Marine phytoplankton vary in their response to chlorinated hydrocarbons

Sensitivity of the green alga Pediastrum duplex Meyen to allelochemicals is strain-specific and not related to co-occurrence with allelopathic macrophytes

Interspecific differences in the response of microalgae to stress have numerous ecological implications. However, little is known of intraspecific sensitivities and the potential role of local genetic adaptation of populations. We compared the allelochemical sensitivity of 23 Pediastrum duplex Meyen strains, a common component of the freshwater phytoplankton. In order to test for local genetic adaptation, strains were isolated from water bodies with and without the allelopathically-active submerged macrophyte Myriophyllum. Strains were assigned to P. duplex on the basis of cell shape and colony morphology and only P. duplex strains that belonged to the same lineage in an ITS rDNA phylogeny were used. Inhibition of strain growth rates and maximum quantum yields of photosystem II were measured after exposure to tannic acid (TA) and co-culture with Myriophyllum spicatum. Growth rate inhibition varied over one order of magnitude between the P. duplex strains. There was no correlation between the presence of Myriophyllum in the source location and the sensitivity of the strains to TA or the presence of Myriophyllum, suggesting that at least strong unidirectional local adaptation to Myriophyllum had not taken place in the studied water bodies. The maximum quantum yield of photosystem II of TA exposed algae decreased, whereas the yield of algae exposed to M. spicatum was slightly higher than that of the controls. The ranking of P. duplex strain sensitivities differed between the types of exposure (single additions of TA versus co-existence with M. spicatum) and the parameter measured (growth rate versus maximum quantum yield), emphasizing the importance of measuring multiple traits when analysing strain-specific sensitivities towards allelochemicals. The observation that sensitivities to allelochemicals vary widely among strains of a single freshwater algal species should be taken into account if evaluating ecological consequences of allelopathic interactions.

Effects of two herbicidal wastewaters on Chlorella sp. and Phaeodactylum tricornutum

The effects on Chlorella sp. and Phaeodactylum tricornutum of two industrial wastewaters known to contain the herbicide residues of Trifluralin and Propanil have been determined by monitoring the number of cells, the chlorophyll fluorescence and the carbon dioxide assimilation simultaneously for a period of 14 days. The growth of the diatom, Phaeodactylum tricornutum, was inhibited by concentrations of herbicidal waste of the order of 0.1-0.5%, apparently because the rate of reproduction was reduced. Chlorella sp. cells, on the other hand, whilst dramatically inhibited by 1% concentrations of herbicidal waste, were able to recover over a period of 14 days. If discharged at concentrations below 0.01%, the industrial wastes appeared not to affect phytoplankton.

The cytology and biochemistry of pesticide microbiology

Widespread use of pesticides has no doubt benefited human beings in one way or another. However, their side effects on various organisms, including nontarget organisms, are largely overlooked. In the recent past, several studies have been done to assess the effects of pesticides on nontarget organisms, including microorganisms. Although pesticide effects on growth parameters of microorganisms have been extensively reviewed, little attention has been paid regarding their cytological and biochemical aspects. Therefore, the present work is mainly concerned with the cytological and biochemical aspects of pesticide microbiology. The effects of pesticides on photosynthesis, respiration, proteins, and nucleic acids are reviewed. Attention is also paid to their effects on cell morphology and morphogenesis and their effect on cell constituents.

Interaction of Endosulfan and malathion with blue-green algae Anabaena and Aulosira fertilissima

The growth of Anabaena and Aulosira fertilissima was adversely affected by endosulfan even at 1 microg ml(-1). The inhibition was significantly above 50% at 20 microg ml(-1) throughout the incubation. Anabaena survived up to 500 microg ml(-1) of malathion, but was completely bleached in the presence of 50 microg ml(-1) of endosulfan. Aulosira was more sensitive to malathion than Anabaena and recovered to control levels only at 10 microg ml(-1). The morphology and hetercyst frequency were not altered in Anabaena. Aulosira cultures were dull brown in colour at 20 microg ml(-1) of endosulfan with the filaments clumping, instead of the usual mat formation. Both malathion and endosulfan considerably lowered (14)C uptake and nitrogenase activities in Aulosira. Nitrogen fixation was unaffected in Anabaena as the amounts of ethylene produced were equal to, or above, control levels. The impact of these insecticides on photosynthesis in Anabaena was only slight.

