Archive for the 'Science' Category

Modeling impact of varying pH due to carbondioxide on the dynamics of prey–predator species system

In this paper, we have considered a nonlinear mathematical model to investigate the effect of pH on prey–predator dynamics with Holling type II functional response. In the model, capture rate, handling time, growth rate and death rate are considered to be pH dependent. From the analysis of the model, it has been observed that as pH level goes below the normal tolerance limit of prey species then the equilibrium density of prey population decreases due to increase in capture rate and decrease in handling time by predator. Further, we have shown that as the growth rate of prey population decreases due to lowering of pH then the density of predator population also decreases and both the populations may tend to extinction if growth rate of prey population becomes negative due to lowering of pH on account of elevated carbondioxide concentration in the aquatic body. Moreover, it is noticed from the simulation that if the mortality of predator population increases because of decrease in pH level then the prey population gets advantage and in-turn their population increases.

Continue reading ‘Modeling impact of varying pH due to carbondioxide on the dynamics of prey–predator species system’

Carbonate dissolution by reef microbial borers: a biogeological process producing alkalinity under different pCO2 conditions

Rising atmospheric CO2 is acidifying the world’s oceans, affecting both calcification and dissolution processes in coral reefs. Among processes, carbonate dissolution by bioeroding microflora has been overlooked, and especially its impact on seawater alkalinity. To date, this biogeological process has only been studied using microscopy or buoyant weight techniques. To better understand its possible effect on seawater alkalinity, and thus on reef carbonate budget, an experiment was conducted under various seawater chemistry conditions (2 ≤ Ωarag ≤ 3.5 corresponding to 440 ≤ pCO2 (µatm) ≤ 940) at 25 °C under night and daylight (200 µmol photons m−2 s−1) with natural microboring communities colonizing dead coral blocks (New Caledonia). Both the alkalinity anomaly technique and microscopy methods were used to study the activity of those communities dominated by the chlorophyte Ostreobium sp. Results show that (1) the amount of alkalinity released in seawater by such communities is significant and varies between 12.8 ± 0.7 at ΩArag ~ 2 and 5.6 ± 0.4 mmol CaCO3 m−2 day−1 at ΩArag ~ 3–3.5 considering a 12:12 photoperiod; (2) although dissolution is higher at night (~ 80 vs. 20% during daylight), the process can occur under significant photosynthetic activity; and (3) the process is greatly stimulated when an acidity threshold is reached (pCO2 ≥ 920 µatm vs. current conditions at constant light intensity). We show that carbonate dissolution by microborers is a major biogeochemical process that could dissolve a large part of the carbonates deposited by calcifying organisms under ocean acidification.

Continue reading ‘Carbonate dissolution by reef microbial borers: a biogeological process producing alkalinity under different pCO2 conditions’

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.

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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.

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

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Ocean acidification in the IPCC AR5 WG II

OUP book