Posts Tagged 'zooplankton'

Marine gametes in a changing ocean: Impacts of climate change stressors on fecundity and the egg

In marine invertebrates, the environmental history of the mother can influence fecundity and egg size. Acclimation of females in climate change stressors, increased temperature and low pH, results in a decrease in egg number and size in many taxa, with the exception of cephalopods, where eggs increase in size. With respect to spawned eggs, near future levels of ocean acidification can interfere with the eggs’ block to polyspermy and intracellular pH. Reduction of the extracellular egg jelly coat seen in low pH conditions has implications for impaired egg function and fertilization. Some fast generation species (e.g. copepods, polychaetes) have shown restoration of female reproductive output after several generations in treatments. It will be important to determine if the changes to egg number and size induced by exposure to climate change stressors are heritable.

Continue reading ‘Marine gametes in a changing ocean: Impacts of climate change stressors on fecundity and the egg’

Special edition of Estuarine, Coastal and Shelf Science – “Ocean acidification in the Mediterranean Sea: pelagic mesocosm experiments”

The topic of ocean acidification has received extensive attention in a recently published special edition of the journal Estuarine, Coastal and Shelf Science. Volume 186, Part A presents a series of 12 research papers focusing on pelagic mesocosm experiments conducted in the Mediterranean Sea in 2012 and 2013. Plankton plays a key role in the global carbon cycle. It is therefore important to project the evolution of plankton community structure and function in a future high-CO2 world. Several results from experiments conducted at the community level have shown increased rates of community primary production and shifts in community composition as a function of increasing pCO2. However, the great majority of these – experiments have been performed under high natural or nutrient-enriched conditions and very few data are available in areas with naturally low levels of nutrient and chlorophyll i.e. oligotrophic areas such as the Mediterranean Sea, although they represent a large and expanding part of the ocean surface. In the frame of the European Mediterranean Sea Acidification in a changing climate project (MedSeA; http://medsea-project.eu), large-scale in situ mesocosms (9 x 50 m3, 12 m deep) have been used to quantify the potential effects of CO2 enrichment in two coastal areas of the Mediterranean Sea: the bay of Calvi (Corsica, France) in June/July 2012 and the bay of Villefranche (France) in February/March 2013. These two experiments gathered the expertise of more than 25 scientists from 7 institutes and 6 countries (France, Greece, Spain, UK, Italy, Belgium, US).

Continue reading ‘Special edition of Estuarine, Coastal and Shelf Science – “Ocean acidification in the Mediterranean Sea: pelagic mesocosm experiments”’

Influence of ocean acidification on plankton community structure during a winter-to-summer succession: An imaging approach indicates that copepods can benefit from elevated CO2 via indirect food web effects

Plankton communities play a key role in the marine food web and are expected to be highly sensitive to ongoing environmental change. Oceanic uptake of anthropogenic carbon dioxide (CO2) causes pronounced shifts in marine carbonate chemistry and a decrease in seawater pH. These changes–summarized by the term ocean acidification (OA)–can significantly affect the physiology of planktonic organisms. However, studies on the response of entire plankton communities to OA, which also include indirect effects via food-web interactions, are still relatively rare. Thus, it is presently unclear how OA could affect the functioning of entire ecosystems and biogeochemical element cycles. In this study, we report from a long-term in situ mesocosm experiment, where we investigated the response of natural plankton communities in temperate waters (Gullmarfjord, Sweden) to elevated CO2 concentrations and OA as expected for the end of the century (~760 μatm pCO2). Based on a plankton-imaging approach, we examined size structure, community composition and food web characteristics of the whole plankton assemblage, ranging from picoplankton to mesozooplankton, during an entire winter-to-summer succession. The plankton imaging system revealed pronounced temporal changes in the size structure of the copepod community over the course of the plankton bloom. The observed shift towards smaller individuals resulted in an overall decrease of copepod biomass by 25%, despite increasing numerical abundances. Furthermore, we observed distinct effects of elevated CO2 on biomass and size structure of the entire plankton community. Notably, the biomass of copepods, dominated by Pseudocalanus acuspes, displayed a tendency towards elevated biomass by up to 30–40% under simulated ocean acidification. This effect was significant for certain copepod size classes and was most likely driven by CO2-stimulated responses of primary producers and a complex interplay of trophic interactions that allowed this CO2 effect to propagate up the food web. Such OA-induced shifts in plankton community structure could have far-reaching consequences for food-web interactions, biomass transfer to higher trophic levels and biogeochemical cycling of marine ecosystems.

