Posts Tagged 'nutrients'

Eutrophication may compromise the resilience of the Red Sea coral Stylophora pistillata to global change

Highlights

• Interactive effects of stressors are variable; coral reefs should be managed on a local scale in accordance with local data.
• Additive effects of nutrients and global stressors result in changes in coral symbionts leading to shifts in overall health.
• Gulf of Aqaba corals may be resilient to OA and warming, yet a rise in nutrients would severely impede the reef.

Abstract

Environmental stressors are adversely affecting coral reef ecosystems. There is ample evidence that scleractinian coral growth and physiology may be compromised by reduced pH, and elevated temperature, and that this is exacerbated by local environmental stressors. The Gulf of Aqaba is considered a coral reef refuge from acidification and warming but coastal development and nutrient effluent may pose a local threat. This study examined the effects of select forecasted environmental changes (acidification, warming, and increased nutrients) individually and in combination on the coral holobiont Stylophora pistillata from the Gulf of Aqaba to understand how corals in a potential global climate change refugia may fare in the face of local eutrophication. The results indicate interactions between all stressors, with elevated nutrient concentrations having the broadest individual and additive impacts upon the performance of S. pistillata. These findings highlight the importance of maintaining oligotrophic conditions to secure these reefs as potential refugia.

Continue reading ‘Eutrophication may compromise the resilience of the Red Sea coral Stylophora pistillata to global change’

Temperature, acidification, and food supply interact to negatively affect the growth and survival of the forage fish, Menidia beryllina (Inland Silverside), and Cyprinodon variegatus (Sheepshead Minnow)

Climate change processes are warming, acidifying, and promoting a reduction of plankton biomass within World oceans. While the effects of these stressors on marine fish have been studied individually, their combined and interactive impacts remain unclear. Here we present experiments investigating the interactive effects of increased pCO2, temperature, and food-limitation on the early life history traits of two species of marine schooling fish native to Northeast US estuaries, Menidia beryllina (inland silverside) and Cyprinodon variegatus (sheepshead minnow). While each stressor significantly altered hatching times, growth rates, and/or survival of fish, significant interactions between stressors resulted in impacts that could not have been predicted based upon exposures to individual stressors. Fish that were unaffected by high pCO2 when reared at ideal temperatures experienced significant declines in survivorship when exposed to elevated pCO2 at temperatures above or below their thermal optimum. Similarly, fish provided with less food were more vulnerable to elevated pCO2 than fish provided with adequate nutrition. These findings highlight the significance of incorporating multiple stressors in studies investigating the impacts of climate change stressors on marine life. Collectively, these results suggest that climate change stressors may interact to synergistically suppress the productivity of fisheries in coastal ecosystems and that these effects may intensify as climate changes continue.

Continue reading ‘Temperature, acidification, and food supply interact to negatively affect the growth and survival of the forage fish, Menidia beryllina (Inland Silverside), and Cyprinodon variegatus (Sheepshead Minnow)’

An integrated response of Trichodesmium erythraeum IMS101 growth and photo-physiology to iron, CO2, and light intensity

We have assessed how varying CO2 (180, 380, and 720 μatm) and growth light intensity (40 and 400 μmol photons m−2 s−1) affected Trichodesmium erythraeum IMS101 growth and photophysiology over free iron (Fe′) concentrations between 20 and 9,600 pM. We found significant iron dependencies of growth rate and the initial slope and maximal relative PSII electron transport rates (rPm). Under iron-limiting concentrations, high-light increased growth rates and rPm; possibly indicating a lower allocation of resources to iron-containing photosynthetic proteins. Higher CO2 increased growth rates across all iron concentrations, enabled growth to occur at lower Fe′ concentrations, increased rPm and lowered the iron half saturation constants for growth (Km). We attribute these CO2 responses to the operation of the CCM and the ATP spent/saved for CO2 uptake and transport at low and high CO2, respectively. It seems reasonable to conclude that T. erythraeum IMS101 can exhibit a high degree of phenotypic plasticity in response to CO2, light intensity and iron-limitation. These results are important given predictions of increased dissolved CO2 and water column stratification (i.e., higher light exposures) over the coming decades.

Continue reading ‘An integrated response of Trichodesmium erythraeum IMS101 growth and photo-physiology to iron, CO2, and light intensity’

Plankton responses to ocean acidification: the role of nutrient limitation

Highlights

• Ocean acidification increases phytoplankton standing stock.
• This increase is more pronounced in smaller-sized taxa.
• Primary consumers reac differently depending on nutrient availability.
• Bacteria and micro-heterotrophs benefited under limiting conditions.
• In general, heterotrophs are negatively affected at nutrient replete periods.

Abstract

In situ mesocosm experiments on the effect of ocean acidification (OA) are an important tool for investigating potential OA-induced changes in natural plankton communities. In this study we combined results from various in-situ mesocosm studies in two different ocean regions (Arctic and temperate waters) to reveal general patterns of plankton community shifts in response to OA and how these changes are modulated by inorganic nutrient availability. Overall, simulated OA caused an increase in phytoplankton standing stock, which was more pronounced in smaller-sized taxa. This effect on primary producers was channelled differently into heterotroph primary consumers depending on the inorganic nutrient availability. Under limiting conditions, bacteria and micro-heterotrophs benefited with inconsistent responses of larger heterotrophs. During nutrient replete periods, heterotrophs were in general negatively affected, although there was an increase of some mesozooplankton developmental stages (i.e. copepodites). We hypothesize that changes in phytoplankton size distribution and community composition could be responsible for these food web responses.

