Contrasting effects of hypoxic conditions on survivorship of planktonic larvae of rocky intertidal invertebrates

Hypoxia is increasing in coastal zones worldwide, with acute effects on demersal fish and benthic invertebrate communities in shallow coastal and estuarine habitats. Less studied are the effects of hypoxia on planktonic larvae of open coastal habitats. Climate change projections suggest intensified hypoxia in open coast upwelling systems, such as the northern California Current Upwelling System, where there has been a recent rise of seasonally persistent inner-shelf hypoxia (dissolved oxygen [DO] < 1.43 ml l−1) and anoxia (DO 0 ml l−1). We examined survivorship of larval invertebrates exposed to low oxygen conditions in controlled laboratory experiments. Multiple-day hypoxic conditions, resembling DO levels in nearshore Oregon waters, were generated by bubbling seawater with nitrogen gas. Tolerance levels among species varied, from larvae of species with little tolerance to hypoxia (e.g. the shore crab Hemigrapsus oregonensis) to species with high tolerance (e.g. the California mussel Mytilus californianus). These contrasting responses among open-coast intertidal taxa suggest that chronic hypoxia or anoxia may have different effects on recruitment success among species and, consequently, on the structure and species composition of open coast intertidal communities.