Give some examples of why it is important to understand how ocean currents flow

Explanation:

Winds, water density, and tides all drive ocean currents. Coastal and sea floor features influence their location, direction, and speed. Earth's rotation results in the Coriolis Effect which also influences ocean currents

it is given that trillions of microbes make up to 1% to 3% of the body mass.

let's take average of this percentage: 2%

consider the average mass of the human body as 70 kg.

then, trillions of microbes would have mass  

therefore, 100 trillion micro-organisms would weigh:

this is an approximate value and could change depending on the mass of the human body and percentage of the microbes present in it.

average mass per microorganism =