Invariant Gametogenic Response of Dominant Infaunal Bivalves From the Arctic Under Ambient and Near-Future Climate Change Conditions

Abstract

Arctic marine ecosystems are undergoing a series of major rapid adjustments to the regional amplification of climate change, but there is a paucity of knowledge about how changing environmental conditions might affect reproductive cycles of seafloor organisms. Shifts in species reproductive ecology may influence their entire life-cycle, and, ultimately, determine the persistence and distribution of taxa. Here, we investigate whether the combined effects of warming and ocean acidification based on near-future climate change projections affects the reproductive processes in benthic bivalves (Astarte crenata and Bathyarca glacialis) from the Barents Sea. Both species present large oocytes indicative of lecithotrophic or direct larval development after ∼4 months exposure to ambient [<2°C, ∼400 ppm (CO2)] and near-future [3–5°C, ∼550 ppm (CO2)] conditions, but we find no evidence that the combined effects of acidification and warming affect the size frequency distribution of oocytes. Whilst our observations are indicative of resilience of this reproductive stage to global changes, we also highlight that the successful progression of gametogenesis under standard laboratory conditions does not necessarily mean that successful development and recruitment will occur in the natural environment. This is because the metabolic costs of changing environmental conditions are likely to be offset by, as is common practice in laboratory experiments, feeding ad libitum. We discuss our findings in the context of changing food availability in the Arctic and conclude that, if we are to establish the vulnerability of species and ecosystems, there is a need for holistic approaches that incorporate multiple system responses to change.

Reproductive traits and population dynamics of benthic invertebrates indicate episodic recruitment patterns across an Arctic polar front

“…Moreover, low frequency of small shell length A. crenata and missing arm length-size classes of C. crispatus within and north of the polar front, suggest that reproduction may be affected at alternative life-history stages after gametogenesis, and that periodic variations (Reed et al, 2021) and in rapidly changing Antarctic regions (Dayton et al, 2019).…”

“…0.5 m -2 , Cochrane et al, 2009;Figure S2b) and a life span up to ~48 years (Moss et al, 2018). Details of reproduction are poorly understood, but broadly align with A. borealis and A. elliptica, which show mature oocytes up to 200 µm diameter throughout the year, with an underlying seasonal intensity in reproduction, and short pelagic larval stages or direct development (Reed et al, 2021;Von Oertzen, 1972).…”

Ocean acidification does not overlook sex: Review of understudied effects and implications of low pH on marine invertebrate sexual reproduction

“…However, no impact of OA on molluscan gametogenesis has also been reported (Le Moullac et al, 2016;Venkataraman et al, 2019). Molluscan egg quality may be resilient to OA, as most studies report no impact to egg size or lipid content (Parker et al, 2017;Parker et al, 2018;Scanes et al, 2018;Parker et al, 2021;Reed et al, 2021;Gibbs et al, 2021a) (but see Spady et al, 2020, the sole non-bivalve study). Two studies do report increased egg size or lipid content in response to OA (Zhao et al, 2019;Gibbs et al, 2021b), which can be indicative of higher energy content and egg quality (Moran and McAlister, 2009).…”

Trait-mediated processes and per capita contributions to ecosystem functioning depend on conspecific density and climate conditions

“…m −2 ; Supplementary Fig. 3, Article weekly, and animals were fed three times week −1 with 5 ml aquarium −1 of microalgal mix consisting of Tetraselmis suecica and Phaedactylum tricornutum (~15 mg organic matter aquarium −1 week −1 ), equating to ~1.1% of ash-free dry mass daily 69,107 . To test the combined effects of individual density and climate change, a subset of species (N. hombergii, T. tricarinata and A. chiajei; representing the three most abundant species at the sampling location) were maintained in either an ambient (12 °C, 410 ppm pCO 2 ) or future climate (+ 2 °C warming, 550 ppm pCO 2 ; Supplementary Fig.…”