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Although iron availability has been shown to limit ocean productivity and influence marine carbon cycling, the rates of processes driving iron's removal and retention in the upper ocean are poorly constrained. Using 234Th‐ and sediment‐trap data, most of which were collected through international GEOTRACES efforts, we perform an unprecedented observation‐based assessment of iron export from and residence time in the upper ocean. The majority of these new residence time estimates for total iron in the surface ocean (0‐250 m) fall between 10 and 100 days. The upper ocean residence time of dissolved iron, on the other hand, varies and cycles on sub‐annual to annual timescales. Collectively, these residence times are shorter than previously thought, and the rates and timescales presented here will contribute to ongoing efforts to integrate iron into global biogeochemical models predicting climate and carbon dioxide sequestration in the ocean in the 21st century and beyond. Plain Language Summary Iron is a key micronutrient for organisms living in the upper ocean and thus, its availability is one of the key factors controlling the removal of carbon dioxide via phytoplankton growth in much of the global ocean. Until very recently, measurements of internal iron cycling were scarce. This includes estimates of how much iron leaves the surface ocean via sinking particles. Due to the lack of observations, models struggle to reproduce observed patterns in global surface iron distributions. For the first time, we constrain the rate of iron loss from the upper ocean along three basin‐wide transects and bring together all preexisting estimates to determine the timescales on which different forms of iron are retained in the upper ocean. Overall, our findings suggest that iron cycles more rapidly between the surface and the subsurface ocean than previously estimated and we encourage the modeling community to utilize the wealth of data presented here to explore the global consequences of these findings.

Ocean circulation plays a fundamental role in governing marine resources. It exhibits cycles that last decades and is likely to be strongly influenced by climate change. This policy brief outlines new knowledge gained as part of the ATLAS and iAtlantic projects on the changing Atlantic Ocean circulation and its impacts on marine natural capital. It highlights the need for sustained in-situ observing and enhanced biological understanding to improve future forecasts of ecosystem response.

Aim To infer cold‐water corals’ (CWC) post‐glacial phylogeography and assess the role of Mediterranean Sea glacial refugia as origins for the recolonization of the northeastern Atlantic Ocean. Location Northeastern Atlantic Ocean and Mediterranean Sea. Taxon Lopheliapertusa, Madreporaoculata. Methods We sampled CWC using remotely operated vehicles and one sediment core for coral and sediment dating. We characterized spatial genetic patterns (microsatellites and a nuclear gene fragment) using networks, clustering and measures of genetic differentiation. Results Inferences from microsatellite and sequence data were congruent, and showed a contrast between the two CWC species. Populations ofL.pertusapresent a dominant pioneer haplotype, local haplotype radiations and a majority of endemic variation in lower latitudes.Madreporaoculatapopulations are differentiated across the northeastern Atlantic and genetic lineages are poorly admixed even among neighbouring sites. Conclusions Our study shows contrasting post‐glacial colonization pathways for two key habitat‐forming species in the deep sea. The CWCL.pertusahas likely undertaken a long‐range (post‐glacial) recolonization of the northeastern Atlantic directly from refugia located along southern Europe (Mediterranean Sea or Gulf of Cadiz). In contrast, the stronger genetic differentiation ofM.oculatapopulations mirrors the effects of long‐term isolation in multiple refugia. We suggest that the distinct and genetically divergent, refugial populations initiated the post‐glacial recolonization of the northeastern Atlantic margins, leading to a secondary contact in the northern range and reaching higher latitudes much later, in the late Holocene. This study highlights the need to disentangle the influences of present‐day dispersal and evolutionary processes on the distribution of genetic polymorphisms, to unravel the influence of past and future environmental changes on the connectivity of cosmopolitan deep‐sea ecosystems associated with CWC. &nbsp

Brucellosis is a zoonotic disease with terrestrial or marine wildlife animals as potential reservoirs for the disease in livestock and human populations. The primary aim of this study was to assess the presence of Brucella pinnipedialis in marine mammals living along the Dutch coast and to observe a possible correlation between the presence of B. pinnipedialis and accompanying pathology found in infected animals. The overall prevalence of Brucella spp. antibodies in sera from healthy wild grey seals (Halichoerus grypus; n=11) and harbor seals (Phoca vitulina; n=40), collected between 2007 and 2013 ranged from 25% to 43%. Additionally, tissue samples of harbor seals collected along the Dutch shores between 2009 and 2012, were tested for the presence of Brucella spp. In total, 77% (30/39) seals were found to be positive for Brucella by IS711 real-time PCR in one or more tissue samples, including pulmonary nematodes. Viable Brucella was cultured from 40% (12/30) real-time PCR-positive seals, and was isolated from liver, lung, pulmonary lymph node, pulmonary nematode, or spleen, but not from any PCR-negative seals. Tissue samples from lung and pulmonary lymph nodes were the main source of viable Brucella bacteria. All isolates were typed as B. pinnipedialis by multiple-locus variable number of tandem repeats analysis-16 clustering and matrix-assisted laser desorption ionization-time of flight mass spectrometry, and of sequence type ST25 by multilocus sequence typing analysis. No correlation was observed between Brucella infection and pathology. This report displays the isolation and identification of B. pinnipedialis in marine mammals in the Dutch part of the Atlantic Ocean.

International audience; During the last few centuries oceanic island biodiversity has been drastically modified by human-mediated activities. These changes have led to the increased homogenization of island biota and to a high number of extinctions lending support to the recognition of oceanic islands as major threatspots worldwide. Here, we investigate the impact of habitat changes on the spider and ground beetle assemblages of the native forests of Madeira (Madeira archipelago) and Terceira (Azores archipelago) and evaluate its effects on the relative contribution of rare endemics and introduced species to island biodiversity patterns. We found that the native laurel forest of Madeira supported higher species richness of spiders and ground beetles compared with Terceira, including a much larger proportion of indigenous species, particularly endemics. In Terceira, introduced species are well-represented in both terrestrial arthropod taxa and seem to thrive in native forests as shown by the analysis of species abundance distributions (SAD) and occupancy frequency distributions (OFD). Low abundance range-restricted species in Terceira are mostly introduced species dispersing from neighbouring man-made habitats while in Madeira a large number of true rare endemic species can still be found in the native laurel forest. Further, our comparative analysis shows striking differences in species richness and composition that are due to the geographical and geological particularities of the two islands, but also seem to reflect the differences in the severity of human-mediated impacts between them. The high proportion of introduced species, the virtual absence of rare native species and the finding that the SADs and OFDs of introduced species match the pattern of native species in Terceira suggest the role of man as an important driver of species diversity in oceanic islands and add evidence for an extensive and severe human-induced species loss in the native forests of Terceira.

We performed nitrogen (N) budgets in the photic layer of three contrasting stations representing different trophic conditions in the western tropical South Pacific (WTSP) Ocean during austral summer conditions (February–March 2015). Using a Lagrangian strategy, we sampled the same water mass for the entire duration of each long-duration (5 days) station, allowing us to consider only vertical exchanges for the budgets. We quantified all major vertical N fluxes both entering (N2 fixation, nitrate turbulent diffusion, atmospheric deposition) and leaving the photic layer (particulate N export). The three stations were characterized by a strong nitracline and contrasted deep chlorophyll maximum depths, which were lower in the oligotrophic Melanesian archipelago (MA, stations LD A and LD B) than in the ultra-oligotrophic waters of the South Pacific Gyre (SPG, station LD C). N2 fixation rates were extremely high at both LD A (593 ± 51 µmol N m−2 d−1) and LD B (706 ± 302 µmol N m−2 d−1), and the diazotroph community was dominated by Trichodesmium. N2 fixation rates were lower (59 ± 16 µmol N m−2 d−1) at LD C, and the diazotroph community was dominated by unicellular N2-fixing cyanobacteria (UCYN). At all stations, N2 fixation was the major source of new N (> 90 %) before atmospheric deposition and upward nitrate fluxes induced by turbulence. N2 fixation contributed circa 13–18 % of primary production in the MA region and 3 % in the SPG water and sustained nearly all new primary production at all stations. The e ratio (e ratio = particulate carbon export ∕ primary production) was maximum at LD A (9.7 %) and was higher than the e ratio in most studied oligotrophic regions (< 5 %), indicating a high efficiency of the WTSP to export carbon relative to primary production. The direct export of diazotrophs assessed by qPCR of the nifH gene in sediment traps represented up to 30.6 % of the PC export at LD A, while their contribution was 5 and < 0.1 % at LD B and LD C, respectively. At the three studied stations, the sum of all N input to the photic layer exceeded the N output through organic matter export. This disequilibrium leading to N accumulation in the upper layer appears as a characteristic of the WTSP during the summer season.

