Posts Tagged 'temperature'

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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Sporophytic photosynthesis and gametophytic growth of the kelp Ecklonia stolonifera affected by ocean acidification and warming

Juvenile sporophytes and gametophytes of Ecklonia stolonifera were incubated in combinations of three pCO2 levels (360, 720 and 980 ppmv) and two temperatures (10 and 15°C for sporophytes; 15 and 20°C for gametophytes) to examine potential effects of climate change on photosynthesis and growth. Sporophytes had significantly higher maximum quantum yields (Fv/Fm) and maximum relative electron transport rates (rETRmax) at 720 ppmv than 360 and 980 ppmv. Also, these parameters were significantly lower at higher temperature of 15°C than at 10°C. Growth of female gametophytes was maximal at 360 ppmv rather than enriched pCO2 levels. Female gametophytes had significantly lower growth at higher temperature of 20°C than at 15°C. These results indicate effects of elevated pCO2 varied between generations: stimulating sporophytic photosynthesis and inhibiting gametophytic growth. Ocean acidification and warming would constitute a grave threat to seedling cultivation of E. stolonifera caused by growth inhibition of gametophytes at high pCO2 levels and temperatures.

Continue reading ‘Sporophytic photosynthesis and gametophytic growth of the kelp Ecklonia stolonifera affected by ocean acidification and warming’

Ocean acidification and warming affect skeletal mineralization in a marine fish

Ocean acidification and warming are known to alter, and in many cases decrease, calcification rates of shell and reef building marine invertebrates. However, to date, there are no datasets on the combined effect of ocean pH and temperature on skeletal mineralization of marine vertebrates, such as fishes. Here, the embryos of an oviparous marine fish, the little skate (Leucoraja erinacea), were developmentally acclimatized to current and increased temperature and CO2 conditions as expected by the year 2100 (15 and 20°C, approx. 400 and 1100 µatm, respectively), in a fully crossed experimental design. Using micro-computed tomography, hydroxyapatite density was estimated in the mineralized portion of the cartilage in jaws, crura, vertebrae, denticles and pectoral fins of juvenile skates. Mineralization increased as a consequence of high CO2 in the cartilage of crura and jaws, while temperature decreased mineralization in the pectoral fins. Mineralization affects stiffness and strength of skeletal elements linearly, with implications for feeding and locomotion performance and efficiency. This study is, to my knowledge, the first to quantify a significant change in mineralization in the skeleton of a fish and shows that changes in temperature and pH of the oceans have complex effects on fish skeletal morphology.

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Impact of temperature, CO2, and iron on nutrient uptake by a late-season microbial community from the Ross Sea, Antarctica

The Southern Ocean is rapidly changing as a result of rising sea surface temperatures, elevated CO2 concentrations, and modifications to iron sources and sinks. The Southern Ocean has seasonally high rates of primary production, making it critical to determine how changes will impact biogeochemical rate processes in this important sink for CO2. During the austral summer, we measured nitrogen and carbon uptake rates by a late-season Ross Sea microbial community under different potential climate change conditions. A natural microbial assemblage was collected from the ice edge, and grown using a semi-continuous culturing followed by a continuous culturing ‘ecostat’ approach. The individual and combined impacts of temperature elevation and iron addition were tested during both approaches, and CO2 level was also manipulated during the continuous experiment. Nutrient concentrations and biomass parameters were measured throughout both experiments. During the continuous experiment we also measured uptake rates of nitrate (NO3-) and dissolved inorganic carbon (DIC) by 2 size classes (0.7-5.0 and >5.0 µm) of microorganisms. Of the parameters tested, temperature elevation had the largest impact, significantly increasing NO3- and DIC uptake rates by larger microorganisms. Iron addition was also important; however, the magnitude of its impact was greater when temperature was also changed. These results indicate that NO3- and DIC uptake rates may increase as sea surface warming occurs in the Southern Ocean, and thus have important implications for estimating new production and potential carbon uptake and eventual export to the deep sea.

