Different types, or isotopes, of oxygen exist in the ocean and are incorporated into the skeletal fragments of animals. What can the ratio of preserved isotopes tell us about climate?

The correct answer is - Certain ratios of oxygen reflect either warmer or cooler ocean temperatures.

Explanation:

Ocean have different isotypes or types of oxygen throughout the ocean and also incorporated in the shells of the marine animals of the particular region and time.

We can found out the climate and more particularly the temperature of the ocean as The more 18^O found in the shell or sediment of the animal, the colder the climate and vice versa, however, it is opposite in relation to that of glacier ice.

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.