The wave energy resource in the Chilean coast shows particularly profitable characteristics for wave energy production, with relatively high mean wave power and low inter-annual resource variability. This combination is as interesting as unusual, since high energetic locations are usually also highly variable, such as the west coast of Ireland. Long-term wave resource variations are also an important aspect when designing wave energy converters (WECs), which are often neglected in resource assessment. The present paper studies the long-term resource variability of the Chilean coast, dividing the 20th century into five do-decades and analysing the variations between the different do-decades. To that end, the ERA20C reanalysis of the European Centre for Medium-Range Weather Forecasts is calibrated versus the ERA-Interim reanalysis and validated against buoy measurements collected in different points of the Chilean coast. Historical resource variations off the Chilean coast are compared to resource variations off the west coast in Ireland, showing a significantly more consistent wave resource. In addition, the impact of historical wave resource variations on a realistic WEC, similar to the Corpower device, is studied, comparing the results to those obtained off the west coast of Ireland. The annual power production off the Chilean coast is demonstrated to be remarkably more regular over the 20th century, with variations of just 1% between the different do-decades. The authors with the Centre for Ocean Energy Research in Maynooth University are supported by Science Foundation Ireland under Grant No. 13/IA/1886. It is also supported by grant CGL2016-76561-R, MINECO/ERDF, UE. Additional funding was received from the University of Basque Country (UPV/EHU, GIU17/002).

Estuaries are often seen as natural filters of riverine nitrate, but knowledge of this nitrogen sink in oligotrophic systems is limited. We measured spring and summer dinitrogen production (denitrification, anammox) in muddy and non-permeable sandy sediments of an oligotrophic estuary in the northern Baltic Sea, to estimate its function in mitigating the riverine nitrate load. Both sediment types had similar denitrification rates, and no anammox was detected. In spring at high nitrate loading, denitrification was limited by likely low availability of labile organic carbon. In summer, the average denitrification rate was similar to 138 mu mol N m(-2) d(-1). The corresponding estuarine nitrogen removal for August was similar to 1.2 t, of which similar to 93% was removed by coupled nitrification-denitrification. Particulate matter in the estuary was mainly phytoplankton derived (> 70% in surface waters) and likely based on the riverine nitrate which was not removed by direct denitrification due to water column stratification. Subsequently settling particles served as a link be tween the otherwise uncoupled nitrate in surface waters and benthic nitrogen removal. We suggest that the riverine nitrate brought into the oligotrophic estuary during the spring flood is gradually, and with a time delay, removed by benthic denitrification after being temporarily ` trapped' in phytoplankton particulate matter. The oligotrophic system is not likely to face eutrophication from increasing nitrogen loading due to phosphorus limitation. In response, coupled nitrification-denitrification rates are likely to stay constant, which might increase the future export of nitrate to the open sea and decrease the estuary's function as a nitrogen sink relative to the load.

Marine Isotope Stage 31 (MIS 31) is an important analogue for ongoing and projected global warming, yet key questions remain about the regional signature of its extreme orbital forcing and intra-interglacial variability. Based on a new direct land-sea comparison in SW Iberian margin IODP Site U1385 we examine the climatic variability between 1100 and 1050 ka including the "super interglacial" MIS 31, a period dominated by the 41-ky obliquity periodicity. Pollen and biomarker analyses at centennial-scale resolution provide new insights into the regional vegetation, precipitation regime and atmospheric and oceanic temperature variability on orbital and suborbital timescales. Our study reveals that atmospheric and SST warmth during MIS 31 was not exceptional in this region highly sensitive to precession. Unexpectedly, this warm stage stands out as a prolonged interval of a temperate and humid climate regime with reduced seasonality, despite the high insolation (precession minima values) forcing. We find that the dominant forcing on the long-term temperate forest development was obliquity, which may have induced a decrease in summer dryness and associated reduction in seasonal precipitation contrast. Moreover, this study provides the first evidence for persistent atmospheric millennial-scale variability during this interval with multiple forest decline events reflecting repeated cooling and drying episodes in SW Iberia. Our direct land-sea comparison shows that the expression of the suborbital cooling events on SW Iberian ecosystems is modulated by the predominance of high or low-latitude forcing depending on the glacial/interglacial baseline climate states. Severe dryness and air-sea cooling is detected under the larger ice volume during glacial MIS 32 and MIS 30. The extreme episodes, which in their climatic imprint are similar to the Heinrich events, are likely related to northern latitude ice-sheet instability and a disruption of the Atlantic Meridional Overturning Circulation (AMOC). In contrast, forest declines during MIS 31 are associated to neither SST cooling nor high-latitude freshwater forcing. Time-series analysis reveals a dominant cyclicity of about 6 ky in the temperate forest record, which points to a potential link with the fourth harmonic of precession and thus low-latitude insolation forcing. (C) 2017 Elsevier Ltd. All rights reserved. WarmClim LEFE-INSU IMAGO project Portuguese Foundation for Science and Technology (FCT) through the project CLIMHOL [PTDC/AAC-CLI/100157/2008] D. Oliveira's doctoral grant [SFRH/BD/9079/2012] F. Naughton's postdoctoral grant [SFRH/BPD/108712/2015] A. Voelker's IF contract Basque Government post-doctoral fellowship [POS_2015_1_0006] B. Martrat by a Ramon y Cajal contract [RYC-2013-14073] Integrated Ocean Drilling Program (IODP) Natural Environment Research Council [NE/J017922/1, NE/K005804/1] info:eu-repo/semantics/publishedVersion

The development of new wave energy converters has shed light on a number of unanswered questions in fluid mechanics, but has also identified a number of new issues of importance for their future deployment. The main concerns relevant to the practical use of wave energy converters are sustainability, survivability, and maintainability. Of course, it is also necessary to maximize the capture per unit area of the structure as well as to minimize the cost. In this review, we consider some of the questions related to the topics of sustainability, survivability, and maintenance access, with respect to sea conditions, for generic wave energy converters with an emphasis on the oscillating wave surge converter. New analytical models that have been developed are a topic of particular discussion. It is also shown how existing numerical models have been pushed to their limits to provide answers to open questions relating to the operation and characteristics of wave energy converters.

In situ viability of oceanic phytoplankton may be relatively low in open oceans. This is assumed to be related to the high-irradiance and low-nutrient conditions typical for oligotrophic regions. However, experimental evidence for this phenomenon was not yet available. In the present study, the importance of nutrient availability in high-irradiance-induced viability loss was therefore studied for three key oceanic phytoplankton species. Prochlorococcus marinus, Ostreococcus sp., and Thalassiosira oceanica were acclimated to two different N:P ratios. Growth, viability, and photophysiology were assessed under nutrient-replete and N- and P-starved conditions. Simultaneously, high-irradiance-induced photoinhibition and viability loss were measured and three inhibitors were used to investigate the underlying physiological mechanisms contributing to viability loss. High-irradiance exposure caused viability loss in P. marinus and Ostreococcus sp., but not in T. oceanica. Low-nutrient availability enhanced survival during high-irradiance exposure, although species-specific differences were observed. The lower sensitivity to high-irradiance intensities at low-nutrient availability was related to conformational changes in photosystem II in P. marinus, to enhanced photoprotection by the xanthophyll pigment cycle and alternative electron transport in Ostreococcus sp., and to enhanced photoprotection by the xanthophyll pigment cycle in T. oceanica. Climate change may lead to enhanced stratification in the open ocean. The resulting increase in the average irradiance intensity phytoplankton experience may promote viability loss in the smallest phytoplankton size fraction. However, this effect may partially be counteracted by the simultaneously expected decrease in nutrient availability.

