Oxidative effects of the harmful algal blooms on primary organisms of the food web

Degraded water quality from nutrient pollution,physical,biological,and other chemical factors contributes to the development and persistence of many harmful algal blooms(HAB s).The complex dynamics of the HAB s is a challenge to marine ecosystems for the toxic effects reported.The consequences include fish,bird,and mammal mortality,respiratory or digestive tract problems,memory loss,seizures,lesions and skin irritation in many organisms.This review is intended to briefly summarize the recent reported information on harmful marine toxin deleterious effects over the primary organisms of the food web,namely algae,zooplankton and invertebrates.Special focus is made on oxidative stress status of cells and tissues.Even though in situ field research is less controlled than laboratory studies,in which the organisms are directly exposed to the toxins under consideration,both types of approaches are required to fully understand such a complex scenario.On top of that,the contribution of the increasing water temperatures in the sea,as a consequence of the global climate change,will be addressed as a topic for further studies,to evaluate the effect on regulating algal growth,species composition,trophic structure,metabolic stress and function of aquatic ecosystems.

Oxidative stress in the hydrophilic medium of algae and invertebrates

The harmful effects of the reactive species may be due to the increase in their steady state concentration either by the enhancement of their production rates and/or the decrease of their consumption rate by antioxidant activity.The ascorbyl radical(A^(·))can be considered as a final product of radical oxidative transformations of ascorbate(AH^(-)).The ratio A^(·)content/AH^(-)content(A^(·)/AH^(-))has been widely used as an interesting tool to estimate mild to moderate oxidative transformations,providing a quick and simple method of diagnosis of stress in the hydrophilic cellular medium.The aim of this work was to summarize studies on the cellular oxidative condition in algae and invertebrates by assessing the A^(·)/AH^(-)ratio under environmentally changing conditions.The use of indices of oxidative stress increasingly sensitive and,somewhat more specific,can bring a new light to the still unknown world of oxidative responses in marine organisms.