Planktonic foraminifera in the latest Maastrichtian of Walvis Ridge, South Atlantic

An abrupt global warming of 3-4°C occurred near the end of the Maastrichtian at 65.45-65.10 Ma. The environmental effects of this warm event are here documented based on stable isotopes and quantitative analysis of planktonic foraminifera at the South Atlantic DSDP Site 525A. Stable isotopes of individual species mark a rapid increase in temperature and a reduction in the vertical water mass stratification that is accompanied by a decrease in niche habitats, reduced species diversity and/or abundance, smaller species morphologies or dwarfing, and reduced photosymbiotic activity. During the warm event, the relative abundance of a large number of species decreased, including tropical-subtropical affiliated species, whereas typical mid-latitude species retained high abundances. This indicates that climate warming did not create favorable conditions for all tropical-subtropical species at mid-latitudes and did not cause a massive retreat in the local mid-latitude population. A noticeable exception is the ecological generalist Heterohelix dentata Stenestad that dominated during the cool intervals, but significantly decreased during the warm event. However, dwarfing is the most striking response to the abrupt warming and occurred in various species of different morphologies and lineages (e.g. biserial, trochospiral, keeled globotruncanids). Dwarfing is a typical reaction to environmental stress conditions and was likely the result of increased reproduction rates. Similarly, photosymbiotic activity appears to have been reduced significantly during the maximum warming, as indicated by decreased delta13C values. The foraminiferal response to climate change is thus multifaceted resulting in decreased species diversity, decreased species populations, increased competition due to reduced niche habitats, dwarfing and reduced photosymbiotic activity.

Global planktonic foraminifera seasonality

Shell fluxes of planktonic Foraminifera species vary intra-annually in a pattern that appears to follow the seasonal cycle. However, the variation in the timing and prominence of seasonal flux maxima in space and among species remains poorly constrained. Thus, although changing seasonality may result in a flux-weighted temperature offset of more than 5° C within a species, this effect is often ignored in the interpretation of Foraminifera-based paleoceanographic records. To address this issue we present an analysis of the intra-annual pattern of shell flux variability in 37 globally distributed time series. The existence of a seasonal component in flux variability was objectively characterised using periodic regression. This analysis yielded estimates of the number, timing and prominence of seasonal flux maxima. Over 80% of the flux series across all species showed a statistically significant periodic component, indicating that a considerable part of the intra-annual flux variability is predictable. Temperature appears to be a powerful predictor of flux seasonality, but its effect differs among species. Three different modes of seasonality are distinguishable. Tropical and subtropical species (Globigerinoides ruber (white and pink varieties), Neogloboquadrina dutertrei, Globigerinoides sacculifer, Orbulina universa, Globigerinella siphonifera, Pulleniatina obliquiloculata, Globorotalia menardii, Globoturborotalita rubescens, Globoturborotalita tenella and Globigerinoides conglobatus) appear to have a less predictable flux pattern, with random peak timing in warm waters. In colder waters, seasonality is more prevalent: peak fluxes occur shortly after summer temperature maxima and peak prominence increases. This tendency is stronger in species with a narrower temperature range, implying that warm-adapted species find it increasingly difficult to reproduce outside their optimum temperature range and that, with decreasing mean temperature, their flux is progressively more focussed in the warm season. The second group includes the temperate to cold-water species Globigerina bulloides, Globigerinita glutinata, Turborotalita quinqueloba, Neogloboquadrina incompta, Neogloboquadrina pachyderma, Globorotalia scitula, Globigerinella calida, Globigerina falconensis, Globorotalia theyeri and Globigerinita uvula. These species show a highly predictable seasonal pattern, with one to two peaks a year, which occur earlier in warmer waters. Peak prominence in this group is independent of temperature. The earlier-when-warmer pattern in this group is related to the timing of productivity maxima. Finally, the deep-dwelling Globorotalia truncatulinoides and Globorotalia inflata show a regular and pronounced peak in winter and spring. The remarkably low flux outside the main pulse may indicate a long reproductive cycle of these species. Overall, our analysis indicates that the seasonality of planktonic Foraminifera shell flux is predictable and reveals the existence of distinct modes of phenology among species. We evaluate the effect of changing seasonality on paleoceanographic reconstructions and find that, irrespective of the seasonality mode, the actual magnitude of environmental change will be underestimated. The observed constraints on flux seasonality can serve as the basis for predictive modelling of flux pattern. As long as the diversity of species seasonality is accounted for in such models, the results can be used to improve reconstructions of the magnitude of environmental change in paleoceanographic records.