WOS:000391139900018; International audience; The importance of the atmospheric deposition of biologically essential trace elements, especially iron, is widely recognized, as are the difficulties of accurately quantifying the rates of trace element wet and dry deposition and their fractional solubility. This paper summarizes some of the recent progress in this field, particularly that driven by the GEOTRACES, and other, international research programmes. The utility and limitations of models used to estimate atmospheric deposition flux, for example, from the surface ocean distribution of tracers such as dissolved aluminium, are discussed and a relatively new technique for quantifying atmospheric deposition using the short-lived radionuclide beryllium-7 is highlighted. It is proposed that this field will advance more rapidly by using a multi-tracer approach, and that aerosol deposition models should be ground-truthed against observed aerosol concentration data. It is also important to improve our understanding of the mechanisms and rates that control the fractional solubility of these tracers. Aerosol provenance and chemistry (humidity, acidity and organic ligand characteristics) play important roles in governing tracer solubility. Many of these factors are likely to be influenced by changes in atmospheric composition in the future. Intercalibration exercises for aerosol chemistry and fractional solubility are an essential component of the GEOTRACES programme. This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.

Knowledge of design waves with long return periods forms an essential input to many engineering applications, including structural design and analysis. Such extreme or long-term waves are conventionally evaluated using observed or hindcast historical wave data. Globally, waves are expected to undergo future changes in magnitude and behavior as a result of climate change induced by global warming. Considering future climate change, this study attempts to reevaluate significant wave height (Hs) as well as average spectral wave period (Tz) with a return period of 100 years for a series of locations along the western Indian coastline. Historical waves are simulated using a numerical wave model forced by wind data extracted from the archives of the National Center for Environmental Prediction and the National Center for Atmospheric Research, while future wave data are generated by a state-of-the-art Canadian general circulation model. A statistical extreme value analysis of past and projected wave data carried out with the help of the generalized Pareto distribution showed an increase in 100-year Hs and Tz along the Indian coastline, pointing out the necessity to reconsider the safety of offshore structures in the light of global warming.

The Fennec climate programme aims to improve understanding of the Saharan climate system through a synergy of observations and modelling. We present a description of the Fennec airborne observations during 2011 and 2012 over the remote Sahara (Mauritania and Mali) and the advances in the understanding of mineral dust and boundary layer processes they have provided. Aircraft instrumentation aboard the UK FAAM BAe146 and French SAFIRE (Service des Avions Français Instrumentés pour la Recherche en Environnement) Falcon 20 is described, with specific focus on instrumentation specially developed for and relevant to Saharan meteorology and dust. Flight locations, aims and associated meteorology are described. Examples and applications of aircraft measurements from the Fennec flights are presented, highlighting new scientific results delivered using a synergy of different instruments and aircraft. These include (1) the first airborne measurement of dust particles sizes of up to 300 microns and associated dust fluxes in the Saharan atmospheric boundary layer (SABL), (2) dust uplift from the breakdown of the nocturnal low-level jet before becoming visible in SEVIRI (Spinning Enhanced Visible Infra-Red Imager) satellite imagery, (3) vertical profiles of the unique vertical structure of turbulent fluxes in the SABL, (4) in situ observations of processes in SABL clouds showing dust acting as cloud condensation nuclei (CCN) and ice nuclei (IN) at −15 °C, (5) dual-aircraft observations of the SABL dynamics, thermodynamics and composition in the Saharan heat low region (SHL), (6) airborne observations of a dust storm associated with a cold pool (haboob) issued from deep convection over the Atlas Mountains, (7) the first airborne chemical composition measurements of dust in the SHL region with differing composition, sources (determined using Lagrangian backward trajectory calculations) and absorption properties between 2011 and 2012, (8) coincident ozone and dust surface area measurements suggest coarser particles provide a route for ozone depletion, (9) discrepancies between airborne coarse-mode size distributions and AERONET (AERosol Robotic NETwork) sunphotometer retrievals under light dust loadings. These results provide insights into boundary layer and dust processes in the SHL region – a region of substantial global climatic importance.

An environmental pollution assessment of the Ebrie lagoon, the largest coastal ecosystem in Western Africa, was executed by applying the Driving force-Pressure-State-Impacts-Response (DPSIR) framework. The domestic and industrial activities in Abidjan and agricultural activities in the wider catchment area were identified as the main driving forces. Two-thirds of Biological Oxygen Demand (BOD) loads and 95% of total nitrogen (N) and phosphorous (P) loads of Abidjan are from domestic effluents, with industry making up the rest. Outside of the direct influence of Abidjan, nutrient levels in the lagoon are governed by the influx of nutrients from the rivers Comoe, Me and Agneby, with nutrient land runoff as the key factors. Total annual N loads to the lagoon for 2000 are estimated at 33 kt, of which 45% from urban sources, 42% from land runoff and 13% from atmospheric deposition. Estimates for P are 2.5 kt, 39%, 48% and 13%, respectively. Scenario analysis has shown that autonomous growth, without pollution reduction measures, would result in an estimated five-fold increase in nutrient inputs to the lagoon over the period 1980-2050. Nutrient concentrations in the lagoon would consequently increase by a factor of 3 1/2, which could escalate to a dramatic level of eutrophication for the complete system. Pollution reduction policies aimed at non-point sources would be most effective in reducing nutrient concentrations. Point-source pollution reduction would improve conditions around Abidjan, but not substantially in the other sections of the lagoon. The approach taken in this study has proven efficient under conditions of relative data scarceness, and sufficiently reliable to allow for policy level conclusions to be drawn. (C) 2003 Elsevier B.V. All rights reserved.

[1] The MSA:nss SO4= ratio, which is a measure of the relative marine biogenic contribution to the total atmospheric sulphur burden, has long been measured in various parts of the globe. Transect studies and observations from a network of stations have provided some idea of the spatial and temporal behavior of the ratio in various regions, but gaps in knowledge still exist in other parts of the globe. Here we present results of a global 3‐D chemical transport modeling study which complement these measurements and provide a globe‐wide picture of the spatial variation and distribution of this ratio. Comparison of modeled versus measured data on the MSA:nss SO4= ratio resulting from all sulphur sources considered shows fair model performance (i.e., a general overestimation of 23%; degrees of freedom = 90) in all areas of the globe where actual measurements of the ratio have been made. On the other hand, the model‐observation comparisons for the MSA:nss SO4= ratio derived solely from the oceanic DMS source are not as satisfactory (an overall overestimation of a factor of 3; degrees of freedom = 50). The MSA:nss SO4= ratio that is derived from the oceanic DMS source alone provides information on the relative yields of MSA and SO4= from atmospheric DMS oxidation. Our model results are consistent with measurements, showing that the ratio is highest around the polar regions and lowest within the tropics. This spatial trend is attributed to the fact that MSA production occurs best under low temperatures (maximum ambient temperature of 27°C). Despite MSA being preferably produced under low temperatures, observations at high latitudes have consistently shown summer maxima and winter minima in the MSA:nss SO4= ratio. This has raised many questions on the robustness of the theory of the MSA production mechanism. Diminished marine biological activity and low seawater DMS conditions in winter have widely been cited as the cause of this observed trend. In this study, we further propose that since photochemical hydroxyl radical (OH) production during the dark winter months at polar latitudes is non‐existent, reduced wintertime oxidation of DMS by OH to form MSA results in summer maxima and winter minima in MSA concentrations at these latitudes. Temperature and marine biological activity are, therefore, not the only major determining factors for MSA production at high latitudes on a seasonal scale. Light conditions are also important. Throughout the year, the highest ratios occur in the Southern Hemisphere, where the atmospheric DMS burden is highest. This is in agreement with both short‐ and long‐term measurements in literature.

