Predicting the impact of ongoing anthropogenic CO2 emissions on calcifying marine organisms is complex, owing to the synergy between direct changes (acidification) and indirect changes through climate change (e.g., warming, changes in ocean circulation, and deoxygenation). Laboratory experiments, particularly on longer-lived organisms, tend to be too short to reveal the potential of organisms to acclimatize, adapt, or evolve and usually do not incorporate multiple stressors. We studied two examples of rapid carbon release in the geological record, Eocene Thermal Maximum 2 (∼53.2 Ma) and the Paleocene Eocene Thermal Maximum (PETM, ∼55.5 Ma), the best analogs over the last 65 Ma for future ocean acidification related to high atmospheric CO2 levels. We use benthic foraminifers, which suffered severe extinction during the PETM, as a model group. Using synchrotron radiation X-ray tomographic microscopy, we reconstruct the calcification response of survivor species and find, contrary to expectations, that calcification significantly increased during the PETM. In contrast, there was no significant response to the smaller Eocene Thermal Maximum 2, which was associated with a minor change in diversity only. These observations suggest that there is a response threshold for extinction and calcification response, while highlighting the utility of the geological record in helping constrain the sensitivity of biotic response to environmental change.
Posts Tagged 'biological response'
Tags: biodiversity, biological response, calcification, morphology, multiple factors, oxygen, paleo, protists, temperature
Physiological compensation for environmental acidification is limited in the deep-sea urchin Strongylocentrotus fragilisPublished 22 May 2013 Science Leave a Comment
Tags: biological response, echinoderms, laboratory, morphology, mortality, multiple factors, North Pacific, oxygen, performance, physiology
Anthropogenic CO2 is now reaching depths over 1000 m in the Eastern Pacific, overlapping the Oxygen Minimum Zone (OMZ). Deep-sea animals – particularly, calcifiers – are suspected to be especially sensitive to environmental acidification associated with global climate change. We have investigated the effects of hypercapnia and hypoxia on the deep-sea urchin Strongylocentrotus fragilis, during two long-term exposure experiments (1 month and 4 month) at three levels of reduced pH at in situ O2 levels of approx. 10% saturation, and also to control pH at 100% O2 saturation. During the first experiment, internal acid-base balance was investigated during a one-month exposure; results show S. fragilis has limited ability to compensate for the respiratory acidosis brought on by reduced pH, due in part to low non-bicarbonate extracellular fluid buffering capacity. During the second experiment, longer-term effects of hypercapnia and variable O2 on locomotion, feeding, growth, and gonadosomatic index (GSI) were investigated; results show significant mortality and correlation of all measured parameters with environmental acidification at pH 6.6. Transient adverse effects on locomotion and feeding were seen at pH 7.2, without compromise of growth or GSI. Based on the expected changes in ocean pH and oxygen, results suggest extinction of S. fragilis in the eastern North Pacific is unlikely. Rather, we expect a shoaling and contraction of its bathymetric range.
CO2-driven ocean acidification reduces larval feeding efficiency and change food selectivity in the mollusk Concholepas concholepasPublished 22 May 2013 Science Leave a Comment
Tags: biological response, laboratory, mollusks, performance, South Pacific
We present experimental data obtained from an experiment with newly hatched veliger larvae of the gastropod Concholepas concholepas exposed to three pCO2 levels. Egg capsules were collected from two locations in northern and central Chile, and then incubated throughout their entire intra-capsular life cycle at three nominal pCO2 levels, ∼400, 700 and 1000 ppm (i.e. corresponding to ∼8.0, 7.8 and 7.6 pH units, respectively). Hatched larvae were fed with natural food assemblages. Food availability at time zero did not vary significantly with pCO2 level. Our results clearly showed a significant effect of elevated pCO2 on the intensity of larval feeding, which dropped by >60%. Incubation also showed that pCO2-driven ocean acidification (OA) may radically impact the selectivity of ingested food by C. concholepas larvae. Results also showed that larvae switched their clearance rate based on large cells, such as diatoms and dinoflagellates to tiny and highly abundant nanoflagellates and cyanobacteria as pCO2 levels increased. Thus, this study reveals the important effect of low pH conditions on larval feeding behavior, in terms of both ingestion magnitude and selectivity. These findings support the notion that larval feeding is a key physiological process susceptible to the effects of OA.
