Chris Lovera

Use of a Free Ocean CO2 Enrichment (FOCE) System to Evaluate the Effects of Ocean Acidification on the Foraging Behavior of a Deep-Sea Urchin

The influence of ocean acidification in deep-sea ecosystems is poorly understood but is expected to be large because of the presumed low tolerance of deep-sea taxa to environmental change. We used a newly developed deep-sea free ocean CO2 enrichment (dp-FOCE) system to evaluate the potential consequences of future ocean acidification on the feeding behavior of a deep-sea echinoid, the sea urchin, Strongylocentrotus fragilis. The dp-FOCE system simulated future ocean acidification inside an experimental enclosure where observations of feeding behavior were performed. We measured the average movement (speed) of urchins as well as the time required (foraging time) for S. fragilis to approach its preferred food (giant kelp) in the dp-FOCE chamber (-0.46 pH units) and a control chamber (ambient pH). Measurements were performed during each of 4 trials (days -2, 2, 24, 27 after CO2 injection) during the month-long period when groups of urchins were continuously exposed to low pH or control conditions. Although urchin speed did not vary significantly in relation to pH or time exposed, foraging time was significantly longer for urchins in the low-pH treatment. This first deep-sea FOCE experiment demonstrated the utility of the FOCE system approach and suggests that the chemosensory behavior of a deep-sea urchin may be impaired by ocean acidification.

A Gas-Controlled Aquarium System for Ocean Acidification Studies

Ocean carbon sequestration by direct carbon dioxide injection to the deep-sea or by the fertilization of the upper ocean with iron to accelerate the biological pump are methods under consideration to mitigate rapidly rising atmospheric carbon dioxide levels and avoid, in part, excessive greenhouse gas warming. Both sequestration efforts will elevate carbon dioxide levels in the deep ocean, which after reaction with the seawater carbonate system, will decrease the pH of the ocean. In addition, ocean acidification is occurring through the passive influx of carbon dioxide through the ocean surface. Efforts to understand the effects of accelerating ocean acidification from carbon sequestration efforts or passive CO2 absorbance will require study of marine ecosystems from the surface to the deep-sea. In many deep-sea environments, hypoxia can also be stressful for marine organisms. Therefore, studies to assess the impacts of ocean acidification in deep-sea habitats should also include examination of the effects of hypoxia, due to the potentially synergistic interaction between these stressors. In this report, we describe the development of a gas-controlled aquarium (GCA) system used for laboratory studies of the effects of hypoxia or ocean acidification or both on marine animals. The GCA system is capable of regulating the temperature, oxygen, and carbon dioxide content of waters in three aquarium tanks for use in assays of growth and metabolic rate studies or various marine animals. The GCA design uses a main reservoir and 3 aquarium tanks in which different set-points for oxygen and carbon dioxide levels are possible. Membrane contactors connected to recirculation pumps and gas sources are used to control gas concentrations in each tank. A LabVIEW software system integrated with mass flow controllers for oxygen, carbon dioxide, and nitrogen sources allows real-time, automated regulation of gas concentrations in each tank.