Answer:
the four types of chemical weathering are:
oxidation 
hydrolysis
hydration
carbonation
 
        
             
        
        
        
It's called hypoxemia, it's low levels of oxygen in the blood, to be more specific, it's oxygen loss in your blood from your arteries. It can cause respiratory disorders, and tissue hypoxia, as a result of the blood not providing much oxygen to your body.
I hope I helped :) 
        
             
        
        
        
Answer:
Explanation:
In a lake, oxygenic phototrophs produce new organic material as  well as O₂. If primary production rates are very high, the resultant  excessive organic matter production can lead to bottom-water O₂ depletion from respiration and the development of anoxic conditions.  This in turn stimulates anaerobic metabolisms, including  anaerobic respirations and fermentations.
Organic matter that is not  consumed in surface layers sinks to the depths and is decomposed  by anaerobes.