Looks like little spots of mold mildew to me.
What are the black spots on my outdoor patio carpet.
Wet and humid conditions can cause algae to spout and spread quickly in an outdoor carpet.
That being said outdoor carpet is an ideal place for mold moss and mildew to attach themselves.
Green stains clean up in 1 2 weeks black stains and moss clean up within a few months.
Green algae black mold and moss begin to die off on contact.
The combination of the wind and the rain breakdown the growth and rinse your surfaces clean over time.
Wet and forget is as simple as spraying your outdoor surface and forgetting it.
It can be more than unsightly.
Outdoor carpet adds a decorative element to cement porches and patios but the flooring is also affected by weather which could result in algae formation.
It can be unsanitary as well.
I would try a product called wet forget outdoor i think i initially read about this product here on home tallk.
Fortunately mold and mildew are easy to clean up.
It is constructed of a pet fiber made with up to 100 recycled post consumer purified plastic bottles and offers superior wear and fade resilience even in direct sunlight.
Resistant to staining and uv damage the elevations resistant to staining and uv damage the elevations carpet is a great fit for either indoor or outdoor spaces.