Stable isotope record and lithic fragments distribution in sediments of MIS9-14 of the North Atlantic

Stable isotope and ice-rafted debris records from three core sites in the mid-latitude North Atlantic (IODP Site U1313, MD01-2446, MD03-2699) are combined with records of ODP Sites 1056/1058 and 980 to reconstruct hydrographic conditions during the middle Pleistocene spanning Marine Isotope Stages (MIS) 9-14 (300-540 ka). Core MD03-2699 is the first high-resolution mid-Brunhes record from the North Atlantic's eastern boundary upwelling system covering the complete MIS 11c interval and MIS 13. The array of sites reflect western and eastern basin boundary current as well as north to south transect sampling of subpolar and transitional water masses and allow the reconstruction of transport pathways in the upper limb of the North Atlantic's circulation. Hydrographic conditions in the surface and deep ocean during peak interglacial MIS 9 and 11 were similar among all the sites with relative stable conditions and confirm prolonged warmth during MIS 11c also for the mid-latitudes. Sea surface temperature (SST) reconstructions further reveal that in the mid-latitude North Atlantic MIS 11c is associated with two plateaus, the younger one of which is slightly warmer. Enhanced subsurface northward heat transport in the eastern boundary current system, especially during early MIS 11c, is denoted by the presence of tropical planktic foraminifer species and raises the question how strongly it impacted the Portuguese upwelling system. Deep water ventilation at the onset of MIS 11c significantly preceded surface water ventilation. Although MIS 13 was generally colder and more variable than the younger interglacials the surface water circulation scheme was the same. The greatest differences between the sites existed during the glacial inceptions and glacials. Then a north - south trending hydrographic front separated the nearshore and offshore waters off Portugal. While offshore waters originated from the North Atlantic Current as indicated by the similarities between the records of IODP Site U1313, ODP Site 980 and MD01-2446, nearshore waters as recorded in core MD03-2699 derived from the Azores Current and thus the subtropical gyre. Except for MIS 12, Azores Current influence seems to be related to eastern boundary system dynamics and not to changes in the Atlantic overturning circulation.

Planktonic foraminifera and their stable isotope record of MICNESS samples off Cape Cod

Monthly samples of stratified plankton tows taken from the slope waters off Cape Cod nearly 25 years ago are used to describe the seasonal succession of planktonic foraminifera and their oxygen isotope ratios. The 15°C seasonal cycle of sea surface temperature (SST) accounts for a diverse mixture of tropical to subpolar species. Summer samples include various Globigerinoides and Neogloboquadrina dutertrei, whereas winter and early spring species include Globigerina bulloides and Neogloboquadrina pachyderma (dextral). Globorotalia inflata lives all year but at varying water depths. Compared with the fauna in 1960-1961 (described by R. Cifelli), our samples seem warmer. Because sea surface salinity varies little during the year, d18O is mostly a function of SST. Throughout the year, there are always species present with d18O close to the calculated isotopic equilibrium of carbonate with surface seawater. This raises the possibility that seasonality can be estimated directly from the range of d18O in a sediment sample provided that the d18O-salinity relationship is the same as today.

Calcification of the Arctic coralline red algae Lithothamnion glaciale in response to elevated CO2