Differentiation of thermal traits (i.e. growth, survival and reproduction) was studied in the green macrophyte Valonia utricularis (Roth) C. Agardh, which has a world-wide tropical to warm-temperate distribution. Ecotypic differentiation between northeast Atlantic/Mediterranean and Indo-west Pacific isolates occurred with respect to all investigated temperature characteristics. The Atlantic/Mediterranean group is more eurythermal and cold-tolerant compared to the Indo-west Pacific group, which is stenothermal and cold-sensitive. Isolates of Atlantic/Mediterranean origin show clearly higher growth rates at low temperatures (lower temperature limit: 5-8 vs. 18-20degreesC) and a much better tolerance to low temperatures than the Indo-west Pacific isolates (0-5 vs. 16degreesC). Large shifts towards low temperatures are accompanied by parallel but smaller shifts at high temperatures. Differences in upper survival temperatures amounted on average to 4degreesC (32-33degreesC vs. 34-37degreesC) and growth ceased in the Atlantic isolates at 30degreesC, whereas the Indo-west Pacific isolates still reached significant growth at 33degreesC. Additionally, temperature requirements for reproduction were shifted towards lower temperatures in the Atlantic/Mediterranean isolates [18-20 and 25degreesC vs. 28-30(33)degreesC]. The, cold-adapted Atlantic/Mediterranean ecotype retained a strong tropical imprint with high temperature tolerance and high growth rates at temperatures > 25degreesC. The northern distribution limit in the northeastern Atlantic Ocean at 39degreesN (at the 13degreesC February and 17degreesC August isotherms) is probably set by a growth and/or reproduction boundary. The northern distribution limit in the Pacific Ocean at 26degreesN (at the 21degreesC February and 29degreesC August isotherms) is probably set by low lethal winter temperatures. The different latitudes of these boundaries must be attributed to the occurrence of more cold-adapted populations in the northeastern Atlantic Ocean compared to the northwestern Pacific Ocean. The development of cold-adaptation in the northeastern Atlantic Ocean and its absence in the northwestern Pacific Ocean has been related to different impacts of Pleistocene glaciations.

Organic carbon (OC) depleted in C-13 is a widely used tracer for terrestrial organic matter (OM) in aquatic systems. Photochemical reactions can, however, change delta C-13 of dissolved organic carbon (DOC) when chromophoric, aromatic-rich terrestrial OC is selectively mineralized. We assessed the robustness of the delta C-13 signature of DOC (delta C-13(DOC)) as a tracer for terrestrial OM by estimating its change during the photobleaching of chromophoric DOM (CDOM) from 10 large rivers. These rivers cumulatively account for approximately one-third of the world's freshwater discharge to the global ocean. Photobleaching of CDOM by simulated solar radiation was associated with the photochemical mineralization of 16 to 43% of the DOC and, by preferentially removing compounds depleted in C-13, caused a 1 to 2.9 parts per thousand enrichment in delta C-13 in the residual DOC. Such solar-radiation-induced photochemical isotopic shift could bias the calculations of terrestrial OM discharge in coastal oceans towards the marine end-member. Shifts in terrestrial delta C-13(DOC) should be taken into account when constraining the terrestrial end-member in global calculation of terrestrially derived DOM in the world ocean.

Effects of irradiance and temperature on the Mediterranean red algae Eupogodon spinellus and Eupogodon planus were tested. Growth of both species was saturated at an irradiance of 10-20 mu mol m(-2) s(-1), which is in accordance with their sublittoral habitat. Eupogodon spinellus and E. planus survived permanently at temperatures between 8 and 30 degrees C. The temperature optimum for growth was 25 degrees C with suboptimal growth occurring at (10-)15 and 30 degrees C in both species. At their collection locality (Corsica), potential monthly growth yields would be highest in summer and in winter would be only about 20% of the maximum. Reproductive requirements could be determined only in E. planus. Gametophytes reproduced both in long and in short days but only at 20 degrees C. Tetrasporophytes reproduced at 15-20 degrees C but only in short days. Geographic distribution boundaries are not set by growth or survival limits. However, the reproductive requirements of E, planus did account for its restricted distribution in the Mediterranean and on the Canary Islands.

Geographic variation in temperature responses (survival and growth) was investigated in two red algae: Digenea simplex (Wulfen) C. Agardh and Champia parvula (C. Agardh) Harvey. D. simplex has a tropical to warm temperate distribution; C. parvula extends from the tropics into the cold temperate zone. Ecoclinal variation was found in both species but was much stronger in C. parvula than in D. simplex. The former species showed variation in upper and lower tolerance limits as well as in the upper and lower limits for growth. The latter species showed variation mainly in its lower tolerance limit. Ecoclinal variation was related to the amount of present and glacial selection pressure along the climate gradient. In both species, isolates from the colder localities had insufficient cold tolerance to have survived low glacial winter temperatures, so these locations must have been colonized after the end of the glaciation. Eastern Mediterranean and Atlantic populations were probably isolated during the glaciation by a thermal barrier at the entrance of the Mediterranean. In C. parvula, evidence existed for a trade-off between the performance at high and at low temperatures, which would enhance selection pressure in opposite directions at either end of the climatic range. No evidence for such a trade-off was found in D. simplex.

Polar regions have great sensitivity to climate forcing; however, understanding of the physical processes coupling the atmosphere and ocean in these regions is relatively poor. Improving our knowledge of high-latitude surface fluxes will require close collaboration among meteorologists, oceanographers, ice physicists, and climatologists, and between observationalists and modelers, as well as new combinations of in situ measurements and satellite remote sensing. This article describes the deficiencies in our current state of knowledge about air–sea surface fluxes in high latitudes, the sensitivity of various high-latitude processes to changes in surface fluxes, and the scientific requirements for surface fluxes at high latitudes. We inventory the reasons, both logistical and physical, why existing flux products do not meet these requirements. Capturing an annual cycle in fluxes requires that instruments function through long periods of cold polar darkness, often far from support services, in situations subject to icing and extreme wave conditions. Furthermore, frequent cloud cover at high latitudes restricts the availability of surface and atmospheric data from visible and infrared (IR) wavelength satellite sensors. Recommendations are made for improving high-latitude fluxes, including 1) acquiring more in situ observations, 2) developing improved satellite-flux-observing capabilities, 3) making observations and flux products more accessible, and 4) encouraging flux intercomparisons.

Monthly replicate samples of 30 plants of each of nine species were collected in the intertidal zone in the Dalnezelenetskaya Inlet, Murman coast, Barents Sea. Germlings and new shoots emerged in great quantities in March when temperature was near 0 degrees C and daylength 10-13 h. All nine intertidal species on the Murman coast exhibit a period of rapid vegetative growth in early spring, at temperatures far below the optimum temperatures in at least five of them for which experimental evidence from the literature is available. The increasing light level in early spring is probably responsible for this growth. In six of them (Ulvaria obscura, Monostroma grevillei, Chorda filum, Chordaria flagelliformis, Stictyosiphon tortilis, Dumontia contorta) summer peaks of reproduction are apparently responsible for the summer decline of the thalli. The last five of these six have heteromorphic life histories in which microthallus stages are thought to ensure approximate synchronization of early spring recruitment (for instance by short day induction of microthallus development at autumnal temperatures, as in D. contorta and M. grevillei). In one species (Membranoptera alata), with an isomorphic diplohaplontic life history, early spring recruitment is thought to be ensured by the release of tetraspores and carpospores in winter. Earlier expectations that southern species would shift their reproduction to the summer near their northern distribution boundary were not confirmed. The general conclusion is that each of the nine species has approximately the same seasonal cycle of growth and reproduction in various parts of its geographic range, with only minor shifts from spring towards summer (but precise data on seasonal cycles elsewhere are scarce). This suggests that there may be subtle differences in temperatures and photoperiods triggering the onset of reproduction; this aspect needs further experimental testing of strains from the Murman coast.

