Scientists have discovered a rare, ancient bacteria thriving on the ocean floor. this bacteria uses sulfur released by thermal vents, as well as dissolved oxygen and carbon dioxide in the water, to create sugar and break it down for energy. this process is called .

Chemosynthesis

Explanation:

All organisms make food either through photosynthesis or Chemosynthesis

.In this case bacteria are creating sugar (food) through all the course of activities mentioned here.  Bacteria that live deep under the ocean uses energy released by any chemical reaction to make food (sugar) for themselves.

The chemical reaction involved here is as follows -  

CO2 + 4H2S + O2 -> CH20 + 4S + 3H2O

estuaries are the partially enclosed coastal bodies of brackish water formed at the mouth of sea where river meets an ocean. it is a transition zone between river and sea water so estuaries are influenced to both marine environment such as tides, waves and to riverine such as flow of fresh water and sediments. the mixing of sea and fresh water provide high level of nutrients, making estuaries a high product habitats.

many estuaries suffers degradation from a variety of human activities like erosion from deforestation, overgrazing, overfishing, drainage and eutrophication.

so from the above statement answers will be

1. false as estuaries are formed due to both brackish and freshwater.

2.true, due to high productivity estuaries are breeding ground for many marine species.

3. direct and indirect activities of man that contribute to pollution and deposition of sediments.