Rising atmospheric CO2 concentrations could cause a calcium carbonate subsaturation of Arctic surface waters in the next 20 yr, making these waters corrosive for calcareous organisms. It is presently unknown what effects this will have on Arctic calcifying organisms and the ecosystems of which they are integral components. So far, acidification effects on crustose coralline red algae (CCA) have only been studied in tropical and Mediterranean species. In this work, we investigated calcification rates of the CCA Lithothamnion glaciale collected in northwest Svalbard in laboratory experiments under future atmospheric CO2 concentrations. The algae were exposed to simulated Arctic summer and winter light conditions in 2 separate experiments at optimum growth temperatures. We found a significant negative effect of increased CO2 levels on the net calcification rates of L. glaciale in both experiments. Annual mean net dissolution of L. glaciale was estimated to start at an aragonite saturation state between 1.1 and 0.9 which is projected to occur in parts of the Arctic surface ocean between 2030 and 2050 if emissions follow 'business as usual' scenarios (SRES A2; IPCC 2007). The massive skeleton of CCA, which consist of more than 80% calcium carbonate, is considered crucial to withstanding natural stresses such as water movement, overgrowth or grazing. The observed strong negative response of this Arctic CCA to increased CO2 levels suggests severe threats of the projected ocean acidification for an important habitat provider in the Arctic coastal ocean.

Seawater carbonate chemistry and severe tissue damage in Atlantic cod larvae under increasing ocean acidification, 2012

Ocean acidification, caused by increasing atmospheric concentrations of CO2, is one of the most critical anthropogenicthreats to marine life. Changes in seawater carbonate chemistry have the potential to disturb calcification, acid-base regulation, blood circulation and respiration, as well as the nervous system of marine organisms, leading to long-term effects such as reduced growth rates and reproduction. In teleost fishes, early life-history stages are particularly vulnerable as they lack specialized internal pH regulatory mechanisms. So far, impacts of relevant CO2concentrations on larval fish have been found in behaviour and otolith size, mainly in tropical, non-commercial species. Here we show detrimental effects of ocean acidification on the development of a mass-spawning fish species of high commercial importance. We reared Atlantic cod larvae at three levels of CO2, (1) present day, (2) end of next century and (3) an extreme, coastal upwelling scenario, in a long-term ( 2.5 1/2 months) mesocosm experiment. Exposure to CO2 resulted in severe to lethal tissue damage in many internal organs, with the degree of damage increasing with CO2 concentration. As larval survival is the bottleneck to recruitment, ocean acidification has the potential to act as an additional source of natural mortality, affecting populations of already exploited fish stocks.

Data compilation of hummingbird-pollinated plant species in the Brazilian Atlantic rain forest

We studied the relationship between flower size and nectar properties of hummingbird-visited flowers in the Brazilian Atlantic Forest. We analysed the nectar volume and concentration as a function of corolla length and the average bill size of visitors for 150 plant species, using the phylogenetic generalized least squares (PGLS) to control for phylogenetic signals in the data. We found that nectar volume is positively correlated with corolla length due to phylogenetic allometry. We also demonstrated that larger flowers provide better rewards for long-billed hummingbirds. Regardless of the causal mechanisms, our results support the hypothesis that morphological floral traits that drive partitioning among hummingbirds correspond to the quantity of resources produced by the flowers in the Atlantic Forest. We demonstrate that the relationship between nectar properties and flower size is affected by phylogenetic constraints and thus future studies assessing the interaction between floral traits need to control for phylogenetic signals in the data.

Avian species identity and predation success in tropical cacao agroforestry of the Napu Valley in Central Sulawesi, Indonesia

Avian ecosystem services such as the suppression of pests are considered being of high ecological and economic importance in a range of ecosystems, especially in tropical agroforestry. But how bird predation success is related to the diversity and composition of the bird community, as well as local and landscape factors, is poorly understood. The author quantified arthropod predation in relation to the identity and diversity of insectivorous birds, using experimental exposure of artificial, caterpillar-like prey on smallholder cacao agroforestry systems, differing in local shade management and distance to primary forest. The bird community was assessed using both mist netting (targeting on active understory insectivores) and point count (higher completeness of species inventories) sampling. The study was conducted in a land use dominated area in Central Sulawesi, Indonesia, adjacent to the Lore Lindu National Park. We selected 15 smallholder cacao plantations as sites for bird and bat exclosure experiments in March 2010. Until July 2011, we recorded several data in this study area, including the bird community data, cacao tree data and bird predation experiments that are presented here. We found that avian predation success can be driven by single and abundant insectivorous species, rather than by overall bird species richness. Forest proximity was important for enhancing the density of this key species, but did also promote bird species richness. The availability of local shade trees had no effects on the local bird community or avian predation success. Our findings are both of economical as well as ecological interest because the conservation of nearby forest remnants will likely benefit human needs and biodiversity conservation alike.

