Effects of ocean acidification on growth and physiology of Ulva lactuca (Chlorophyta) in a rockpool-scenario, link to supplementary data

Rising atmospheric CO2-concentrations will have severe consequences for a variety of biological processes. We investigated the responses of the green alga Ulva lactuca (Linnaeus) to rising CO2-concentrations in a rockpool scenario. U. lactuca was cultured under aeraton with air containing either preindustrial pCO2 (280µatm) or for the end of the 21st century predicted (700µatm) pCO2 for 31 days. We addressed the following question: Will elevated CO2-concentrations affect photosynthesis (net photosynthesis, rETR(max), Fv/Fm, pigment composition) and growth of U. lactuca in rockpools with limited water exchange? Two phases of the experiment were distinguished: In the initial phase (day 1-4) the Seawater Carbonate System (SWCS) of the culture medium could be adjusted to the selected atmospheric pCO2 condition by continuous aeration with target pCO2 values. In the second phase (day 4-31) the SWCS was largely determined by the metabolism of the growing U. lactuca biomass. In the initial phase, Fv/Fm and rETR(max) were only slightly elevated at high CO2-concentrations whereas growth was significantly enhanced. After 31 days the Chl a content of the thalli was significantly lower under future conditions and the photosynthesis of thalli grown under preindustrial conditions was not dependent on external carbonic anhydrase. Biomass increased significantly at high CO2-concentrations. At low CO2-concentrations most adult thalli disintegrated between day 14 and 21, whereas at high CO2-concentrations most thalli remained integer until day 31. Thallus disintegration at low CO2-concentrations was mirrored in a drastic decline in seawater DIC and HCO3-. Accordingly, the SWCS differed significantly between the treatments. Our results indicated a slight enhancement of photosynthetic performance and significantly elevated growth of U. lactuca at future CO2-concentrations. The accelerated thallus disintegration at high CO2-concentrations under conditions of limited water exchange indicates additional CO2 effects on the life cycle of U. lactuca when living in rockpools.

(Table 2) Stable isotopes in foraminifers at DSDP Leg 78

Analyses of stable isotopes of monospecific planktonic foraminifers (G. quadrilobatus group) and monogeneric benthic foraminifers (Cibicidoides spp.) from late Neogene Atlantic Site 502 and Pacific Site 503 were conducted in order to determine the paleoceanographic changes resulting from the late Neogene uplift of the Panama Isthmus and from climatic cooling. In general, results at each site are similar to those from previous studies for the late Miocene and late Pliocene time interval, documenting the late Miocene (6 Ma) shift in carbon isotopes and the inferred growth of permanent Northern Hemisphere continental ice sheets beginning about 3.2 Ma. Comparison of Atlantic-Pacific planktonic-benthic isotope data for four stratigraphic intervals (~6-8, ~5-6, ~3-5, and ~2-3 Ma) suggests that increasing isolation of Atlantic and Pacific low-latitude waters may be related to the emergence of the Panama Isthmus. The contrast between Atlantic and Pacific benthic foraminiferal d13C increased in two steps from 0.60 per mil to 1 per mil (the modern contrast) at about 6 Ma and 3 Ma. The first increase (0.15 per mil) may represent the end of previously limited deep-water communication between the Atlantic and Pacific at the present location of Panama. The second increase (0.25 per mil) may be due to increased production of North Atlantic Deep Water. This probably reflects the development of modern deep-sea circulation. The d18O of planktonic foraminifers begins to increase in Atlantic Site 502 at 4.2 Ma and may reflect the increasing salinity of the North Atlantic Ocean arising from diminishing surface-water exchange across Panama. This increase is clearly shown by contrasting the d18O of Atlantic and Pacific planktonic foraminifers, as well as the d18O of planktonic and benthic foraminifers at Site 502. This inferred increase in surface-water salinity begins at the time of increasing provinciality of Atlantic and Pacific planktonic foraminifers.

Seawater Nd and Pb isotopic record in central Pacific and Caribbean sediments

The shoaling and final closure of the Central American Seaway (CAS) resulted in a major change of the global ocean circulation and has been suggested as an essential driver for strengthening of Atlantic Meridional Overturning Circulation (AMOC). The exact timing of CAS closure is key to interpreting its importance. Here we present a reconstruction of deep and intermediate water Nd and Pb isotope compositions obtained from fossil fish teeth and the authigenic coatings of planktonic foraminifera in the eastern equatorial Pacific (Ocean Drilling Program (ODP) Site 1241) and the Caribbean (ODP Sites 998, 999, and 1000) covering the final stages of CAS closure between 5.6 and 2.2 Ma. The data for the Pacific site indicate no significant Atlantic/Caribbean influence over this entire period. The Caribbean sites show a continuous trend to less radiogenic Nd isotope compositions during the Pliocene, consistent with an enhancement of Upper North Atlantic Deep Water (UNADW) inflow and a strengthening of the AMOC. Superimposed onto this long-term trend, shorter-term changes of intermediate Caribbean Nd isotope signatures approached more UNADW-like values during intervals when published reconstructions of seawater salinity suggested complete closure of the CAS. The data imply that significant deep water exchange with the Pacific essentially stopped by 7 Ma and that shallow exchange, which still occurred at least periodically until approximately 2.5 Ma, may have been linked to the strength of the AMOC but did not have any direct effect on the intermediate and deep Caribbean Nd isotope signatures through mixing with Pacific waters.