Tidal downwelling and implications for the carbon biogeochemistry of cold-water corals in relation to future ocean acidification and warmingPublished 22 May 2013 Science Leave a Comment
Tags: biological response, chemistry, corals, field, modeling, multiple factors, North Atlantic, regional, temperature
Cold-water coral (CWC) reefs are recognised as ecologically and biologically significant areas that generate habitats and diversity. The interaction between hydrodynamics and CWCs has been well-studied at the Mingulay Reef Complex, a relatively shallow area of reefs found on the continental shelf off Scotland, UK. Within ‘Mingulay Area 01’ a rapid tidal downwelling of surface waters, brought about as an internal wave, is known to supply warmer, phytoplankton-rich waters to corals growing on the northern flank of an east-west trending seabed ridge. This study shows that this tidal downwelling also causes short-term perturbations in the inorganic carbon and nutrient dynamics through the water column and immediately above the reef. Over a 14 h period, corresponding to one semi-diurnal tidal cycle, seawater pH overlying the reef varied by ~0.1 pH unit, while pCO2 shifted by > 60 μatm, a shift equivalent to a ~25 year jump into the future, with respect to atmospheric pCO2. During the summer stratified period, these downwelling events result in the reef being washed over with surface water that has higher pH, is warmer, nutrient-depleted, but rich in phytoplankton-derived particles compared to the deeper waters in which the corals sit. Empirical observations, together with outputs from the European Regional Shelf Sea Ecosystem Model, demonstrate that the variability that the CWC reefs experience changes through the seasons and into the future. Hence, as ocean acidification and warming increase into the future, the downwelling event specific to this site could provide short-term amelioration of corrosive conditions at certain times of the year; however it could additionally result in enhanced detrimental impacts of warming on CWCs. Natural variability in the inorganic carbon and nutrient conditions, as well as local hydrodynamic regimes, must be accounted for in any future predictions concerning the responses of marine ecosystems to climate change.
Tags: biological response, crustaceans, laboratory, multiple factors, physiology, temperature
The injection of anthropogenically-produced CO2 into the atmosphere will lead to an increase in temperature and a decrease in pH at the surface of the oceans by 2100. Marine intertidal organisms possess the ability to cope in the short term with environmental fluctuations exceeding predicted values. However, how they will cope with chronic exposure to elevated temperature and pCO2 is virtually unknown. In addition, individuals from the same species/population often show remarkable levels of variation in their responses to complex climatic changes: in particular, variation in metabolic rates often is linked to differences in individuals’ performances and fitness. Despite its ecological and evolutionary importance, inter-individual variation has rarely been investigated within the context of climatic changes, and most investigations have typically employed orthogonal experimental designs paired to analyses of independent samples. Although this is undoubtedly a powerful and useful approach, it may not be the most appropriate for understanding all alterations of biological functions in response to environmental changes. An individual approach arguably should be favored when trying to describe organisms’ responses to climatic change. Consequently, to test which approach had the greater power to discriminate the intensity and direction of an organism’s response to complex climatic changes, we investigated the extracellular osmo/iono-regulatory abilities, upper thermal tolerances (UTTs), and metabolic rates of individual adults of an intertidal amphipod, Echinogammarus marinus, exposed for 15 days to combined elevated temperature and pCO2. The individual approach led to stronger and different predictions on how ectotherms will likely respond to ongoing complex climatic change, compared with the independent approaches. Consequently, this may call into question the relevance, or even the validity, of some of the predictions made to date. Finally, we argue that treating individual differences as biologically meaningful can lead to a better understanding of the physiological responses themselves and the selective processes that will occur with complex climatic changes; selection will likely play a crucial role in defining species’ responses to future environmental changes. Individuals with higher metabolic rates were also characterized by greater extracellular osmo/iono-regulative abilities and higher UTTs, and thus there appeared to be no evolutionary trade-offs between these functions. However, as individuals with greater metabolic rates also have greater costs for maintenance and repair, and likely a lower fraction of energy available for growth and reproduction, trade-offs between life-history and physiological performance may still arise.
