Quantifying the effects of changing temperature, dissolved oxygen, and pH associated with upwelling on the growth and survivorship of juvenile Haliotis rufescens

Climate-related changes in ocean conditions, including warming, reduced dissolved oxygen (DO), increased upwelling, and ocean acidification (OA), are impacting marine ecosystems. Although understanding of these effects is emerging, knowledge of their combined effects on marine life in the California Current Large Marine Ecosystem (CCLME) is limited. To gain a better understanding, we aim to quantify the effects of three environmental drivers: temperature, DO, and pH on the growth and survivorship of the relatively sedentary nearshore species, Haliotis rufescens (red abalone). Species residing in shallow coastal waters are subject to upwelling events which can deliver these potentially stressful conditions by bringing up cold, low DO, low pH waters, which are then advected into nearshore habitats. Red abalone in three size classes (10-20, 20-30, 30-40mm) were exposed to one of six treatments representing the varying exposure of temperature, DO, and pH associated with current and future upwelling scenarios. Mortality and growth, measured as change in buoyant mass, somatic mass, shell size and mass, and mortality was obtained after four weeks. Size classes 20-30mm and 30-40mm had a trend of showing highest percent growth overall within moderate upwelling conditions. All size classes had a trend of showing low percent growth overall within the most futuristic upwelling conditions. Mortalities were only observed in the smallest size class, with those exposed to moderate upwelling conditions having the lowest mortality and those exposed to the most futuristic upwelling conditions experiencing the highest mortality. Knowledge gained from this experiment can provide insight on how marine population dynamics and associated ecosystem services, such as commercial and recreational fishing, might respond to climate change. This information can also help the management and sustainability of upwelling driven marine ecosystems beyond the CCLME into the future.

Continue reading ‘Quantifying the effects of changing temperature, dissolved oxygen, and pH associated with upwelling on the growth and survivorship of juvenile Haliotis rufescens’

Marine CO2 patterns in the northern Salish Sea

Marine carbon dioxide (CO2) system data has been collected from December 2014 to June 2018 in the Northern Salish Sea (NSS; British Columbia, Canada) and consisted of continuous measurements at two sites as well as spatially- and seasonally distributed discrete seawater samples. The array of CO2 observing activities included high-resolution CO2 partial pressure (pCO2) and pHT (total scale) measurements made at the Hakai Institute’s Quadra Island Field Station (QIFS) and from an Environment Canada weather buoy, respectively, as well as discrete seawater measurements of pCO2 and total dissolved inorganic carbon (TCO2) obtained during a number of field campaigns. A relationship between NSS alkalinity and salinity was developed with the discrete datasets and used with the continuous measurements to highly resolve the marine CO2 system. Collectively, these datasets provided insights into the seasonality in this historically under-sampled region and detail the area’s tendency for aragonite saturation state (Ωarag) to be at non-corrosive levels (i.e., Ωarag > 1) only in the upper water column during spring and summer months. This depth zone and time period of reprieve can be periodically interrupted by strong northwesterly winds that drive short-lived (∼1 week) episodes of high-pCO2, low-pH, and low-Ωarag conditions throughout the region. Interannual variability in summertime conditions was evident and linked to reduced northwesterly winds and increased stratification. Anthropogenic CO2 in NSS surface water was estimated using data from 2017 combined with the global atmospheric CO2 forcing for the period 1765 to 2100, and projected a mean value of 49 ± 5 μmol kg-1 for 2018. The estimated trend in anthropogenic CO2 was further used to assess the evolution of Ωarag and pHT levels in NSS surface water, and revealed that wintertime corrosive Ωarag conditions were likely absent pre-1900. The percent of the year spent above Ωarag = 1 has dropped from ∼98% in 1900 to ∼60% by 2018. Over the coming decades, winter pHT and spring and summer Ωarag are projected to decline to conditions below identified biological thresholds for select vulnerable species.

Continue reading ‘Marine CO2 patterns in the northern Salish Sea’

Antarctic marine biodiversity: adaptations, environments and responses to change

Animals living in the Southern Ocean have evolved in a singular environment. It shares many of its attributes with the high Arctic, namely low, stable temperatures, the pervading effect of ice in its many forms and extreme seasonality of light and phytobiont productivity. Antarctica is, however, the most isolated continent on Earth and is the only one that lacks a continental shelf connection with another continent. This isolation, along with the many millions of years that these conditions have existed, has produced a fauna that is both diverse, with around 17,000 marine invertebrate species living there, and has the highest proportions of endemic species of any continent. The reasons for this are discussed. The isolation, history and unusual environmental conditions have resulted in the fauna producing a range and scale of adaptations to low temperature and seasonality that are unique. The best known such adaptations include channichthyid icefish that lack haemoglobin and transport oxygen around their bodies only in solution, or the absence, in some species, of what was only 20 years ago termed the universal heat shock response. Other adaptations include large size in some groups, a tendency to produce larger eggs than species at lower latitudes and very long gametogenic cycles, with egg development (vitellogenesis) taking 18–24 months in some species. The rates at which some cellular and physiological processes are conducted appear adapted to, or at least partially compensated for, low temperature such as microtubule assembly in cells, whereas other processes such as locomotion and metabolic rate are not compensated, and whole-animal growth, embryonic development, and limb regeneration in echinoderms proceed at rates even slower than would be predicted by the normal rules governing the effect of temperature on biological processes. This review describes the current state of knowledge on the biodiversity of the Southern Ocean fauna and on the majority of known ecophysiological adaptations of coldblooded marine species to Antarctic conditions. It further evaluates the impacts these adaptations have on capacities to resist, or respond to change in the environment, where resistance to raised temperatures seems poor, whereas exposure to acidified conditions to end-century levels has comparatively little impact