Temperature tolerances were determined for Caribbean isolates (total 31) of seaweeds belonging to three distributional groups: 1) species confined to the tropical western Atlantic (Botryocladia spinulifera, Chamaedoris peniculum, Cladophoropsis sundanensis, Dictyopteris justii, Dictyurus occidentalis, Haloplegma duperreyi, and Heterosiphonia gibbesii); 2) amphi-Atlantic species with a (sub)tropical distribution that have their northern boundary in the eastern Atlantic at the tropical Cape Verde Islands (Bryothamnion triquetrum and Ceramium nitens) or the subtropical Canary Islands (Ceratodictyon intricatum, Coelothrix irregularis, Dictyopteris delicatula, Ernodesmis verticillata, and Lophocladia trichoclados; and 3 species with an amphi-Atlantic tropical to warm-temperate distribution also occurring in the Mediterranean (Cladophoropsis membranacea, Digenea simplex, Microdictyon boergesenii, and Wurdemannia miniata). For some isolates, growth response curves and temperature requirements for reproduction were also determined. Growth occurred in the range (18)20 degrees-30 degrees C with optimum growth rates at 25 degrees-30 degrees C, irrespective of distribution group. Reproduction generally occurred at (20)25 degrees-30 degrees C although there were some exceptions. Species were extremely stenothermal, with those restricted to the western Atlantic surviving a total range of only 10 / 13 degrees C (between 18 / 20 degrees and 30 / 33 degrees C). Tolerance to high temperatures was correlated with vertical position in the intertidal/subtidal zone rather than biogeographic grouping. Species restricted to the subtidal were the beast tolerant, with permanent survival at 30 degrees C but not at 33 degrees C. Tolerance to low temperatures was not different in subtidal and intertidal species but was significantly better in amphi-Atlantic than in western Atlantic species. In the former group, damage occurred at 15 degrees-18 degrees C but in the latter group at 18 degrees-20 degrees C. We propose that these differences in low-temperature tolerances in Caribbean populations of species from different distribution groups reflect adaptations to glacial cold-stress in the tropical eastern Atlantic and subsequent trans-Atlantic dispersal.

The Meteorological Synthesizing Centre-West (MSC-W) of the European Monitoring and Evaluation Programme (EMEP) has been performing model calculations in support of the Convention on Long Range Transboundary Air Pollution (CLRTAP) for more than 30 years. The EMEP MSC-W chemical transport model is still one of the key tools within European air pollution policy assessments. Traditionally, the model has covered all of Europe with a resolution of about 50 km × 50 km, and extending vertically from ground level to the tropopause (100 hPa). The model has changed extensively over the last ten years, however, with flexible processing of chemical schemes, meteorological inputs, and with nesting capability: the code is now applied on scales ranging from local (ca. 5 km grid size) to global (with 1 degree resolution). The model is used to simulate photo-oxidants and both inorganic and organic aerosols. In 2008 the EMEP model was released for the first time as public domain code, along with all required input data for model runs for one year. The second release of the EMEP MSC-W model became available in mid 2011, and a new release is targeted for summer 2012. This publication is intended to document this third release of the EMEP MSC-W model. The model formulations are given, along with details of input data-sets which are used, and a brief background on some of the choices made in the formulation is presented. The model code itself is available at www.emep.int, along with the data required to run for a full year over Europe.

Responses to temperature and daylength were determined in laboratory culture for isolates of the red alga Phyllophora pseudoceranoides (Gmelin) Newroth et A.R.A. Taylor from Nova Scotia, Iceland, Roscoff (France), and Helgoland (Germany). All isolates grew from 3 degrees to 25 degrees C and survived from -2 degrees or 0 degrees C to 27 degrees C but not 30 degrees C. Reproductive requirements differed between life history phases and isolates. Isolates from Helgoland and Roscoff formed sporangial sori at 3 degrees-20 degrees C, tetraspores at 3 degrees-12 degrees C, and procarps at 10 degrees-20 degrees C, irrespective of daylength. Spermatangia developed at 10 degrees-23 degrees C but only in long days. As the other European isolates, the isolate from Iceland formed tetrasporangia at 3 degrees-12 degrees C, but it had an additional requirement for short days. The Nova Scotian isolate formed sori at 10 degrees-20 degrees C and sporulated at 10 degrees-18 degrees C. When grown plants were transferred from noninductive to inductive conditions, sori were formed after 4 months and tetraspores developed and were shed (1-)3 months later. Procarps formed 1(-3) months after transfer. The phenology of P. pseudoceranoides was studied at Helgoland and Roscoff, where similar seasonal patterns were observed. Plants were perennial,forming new blades from October to June, which degenerated between August and February. In June, reproductive structures (sori, spermatangia, and procarps) started to appear on the new blades. From October to April, mature cystocarps were found. Mature tetrasporangia were observed only in February. The life history of P. pseudoceranoides is regulated by temperature and daylength. Differential effects on the different life history phases all serve to confine the production of spores (both carpospores and tetraspores) to the winter season. Differences in response between isolates from different geographic regions bring about the same effect: spores are only shed in winter. The nature of the geographic boundaries of p. pseudoceranoides is discussed.

The temperature requirements for growth and survival of cold water seaweeds from both Hemispheres are compared and discussed in relation to the climatic history of the various regions and in relation to the origin of amphiequatorial distribution patterns. Endemic Antarctic species are most strongly adapted to low temperatures. In contrast, endemic Arctic macroalgae show higher temperature demands and correspond in their temperature responses to many Antarctic cold-temperate species. Arctic cold-temperate species show similar temperature requirements to cold-temperate species from southernmost South America. The temperature requirements of cold-temperate N. Atlantic species are somewhat higher than those of cold-temperate N. E. Pacific species. These differences are the result of the different times of exposure of these groups to low temperatures. The first steps in the adaptation of macroalgae to low temperatures are an increase in cold tolerance and an increase of growth and reproduction rates at low temperatures. Later, the ability to grow and reproduce at greater-than-or-equal-to 15 to 20-degrees-C and to survive temperatures greater-than-or-equal-to 20-degrees-C is lost. This temperature response type is exemplified in endemic Arctic and Arctic cold-temperate seaweeds exposed to low temperatures since about 3 My. The last steps in the adaptation to low temperatures include the loss of ability to grow and reproduce at greater-than-or-equal-to 5 or 10-degrees-C and a strong reduction in the upper survival temperatures (UST) down to 10-13-degrees-C. This temperature response type is typical for endemic Antarctic species exposed to cold waters for at least 14 My. Amphiequatorial filamentous green and brown algal taxa and microthalli of amphiequatorial brown algae mostly show UST's of 23 to 28.5-degrees-C, significantly higher compared to single Hemisphere taxa from the same regions. These findings strongly favour a migrationist jump across the equator to the other Hemisphere during Pleistocene lowering of the water temperatures in the tropics. Reproduction and growth during the passage across the equator would not have been possible in all species except Ectocarpus siliculosus due to the narrow temperature-reproduction and temperature-growth windows.

Lower and upper survival temperatures of microthalli of 25 species of South American Phaeophyceae isolated from central Peru (14-degrees-S) to the Canal Beagle (55-degrees-S) were determined using 2-wk exposure for the upper and 4-wk exposure for the lower limit. All species survive 4 wks at - 2-degrees-C. With respect to the upper limit, species reported only from southernmost South America tolerate 19.9 to 24.5-degrees-C (n = 8), and species occurring from Cape Horn to central Chile 24.6 to 27.4-degrees-C (n = 7). Three species that occurred as far north as northern Chile and Peru before the 1982-1983 El Nino event, and whose northern limit was dramatically shifted southwards in 1983, tolerate 20.8 to 25.3-degrees-C, whereas five species that have survived in Peru tolerate 25.6 to 28.5-degrees-C. Tinocladia falklandica which tolerates 27.8 to 28.1-degrees-C but lives only in southernmost South America and Striaria attenuata, which tolerates 31.6 to 31.9-degrees-C but occurs at ca. 42-degrees-S, are exceptional. Their high temperature tolerance may have no adaptive value in South America. They are restricted to the cold-temperate region due to low temperature requirements for reproduction or for reasons yet unknown. In general, the northern distributional limits of the Phaeophyceae studied along the temperate Pacific coast of South America are reproduction boundaries, except in El Nino years when they are redefined according to the species' upper suvival limits. Temperature tolerance of isolates from northern Chile and Peru agrees well with maximum temperatures reached during the 1983 El Nino.