Species-dependent variation in algal sensitivity to chemical compounds

Nineteen miscellaneous chemical compounds were tested on thirteen freshwater algal species grown in 250-microliter liquid cultures on plastic microtitration plates. It was demonstrated that the species-dependent variation in algal sensitivity (EC100) may reach over three orders of magnitude, the degree of variation depending on the chemical tested. No generally sensitive or generally insensitive species could be identified. An effort was made to quantify the predictive value of algal test batteries, at a given confidence level with respect to chemicals. The predictive value of small test batteries was low. Although it did increase with size it took the presence of more than nine members in the test batteries to improve the value to 0.1. This means that a nine-membered test battery might underestimate the sensitivity of the most susceptible algae by a factor of 0.1. A predictive value of 0.01 requires a three-membered test battery when accounting for 95% of the chemicals and a five-membered battery at the 99% confidence level. Implications for toxicity test strategies are discussed and it is suggested that algal test batteries, using simple test techniques, replace single unialgal cultures in routine work.

Chlorinated hydrocarbon pollutants and photosynthesis of marine phytoplankton: a reassessment

The chlorinated hydrocarbons DDT and PCB's (polychlorinated biphenyls), ubiquitous pollutants of the marine environment, have been observed to reduce the cell division rate of marine phytoplankton, thereby indirectly reducing the total photosynthetic carbon fixation in treated cultures. The photosynthetic capacity of each cell was not affected. Total marine photosynthesis will likely remain undiminished by these compounds, although alterations in phytoplankton communities through selective toxicity could effect herbivore populations.

Effects of PCB on interspecific competition in natural and gnotobiotic phytoplankton communities in continuous and batch cultures

The toxicity of polychlorinated biphenyls (PCB) to the diatomThalassiosira pseudonana (formerlyCyclotella nana), grown in pure and mixed cultures, was greatest when in competition with other species. Continuous cultures were superior to batch cultures for studying competitive interactions, and PCB caused greater alteration of species composition in continuous cultures than it did in batch cultures. Natural phytoplankton communities from Vineyard Sound, maintained in continuous culture, responded to PCB stress the same as did gnotobiotic communities, withT. pseudonana showing similar responses in both communities.A PCB concentration of 0.1 μg/liter (0.1 part per billion), a level not uncommon in natural waters, did not affect algal growth in pure cultures but caused substantial disruption of continuous culture communities. The possible impact of PCB pollution on natural phytoplankton communities is discussed.

DDT: inhibition of sodium chloride tolerance by the blue-green alga Anacystis nidulans

Anacystis nidulans, a freshwater blue-green alga, has been found to lerate sodium chloride (1 percent by weight) and DDT [1,1,1-trichloro-2,2-bis chlorophenyl) ethane] (800 parts per billion) separately, but growth was inhibited in the presence of both compounds. This inhibition was reversed by an increased calcium concentration. It is possible that inhibition of (Na+,K+)-activated adenosine triphosphatase) by DDT causes this species to lose the ability to lerate sodium chloride.

Polychlorinated biphenyls and DDT alter species composition in mixed cultures of algae

Either DDT or polychlorinated biphenyls were added to mixed cultures containing a marine diatom and a marine green alga that were sensitive and resistant, respectively, to these organochlorine compounds. The diatom grew faster and was therefore dominant in control cultures, but its dominance diminished in treated cultures, even at concentrations of chlorinated hydrocarbons that had no apparent effect in pure cultures. Such stable pollutants could disrupt the species composition of phytoplankton communities, thereby affecting whole eco-systems.

Polychlorinated biphenyls: toxicity to certain phytoplankters

The growth rates of two species of marine diatoms were reduced by polychlorinated biphenyls (PCB's), widespread pollutants of the marine environment, at concentrations as low as 10 to 25 parts per billion. In contrast, a marine green alga and two species of freshwater algae were not inhibited at these or higher concentrations. The sensitivity of these species to PCB's paralleled their sensitivity to DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane].

Primary production: Depression of oxygen evolution in algal cultures by organophosphorus insecticides

Photosynthesis of four estuarine phytoplankters was inhibited by Baytex and Abate (organophosphates), Baygon (carbamate) and DDT (chlorinated hydrocarbon). Responses varied with the algal species and with the insecticide. The order from most to least toxic insecticide was Baytex, Baygon, DDT, Abate and the order from least to most sensitive alga wasC. nana,P. cornutum=S. costatum,D. euchlora.