Effects of ocean warming and acidification on survival, growth and skeletal development in the early benthic juvenile sea urchin (Heliocidaris erythrogramma)Published 22 May 2013 Science Leave a Comment
Tags: biological response, echinoderms, laboratory, morphology, multiple factors, survival, temperature
Co-occurring ocean warming, acidification and reduced carbonate mineral saturation have significant impacts on marine biota, especially calcifying organisms. The effects of these stressors on development and calcification in newly metamorphosed juveniles (ca. 0.5 mm test diam) of the intertidal sea urchin Heliocidaris erythrogramma, an ecologically important species in temperate Australia, were investigated in context with present and projected future conditions. Habitat temperature and pH/pCO2 were documented to place experiments in a biologically and ecologically relevant context. These parameters fluctuated diurnally up to 10°C and 0.45 pH units. The juveniles were exposed to three temperature (21°C, 23°C, 25°C) and four pH (8.1, 7.8, 7.6, 7.4) treatments in all combinations, representing ambient sea surface conditions (21°C, pH 8.1; pCO2 397; ΩCa 4.7; ΩAr 3.1), near-future projected change (+2-4°C, -0.3-0.5 pH units; pCO2 400-1820; ΩCa 5.0-1.6; ΩAr 3.3-1.1), and extreme conditions experienced at low tide (+4°C, -0.3-07 pH units; pCO2 2850-2967; ΩCa 1.1-1.0; ΩAr 0.7-0.6). The lowest pH treatment (pH 7.4) was used to assess tolerance levels. Juvenile survival and test growth were resilient to current and near-future warming and acidification. Spine development, however, was negatively effected by near-future increased temperature (+2-4°C) and extreme acidification (pH 7.4), with a complex interaction between stressors. Near-future warming was the more significant stressor. Spine tips were dissolved in the pH 7.4 treatments. Adaptation to fluctuating temperature-pH conditions in the intertidal may convey resilience to juvenile H. erythrogramma to changing ocean conditions, however, ocean warming and acidification may shift baseline intertidal temperature and pH/pCO2 to levels that exceed tolerance limits.
Tags: abundance, algae, biological response, community composition, field, Mediterranean
Marine algae exhibit different responses to ocean acidification, suggesting that a decrease in pH does not always favour marine photosynthetic organisms. In order to understand the effect of acidification on algal community development, early colonization stages were investigated using carbon dioxide vents around the Castello Aragonese (Ischia, Italy) as a natural laboratory. Settlement tiles were placed in zones with different pH (normal, medium and low), and species composition and coverage measured after 2, 3 and 4 months of deployment. The number of species decreased by 4 and 18 % at medium and low pH zones, respectively (P < 0.05). The structure of the algal assemblage differed between pH zones during the 4 months of the experiment, due to the addition and/or replacement of new species. This leads to a change in the succession of morphological forms as soft crustose algae replaced calcareous species, and turf species were dominant in cover; more complex thalli started to occur only at medium pH. These results support previous findings that ocean acidification will induce changes in benthic algal communities.
