On 21 May 2014 an article appeared in Science News Magazine about didymo blooms. This analysis is an example of a possible abduction outline from this article.

Initial Observation

An initial observation is that didymo blooms occur.

Preliminary Conditions

There are two theories posed to explain how didymo blooms occur:

A₁: Invasion. Didymosphenia geminata (didymo), a foreign or a mutant alga agressively invades clean watersheads resulting in the blooms.
A₂: Environmental. Didymo is native to much of the globe, and that changes in water conditions are to blame for the blooms.

Each of the theories could explain the initial observation (as described above).

Both of these theories satisfy at least half of the criteria for a scientific theory and therefore have scientific merit as is shown by the following tables (the criteria, #1, #2, etc., is given in a previous section).

Criteria	Condition Met?	Rationale for the Invasion Theory
#1	yes	The theory is not complicated and has no inconsistencies
#2	yes	No fundamental principles are violated.
#3	yes	This theory explains the initial observation.
#4	yes	The theory applies to the area of investigation and does not go far beyond.
#5	yes	Competent, well-known researchers put forward the theory.
#6	no	No information about this.
#7	no	No math is mentioned.
#8	yes	No outside agenda is known.

Criteria	Condition Met?	Rationale for the Environmental Theory
#1	yes	The theory is not complicated and has no inconsistencies
#2	yes	No fundamental principles are violated.
#3	yes	This theory explains the initial observation.
#4	yes	The theory applies to the area of investigation and does not go far beyond.
#5	yes	Competent, well-known researchers put forward the theory.
#6	no	Not known.
#7	no	Not known.
#8	yes	No outside agenda is known.

Data

D₁: Didymo blooms have cropped up in rivers worldwide.
D₂: Didymo has been in most of the bloom locations for decades, if not centuries.
D₃: Blooms after 2004 occur only when a river’s phosphorus levels drop extremely low.
D₄: New Zealand rivers hit by didymo had low phosphorus long before the 2004 blooms.

Evaluation Chart

	Invasion	Environmental
D1	yes	yes
D2	no	yes
D3	no	yes
D4	yes	no

Result

From this data (Invasion - 2, Environmental - 3), the environmental theory would be the better theory between these two options.