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Lower pH kills spirorbids but favors sponges

A 0.2-unit drop in seawater pH over 100 days thins calcareous tube worms and algae while sponges and some sea squirts increase.

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What pH treatments were compared?

Ambient pH 7.9 versus lowered pH 7.7 at 23°C.

How long did the community trials last?

100 days, covering multiple generations of the commonest species.

Which taxon initially dominated precolonized pipes?

The spirorbid polychaete Neodexiospira pseudocorrugata (79.5–92.6% of individuals).

What happened to live spirorbid density at pH 7.7?

It fell from 11.1 to 2.0 individuals per 10 cm².

What fraction of spirorbids were dead at the end of low-pH trials?

72.8%, versus 23.3% in pH 7.9 controls.

Which taxa increased at low pH?

Leucosolenia sponges (2.5-fold) and Molgula ascidians (fourfold); Aplidium declined.

Was carbonate mineral undersaturation required for the community shift?

No; calcite and aragonite stayed saturated at pH 7.7.

How did new-surface spirorbid colonization change at low pH?

Densities fell nearly sixfold on tank walls, 3.5-fold on pipe, and nearly fivefold on tiles.

What happened to algal films on new HDPE pipe?

Visual colonization scores dropped from 4.4 to 1.8.

Where was the source community collected?

Ria Formosa Lagoon, southern Portugal.

How did low-pH spirorbid tubes look under SEM?

Frequently breached, revealing internal structures, unlike smooth control tubes.