Tags: abundance, algae, Arctic Ocean, biological response, chemistry, field
Coralline algae (Corallinales, Rhodophyta) that form rhodoliths are important ecosystem engineers and carbonate producers in many polar coastal habitats. This study deals with rhodolith communities from Floskjeret (78°18′N), Krossfjorden (79°08′N), and Mosselbukta (79°53′N), off Spitsbergen Island, Svalbard Archipelago, Norway. Strong seasonal variations in temperature, salinity, light regime, sea-ice coverage, and turbidity characterize these localities. The coralline algal flora consists of Lithothamnion glaciale and Phymatolithon tenue. Well-developed rhodoliths were recorded between 27 and 47 m water depth, while coralline algal encrustations on lithoclastic cobbles were detected down to 77 m water depth. At all sites, ambient waters were saturated with respect to both aragonite and calcite, and the rhodolith beds were located predominately at dysphotic water depths. The rhodolith-associated macrobenthic fauna included grazing organisms such as chitons and echinoids. With decreasing water depth, the rhodolith pavements were regularly overgrown by non-calcareous Polysiphonia-like red algae. The corallines are thriving and are highly specialized in their adaptations to the physical environment as well as in their interaction with the associated benthic fauna, which is similar to other polar rhodolith communities. The marine environment of Spitsbergen is already affected by a climate-driven ecological regime shift and will lead to an increased borealization in the near future, with presently unpredictable consequences for coralline red algal communities.
Tags: abundance, biological response, chemistry, corals, field, South Pacific
Increasing dissolution of anthropogenic-released carbon dioxide into the world’s oceans is causing ocean acidification (OA). OA is thought to negatively affect most marine-calcifying organisms, notably cold-water corals (CWC), which may be especially sensitive due to the deep and cold waters they normally thrive in. However, the impact of OA on CWC is difficult to predict. Recorded distributions of CWC are rarely linked to in situ water chemistry, and the boundaries of their distributions are not clearly defined. The fjord Comau in Chilean Patagonia features pronounced pH gradients, and up to 0.5 pH units have been recorded both vertically (at some sites within 50 m depth) and less distinct horizontally (from head to mouth). The cosmopolite coral Desmophyllum dianthus grows along the course of the fjord and of the entire pH range. It occurs in shallow depths (below 12 m, pH 8.1) as part of a deep-water emergence community, but also in 225 m depth at a pH of 7.4. Based on pH and total alkalinity, data calculations of the associated carbonate chemistry revealed that this CWC thrives commonly close the aragonite (the orthogonal crystal form of calcium carbonate, the mineral structure of coral skeletons) saturation horizon and even below. This suggests a high adaptation potential of D. dianthus to adjust its calcification performance to conditions thermodynamically unfavourable for the precipitation of aragonite.
Results of laboratory and field experiments of the direct effect of increasing CO2 on net primary production of macroalgal species in brackish-water ecosystemsPublished 22 May 2013 Science Leave a Comment
Tags: algae, Baltic Sea, biological response, field, laboratory, mesocosms, primary production
Studies on the effects of increasing acidification on marine communities have been previously mostly carried out in truly marine areas whereas brackish-water ecosystems such as the Baltic Sea have been less studied. The current study analyses how acidification induced by elevated atmospheric carbon dioxide affects the photosynthetic net production of different macroalgal species in the brackish Baltic Sea. Research methods include sets of laboratory and field experiments carried out in shallow coastal brackish waters. The aim of the laboratory experiments was to develop the necessary techniques and experience for the mesocosm experiments. Laboratory experiments were carried out using specimens of the red alga Furcellaria lumbricalis collected from Kakumäe Bay. The mesocosm experiments were conducted in Kõiguste Bay during the field season of 2011. Separate mesocosms were operated in each set with different CO2 concentrations and a control treatment in natural conditions. Field experiments were carried out with three species representing three different morphological and ecological groups: Ulva intestinalis, a fast-growing green alga; Fucus vesiculosus, a perennial brown alga with a slow metabolism; and Furcellaria lumbricalis, a perennial red alga. Photosynthetic activity was used as the response variable. In the laboratory decreasing pH increased the net primary production of F. lumbricalis with the lowest net primary production values measured at pH 8.0 and the highest at pH 6.5. Results of the field experiments indicated that increased CO2 levels in seawater favoured photosynthetic activity of the macroalgae U. intestinalis and F. lumbricalis, but F. vesiculosus showed no response to elevated CO2. Elevated CO2 levels are suggested to favour the production of fast-growing filamentous species, which thus may indirectly enhance the effect of eutrophication in the shallow coastal brackish waters.