 9.1 Background 9.2 Nutrients and Physical Factors 9

Allelopathy in phytoplankton - biochemical, ecological and evolutionary aspects

Abstract It is considered self-evident that chemical interactions are a component of competition in terrestrial systems, but they are largely unknown in aquatic systems. In this review, we propose that chemical interactions, specifically allelopathy, are an important part of phytoplankton competition. Allelopathy, as defined here, applies only to the inhibitory effects of secondary metabolites produced by one species on the growth or physiological function of another phytoplankton species. A number of approaches are used to study allelopathy, but there is no standard methodology available. One of the methods used is cross-culturing, in which the cell-free filtrate of a donor alga is added to the medium of the target species. Another is to study the effect of cell extracts of unknown constituents, isolated exudates or purified allelochemicals on the growth of other algal species. There is a clear lack of controlled field experiments because few allelochemicals have been identified. Molecular methods will be important in future to study the expression and regulation of allelochemicals. Most of the identified allelochemicals have been described for cyanobacteria but some known toxins marine dinoflagellates and freshwater cyanobacteria also have an allelochemical effect. The mode of action of allelochemicals spans a wide range. The most common effect is to cause cell lysis, blistering, or growth inhibition. The factors that affect allelochemical production have not been studied much, although nutrient limitation, pH, and temperature appear to have an effect. The evolutionary aspects of allelopathy remain largely unknown, but we hypothesize that the producers of allelochemicals should gain a competitive advantage over other phytoplankton. Finally, we discuss the possibility of using allelochemicals to combat harmful algal blooms (HABs). Allelopathic agents are used for biological control in agriculture, e.g. green manures to control soil diseases in Australia, but they have not yet been applied in the context of HABs. We suggest that phytoplankton allelochemicals have the potential for management of HABs in localized areas.

Positive feedback and the development and persistence of ecosystem disruptive algal blooms

Harmful algal blooms (HABs) have occurred with increasing frequency in recent years with eutrophication and other anthropogenic alterations of coastal ecosystems. Many of these blooms severely alter or degrade ecosystem function, and are referred to here as ecosystem disruptive algal blooms (EDABs). These blooms are often caused by toxic or unpalatable species that decrease grazing rates by planktonic and benthic herbivores, and thereby disrupt the transfer of nutrients and energy to higher trophic levels, and decrease nutrient recycling. Many factors, such as nutrient availability and herbivore grazing have been proposed to separately influence EDAB dynamics, but interactions among these factors have rarely been considered. Here we discuss positive feedback interactions among nutrient availability, herbivore grazing, and nutrient regeneration, which have the potential to substantially influence the dynamics of EDAB events. The positive feedbacks result from a reduction of grazing rates on EDAB species caused by toxicity or unpalatability of these algae, which promotes the proliferation of the EDAB species. The decreased rates also lower grazer‐mediated recycling of nutrients and thereby decrease nutrient availability. Since many EDAB species are well‐adapted to nutrient‐stressed environments and many exhibit increased toxin production and toxicity under nutrient limitation, positive feedbacks are established which can greatly increase the rate of bloom development and the adverse effects on the ecosystem. An understanding of how these feedbacks interact with other regulating factors, such as benthic/pelagic nutrient coupling, physical forcing, and life cycles of EDAB species provides a substantial future challenge.

Increase in the production of allelopathic substances by Prymnesium parvum cells grown under N- or P- deficient conditions

Increase in the production of allelopathic substances by Prymnesium parvum cells grown under N- or P- deficient conditions

Influence of different nutrient conditions on cell density, chemical composition and toxicity of Prymnesium parvum (Haptophyta) in semi-continuous cultures

Abstract The influence of various nitrogen (N) and phosphorus (P) levels on the cell density, chemical composition and toxicity of the marine haptophyte Prymnesium parvum were studied. A non-axenic strain of P. parvum was grown in semi-continuous cultures under either N- or P-limited conditions or nutrient-sufficient conditions (N:P=1:1, 160:1 and 16:1, respectively). Cell toxicity was measured on two occasions at steady state using a haemolytic test. Haemolytic activity was determined as saponin nano-equivalents (SnE) and HE 50 (50% haemolysis). Haemolytic activity was demonstrated in all treatments. However, haemolytic activity was significantly higher in P. parvum cells grown under N- or P-limited conditions (287.7±14.0 and 256.8±38.1 SnE cell −1 , respectively) compared to cells grown under non-limiting conditions (42.4±3.3 SnE cell −1 ). Our results document, for the first time, enhanced haemolytic activity in P. Parvum cells irrespective of which nutrient (N or P) was limiting growth. Our results suggest that the toxicity of P. parvum is related to cellular physiological stress, due to nutrient limitation rather than to the direct involvement of either N or P in toxin synthesis.

Allelopathy in harmful algae : A mechanism to compete for resources?

Some phytoplankton species produce and release secondary metabolites that negatively affect the growth of other organisms; i.e., they are allelopathic (e.g., Rizvi and Rizvi 1992). The production of such allelopathic chemicals by phytoplankton is known among several different algal groups: cyanobacteria, dinoflagellates, prymnesiophytes, and raphidophytes (Table 15.1). Some reports suggest that allelochemicals are also produced in diatoms and green algae (e.g., Subba Rao and Smith 1995; Chiang et al. 2004). A comprehensive list of freshwater and marine algae suspected of production of allelopathic substances was compiled by Legrand et al. (2003). In this chapter, we focus on unicellular organisms (protists and cyanobacteria) as target cells, because many so-called phytoplankton cells actually are mixotrophic or heterotrophic, and because many so-called protozoa functionally are mixotrophic. This requires that we address the negative effects of allopathic marine phytoplankton on both competitors and grazers.