Species-specific consequences of ocean acidification for the calcareous tropical green algae Halimeda, 2011

Ocean acidification (OA), resulting from increasing dissolved carbon dioxide (CO2) in surface waters, is likely to affect many marine organisms, particularly those that calcify. Recent OA studies have demonstrated negative and/or differential effects of reduced pH on growth, development, calcification and physiology, but most of these have focused on taxa other than calcareous benthic macroalgae. Here we investigate the potential effects of OA on one of the most common coral reef macroalgal genera,Halimeda. Species of Halimeda produce a large proportion of the sand in the tropics and are a major contributor to framework development on reefs because of their rapid calcium carbonate production and high turnover rates. On Palmyra Atoll in the central Pacific, we conducted a manipulative bubbling experiment to investigate the potential effects of OA on growth, calcification and photophysiology of 2 species of Halimeda. Our results suggest that Halimeda is highly susceptible to reduced pH and aragonite saturation state but the magnitude of these effects is species specific. H. opuntiasuffered net dissolution and 15% reduction in photosynthetic capacity, while H. taenicola did not calcify but did not alter photophysiology in experimental treatments. The disparate responses of these species to elevated CO2 partial -pressure (pCO2) may be due to anatomical and physiological differences and could represent a shift in their relative dominance in the face of OA. The ability for a species to exert biological control over calcification and the species specific role of the carbonate skeleton may have important implications for the potential effects of OA on ecological function in the future.

DNA alignment and Bayesian trees of partial sequences of COI, COIII and the haemocyanin functional unit f-g of 28 octopod species

Background: Octopods have successfully colonised the world's oceans from the tropics to the poles. Yet, successful persistence in these habitats has required adaptations of their advanced physiological apparatus to compensate impaired oxygen supply. Their oxygen transporter haemocyanin plays a major role in cold tolerance and accordingly has undergone functional modifications to sustain oxygen release at sub-zero temperatures. However, it remains unknown how molecular properties evolved to explain the observed functional adaptations. We thus aimed to assess whether natural selection affected molecular and structural properties of haemocyanin that explains temperature adaptation in octopods. Results: Analysis of 239 partial sequences of the haemocyanin functional units (FU) f and g of 28 octopod species of polar, temperate, subtropical and tropical origin revealed natural selection was acting primarily on charge properties of surface residues. Polar octopods contained haemocyanins with higher net surface charge due to decreased glutamic acid content and higher numbers of basic amino acids. Within the analysed partial sequences, positive selection was present at site 2545, positioned between the active copper binding centre and the FU g surface. At this site, methionine was the dominant amino acid in polar octopods and leucine was dominant in tropical octopods. Sites directly involved in oxygen binding or quaternary interactions were highly conserved within the analysed sequence. Conclusions: This study has provided the first insight into molecular and structural mechanisms that have enabled octopods to sustain oxygen supply from polar to tropical conditions. Our findings imply modulation of oxygen binding via charge-charge interaction at the protein surface, which stabilize quaternary interactions among functional units to reduce detrimental effects of high pH on venous oxygen release. Of the observed partial haemocyanin sequence, residue 2545 formed a close link between the FU g surface and the active centre, suggesting a role as allosteric binding site. The prevalence of methionine at this site in polar octopods, implies regulation of oxygen affinity via increased sensitivity to allosteric metal binding. High sequence conservation of sites directly involved in oxygen binding indicates that functional modifications of octopod haemocyanin rather occur via more subtle mechanisms, as observed in this study.

