Date of Award

Spring 5-11-2018

Level of Access

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Marine Biology

Advisor

Rhian Waller

Second Committee Member

Bob Steneck

Third Committee Member

Aaron Strong

Abstract

Primnoa pacifica, otherwise known as the Red Tree Coral, is one of the most ecologically important corals in the North Pacific. This species is an ecosystem engineer, providing essential habitat for commercially important fish and invertebrate species. Ocean acidification (OA) threatens corals and all calcifying organisms and is more prevalent in polar and sub-polar regions as the concentration of CO2 is higher and there is a lowered buffering capacity due to low alkalinity in colder waters. The impact from a chemical shift in the oceans could alter the role of P. pacifica as an ecosystem engineer in predicted ocean conditions. An experiment was conducted to assess the impacts of OA on the gametogenesis of Red Tree Corals from Tracy Arm fjord in Alaska. Primnoa pacifica colonies were cultured for six to nine months in either projected 2100 pH (7.55 pH units) or Ambient pH (7.75 pH units), then were prepared for histology to investigate any changes in gametogenesis in acidified water. Oocyte diameters and fecundities were significantly lower in the 2100 samples. The females from the experiment also had a higher proportion of individuals experiencing reabsorption of vitellogenic oocytes, potentially to preserve the lipids for other ecological processes as a stress response. The highest percentage of oosorption was seen in the 2100 females, as well as the smallest oocytes and the lowest fecundities. There was a “null tank effect” observed in all measurement types, however these only significantly affected the analyses of the exterior measurements and spermatogenesis. When compared to a published 2014 reproductive dataset, all the tank samples were statistically different from previous years and were significantly lower. These results indicate that reproduction in this species may not be possible in the current pH predictions for 2100, or that if spawning could still occur, any spawned oocyte may not be sufficiently equipped to support a larva. This study only investigated one life history stage of these long-lived organisms and more research spanning multiple life history stages needs to be done in their natural habitat as well as in homogeneous laboratory conditions. There is also a need to investigate the probability of these corals spawning under environmental stressors to identify if these important species will be present in the future.

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