Aquatic biogeochemistry — The Redfield ratio refers to the canonical stoichiometric proportions of which elements in planktonic biomass and seawater nutrients?

Introduction / Context:
The Redfield ratio is a foundational concept in oceanography and microbial ecology. It describes the average elemental composition of marine organic matter and the corresponding dissolved nutrients, linking microbial growth to nutrient cycles and primary productivity.

Given Data / Assumptions:

• The classical Redfield atomic ratio for plankton biomass is approximately C:N:P = 106:16:1.
• The question asks which set of elements are represented by this ratio, not the numeric values themselves.
• We focus on macronutrients driving biomass formation and nutrient limitation.

Concept / Approach:
Recall that the Redfield ratio addresses carbon (C), nitrogen (N), and phosphorus (P) in plankton and seawater. Hydrogen and oxygen are abundant in water and organic molecules but are not the limiting nutrient focus. Potassium and iron are important but are not in the classic Redfield triplet (iron often discussed in micronutrient limitation, but separately).

Step-by-Step Solution:

Verification / Alternative check:
The Redfield C:N:P of 106:16:1 emerges from global datasets of plankton and deep ocean nutrients, widely cited in marine biogeochemistry.

Why Other Options Are Wrong:

• Carbon, hydrogen, oxygen: not the Redfield nutrient focus.
• Nitrogen, potassium, iron: important nutrients, but not the Redfield trio.
• Carbon, phosphorus, sulfur: sulfur not part of the classical Redfield ratio.

Common Pitfalls:
Confusing macro- with micronutrient ratios or mixing in trace metals like iron, which are studied under separate limitation frameworks.

Final Answer:
carbon, nitrogen and phosphorous