Potential effects of ocean acidification on cold-winter marine invertebrates

Verkaik, Katie Helena (2015) Potential effects of ocean acidification on cold-winter marine invertebrates. Masters thesis, Memorial University of Newfoundland.

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Abstract

Anthropogenic emissions of carbon dioxide are causing an overall decrease of ocean pH, now termed ocean acidification (OA). This change in water chemistry has potentially dire implications for organisms living in marine environments, especially at high latitudes where carbonate saturation states are already low. OA has been shown to affect processes such as calcification, physiology, reproduction and development, with species-specific differences being observed. The goal of the present study was to better understand the effects of OA on weakly calcifying, cold-water species with lecitotrophic larvae, using the sea cucumber Cucumaria frondosa. In addition, it aimed to gain information on how OA might affect deep-sea organisms, using the hermaphroditic polychaete Ophryotrocha sp. Focal species were exposed to a ~0.4 unit decrease in pH for 19-26 weeks using a realistic flow-through system. I then investigated the reproductive output of each species, as well as its behaviour, spawning, larval development and calcification. Lipid and fatty acid profiles were also examined in C. frondosa. Findings varied between the two species. Gamete synthesis was disrupted by low pH in C. frondosa. Consequently, mature oocytes exhibited morphological discrepancies and negative buoyancy, leading to high embryonic mortality. Skeletal ossicles were affected in terms of abundance, microstructural appearance and chemical composition. In comparison, Ophryotrocha sp. exhibited a decrease in spermatozoa production but an increase in the number and size of oocytes under low pH. There was a trend towards a lower effective fecundity and development appeared to be slower under OA conditions, however these observations will require further investigation. The present analysis contributes to a growing understanding of the potential impacts of predicted near future OA gathered through long-term transgenerational exposure. It will assist in filling gaps in OA research pertaining to weakly calcifying species from cold-water and deep-sea environments that rely on lecithotrophic (maternally-provisioned) development. Together, the results suggest that these species may undergo significant challenges under future OA conditions, with cascading effects on the environments of which they are vital components.

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