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Fish brain development in a changing ocean

Unravelling how marine species invest in brain tissues (or brain regions) matching the fitness-relevant cognitive demands dictated by a changing environment is a priority in climate change-related (ocean warming and acidification) research. Within this context, this dissertation aimed to assess the combined effects of ocean warming (Δ 4 °C) and acidification (Δ 700 μatm pCO2 and Δ 0.4 pH) in the brain development (brain/body mass ratio and brain macro-region growth) of several juvenile fish species from different climate regions. Namely: three species adapted to a more stable (tropical) environment (clown anemonefish Amphiprion ocellaris, orchid dottyback Pseudochromis fridmani and neon goby Elacatinus oceanops), and other three adapted to a less stable (more seasonal; temperate) environment (seabream Diplodus sargus, flatfish Solea senegalensis and meagre Argyrosomus regius). The results show that the temperate species used in this study are only affected by ocean acidification in both total brain and specific brain regions, while the used tropical species are affected by ocean acidification, ocean warming and also by the interaction of ocean warming and ocean acidification. In fact, both total brain and every brain-region except for Telencephalon are affected by future conditions of ocean warming and ocean acidification differently according to each species. The lack of responses to ocean warming by the temperate species is here attributed to the widespread latitudinal distribution of those species, and thus the adaptation to a wider temperature range than tropical species. Curiously, all the significant interactions between the two studied stressors are antagonistic interactions with a cross-tolerance mechanism, meaning that under those interactions, the brain weight is closer to control levels than under each of the stressors separately. Possible behavioural and ecological implications of those results are also discussed. Despite the distinct dichotomic pattern between temperate and tropical habitats, the results among fish species and specific brain macro-regions do not exhibit a subjacent pattern. These different results highlight the idea of species-specific phenotypic responses to these climate change-related stressors.

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Infographic: impacts of OA on California’s living marine resources

A summary of the latest research on ocean acidification (OA) impacts to important species and ecosystems in California, from crab to squid, rockfish to urchins. This tool provides a tangible illustration of our current knowledge to support decision-makers in prioritizing efforts and resources to address OA impacts.

Ocean Science Trust, working closely with scientists at UC Davis Bodega Marine Lab, the Ocean Protection Council (OPC) and other partners, undertook this synthesis to help identify data gaps and prioritize where to allocate resources to further increase understanding of OA impacts to California fishery resources.

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A potential role for epigenetic processes in the acclimation response to elevated pCO2 in the model diatom Phaeodactylum tricornutum

Understanding of the molecular responses underpinning diatom responses to ocean acidification is fundamental for predicting how important primary producers will be shaped by the continuous rise in atmospheric CO2. In this study, we have analyzed global transcriptomic changes of the model diatom Phaeodactylum tricornutum following growth for 15 generations in elevated pCO2 by strand-specific RNA sequencing (ssRNA-seq). Our results indicate that no significant effects of elevated pCO2 and associated carbonate chemistry changes on the physiological performance of the cells were observed after 15 generations whereas the expression of genes encoding histones and other genes involved in chromatin structure were significantly down-regulated, while the expression of transposable elements (TEs) and genes encoding histone acetylation enzymes were significantly up-regulated. Furthermore, we identified a series of long non-protein coding RNAs (lncRNAs) specifically responsive to elevated pCO2, suggesting putative regulatory roles for these largely uncharacterized genome components. Taken together, our integrative analyses reveal that epigenetic elements such as TEs, histone modifications and lncRNAs may have important roles in the acclimation of diatoms to elevated pCO2 over short time scales and thus may influence longer term adaptive processes in response to progressive ocean acidification.

Continue reading ‘A potential role for epigenetic processes in the acclimation response to elevated pCO2 in the model diatom Phaeodactylum tricornutum’

Boron isotope systematics of cultured brachiopods: response to acidification, vital effects and implications for palaeo-pH reconstruction

CO2-induced ocean acidification and associated decrease of seawater carbonate saturation state contributed to multiple environmental crises in Earth’s history, and currently poses a major threat for marine calcifying organisms. Owing to their high abundance and good preservation in the Phanerozoic geological record, brachiopods present an advantageous taxon of marine calcifiers for palaeo-proxy applications as well as studies on biological mechanism to cope with environmental change. To investigate the geochemical and physiological responses of brachiopods to prolonged low-pH conditions we cultured Magellania venosa, Terebratella dorsata and Pajaudina atlantica under controlled experimental settings over a period of more than two years. Our experiments demonstrate that brachiopods form their calcite shells under strong biological control, which enables them to survive and grow under low-pH conditions and even in seawater strongly undersaturated with respect to calcite (pH = 7.35, Ωcal = 0.6). Using boron isotope (δ11B) systematics including MC-ICP-MS as well as SIMS analyses, validated against in vivo microelectrode measurements, we show that this resilience is achieved by strict regulation of the calcifying fluid pH between the epithelial mantle and the shell. We provide a culture-based δ11B−pH calibration, which as a result of the internal pH regulatory mechanisms deviates from the inorganic borate ion to pH relationship, but confirms a clear yet subtle pH dependency for brachiopods. At a micro-scale level, the incorporation of 11B appears to be principally driven by a physiological gradient across the shell, where the δ11B values of the innermost calcite record the internal calcifying fluid pH while the composition of the outermost layers is also influenced by seawater pH. These findings are of consequence to studies on biomineralisation processes, physiological adaptations as well as past climate reconstructions.

Continue reading ‘Boron isotope systematics of cultured brachiopods: response to acidification, vital effects and implications for palaeo-pH reconstruction’

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Ocean acidification in the IPCC AR5 WG II

OUP book