Continue reading ‘Influence of ocean acidification on plankton community structure during a winter-to-summer succession: An imaging approach indicates that copepods can benefit from elevated CO2 via indirect food web effects’

Pteropoda (Mollusca, Gastropoda, Thecosomata) from the Paleocene-Eocene Thermal Maximum (United States Atlantic Coastal Plain)

The response of many organisms to the Paleocene-Eocene Thermal Maximum (PETM; ~56 Ma) has been documented, but marine mollusks are not known from any deposits of that age. For the first time, we describe a PETM assemblage of pteropods (planktic mollusks), consisting of six species representing three genera ( Altaspiratella, Heliconoides and Limacina). Four species could be identified to species level, and one of these, Limacina novacaesarea sp. nov., is described as new. Only the genus Heliconoides was previously known from pre-Eocene sediments, with a single Campanian specimen and one latest Paleocene species. We recovered pteropods from the Marlboro Clay (United States Atlantic Coastal Plain), deposited at paleodepths from inner shelf (southern Salisbury Embayment) to middle-outer shelf (New Jersey Coastal Plain). Most living pteropod assemblages inhabit water depths of 200 m or more, so their occurrence at shelf depths may reflect transport from more open waters. During the PETM, pH in the upper waters of the ocean may have declined, but this did not cause dissolution of pteropods before they reached the seafloor, possibly due to buffering in coastal waters. The apparently sudden appearance of three genera could reflect better preservation due to high sedimentation rates, since the underlying and overlying formations show poor preservation of calcareous microfossils. Potential ancestors, however, have not been found anywhere, so we consider it more likely that the rapid environmental changes during the PETM, such as temperature, runoff and nutrient fluxes, and ocean water chemistry, may have triggered pteropod diversification.

Continue reading ‘Pteropoda (Mollusca, Gastropoda, Thecosomata) from the Paleocene-Eocene Thermal Maximum (United States Atlantic Coastal Plain)’

Metabolic response of Arctic pteropods to ocean acidification and warming during the polar night/twilight phase in Kongsfjord (Spitsbergen)

Thecosome pteropods are considered highly sensitive to ocean acidification. During the Arctic winter, increased solubility of CO2 in cold waters intensifies ocean acidification and food sources are limited. Ocean warming is also particularly pronounced in the Arctic. Here, we present the first data on metabolic rates of two pteropod species (Limacina helicina, Limacina retroversa) during the Arctic winter at 79°N (polar night/twilight phase). Routine oxygen consumption rates and the metabolic response [oxygen consumption (MO2), ammonia excretion (NH3), overall metabolic balance (O:N)] to elevated levels of pCO2 and temperature were examined. Our results suggest lower routine MO2 rates for both Limacina species in winter than in summer. In an 18-h experiment, both pCO2 and temperature affected MO2 of L. helicina and L. retroversa. After a 9-day experiment with L. helicina all three metabolic response variables were affected by the two factors with interactive effects in case of NH3 and O:N. The response resembled a “hormesis-type” pattern with up-regulation at intermediate pCO2 and the highest temperature level. For L. retroversa, NH3 excretion was affected by both factors and O:N only by temperature. No significant effects of pCO2 or temperature on MO2 were detected. Metabolic up-regulation will entail higher energetic costs that may not be covered during periods of food limitation such as the Arctic winter and compel pteropods to utilize storage compounds to a greater extent than usual. This may reduce the fitness and survival of overwintering pteropods and negatively impact their reproductive success in the following summer.

