Distribution of deep-sea foraminifera in surface sediments east of New Zealand

Paleobathymetric assessments of fossil foraminiferal faunas play a significant role in the analysis of the paleogeographic, sedimentary, and tectonic histories of New Zealand's Neogene marine sedimentary basins. At depths >100 m, these assessments often have large uncertainties. This study, aimed at improving the precision of paleodepth assessments, documents the present-day distribution of deep-sea foraminifera (>63 µm) in 66 samples of seafloor sediment at 90-700 m water depth (outer shelf to mid-abyssal), east of New Zealand. One hundred and thirty-nine of the 465 recorded species of benthic foraminifera are new records for the New Zealand region. Characters of the foraminiferal faunas which appear to provide the most useful information for estimating paleobathymetry are, in decreasing order of reliability: relative abundance of common benthic species; benthic species associations; upper depth limits of key benthic species; and relative abundance of planktic foraminifera. R mode cluster analysis on the quantitative census data of the 58 most abundant species of benthic foraminifera produced six species associations within three higher level clusters: (1) calcareous species most abundant at mid-bathyal to outer shelf depths (<1000 m); (2) calcareous species most abundant at mid-bathyal and greater depths (>600 m); (3) agglutinated species mostly occurring at deep abyssal depths (>3000 m). A detrended correspondence analysis ordination plot exhibits a strong relationship between these species associations and bathymetry. This is manifest in the bathymetric ranges of the relative abundance peaks of many of the common benthic species (e.g., Abditodentrix pseudothalmanni 500-2800 m, Bolivina robusta 200-650 m, Bulimina marginata f. marginata 20-600 m, B. marginata f. aculeata 400-3000 m, Cassidulina norvangi 1000-4500 m, Epistominella exigua 1000-4700 m, and Trifarina angulosa 10-650 m), which should prove useful in paleobathymetric estimates. The upper depth limits of 28 benthic foraminiferal species (e.g., Fursenkoina complanata 200 m, Bulimina truncana 450 m, Melonis affinis 550 m, Eggerella bradyi 750 m, and Cassidulina norvangi 1000 m) have potential to improve the precision of paleobathymetric estimates based initially on the total faunal composition. The planktic percentage of foraminiferal tests increases from outer shelf to upper abyssal depths followed by a rapid decline within the foraminiferal lysocline (below c. 3600 m). A planktic percentage <50% is suggestive of shelf depths, and >50% is suggestive of bathyal or abyssal depths above the CCD. In the abyssal zone there is dramatic taphonomic loss of most agglutinated tests (except some textulariids) at burial depths of 0.1-0.2 m, which negates the potential usefulness of these taxa in paleobathymetric assessments.

(Table 1) Variation in chemical composition of Black Sea ctenophores depending on size

Data of chemical analysis of Black Sea ctenophore Mnemiopsis leidyi indicates that their body contains on average 5.28% carbon, 3.48% nitrogen, 0.11% phosphorus, and 0.03% silicon on dry weight. Mean ratios of the main biogenic elements in ctenophores is C:N=1.4, N:P=10.9, and C:P=32.2. Comparing concentration of the main biogenic elements in the surface layer with their concentrations in ctenophores it is concluded that mass development of M. leidyi has negative effect on the hydrochemical structure of the Black Sea.

Effects of seawater acidification on early development of the intertidal sea urchin Paracentrotus lividus, seawater carbonate chemistry and biological processes

The effect of pH ranging from 8.0 to 6.8 (total scale - pHT) on fertilization, cleavage and larval development until pluteus stage was assessed in an intertidal temperate sea urchin. Gametes were obtained from adults collected in two contrasting tide pools, one showing a significant nocturnal pH decrease (lowest pHT = 7.4) and another where pH was more stable (lowest pHT = 7.8). The highest pHT at which significant effects on fertilization and cleavage were recorded was 7.6. On the contrary, larval development was only affected below pHT 7.4, a value equal or lower than that reported for several subtidal species. This suggests that sea urchins inhabiting stressful intertidal environments produce offspring that may better resist future ocean acidification. Moreover, at pHT 7.4, the fertilization rate of gametes whose progenitors came from the tide pool with higher pH decrease was significantly higher, indicating a possible acclimatization or adaptation of gametes to pH stress.

