Table 2.

Predicted and observed responses of macroinvertebrates to OA. Predictions are based on the generalized main conclusions of meta-analyses and reviews of physiological laboratory experiments [5,6,33]. Observed in situ responses are from the CO₂ seeps in PNG (this study), and the Mediterranean at a pH of more than 7.7 [8,10,11]. Thick arrows represent widespread responses from many taxa; thin arrows represent data from fewer taxa; direction of arrows represents increase (⇑, ↑), little difference (⇔, ↔) or decline/greater reduction (⇓, ↓).

	predicted response (laboratory)	observed in situ response (CO2 seeps)
		PNG	Mediterranean
decapod crustaceans	⇔ ↓	⇓	⇓
molluscs	↔ ⇓	⇔	⇔
echinoderms	↔ ⇓	↑ ⇔ ↓	↑ ⇓
polychaetes	↔ ↓	↔ ↓	↔ ⇓
ascidians	↑	⇓
mobile groups (cf. sessile groups)	⇑	⇓
calcifying groups (cf. non-calcifying groups)	⇓	⇔