Continue reading ‘Impact of temperature, CO2, and iron on nutrient uptake by a late-season microbial community from the Ross Sea, Antarctica’

Oxidative stress and biomarker responses in the Atlantic halibut after long term exposure to elevated CO2 and a range of temperatures

Oceans are warming and pH levels are decreasing as a consequence of increasing levels of dissolved CO2 concentrations. The CO2 emissions are predicted to be produce in greater and faster changes in the ocean than any other event in geological and historical records over the past 300 million years. Marine organisms will need to respond to multiple stressors but the potential consequences of global change-related effects in fish are not fully understood. Since fish are affected by many biotic and abiotic environmental variables, including temperature and CO2 fluctuations, it is critical to investigate how these variables may affect physiological and biochemical processes. We investigated the effects of elevated CO2 levels (pH of 8.0, which served as a control, or 7.6, which is predicted for the year 2100) combined with exposure to different temperatures (5, 10, 12, 14, 16, and 18 C ) in the Atlantic halibut (Hippoglossus hippoglossus) during a three month experiment. We assessed effects on antioxidant and cholinesterase enzymes (AChE and BChE), and CYP1A enzyme activities (EROD). The treatments resulted in oxidative stress, and damage was evident in the form of protein carbonyls which were consistently higher in the elevated CO2-treated fish at all temperatures. Analyses of antioxidant enzymes did not show the same results, suggesting that the exposure to elevated CO2 increased ROS formation but not defences. The antioxidant defence system was insufficient, and the resulting oxidative damage could impact physiological function of the halibut on a cellular level.

Continue reading ‘Oxidative stress and biomarker responses in the Atlantic halibut after long term exposure to elevated CO2 and a range of temperatures’

Obligate ectosymbionts increase the physiological resilience of a scleractinian coral to high temperature and elevated pCO2

Invertebrate ectosymbionts within the coralla of scleractinians enhance host fitness through protection from corallivores and nutrient addition. Here, we explore the ectosymbiotic relationship between the coral Pocillopora verrucosa and the crab Trapezia serenei and the shrimp Alpheus spp., to test for effects on coral calcification under contrasts of seawater temperature (27.7 °C and 29.9 °C) and pH (ambient, 8.0 and reduced, 7.7). Regardless of temperature, ectosymbionts depressed calcification by 55% (vs without ectosymbionts) at ambient pH; however, ectosymbionts only depressed calcification under ambient pH but not at reduced pH. These results suggest that P. verrucosa grows fastest at ambient pH without ectosymbionts, but when ectosymbionts are present, colonies are protected from further declines in calcification at reduced pH. This implies that there may be a change from a currently parasitic ectosymbiont–coral relationship to a commensal relationship that could increase fitness advantages for corals hosting crustacean ectosymbionts under ocean acidification conditions.

Continue reading ‘Obligate ectosymbionts increase the physiological resilience of a scleractinian coral to high temperature and elevated pCO2’

Distinct bleaching resilience of photosynthetic plastid-bearing mollusks under thermal stress and high CO2 conditions

The impact of temperature on photo-symbiotic relationships has been highly studied in the tropical reef-forming corals but overlooked in less charismatic groups such as solar-powered sacoglossan sea slugs. These organisms display one of the most puzzling symbiotic features observed in the animal kingdom, i.e., their mollusk-plastid association, which enables them to retain photosynthetic active chloroplasts (i.e., kleptoplasts) retrieved from their algae feed sources. Here we analyze the impact of thermal stress (+4∘C) and high pCO2 conditions (ΔpH = 0.4) in survival, photophysiology (i.e., bleaching, photosynthetic efficiency, and metabolism) and stress defense mechanisms (i.e., heat shock and antioxidant response) of solar-powered sacoglossan sea slugs, from tropical (Elysia crispata) and temperate (E. viridis) environments. High temperature was the main factor affecting the survival of both species, while pH only affected the survival of the temperate model. The photobiology of E. viridis remained stable under the combined scenario, while photoinhibition was observed for E. crispata under high temperature and high pCO2. In fact, bleaching was observed within all tropical specimens exposed to warming (but not in the temperate ones), which constitutes the first report where the incidence of bleaching in tropical animals hosting photosynthetic symbionts, other than corals, occurs. Yet, the expulsion of kleptoplasts by the tropical sea slug, allied with metabolic depression, constituted a physiological response that did not imply signs of vulnerability (i.e., mortality) in the host itself. Although the temperate species revealed greater heat shock and antioxidant enzyme response to environmental stress, we argue that the tropical (stenotherm) sea slug species may display a greater scope for acclimatization than the temperate (eurytherm) sea slug. E. crispata may exhibit increased capacity for phenotypic plasticity by increasing fitness in a much narrower thermal niche (minimizing maintenance costs), which ultimately may allow to face severe environmental conditions more effectively than its temperate generalist counterpart (E. viridis).

Continue reading ‘Distinct bleaching resilience of photosynthetic plastid-bearing mollusks under thermal stress and high CO2 conditions’

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Ocean acidification in the IPCC AR5 WG II

OUP book