MEPS 275:211-217 (2004)  -  doi:10.3354/meps275211

ABSTRACT: The impact of hypoxia upon predator-prey interactions between juvenile Mediterranean shore crabs Carcinus aestuarii and the mytilid Musculista senhousia was investigated in laboratory and mesocosm experiments. These species are among the most abundant macrobenthic organisms in the Sacca di Goro, a lagoon in the Po River deltaic system (Adriatic Sea, Italy). The effect of normoxia and hypoxia on juvenile C. aestuarii predatory behaviour was examined in laboratory experiments; factors were prey size (small, medium and large) and oxygen level (normoxic: >6.0 mg O₂ l^-1; moderately hypoxic: 3.0 to 1.5 mg O₂ l^-1; severely hypoxic: <1.5 mg O₂ l^-1). The prey-handling time of crabs was largely increased by hypoxia. In mesocosm experiments, 2 densities of M. senhousia (40 and 200 mussels tank^-1) were exposed to juvenile C. aestuarii (1 crab tank^-1) at 2 oxygen levels (normoxic: >6.0 mg O₂ l^-1; severely hypoxic: <1.5 mg O₂ l^-1). Consumption rates of C. aestuarii were lower under hypoxia, resulting in reduced mortality rates of mussels. Predation was inversely dependent. Short-term hypoxia, therefore, reduced the ability of crabs to forage on mussels efficiently and increased mussel survival, probably reducing the transfer of bivalve prey to predatory crabs.

KEY WORDS: Hypoxia · Predator-prey · Carcinus aestuarii · Musculista senhousia · Sacca di Goro