Continue reading ‘Metabolic response of Arctic pteropods to ocean acidification and warming during the polar night/twilight phase in Kongsfjord (Spitsbergen)’

Ciliate and mesozooplankton community response to increasing CO2 levels in the Baltic Sea: insights from a large-scale mesocosm experiment (update)

Community approaches to investigating ocean acidification (OA) effects suggest a high tolerance of micro- and mesozooplankton to carbonate chemistry changes expected to occur within this century. Plankton communities in the coastal areas of the Baltic Sea frequently experience pH variations partly exceeding projections for the near future both on a diurnal and seasonal basis. We conducted a large-scale mesocosm CO2 enrichment experiment ( ∼  55 m3) enclosing the natural plankton community in Tvärminne–Storfjärden for 8 weeks during June–August 2012 and studied community and species–taxon response of ciliates and mesozooplankton to CO2 elevations expected for this century. In addition to the response to fCO2, we also considered temperature and chlorophyll a variations in our analyses. Shannon diversity of ciliates significantly decreased with fCO2 and temperature with a greater dominance of smaller species. The mixotrophic Myrionecta rubra seemed to indirectly and directly benefit from higher CO2 concentrations in the post-bloom phase through increased occurrence of picoeukaryotes (most likely Cryptophytes) and Dinophyta at higher CO2 levels. With respect to mesozooplankton, we did not detect significant effects for either total abundance or for Shannon diversity. The cladocera Bosmina sp. occurred at distinctly higher abundance for a short time period during the second half of the experiment in three of the CO2-enriched mesocosms except for the highest CO2 level. The ratio of Bosmina sp. with empty to embryo- or resting-egg-bearing brood chambers, however, was significantly affected by CO2, temperature, and chlorophyll a. An indirect CO2 effect via increased food availability (Cyanobacteria) stimulating Bosmina sp. reproduction cannot be ruled out. Although increased regenerated primary production diminishes trophic transfer in general, the presence of organisms able to graze on bacteria such as cladocerans may positively impact organic matter transfer to higher trophic levels. Thus, under increasing OA in cladoceran-dominated mesozooplankton communities, the importance of the microbial loop in the pelagic zone may be temporarily enhanced and carbon transfer to higher trophic levels may be stimulated.

Continue reading ‘Ciliate and mesozooplankton community response to increasing CO2 levels in the Baltic Sea: insights from a large-scale mesocosm experiment (update)’

Comparison of Mediterranean pteropod shell biometrics and ultrastructure from historical (1910 and 1921) and present day (2012) samples provides baseline for monitoring effects of global change

Anthropogenic carbon perturbation has caused decreases in seawater pH and increases in global temperatures since the start of the 20th century. The subsequent lowering of the saturation state of CaCO3 may make the secretion of skeletons more problematic for marine calcifiers. As organisms that precipitate thin aragonite shells, thecosome pteropods have been identified as being particularly vulnerable to climate change effects. Coupled with their global distribution, this makes them ideal for use as sentinel organisms. Recent studies have highlighted shell dissolution as a potential indicator of ocean acidification; however, this metric is not applicable for monitoring pH changes in supersaturated basins. In this study, the novel approach of high resolution computed tomography (CT) scanning was used to produce quantitative 3-dimensional renderings pteropod shells to assess the potential of using this method to monitor small changes in shell biometrics that may be driven by climate change drivers. An ontogenetic analysis of the shells of Cavolinia inflexa and Styliola subula collected from the Mediterranean was used to identify suitable monitoring metrics. Modern samples were then compared to historical samples of the same species, collected during the Mediterranean leg of the Thor (1910) and Dana (1921) cruises to assess whether any empirical differences could be detected. Shell densities were calculated and scanning electron microscopy was used to compare the aragonite crystal morphology. pH for the collection years was hind-cast using temperature and salinity time series with atmospheric CO2 concentrations from ice core data. Historical samples of S. subula were thicker than S. subula shells of the same size from 2012 and C. inflexa shells collected in 1910 were significantly denser than those from 2012. These results provide a baseline for future work to develop monitoring techniques for climate change in the oceans using the novel approach of high-resolution CT scanning.

Continue reading ‘Comparison of Mediterranean pteropod shell biometrics and ultrastructure from historical (1910 and 1921) and present day (2012) samples provides baseline for monitoring effects of global change’


Subscribe to the RSS feed

Powered by FeedBurner

Follow AnneMarin on Twitter

Blog Stats

  • 976,475 hits

OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book