Chemical composition and alkaline phosphatase activity of nutrient-saturated and P-deficient cells of four marine dinoflagellates

Four marine dinoflagellates, Amphidinium carterae Hulburt, Ceratium tripos (O.F. Mull.) Nitzsch, Prorocentrum minimum (Pav.) J. Schiller, and Scrippsiella trochoidea (Stein) Loeblich III were grown ...

The response of planktonic and microbenthic algal assemblages to nutrient enrichment in shallow coastal waters, Southwest Sweden

Abstract Field and laboratory nutrient (nitrogen and phosphorus) enrichment experiments were performed using natural phytoplankton and microphytobenthic assemblages from the brackish water Oresund, S.W. Sweden. The response of algae from a low-nutrient area (Falsterbo Canal) was compared to that of algae from a polluted, nutrient-rich area (Lomma Bay). The biomass (measured as chlorophyll a ) of both phytoplankton and microphytobenthos from the Falsterbo Canal increased after the addition of nitrogen. Phytoplankton growth was stimulated by the addition of phosphorus to the nitrogen-rich water of the polluted Lomma Bay. Sediment chlorophyll a showed no significant increase after the addition of nutrients in the Lomma Bay. In containers without sediment, phytoplankton uptake was calculated to account for ≈ 90% of the disappearance of inorganic fixed nitrogen from the water. In the sediment containers the microphytobenthos was estimated to account for ≈20% of the nitrogen uptake. The rest was presumably lost mainly through denitrification. When containers with microphytobenthos from Lomma Bay were kept in the dark, phosphorus was released at a rate of up to ≈ 180 μM · m −2 · day −1 . We suggest that by producing oxygen microbenthic algae keep the sediment surface oxygenated thereby decreasing phosphorus transport from the sediment to the overlying water.

Dinophysis blooms in the deep euphotic zone of the Baltic Sea: do they grow in the dark?

In situ growth rates of the toxin-producing dinoflagellate Dinophysis norvegica collected in the central Baltic Sea were estimated during the summers of 1998 and 1999. Flow cytometric measurements of the DNA cell cycle of D. norvegica yielded specific growth rates (μ) ranging between 0.1 and 0.4 per day, with the highest growth rates in stratified populations situated at 15–20 m depth. Carbon uptake rates, measured using 14C incubations followed by single-cell isolation, at irradiances corresponding to depths of maximum cell abundance were sufficient to sustain growth rates of 0.1–0.2 per day. The reason for D. norvegica accumulation in the thermocline, commonly at 15–20 m depth, is thus enigmatic. Comparison of depth distributions of cells with nutrient profiles suggests that one reason could be to sequester nutrients. Measurements of single-cell nutrient status of D. norvegica, using nuclear microanalysis, revealed severe deficiency of both nitrogen and phosphorus as compared to the Redfield ratio. It is also possible that suitable prey or substrate for mixotrophic feeding is accumulating in the thermocline. The fraction of cells containing digestive vacuoles ranged from 2 to 22% in the studied populations. Infection by the parasitic dinoflagellate Amoebophrya sp. was observed in D. norvegica in all samples analysed. The frequency of infected cells ranged from 1 to 3% of the population as diel averages, ranging from 0.2 to 6% between individual samples. No temporal trends in infection frequency were detected. Estimated loss rates based on observed infection frequencies were 0.5–2% of the D. norvegica population daily, suggesting that these parasites were not a major loss factor for D. norvegica during the periods of study. (Less)

Effects of river water of different origin on the growth of marine dinoflagellates and diatoms in laboratory cultures

The hypothesis that acid humic-rich river water selectively favours dinoflagellates in comparison to diatoms in coastal waters was tested in two sets of laboratory experiments using unialgal cultures of marine phytoplankton. In the first experiment, three dinoflagellates, i.e., Prorocentrum minimum (Pav.) J. Schiller, P. micans Ehrenberg and Amphidinium carterae Hulburt, and three diatoms, i.e., Attheya decora T. West, Skeletonema costatum (Grev.) Cleve and Phaeodactylum tricornutum Bohlin, were grown in a mixture of 80% coastal (S 20%.) and 20% river water. Water from seven different rivers was used. Four rivers had a high humic content (yellow substance 22.1 ± 0.9 · m−1) but lower inorganic N and P concentrations (“forest rivers”) while three rivers (“agricultural rivers”) had a lower humic content (10.7 ± 1.3 · m−1) but inorganic nutrient concentrations approximately three times as high as the forest rivers. The growth rates for the dinoflagellates were significantly higher in the medium with forest river water compared to the mixtures with agricultural river water while the opposite was true for the diatoms. In the second type of experiment, the diatom Ditylum brightwellii (T. West) Grun and the dinoflagellate P. minimum were grown, as semicontinuous dilution cultures, in mixtures of 90% coastal water (S 20%.) and 10% river water. Water from four different rivers was used, one draining mainly agricultural soils and the other acidified humic-rich forested soils. River water of agricultural origin supported a higher D. brightwellii biomass and growth rate than river water draining forested soils while for P. minimum the opposite was true. Decreasing cell P quotas and increasing alkaline phosphatase activity indicated that D. brightwellii was P-deficient, especially when agricultural river water was added, while these physiological indices suggested that P. minimum cultures were not P-starved. Our results support the hypothesis that the discharge of acidified river water, rich in humic substances, to coastal waters, can play a role in shifting the species composition from diatoms to dinoflagellates.