Plankton, toxicity studies

This book presents information on evaluating sediment contamination and its effects on aquatic ecosystems. Contents include effective assessment methods effects on marine and fresh water benthos, plankton, and fish defining physical and chemical habitat conditions bioavalability influencing factors biomarkers acute and chronic toxicity study design collection methods and EPA management strategies. 

If the chemical composition of the samples is known or at least partly known (in a stepwise TIE approach) or existing data allow for QSAR calculation, the samples can be ranked by TUs. Arts et al. (2006) studied, in 12 outdoor ditch mesocosms, the effects of sequential contamination with 5 pesticides in a regression design. They applied dosages equivalent with 0.2%, 1%, and 5% of the predicted environmental concentration (PEC) subsequently over 17 weeks. Endpoints recorded over 30 weeks included community composition of macroinvertebrates, plankton, and macrophytes, and leaf litter decomposition as functional ecosystem parameters. TUs were calculated in relation to acute toxicity data for the most sensitive standard species Daphnia magna and Lemna minor. Principal response curves (PRCs), a special form of constrained PCA, and Williams test (NOEC, class 2 LOEC) were used to identify the most sensitive taxa. Next to direct effects on certain species, also indirect effects, for example, how the change in abundance of a sensitive species affects the abundance of another, more tolerant species, can be detected only in mesocosm or in situ experiments. All observed effects were summarized in effect classes in a descriptive manner. 

More immediate goals differ from one scientific discipline to another. One goal of which I am most aware is the prediction of the role of aqueous speciation on the bioavailability and toxicity of trace elements to plankton and estuarine detritusfeeding invertebrates. In the longer range, these studies would be extended to include the various aquatic organisms higher in the... 

Studies on plankton and conditions favoring its proliferation with a view to predict when toxic marine blooms are going to take place and to detect as early as possible their existence (red tides). 

Studies investigating the effects of pesticides on crustaceans should be of high priority. Crustaceans are very important consumers and prey in various aquatic systems and there are delicate relationships between crustacean plankton prey and fish predators in the pelagic zone that can and have been shown to be disturbed. It is known that pesticides are present in surface waters and it is especially urgent to study the effects of insecticides on freshwater species and species that are present in estuaries and coastal waters with high risks of contamination due to vicinity to the sources. In acute toxicity tests crustaceans were much more (often 10-times more) sensitive to insecticides than fish (Maltby et al. 2005), and some of the chemicals probably affect behaviors at very low concentrations. As there are very few studies done on pesticide effects on crustacean chemoreception it is not possible to compare their sensitivity with fish, but it is likely that there are differences. The few crustaceans studied concerning effects of copper indicate that they are less sensitive to the metal compared with fish. 

Studies have been carried out on a number of animals, particularly species of crab, lobster and zooplankton, and on the in vivo metabolism of a wide range of xenobiotics. Cytochrome P-450 and the MFO system, and to a lesser extent glutathione S-transferase, have been characterized most. Much less is known of other enzymes and of mechanisms of xenobiotic activation and toxicity. Aspects reviewed include cytochrome P-450 monooxygenases (Bend et al. 1981 James 1989b), and petroleum hydrocarbon metabolism in marine plankton (Corner 1978). 

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