(Table 1) Content of sand fraction components in sediments of the interglacial MIS 7 optimum from Core LV28-42-4

Distribution of diatoms, radiolarians, planktonic and benthic foraminifers, and sediment components in fraction >0.125 mm was analyzed in a core obtained from the central Sea of Okhotsk within frameworks of the Russian-German KOMEX Project. The core section characterizes the period 190-350 ka, which corresponds to marine-isotopic stages (MIS) 7 to 10. During glacial MIS 10 and MIS 8, the basin accumulated terrigenous material lacking microfossils or containing them in low abundance, which reflects, along with their composition, heavy sea-ice conditions, suppressed bioproductivity, and bottom environment aggressive toward calcium carbonate. Interglacial MIS 9 was characterized by elevated bioproductivity with accumulation of diatomaceous ooze during the climatic optimum (328 to 320 ka). Water exchange with the Pacific was maximal from 328 to 324 ka ago. Environment became moderate and close to the present-day one at the end of the optimum exhibiting possible existence of a dichothermal layer with substantial amounts of surface Pacific water still flowing into the basin. Similar to interglacial MIS 5e and MIS 1, ''old'' Pacific water determined near-bottom environment in the central Sea of Okhotsk during that period, although influx of terrigenous material was higher, probably reflecting more humid climate of the region. Slight warming marked the terminal MIS 8 (approximately 260 ka ago). Paleoceanographic situation during the interglacial MIS 7 was highly variable: from warm-water to almost glacial. The main climatic optimum of MIS 7 occurred within 220-210 ka, when subsurface stratification increased and the dichothermal layer developed. Bottom environment during the studied time interval, except for the optimum of interglacial MIS 9, resembled those characteristic of glacial periods: actively formed ''young'' Okhotsk water displaced ''old'' Pacific deep water.

(Table 2) Relative abundance of planktonic foraminifera species in Pliocene - Early Quaternary sediments from ODP Hole 111-677A

Planktonic foraminifera from Pliocene - Early Quaternary sediments of ODP Hole 111-677A were studied in detail. It was shown that the majority of detected zonal taxa are reliable biostratigraphic reference points. Between 30 and 210 m in the core zones of planktonic foraminifera from PL1b to Pt1 (according to the W.A. Berggren scale) were distinguished. Changes of planktonic foraminifera complexes from sediments of Hole 111-677A are closely associated with climate-controlled development of surface water masses of the Eastern Equatorial Pacific during 4.6-0.65 million years ago. Sharp decrease in equatorial-tropical species about 3.4 million years ago correlated with cessation of surface water exchange between tropical regions of the Pacific and Atlantic oceans due to formation of the Central American isthmus. The paleotemperature method of M.S Barash was used for reconstructing surface temperatures. Maximum temperatures were reconstructed in late Early Pliocene (26.4°C) and in Late Pliocene (26.6°C) and minimum ones - in the beginning of Early Pliocene (18.4°C), in the middle of Late Pliocene (19.6°C). Cold events occurred: 4.6-4.3, 2.8-2.5, and 1.7-1.2 million years ago, and warm: 4.3, 4.18-3.4, 2.5-2.3, and 1 million years ago. In general, the middle of Early Pliocene, the middle of late Pliocene and early Pleistocene are characterized by cold-water conditions, and the end of Early and the end of Late Pliocene - by warm-water conditions.

Distribution of planktonic and benthic foraminifers in bottom sediments from Core LV28-42-5, Sea of Okhotsk

Distribution of diatoms and planktonic and benthic foraminifers, as well as correlation of components of sandy grain size fraction were studied in the Quaternary sediment core LV28-42-5 (720 cm long) col¬lected on the southeastern slope (1045 m depth) of the Institute of Oceanology Rise, Sea of Okhotsk. This study allowed to reconstruct principle features of paleoceanographic evolution. In the course of penultimate and last continental glaciations (isotope stages 6 and 4-2) and during the later period of the last interglacial (substages 5.d-5.a) the following conditions were characteristic of this area: low temperatures of surface water, terrigenous sediment accumulation including coarse grained ice-rafted material, minimum bioproductivity and microfossil content in sediments, low sea level, reduced water exchange with the ocean, low position of old deep Pacific water. During the interglacial optimum (substage 5.e), as well as in the last deglaciation and Holocene (stage 1) water temperature and bioproductivity increased, sea level rose, and active surface water exchange between the Sea of Okhotsk and the Pacific Ocean and the Sea of Japan took place. This resulted in intensive inflow of the old deep Pacific water into the Sea of Okhotsk and elevation of its upper boundary by few hundred meters. During the later intervals of these warm periods a dichothermal structure of the upper water layer formed and diatom oozes accumulated.

