The effects of in-vitro pH decrease on the gametogenesis of the red tree coral, Primnoa pacifica

Abstract

Primnoa pacifica is the most ecologically important coral species in the North Pacific Ocean where it provides important habitat for commercially important fish and invertebrates. Ocean acidification (OA) is more rapidly increasing in high-latitude seas because anthropogenic CO2 uptake is greater in these regions. This is due to the solubility of CO2 in cold water and the reduced buffering capacity due to low alkalinity of colder waters. Primnoa pacifica colonies were cultured for six to nine months in either pH 7.55 (predicted 2100 pH levels) or pH 7.75 (control). Oocyte development and fecundity in females, and spermatocyst stages in males were measured to assess the effects of pH on gametogenesis. Oocyte diameters were 13.6% smaller and fecundities were 30.9% lower in the Year 2100 samples, indicating that OA may limit oocyte formation, potentially through lipid limitation. A higher proportion of vitellogenic oocytes (65%) were also reabsorbed (oosorption) in the Year 2100 treatment. Lowered pH appeared to advance the process of spermatogenesis with a higher percentage of later stage sperm compared to control controls. There was a laboratory effect observed in all measurement types, however these only significantly affected the analyses of spermatogenesis. These results indicate that reproduction may not be possible in an acidified ocean, or that if spawning could occur, spawned oocytes would not be sufficiently equipped to support the normal development of larvae.

Rapid deep ocean deoxygenation and acidification threaten life on Northeast Pacific seamounts

“…OA impacts many aspects of reproduction; spawning, larval development, and juvenile mortality. For example, Primnoa pacifica (same suborder as the bamboo coral; inhabits the study seamounts; data not shown) experienced reduced spawning in low pH (pH = 7.55; Rossin, 2018). The keystone brittle star Ophiothrix fragilis is especially sensitive to OA, with 100% mortality of larvae with a modest increase in acidity (pH = 7.9; Dupont, Havenhand, Thorndyke, Peck, & Thorndyke, 2008).…”