Clearance rates of two batches (1 and 2) of cultured G. childressi mussels filtering phytoplankton. Batch 1 mussels ('small': 51 ± 3 mm SD, 'large': 77 ± 4 mm SD) received either Rhodomonas or Nannochloropsis cells. Batch 2 mussels from were cultured under different nutritional treatments (CH4: 'M', algae + CH4: MA', only algae: 'A'). The measurement of clearance rates of batch 2 G. childressi cultured in the 'A' treatment (without CH4 supply) was conducted twice: once while mussels were placed in CH4-enriched seawater, and, subsequently, once without CH4.