Low-Level Dissolved Oxygen and pH Environmental Effects on the Early Development of California's Most Lucrative Commercial Fishery Species, Doryteuthis opalescens, the Market Squid

Spawning aggregations of market squid can cover the benthos with “beds” of capsules.  Increased upwelling, ENSO frequency, and other environmental conditions associated with climate change sometimes work together to shoal oxygen minimum zone waters to depths < 90 m, exposing embryos to low levels of dissolved oxygen (DO) and pH.  We hypothesized that low DO (90 µmol/kg) and pH (7.5) levels affect squid embryonic development.  In the laboratory, squid embryos were initially exposed to two treatments at a constant temperature (11 °C): one with low levels of DO and pH (90 µmol/kg, pH=7.5) and the other with “normal” levels (i.e. DO=240 µmol/kg, pH=7.9).  At the end of the experiment, squid were photographed, morphometric data were collected using imagej™ software, and JMP ™ software was used for statistical analysis. Low DO and pH caused significant slowing of embryogenesis, delaying development by approximately 5-7 days.  A second experiment, imposing low DO and pH separately, suggests that DO is responsible for most of the observed developmental delays. These delays may exert carry-over effects into the paralarval stage such as match-mismatch in timing of their hatching with availability of their prey, zooplankton, during their critical period of first feeding.  If so, suitable habitat for market squid embryogenesis may be significantly compressed with only the most shallow areas (<20 m depth) producing paralarvae able to find adequate food for survival.   Ongoing studies are using samples from these studies to investigate physiological effects on embryos and geochemical changes in statolith elemental composition during embryogenesis.