UC San Diego

Increases in water precipitation and ocean acidification___consequences of climate change and CO2 emissions___affects the physiology and behavior of marine invertebrates. We postulated changes would occur in nervous system-controlled predator defense mechanisms, including bioluminescence, arm regeneration, and neuro-coordination abilities, such as the ability to return to upright after being flipped upside down. This hypothesis was tested by exposing the luminous brittlestar Amphipholis squamata (Echinodermata) to conditions of lower pH (pH 7.7, from pH 7.9), lower salinity (25 PSU, from 33 PSU), and lower pH and salinity combined. Exposure to the changes in experimental seawater chemistry for up to 7 weeks resulted in slower flipping times in the low salinity and in the low pH treatments and in high levels of leaking light in their bioluminescence response. These results indicated a negative effect on the neuro-muscular coordination and possibly the neuro-control of the light production. Brittlestar arms exposed to lower pH and salinity conditions experienced stunted regenerative growth, evidenced by shorter and narrower regenerative arm tips that were also less calcified. Brittlestars demonstrated difficulty expressing normal (control) predator defense functions following a 7-week exposure to low salinity conditions suggesting long term exposure resulted in prolonged effects on maintenance and repair mechanisms sustaining the brittlestar defense strategies. These data suggest compensatory energy reallocation toward maintaining normal function of other vital processes under stress. Quantifying the brittlestars behavioral and physiological responses can provide a clue for how their survivability will be impacted under projected low pH and low salinity conditions in the future.