Radiocarbon dating, oxygen isotopes, and sea-level reconstruction of sediment core GeoB5844-2 from the northern end of the Red Sea

Based on a radiocarbon and paleomagnetically dated sediment record from the northern Red Sea and the exceptional sensitivity of the regional changes in the oxygen isotope composition of sea water to the sea-level-dependent water exchange with the Indian Ocean, we provide a new global sea-level reconstruction spanning the last glacial period. The sea-level record has been extracted from the temperature-corrected benthic stable oxygen isotopes using coral-based sea-level data as constraints for the sea-level/oxygen isotope relationship. Although, the general features of this millennial-scale sea-level records have strong similarities to the rather symmetric and gradual Southern Hemisphere climate patterns, we observe, in constrast to previous findings, pronounced sea level rises of up to 25 m to generally correspond with Northern Hemisphere warmings as recorded in Greenland ice-core interstadial intervals whereas sea-level lowstands mostly occur during cold phases. Corroborated by CLIMBER-2 model results, the close connection of millennial-scale sea-level changes to Northern Hemisphere temperature variations indicates a primary climatic control on the mass balance of the major Northern Hemisphere ice sheets and does not require a considerable Antarctic contribution.

Stable isotopes of benthic foraminifera from Site ODP 184-1146

We generated a high resolution (~8 ky) benthic record from a West Pacific marginal basin to investigate the detailed structure and spectral characteristics of deep water isotope fluctuations during the middle Miocene. The benthic record from ODP Site 1146 allows unprecedented resolution of the structure of the middle Miocene delta13C excursion, as well as tighter control on the chronology of climatic events. Spectral analysis of the variance in the delta18O and delta13C records from ODP Site 1146 reveals spectral power concentrated in the eccentricity band (400-, ~100-ky) over the time interval between 13 and 17 Ma. The amplitude evolution in the 400-ky band is strikingly similar to that of the long eccentricity in Laskar's solution. There is an abrupt switch to the obliquity band in the delta18O record at -14.9 Ma, suggesting a shift in the ocean/climate response to orbital forcing (from low latitude eccentricity to high latitude obliquity forcing). The obliquity signal is pervasive in the delta18O record until -13.9 Ma, when a sharp increase in delta18O values indicates a major climatic transition. Comparison of delta18O and delta13C profiles from DSDP Site 588 (SW Pacific Ocean), ODP Site 761 (E Indian Ocean) and ODP Site 1146 (South China Sea) reveals significantly cooler deep water in the NE Indian Ocean throughout the middle Miocene and a restricted deep water exchange between the Pacific Ocean and Indian Ocean.

Egg and early larval stages of Baltic cod, Gadus morhua duirng ocean acidification experiments, 2012

The accumulation of carbon dioxide in the atmosphere will lower the pH in ocean waters, a process termed ocean acidification (OA). Despite its potentially detrimental effects on calcifying organisms, experimental studies on the possible impacts on fish remain scarce. While adults will most likely remain relatively unaffected by changes in seawater pH, early life-history stages are potentially more sensitive, due to the lack of gills with specialized ion-regulatory mechanisms. We tested the effects of OA on growth and development of embryos and larvae of eastern Baltic cod, the commercially most important fish stock in the Baltic Sea. Cod were reared from newly fertilized eggs to early non-feeding larvae in 5 different experiments looking at a range of response variables to OA, as well as the combined effect of CO2 and temperature. No effect on hatching, survival, development, and otolith size was found at any stage in the development of Baltic cod. Field data show that in the Bornholm Basin, the main spawning site of eastern Baltic cod, in situ levels of pCO2are already at levels of 1,100 µatm with a pH of 7.2, mainly due to high eutrophication supporting microbial activity and permanent stratification with little water exchange. Our data show that the eggs and early larval stages of Baltic cod seem to be robust to even high levels of OA (3,200 µatm), indicating an adaptational response to CO2.

Cation exchange capacity and water content of ODP sites from Nankai

Pore fluid chlorinity lower than seawater is often observed in accretionary wedges and one of the possible causes of pore water freshening is the smectite to illite reaction. This reaction occurs during diagenesis in the 80-150°C temperature range. Low chlorinity anomalies observed at the toe of accretionary wedges have thus been interpreted as evidence for lateral fluid migration from inner parts of the wedge and the seismogenic zone. However, temperature conditions in Nankai Trough are locally high enough for the smectite to illite transition to occur in situ. Cation exchange capacity is here used as a proxy for smectite content in the sediment and the amount of interlayer water released during the smectite to illite reaction represents in average 12 water molecules per cation charge. Water and chloride budget calculations show that there is enough smectite to explain the chlorinity anomalies by in situ reactions. The shape of the pore fluid chlorinity profiles can be explained if compaction is also taken into account in the model. Lateral flow is not needed. This argument, based solely on chloride concentration, does not imply that lateral flow is absent. However, previous estimations of lateral fluid fluxes, and of the duration of transient flow events along the de.collement, should be reconsidered.