Phytoplankton, dissolved inorganic nutrients and hydrography during the ACEx/SIMTECO campaign in the southern Brazilian shelf in June 2012 (SW Atlantic - Winter 2012)

The response of phytoplankton assemblages to hydrographical forcing across the southern Brazilian shelf was studied based on data collected during wintertime (June/2012), complemented with MODIS-Aqua satellite imagery. The in situ data set was comprised by water column structure properties (derived from CTD casts), dissolved inorganic nutrients (ammonium, nitrite, nitrate, phosphate and silicate) and phytoplankton biomass [chlorophyll a (Chl a) concentration] and composition. Phytoplankton assemblages were assessed by both microscopy and HPLC-CHEMTAX approaches. A canonical correspondence analysis associating physical, chemical and phytoplankton composition data at surface evinced a tight coupling between the phytoplankton community and hydrographic conditions, with remarkable environmental gradients across three different domains: the pelagic, outer shelf Tropical Water (TW); the mid shelf domain under influence of Subtropical Shelf Water (STSW); and the inner shelf domain mainly under influence of riverine outflow of the Plata River Plume Water (PPW). Results showed that intrusion of low salinity and nutrient-rich PPW stimulated the phytoplankton growth and diversity within the inner shelf region, with enhanced Chl a levels (>1.3 mg/m**3) and a great abundance of diatoms, ciliates, dinoflagellates, raphidophyceans and cryptophytes. Conversely, other diatoms (e.g. Rhizosolenia clevei), tiny species of prochlorophytes and cyanobacteria and a noticeable contribution of dinoflagellates and other flagellates associated with lower Chl a levels (<0.93 mg/m**3), characterized the TW domain, where low nutrient concentrations and deep upper mixed layer were found. The transitional mid shelf domain showed intermediate levels of both nutrients and Chl a (ranging 1.06-1.59 mg/m**3), and phytoplankton was mainly composed by dinoflagellates, such as Dinophysis spp., and gymnodinioids. Results have shown considerable phytoplankton diversity in winter at that section of the southwestern Atlantic Ocean.

Responses of three tropical seagrass species to CO2 enrichment

Increased atmospheric carbon dioxide leads to ocean acidification and carbon dioxide (CO2) enrichment of seawater. Given the important ecological functions of seagrass meadows, understanding their responses to CO2 will be critical for the management of coastal ecosystems. This study examined the physiological responses of three tropical seagrasses to a range of seawater pCO2 levels in a laboratory. Cymodocea serrulata, Halodule uninervis and Thalassia hemprichii were exposed to four different pCO2 treatments (442-1204 µatm) for 2 weeks, approximating the range of end-of-century emission scenarios. Photosynthetic responses were quantified using optode-based oxygen flux measurements. Across all three species, net productivity and energetic surplus (PG:R) significantly increased with a rise in pCO2 (linear models, P < 0.05). Photosynthesis-irradiance curve-derived photosynthetic parameters-maximum photosynthetic rates (P max) and efficiency (alpha) also increased as pCO2 increased (linear models, P < 0.05). The response for productivity measures was similar across species, i.e. similar slopes in linear models. A decrease in compensation light requirement (Ec) with increasing pCO2 was evident in C. serrulata and H. uninervis, but not in T. hemprichii. Despite higher productivity with pCO2 enrichment, leaf growth rates in C. serrulata did not increase, while those in H. uninervis and T. hemprichii significantly increased with increasing pCO2 levels. While seagrasses can be carbon-limited and productivity can respond positively to CO2 enrichment, varying carbon allocation strategies amongst species suggest differential growth response between species. Thus, future increase in seawater CO2 concentration may lead to an overall increase in seagrass biomass and productivity, as well as community changes in seagrass meadows.

Relative abundance of diatom species in surface samples from the Southern Ocean, Tropical/Subtropical species

This paper gives a modern circumscription of Tropical/Subtropical diatoms regarding their relationship with sea-surface temperatures (SST) and sea ice cover. Diatoms from 228 core-top sediment samples collected from the Southern Ocean were studied to determine the geographic distribution of eight major diatom species/taxa preserved in surface sediments generally located north of the Subantarctic Front. The comparison of the relative contribution of diatom species with modern February SST and sea-ice cover reveals species-specific sedimentary distributions regulated both by water temperatures and sea ice conditions. Although selective preservation might have played some role, their presence in surface and downcore sediments from the Southern Ocean are reliable indicators of high SST and poleward transport of waters from the Tropical/Subtropical Atlantic. Our work supports the use of diatom remains to reconstruct past variations of these environmental parameters via qualitative and transfer function approaches.