Assertion : Oceans are a low productivity ecosystems despite occupying about 70% of the earth's surf

Question

Assertion : Oceans are a low productivity ecosystems despite occupying about 70% of the earth's surface.\ Reason: In aquatic ecosystems, productivity is limited by light which decreases with increasing water depth.\

Professor PC Thomas Classes · Answer

(a) : Productivity levels of an ecosystem depend upon plant species inhabiting a particular area, their photosynthetic capacity, availability of nutrients, sunlight, moisture and a variety of other environmental factors. The annual net primary productivity of the whole biosphere is approx. 170 billion tons (dry weight) of organic matter. Of this, despite occupying about $70 \%$ of earth's surface, oceans contribute only $32 \%$ of the total productivity ( 55 billion tons out of 170 billion tons). Thus, oceans are a low productivity ecosystems. It is because in oceans, productivity is limited by light which decreases with increasing depth.