Continue reading ‘Plankton responses to ocean acidification: the role of nutrient limitation’

Predictable ecological response to rising CO2 of a community of marine phytoplankton

Rising atmospheric CO2 and ocean acidification are fundamentally altering conditions for life of all marine organisms, including phytoplankton. Differences in CO2 related physiology between major phytoplankton taxa lead to differences in their ability to take up and utilize CO2. These differences may cause predictable shifts in the composition of marine phytoplankton communities in response to rising atmospheric CO2. We report an experiment in which seven species of marine phytoplankton, belonging to four major taxonomic groups (cyanobacteria, chlorophytes, diatoms, and coccolithophores), were grown at both ambient (500 μatm) and future (1,000 μatm) CO2 levels. These phytoplankton were grown as individual species, as cultures of pairs of species and as a community assemblage of all seven species in two culture regimes (high‐nitrogen batch cultures and lower‐nitrogen semicontinuous cultures, although not under nitrogen limitation). All phytoplankton species tested in this study increased their growth rates under elevated CO2 independent of the culture regime. We also find that, despite species‐specific variation in growth response to high CO2, the identity of major taxonomic groups provides a good prediction of changes in population growth and competitive ability under high CO2. The CO2‐induced growth response is a good predictor of CO2‐induced changes in competition (R2 > .93) and community composition (R2 > .73). This study suggests that it may be possible to infer how marine phytoplankton communities respond to rising CO2 levels from the knowledge of the physiology of major taxonomic groups, but that these predictions may require further characterization of these traits across a diversity of growth conditions. These findings must be validated in the context of limitation by other nutrients. Also, in natural communities of phytoplankton, numerous other factors that may all respond to changes in CO2, including nitrogen fixation, grazing, and variation in the limiting resource will likely complicate this prediction.

Continue reading ‘Predictable ecological response to rising CO2 of a community of marine phytoplankton’

Carbonate-sensitive phytotransferrin controls high-affinity iron uptake in diatoms

In vast areas of the ocean, the scarcity of iron controls the growth and productivity of phytoplankton. Although most dissolved iron in the marine environment is complexed with organic molecules, picomolar amounts of labile inorganic iron species (labile iron) are maintained within the euphotic zone and serve as an important source of iron for eukaryotic phytoplankton and particularly for diatoms. Genome-enabled studies of labile iron utilization by diatoms have previously revealed novel iron-responsive transcripts, including the ferric iron-concentrating protein ISIP2A8, but the mechanism behind the acquisition of picomolar labile iron remains unknown. Here we show that ISIP2A is a phytotransferrin that independently and convergently evolved carbonate ion-coordinated ferric iron binding. Deletion of ISIP2A disrupts high-affinity iron uptake in the diatom Phaeodactylum tricornutum, and uptake is restored by complementation with human transferrin. ISIP2A is internalized by endocytosis, and manipulation of the seawater carbonic acid system reveals a second-order dependence on the concentrations of labile iron and carbonate ions. In P. tricornutum, the synergistic interaction of labile iron and carbonate ions occurs at environmentally relevant concentrations, revealing that carbonate availability co-limits iron uptake. Phytotransferrin sequences have a broad taxonomic distribution and are abundant in marine environmental genomic datasets, suggesting that acidification-driven declines in the concentration of seawater carbonate ions will have a negative effect on this globally important eukaryotic iron acquisition mechanism.

Continue reading ‘Carbonate-sensitive phytotransferrin controls high-affinity iron uptake in diatoms’

Effects of ocean warming and acidification combined with eutrophication on chemical composition and functional properties of Ulva rigida

Highlights

• Ocean warming and eutrophication increased total amino acids.
• Ocean warming, acidification, and eutrophication increased total fatty acids.
• Ocean warming enhanced swelling capacity and water holding capacity.
• Ocean warming promoted oil holding capacity.

Abstract

Ulva is increasingly viewed as a food source in the world. Here, Ulva rigida was cultured at two levels of temperature (14, 18°C), pH (7.95, 7.55, corresponding to low and high pCO2), and nitrate conditions (6 μmol L-1, 150 μmol L-1), to investigate the effects of ocean warming, acidification, and eutrophication on food quality of Ulva species. High temperature increased the content of each amino acid. High nitrate increased the content of all amino acid except aspartic acid and cysteine. High temperature, pCO2, and nitrate also increased content of most fatty acids. The combination of high temperature, pCO2, and nitrate increased the swelling capacity, water holding capacity, and oil holding capacity by 15.60%, 7.88%, and 16.32% respectively, compared to the control. It seems that future ocean environment would enhance the production of amino acid and fatty acid as well as the functional properties in Ulva species.

Continue reading ‘Effects of ocean warming and acidification combined with eutrophication on chemical composition and functional properties of Ulva rigida’


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