Effect of increasing sea water pCO2 on the northern Atlantic krill species Nyctiphanes couchii

Surprisingly little is known about potential effects of ocean acidification on krill of the Northern Hemisphere as ecologically very important food web component. Sub-adult individuals of the northern Atlantic krill species Nyctiphanes couchii (caught at Austevoll near Bergen, Norway, in January 2013) were exposed in the laboratory to four different levels of pCO2 (430, 800, 1,100, and 1,700 µatm) for 5 weeks in order to assess potential changes in a set of biological response variables. Survival decreased and the frequency of moulting-related deaths increased with increasing pCO2. Survival was considerably reduced at relatively high pCO2 of 1,700 µatm and tended to be negatively affected at 1,100 µatm pCO2. However, the experimental results show no significant effects of pCO2 on inter-moult period and growth at pCO2 levels below 1,100 µatm. No differences in length measurements of the carapace and uropod were observed across pCO2 levels, indicating no effect of changing carbonate chemistry on the morphology of those calciferous parts of the exoskeleton. The results suggest that sub-adult N. couchii may not suffer dramatically from predicted near-future changes in pCO2. However, potential detrimental effects on the moulting process and associated higher mortality at 1,100 µatm pCO2 cannot be excluded. Further experiments are needed in order to investigate whether early life stages of N. couchii show a different sensitivity to elevated sea water pCO2 and whether those results are transferable to other krill species of the Northern Hemisphere.

Physical oceanography and current meter measurements on the Gulf of Lion continental margin between June 1993 and July 1996

Nine hydrographic cruises were performed on the Gulf of Lion continental margin between June 1993 and July 1996. These observations are analysed to quantify the fluxes of particulate matter and organic carbon transported along the slope by the Northern Current and to characterise their seasonal variability. Concentration of particulate matter and organic carbon are derived from light-transmission data and water sample analyses. The circulation is estimated from the geostrophic current field. The uncertainty on the transport estimate, related to the error on the prediction of particle concentrations from light-transmission data and the error on velocities, is assessed. The particulate matter inflow entering the Gulf of Lion off Marseille is comparable to the Rhône River input and varies seasonally with a maximum transport between autumn and spring. These modifications result from variations of the water flux rather than variations of the particulate matter concentration. Residual transports of particulate matter and organic carbon across the entire Gulf of Lion are calculated for two cruises enclosing the domain that were performed in February 1995 and July 1996. The particulate matter budgets indicate a larger export from the shelf to deep ocean in February 1995 (110 ± 20 kg/s) than in July 1996 (25 ± 18 kg/s). Likewise, the mean particulate organic carbon export is 12.8 ± 0.5 kg/s in February 1995 and 0.8 ± 0.2 kg/s in July 1996. This winter increase is due to larger allochthonous and autochthonous inputs and also to enhanced shelf-slope exchange processes, in particular the cascading of cold water from the shelf. The export of particulate matter by the horizontal currents is moreover two orders of magnitude larger than the vertical particulate fluxes measured at the same time with sediment traps on the continental slope.

Mg/Ca values for planktonic foraminifera N. pachyderma and G. bulloides from ocean sediment core MD02-2496 on the Vancouver margin, Northeastern Pacific Ocean

A new, high-resolution planktonic foraminiferal Mg/Ca-based ocean temperature record has been generated for deep sea core MD02-2496, sited offshore of Vancouver Island, Western Canada during the last deglaciation (21-12 ka). The relationship between Cordilleran Ice Sheet (CIS) retreat and changing regional ocean temperatures has been reconstructed through glaciomarine sediments in MD02-2496 that capture tidewater glacier response to surface ocean thermal forcing. At CIS maximum extent, the marine margin of the ice sheet advanced onto the continental shelf. During this interval, ocean temperatures recorded by surface ocean dwelling Globigerina bulloides remained a relatively constant ~7.5°C while subsurface dwelling Neogloboquadrina pachyderma (s.) recorded temperatures of ~5°C. These ocean temperatures were sufficiently warm to induce significant melt along the tidewater ice terminus similar to modern Alaskan tidewater glacial systems. During the deglacial retreat of the CIS, the N. pachyderma temperature record shows two distinct warming steps of ~2 and 2.5°C between 17.2-16 and 15.5-14 ka respectively, coincident with ice rafting events from the CIS, while G. bulloides records an ~3°C warming from 15 to14 ka. We hypothesize that submarine melting resulting from relatively warm ocean temperatures was an important process driving ice removal from CIS tidewater glaciers during the initial stages of deglaciation.