The Effects of Ocean Acidification on the Development, Behavior and Survival of Marine Fish Eggs and Larvae Inferred from Laboratory and Natural Experiments
- Author(s): Shen, Sara
- Advisor(s): Checkley, Jr, David M
- et al.
The physiology, development, behavior and survival of the early life history stages
of marine fish are challenged by increasing carbon dioxide concentrations in the ocean,
known as ocean acidification. A widespread effect of elevated pCO2 on fish larvae is
increased otolith size. To understand the functional consequences of larger otoliths on the
vestibular system of fish larvae, Chapter 2 investigated the vestibulo-ocular reflex (VOR)
of white seabass (Atractoscion nobilis) larvae reared at 2500 μatm pCO2. The VOR is
an otolith-dependent response in fish that stabilizes vision during body movement. Larvae
reared at high pCO2 possessed saccular and utricular otoliths that were 17% and 38% larger in size. Despite the increased otolith size, the gain of the VOR, which describes the
ratio of eye to head amplitude, was not statistically different between treatment (0.39 +-
0.05, n = 28) and control (0.30 +- 0.03, n = 20) larvae.
Fish spawning habitat and survival of offspring are greatly influenced by environmental
conditions. In Chapter 3, the effects of pCO2 on the spawning habitat of Anchoveta
(Engraulis ringens) and mortality of eggs and early stage larvae were investigated. Eggs,
larvae, and oceanographic data, were collected across an onshore-offshore gradient in pCO2 that ranged from 167-1392 μatm. pCO2 was statistically significant in explaining egg presence. The abundance of eggs and relative absence of larvae at high pCO2 suggests that Anchoveta preferentially spawned at high pCO2 (>800 μatm) and that these eggs had lower survival.
Fish living in a high-pCO2 world may have to spend more energy on acid-base
balance. Chapter 4 explores the effects of elevated pCO2 on the oxygen consumption rate
(OCR) and abundance of Na+-K+-ATPase (NKA) proteins in white seabass larvae reared at 2000 μatm pCO2. OCR, a proxy for aerobic metabolic rate, did not differ significantly
between larvae reared at present-day (0.18 +- 0.03 μL O2 individual-1 h-1, n = 80) and future (0.19 +- 0.03 μL O2 individual-1 h-1, n = 80) pCO2. Consistent with this finding, the relative abundance of NKA proteins that fuel important ion exchangers for acid-base balance did not differ between control and treatment larvae in Western blot and immunohistochemistry analyses. Mass and length were also unchanged at high pCO2, suggesting larvae were physiologically robust in these variables to ocean acidification conditions.