The primary nutrients that limit marine phytoplankton growth rates include nitrogen (N), phosphorus (P), iron (Fe), and silicon (Si). Atmospheric transport and deposition provides a source for each of these nutrients to the oceans. We utilize an ocean biogeochemical model to examine the relative importance of these atmospheric inputs for ocean biogeochemistry and export production. In the current era, simulations with the biogeochemical elemental cycling ocean model suggest that globally, atmospheric Fe inputs could support roughly 50% of the Fe exported from the euphotic zone by sinking organic and inorganic particles. Variations in atmospheric iron inputs strongly impact spatial patterns of phytoplankton growth limitation and the areal extent of the high-nutrient, low-chlorophyll regions. Atmospheric inputs of N, Si, and P have smaller impacts, potentially accounting for 5.1%, 0.21%, and 0.12% of the biogenic export of these elements from the euphotic zone, respectively. Soluble Fe input from the atmosphere is sufficient to support most of the export production in many ocean regions, whether we use a spatially variable aerosol Fe solubility, or a globally constant 2% solubility. Regionally atmospheric N inputs can have significant impacts on marine biogeochemistry, potentially supporting >25% of the export production, an impact that is increasing due to human activities. Atmospheric Si and P inputs have only minimal impacts on marine ecosystem productivity and biogeochemistry, as these inputs are typically quite small relative to the flux of these nutrients from below the euphotic zone.

We examined the temperature tolerance of microscopic phases from geographically disjunct isolates of eight species or closely related, putatively conspecific taxa of temperate brown algae with disjunct distributions. Maximum within-taxon differences were small and ranged from 1.6-degrees to 4.3-degrees-C. Desmarestia aculeata and Sphaerotrichia divaricata, both with northern hemisphere amphioceanic distributions, showed little or no significant intraspecific variation between the mean upper survival limits (USL) of Atlantic and Pacific strains (delta-USL less-than-or-equal-to 1.4-degrees-C), which would agree with a relatively recent separation of the respective populations. Among the plants with bipolar distributions, there was likewise very little difference (delta-USL 0-1.1-degrees-C) between northern and southern hemisphere strains in Striaria attenuata and in the species pair Desmarestia viridis/D. willii. In Desmarestia ligulata, and in the species pairs Desmarestia firma/D. munda, Dictyosiphon foeniculaceus/D. hirsutus, and Scytothamnus australis/Scytothamnus sp., significant differences occurred, which indicate longer divergence times. Delta-USL in these cases ranged from 1.7-degrees to 2.7-degrees-C, without overlap between strains from the northern and southern hemispheres. All species that passed the equator during cooler epochs had a USL of 26-27-degrees-C, at least in some geographical isolates. The NE Asian kelp Undaria pinnatifida, which passed the equator in recent times, had a USL of 29.6-degrees-C. We hypothesize that the mechanism of spreading in the amphipolar species studied was migration of vegetative microthalli. The more unlikely alternative hypothesis of continuous populations through the tropics during a cooler epoch would imply a drop in seawater temperatures to approximately 20-degrees-C in summer and 15-degrees-C in winter, which is not supported by paleoclimatic evidence.

SUMMARY Marine picocyanobacteria of the genera Prochlorococcus and Synechococcus numerically dominate the picophytoplankton of the world ocean, making a key contribution to global primary production. Prochlorococcus was isolated around 20 years ago and is probably the most abundant photosynthetic organism on Earth. The genus comprises specific ecotypes which are phylogenetically distinct and differ markedly in their photophysiology, allowing growth over a broad range of light and nutrient conditions within the 45°N to 40°S latitudinal belt that they occupy. Synechococcus and Prochlorococcus are closely related, together forming a discrete picophytoplankton clade, but are distinguishable by their possession of dissimilar light-harvesting apparatuses and differences in cell size and elemental composition. Synechococcus strains have a ubiquitous oceanic distribution compared to that of Prochlorococcus strains and are characterized by phylogenetically discrete lineages with a wide range of pigmentation. In this review, we put our current knowledge of marine picocyanobacterial genomics into an environmental context and present previously unpublished genomic information arising from extensive genomic comparisons in order to provide insights into the adaptations of these marine microbes to their environment and how they are reflected at the genomic level.

Analysis of the reassociation kinetics of the DNA from Cladophora pellucida (Huds.) Kutz. indicates that the genome of this benthic alga is comprised of approximately 75% repetitive sequences. Single-copy sequences reassociated with a rate constant of 1.8 x 10(-3) M-1.s-1, which corresponds to a haploid genome size of 4.7 x 10(8) bp. Genotypic relationships between members of the form section Longiarticulatae were determined by the method of DNA-DNA hybridization. No significant divergence was observed between the single-copy sequences of C. pellucida isolates from the East Atlantic coast and Mediterranean Sea. Cladophora feredayi Harv. and C. att. ad pellucida from Australia and C. pellucidoidea van den Hoek from the West Atlantic coast were highly and about equally divergent from C. pellucida. The data support the hypothesis that the West Atlantic-West Pacific divergence reflects the middle Miocene closure of the Mediterranean-Indo-Pacific seaways, and the hypothesis that the Northwest Atlantic-Northeast Atlantic divergence reflects the middle Miocene thermal separation of these coasts.

Towards more rapid ultraclean sampling of deep ocean waters for trace elements, a novel rectangular frame was constructed of titanium, holding two rows of 12 samplers, as well as various sensors. The frame is deployed to deep ocean waters by an 8000 m length Kevlar wire with internal power and signal cables. Closing of each sampler is by seawater hydraulics via silicone tubings connecting each sampler with a central 24 position Multivalve. Upon recovery the complete frame with 24 samplers is placed inside an ultraclean laboratory van, where water is drawn via filters into bottles. Previously the clean sampling of ocean waters has been very time-consuming by attachment of individual ultraclean bottle samplers one by one to a metal-free (e.g. all-Kevlar) hydrowire. The novel Titan system is 3-4 times faster and permits routine collection of deep ocean sections while economizing required shiptime. In a test of the new system in November 2005 in the Canary Basin excellent low dissolved Fe concentrations (similar to 0.1to similar to 0.4nM) are consistent with values obtained of individual samplers on a simple wire, and previous values in a pilot study of 2002 in the same basin, as well as published dissolved Fe values elsewhere in the northeast Atlantic Ocean. (C) 2007 Elsevier B.V. All rights reserved.

An accurate estimation of Lagrangian transport in the ocean is important for a number of practical problems such as dispersion of pollutants, biological species, and sediments. Forecasting of the Lagrangian pathways necessarily relies on the accuracy of ocean and coastal models. However, these models include a number of errors that propagate directly from the Eulerian velocity field to the Lagrangian transport. In this study, so-called Lagrangian sub-grid-scale, or LSGS, model is developed to reduce errors projected to Lagrangian transport from errors arising from missing physics, uncertainties in forcing and unresolved scales in OGCMs. The LSGS method acts on the diagnostics of particle transport computed from coastal or ocean models, and it allows to minimize the discrepancy between the statistical behavior of the modeled (synthetic) and real (observed) trajectories. The method is shown to work well using both a so-called Markov velocity field model, representing an idealized turbulent flow field, and in the context of the Navy Coastal Ocean Model (NCOM) configured in the Adriatic Sea for realistic, high-resolution, complex ocean flows. The simplicity and computational efficiency of this technique, combined with applicability to ocean models at a wide range of resolutions, appears promising in light of the challenge of capturing exactly the oceanic turbulent fields, which is critical for Lagrangian dispersion.

International audience; To increase our understanding of the carbon cycle, we compare regional estimates of CO2 flux variability for 1980 - 1998 from atmospheric CO2 inversions and from process-based models of the land (SLAVE and LPJ) and ocean (OPA and MIT). Over the land, the phase and amplitude of the different estimates agree well, especially at continental scale. Flux variations are predominantly controlled by El Nino events, with the exception of the post-Pinatubo period of the early 1990s. Differences between the two land models result mainly from the response of heterotrophic respiration to precipitation and temperature. The "Lloyd and Taylor'' formulation of LPJ [Lloyd and Taylor, 1994] agrees better with the inverse estimates. Over the ocean, inversion and model results agree only in the equatorial Pacific and partly in the austral ocean. In the austral ocean, an increased CO2 sink is present in the inversion and OPA model, and results from increased stratification of the ocean. In the northern oceans, the inversions estimate large flux variations in line with time-series observations of the subtropical Atlantic, but not supported by the two model estimates, thus suggesting that the CO2 variability from high-latitude oceans needs further investigation.

Differentiation of thermal traits (i.e. growth, survival and reproduction) was studied in the green macrophyte Valonia utricularis (Roth) C. Agardh, which has a world-wide tropical to warm-temperate distribution. Ecotypic differentiation between northeast Atlantic/Mediterranean and Indo-west Pacific isolates occurred with respect to all investigated temperature characteristics. The Atlantic/Mediterranean group is more eurythermal and cold-tolerant compared to the Indo-west Pacific group, which is stenothermal and cold-sensitive. Isolates of Atlantic/Mediterranean origin show clearly higher growth rates at low temperatures (lower temperature limit: 5-8 vs. 18-20degreesC) and a much better tolerance to low temperatures than the Indo-west Pacific isolates (0-5 vs. 16degreesC). Large shifts towards low temperatures are accompanied by parallel but smaller shifts at high temperatures. Differences in upper survival temperatures amounted on average to 4degreesC (32-33degreesC vs. 34-37degreesC) and growth ceased in the Atlantic isolates at 30degreesC, whereas the Indo-west Pacific isolates still reached significant growth at 33degreesC. Additionally, temperature requirements for reproduction were shifted towards lower temperatures in the Atlantic/Mediterranean isolates [18-20 and 25degreesC vs. 28-30(33)degreesC]. The, cold-adapted Atlantic/Mediterranean ecotype retained a strong tropical imprint with high temperature tolerance and high growth rates at temperatures > 25degreesC. The northern distribution limit in the northeastern Atlantic Ocean at 39degreesN (at the 13degreesC February and 17degreesC August isotherms) is probably set by a growth and/or reproduction boundary. The northern distribution limit in the Pacific Ocean at 26degreesN (at the 21degreesC February and 29degreesC August isotherms) is probably set by low lethal winter temperatures. The different latitudes of these boundaries must be attributed to the occurrence of more cold-adapted populations in the northeastern Atlantic Ocean compared to the northwestern Pacific Ocean. The development of cold-adaptation in the northeastern Atlantic Ocean and its absence in the northwestern Pacific Ocean has been related to different impacts of Pleistocene glaciations.

Differentiation of thermal traits (i.e. growth, survival and reproduction) was studied in the green macrophyte Valonia utricularis (Roth) C. Agardh, which has a world-wide tropical to warm-temperate distribution. Ecotypic differentiation between northeast Atlantic/Mediterranean and Indo-west Pacific isolates occurred with respect to all investigated temperature characteristics. The Atlantic/Mediterranean group is more eurythermal and cold-tolerant compared to the Indo-west Pacific group, which is stenothermal and cold-sensitive. Isolates of Atlantic/Mediterranean origin show clearly higher growth rates at low temperatures (lower temperature limit: 5-8 vs. 18-20degreesC) and a much better tolerance to low temperatures than the Indo-west Pacific isolates (0-5 vs. 16degreesC). Large shifts towards low temperatures are accompanied by parallel but smaller shifts at high temperatures. Differences in upper survival temperatures amounted on average to 4degreesC (32-33degreesC vs. 34-37degreesC) and growth ceased in the Atlantic isolates at 30degreesC, whereas the Indo-west Pacific isolates still reached significant growth at 33degreesC. Additionally, temperature requirements for reproduction were shifted towards lower temperatures in the Atlantic/Mediterranean isolates [18-20 and 25degreesC vs. 28-30(33)degreesC]. The, cold-adapted Atlantic/Mediterranean ecotype retained a strong tropical imprint with high temperature tolerance and high growth rates at temperatures > 25degreesC. The northern distribution limit in the northeastern Atlantic Ocean at 39degreesN (at the 13degreesC February and 17degreesC August isotherms) is probably set by a growth and/or reproduction boundary. The northern distribution limit in the Pacific Ocean at 26degreesN (at the 21degreesC February and 29degreesC August isotherms) is probably set by low lethal winter temperatures. The different latitudes of these boundaries must be attributed to the occurrence of more cold-adapted populations in the northeastern Atlantic Ocean compared to the northwestern Pacific Ocean. The development of cold-adaptation in the northeastern Atlantic Ocean and its absence in the northwestern Pacific Ocean has been related to different impacts of Pleistocene glaciations.

Differentiation in temperature responses (survival and growth) was investigated among isolates of two tropical to temperate green algal lineages: the Cladophora vagabunda complex and the C. albida/sericea complex. The results were analysed in relation to published data on 18S rRNA and ITS sequence divergence, which have shown that the overall degree of genetic divergence is similar in the two lineages but that very different patterns of radiation have occurred. In the C. vagabunda complex, the two main clades in the well-resolved phylogenetic tree differed mainly in their tolerance to low temperatures. Within-clade variation was no stronger in the Atlantic/Pacific than in the all-Pacific clade. In the C. albida/sericea complex, six distinctive ITS types indicated early radiation. Although distinctive differences were found between some of these types. the thermal responses of others were very similar, indicating physiological stasis. In both lineages there was evidence for some adaptation to local temperature regimes but phylogenetic constraints were generally more important, Isolates with the same ITS sequences showed similar temperature responses even though collected from different climate zones. Evidence was found for a physiological trade-off between growth at high and at low temperatures in the C. albida/sericea complex, whereas, in the C. vagabunda complex. one clade showed more eurythermal growth responses than the other. In the C. vagabunda complex, which is the ancestral lineage of the C. albida/sericea complex, major differentiation was found in cold tolerance but not in heat tolerance, whereas the reverse pattern was found in the derived C. albida/sericea complex. These findings suggest that an acquisition of cold tolerance preceded the loss of heat tolerance during adaptation to colder climates.

Effects of irradiance and temperature on the Mediterranean red algae Eupogodon spinellus and Eupogodon planus were tested. Growth of both species was saturated at an irradiance of 10-20 mu mol m(-2) s(-1), which is in accordance with their sublittoral habitat. Eupogodon spinellus and E. planus survived permanently at temperatures between 8 and 30 degrees C. The temperature optimum for growth was 25 degrees C with suboptimal growth occurring at (10-)15 and 30 degrees C in both species. At their collection locality (Corsica), potential monthly growth yields would be highest in summer and in winter would be only about 20% of the maximum. Reproductive requirements could be determined only in E. planus. Gametophytes reproduced both in long and in short days but only at 20 degrees C. Tetrasporophytes reproduced at 15-20 degrees C but only in short days. Geographic distribution boundaries are not set by growth or survival limits. However, the reproductive requirements of E, planus did account for its restricted distribution in the Mediterranean and on the Canary Islands.

Geographic variation in temperature responses (survival and growth) was investigated in two red algae: Digenea simplex (Wulfen) C. Agardh and Champia parvula (C. Agardh) Harvey. D. simplex has a tropical to warm temperate distribution; C. parvula extends from the tropics into the cold temperate zone. Ecoclinal variation was found in both species but was much stronger in C. parvula than in D. simplex. The former species showed variation in upper and lower tolerance limits as well as in the upper and lower limits for growth. The latter species showed variation mainly in its lower tolerance limit. Ecoclinal variation was related to the amount of present and glacial selection pressure along the climate gradient. In both species, isolates from the colder localities had insufficient cold tolerance to have survived low glacial winter temperatures, so these locations must have been colonized after the end of the glaciation. Eastern Mediterranean and Atlantic populations were probably isolated during the glaciation by a thermal barrier at the entrance of the Mediterranean. In C. parvula, evidence existed for a trade-off between the performance at high and at low temperatures, which would enhance selection pressure in opposite directions at either end of the climatic range. No evidence for such a trade-off was found in D. simplex.

Monthly replicate samples of 30 plants of each of nine species were collected in the intertidal zone in the Dalnezelenetskaya Inlet, Murman coast, Barents Sea. Germlings and new shoots emerged in great quantities in March when temperature was near 0 degrees C and daylength 10-13 h. All nine intertidal species on the Murman coast exhibit a period of rapid vegetative growth in early spring, at temperatures far below the optimum temperatures in at least five of them for which experimental evidence from the literature is available. The increasing light level in early spring is probably responsible for this growth. In six of them (Ulvaria obscura, Monostroma grevillei, Chorda filum, Chordaria flagelliformis, Stictyosiphon tortilis, Dumontia contorta) summer peaks of reproduction are apparently responsible for the summer decline of the thalli. The last five of these six have heteromorphic life histories in which microthallus stages are thought to ensure approximate synchronization of early spring recruitment (for instance by short day induction of microthallus development at autumnal temperatures, as in D. contorta and M. grevillei). In one species (Membranoptera alata), with an isomorphic diplohaplontic life history, early spring recruitment is thought to be ensured by the release of tetraspores and carpospores in winter. Earlier expectations that southern species would shift their reproduction to the summer near their northern distribution boundary were not confirmed. The general conclusion is that each of the nine species has approximately the same seasonal cycle of growth and reproduction in various parts of its geographic range, with only minor shifts from spring towards summer (but precise data on seasonal cycles elsewhere are scarce). This suggests that there may be subtle differences in temperatures and photoperiods triggering the onset of reproduction; this aspect needs further experimental testing of strains from the Murman coast.

Monthly replicate samples of 30 plants of each of nine species were collected in the intertidal zone in the Dalnezelenetskaya Inlet, Murman coast, Barents Sea. Germlings and new shoots emerged in great quantities in March when temperature was near 0 degrees C and daylength 10-13 h. All nine intertidal species on the Murman coast exhibit a period of rapid vegetative growth in early spring, at temperatures far below the optimum temperatures in at least five of them for which experimental evidence from the literature is available. The increasing light level in early spring is probably responsible for this growth. In six of them (Ulvaria obscura, Monostroma grevillei, Chorda filum, Chordaria flagelliformis, Stictyosiphon tortilis, Dumontia contorta) summer peaks of reproduction are apparently responsible for the summer decline of the thalli. The last five of these six have heteromorphic life histories in which microthallus stages are thought to ensure approximate synchronization of early spring recruitment (for instance by short day induction of microthallus development at autumnal temperatures, as in D. contorta and M. grevillei). In one species (Membranoptera alata), with an isomorphic diplohaplontic life history, early spring recruitment is thought to be ensured by the release of tetraspores and carpospores in winter. Earlier expectations that southern species would shift their reproduction to the summer near their northern distribution boundary were not confirmed. The general conclusion is that each of the nine species has approximately the same seasonal cycle of growth and reproduction in various parts of its geographic range, with only minor shifts from spring towards summer (but precise data on seasonal cycles elsewhere are scarce). This suggests that there may be subtle differences in temperatures and photoperiods triggering the onset of reproduction; this aspect needs further experimental testing of strains from the Murman coast.

Temperature tolerances were determined for Caribbean isolates (total 31) of seaweeds belonging to three distributional groups: 1) species confined to the tropical western Atlantic (Botryocladia spinulifera, Chamaedoris peniculum, Cladophoropsis sundanensis, Dictyopteris justii, Dictyurus occidentalis, Haloplegma duperreyi, and Heterosiphonia gibbesii); 2) amphi-Atlantic species with a (sub)tropical distribution that have their northern boundary in the eastern Atlantic at the tropical Cape Verde Islands (Bryothamnion triquetrum and Ceramium nitens) or the subtropical Canary Islands (Ceratodictyon intricatum, Coelothrix irregularis, Dictyopteris delicatula, Ernodesmis verticillata, and Lophocladia trichoclados; and 3 species with an amphi-Atlantic tropical to warm-temperate distribution also occurring in the Mediterranean (Cladophoropsis membranacea, Digenea simplex, Microdictyon boergesenii, and Wurdemannia miniata). For some isolates, growth response curves and temperature requirements for reproduction were also determined. Growth occurred in the range (18)20 degrees-30 degrees C with optimum growth rates at 25 degrees-30 degrees C, irrespective of distribution group. Reproduction generally occurred at (20)25 degrees-30 degrees C although there were some exceptions. Species were extremely stenothermal, with those restricted to the western Atlantic surviving a total range of only 10 / 13 degrees C (between 18 / 20 degrees and 30 / 33 degrees C). Tolerance to high temperatures was correlated with vertical position in the intertidal/subtidal zone rather than biogeographic grouping. Species restricted to the subtidal were the beast tolerant, with permanent survival at 30 degrees C but not at 33 degrees C. Tolerance to low temperatures was not different in subtidal and intertidal species but was significantly better in amphi-Atlantic than in western Atlantic species. In the former group, damage occurred at 15 degrees-18 degrees C but in the latter group at 18 degrees-20 degrees C. We propose that these differences in low-temperature tolerances in Caribbean populations of species from different distribution groups reflect adaptations to glacial cold-stress in the tropical eastern Atlantic and subsequent trans-Atlantic dispersal.

Responses to temperature and daylength were determined in laboratory culture for isolates of the red alga Phyllophora pseudoceranoides (Gmelin) Newroth et A.R.A. Taylor from Nova Scotia, Iceland, Roscoff (France), and Helgoland (Germany). All isolates grew from 3 degrees to 25 degrees C and survived from -2 degrees or 0 degrees C to 27 degrees C but not 30 degrees C. Reproductive requirements differed between life history phases and isolates. Isolates from Helgoland and Roscoff formed sporangial sori at 3 degrees-20 degrees C, tetraspores at 3 degrees-12 degrees C, and procarps at 10 degrees-20 degrees C, irrespective of daylength. Spermatangia developed at 10 degrees-23 degrees C but only in long days. As the other European isolates, the isolate from Iceland formed tetrasporangia at 3 degrees-12 degrees C, but it had an additional requirement for short days. The Nova Scotian isolate formed sori at 10 degrees-20 degrees C and sporulated at 10 degrees-18 degrees C. When grown plants were transferred from noninductive to inductive conditions, sori were formed after 4 months and tetraspores developed and were shed (1-)3 months later. Procarps formed 1(-3) months after transfer. The phenology of P. pseudoceranoides was studied at Helgoland and Roscoff, where similar seasonal patterns were observed. Plants were perennial,forming new blades from October to June, which degenerated between August and February. In June, reproductive structures (sori, spermatangia, and procarps) started to appear on the new blades. From October to April, mature cystocarps were found. Mature tetrasporangia were observed only in February. The life history of P. pseudoceranoides is regulated by temperature and daylength. Differential effects on the different life history phases all serve to confine the production of spores (both carpospores and tetraspores) to the winter season. Differences in response between isolates from different geographic regions bring about the same effect: spores are only shed in winter. The nature of the geographic boundaries of p. pseudoceranoides is discussed.

The temperature requirements for growth and survival of cold water seaweeds from both Hemispheres are compared and discussed in relation to the climatic history of the various regions and in relation to the origin of amphiequatorial distribution patterns. Endemic Antarctic species are most strongly adapted to low temperatures. In contrast, endemic Arctic macroalgae show higher temperature demands and correspond in their temperature responses to many Antarctic cold-temperate species. Arctic cold-temperate species show similar temperature requirements to cold-temperate species from southernmost South America. The temperature requirements of cold-temperate N. Atlantic species are somewhat higher than those of cold-temperate N. E. Pacific species. These differences are the result of the different times of exposure of these groups to low temperatures. The first steps in the adaptation of macroalgae to low temperatures are an increase in cold tolerance and an increase of growth and reproduction rates at low temperatures. Later, the ability to grow and reproduce at greater-than-or-equal-to 15 to 20-degrees-C and to survive temperatures greater-than-or-equal-to 20-degrees-C is lost. This temperature response type is exemplified in endemic Arctic and Arctic cold-temperate seaweeds exposed to low temperatures since about 3 My. The last steps in the adaptation to low temperatures include the loss of ability to grow and reproduce at greater-than-or-equal-to 5 or 10-degrees-C and a strong reduction in the upper survival temperatures (UST) down to 10-13-degrees-C. This temperature response type is typical for endemic Antarctic species exposed to cold waters for at least 14 My. Amphiequatorial filamentous green and brown algal taxa and microthalli of amphiequatorial brown algae mostly show UST's of 23 to 28.5-degrees-C, significantly higher compared to single Hemisphere taxa from the same regions. These findings strongly favour a migrationist jump across the equator to the other Hemisphere during Pleistocene lowering of the water temperatures in the tropics. Reproduction and growth during the passage across the equator would not have been possible in all species except Ectocarpus siliculosus due to the narrow temperature-reproduction and temperature-growth windows.